Scientific Team

Pests of the Date Palm (Phoenix dactylifera)

Mohamed Saeed Gassouma

Plant Protection Expert (Entomologist)

saeedgassouma@hotmail.com

Abstract

The paper includes surveys and studies made over the last two decades on the “Arthropod Pests of the Date Palm”, in UAE. They are to be considered, more or less, as representative for the whole region, because of the similarity of the terrain, similarity of growing conditions and the passage of planting material throughout the years.

The studies revealed the indigenous occurrence of

·               the dubas bug Ommatissus lybicus

·               the scale insects Parlatoria blanchardi and Phoenicococcus marlatti

·               the ‘the giant mealy’ Pseudaspidoproctus hypheniacus

·               the trunk-borer Jebusaea hammerschmidtii

·               two rhinoceros beetles Oryctes agamemnon and O. elegans

·               the two date moths Batrachedra amydraula and Aphomia sabella

·               the date mite Oligonychus afrasiaticus

·               the frond crimson mite Raoiella indica

Over the years the author witnessed the arrival of more (exotic) pests imported with planting material

·               the Red Palm Weevil Rhynchophorus ferrugineus

·               the third rhinoceros beetle Oryctes rhinoceros

·               the third scale insect Fiorinia phoenicis

The author also discovered and described a new pest the inflorescence beetle Macrocoma sp.nov.

There is a recent growing importance of some of these pests; attention is also needed to be paid to the slowly spreading ‘Al wijam’ of the undetermined aetiology.

With a limited knowledge of  phytopathology, the author also recorded the common and most important fungal diseases of the date palm, in UAE

The paper is composed of a pictorial  and textual presentation of morphology, life cycles and management of the different pests.

Introduction

Although the management of pests is a major aspect of agricultural development, yet it has been noticed from the different country reports, submitted to this workshop, that surveys and studies of the pests of the date palm have not been adequately done. There were very limited data that need correction and expansion.

The date palm like no other planted tree is targeted by a large number of pests; whether Arthropods, fungi, nematode or now phytoplasma; some are serious and difficult to control, thus threatening its existence in many cases. In UAE, the Red Palm Weevil (Rhynchophorus ferrugineus) has been a big menace to the date palm during the last twenty years costing a lot of money and a lot of effort to control; its importance which has recently dwindled is now equally shared by the ‘longhorn’ trunk-borer (Jebusaea hammerschmidtii) and three ‘rhinoceros beetles’ (Oryctes agamemnon, O. elegans and O. rhinoceros). Other pests are less serious and easier to control.

There should be strong measures of external and internal quarantine procedure to prevent additions to what is occurring in a country or in other parts of a country and to stop making bad conditions worse – better still is to strictly prevent personal importation of planting material; what is in any country of pests now is more than enough.

The paper includes surveys and studies made by the author over the last two decades on the “Arthropod Pests of the Date Palm” and observations on diseases, particularly fungal diseases on this valuable tree, in UAE. Resultant data are to be considered as representative for the whole region, because of similarity of the terrain, similarity of growing conditions and the passage of planting material throughout the years.

Arthropod Pests

As was shown in the presentation and what will be summarized hereunder, there is a comparatively large number of Arthropod Pests causing plenty of damage and perhaps death to this important tree; most of them are difficult and expensive to manage. The studies revealed the occurrence of 11 indigenous arthropod pests and the arrival, during these studies of 3 exotic pests imported with date palm planting material.

The author also discovered and described a new pest the inflorescence beetle Macrocoma sp. nov.

The pests are arranged according to the insect and mite Orders.

1 Order Homoptera

The Order Homoptera contains the sucking insects; the insects that suck the sap from the date palm and weaken it. In the case of the “dubas bug” which is one of its members, a heavy infestation might reduce the crop to less than 50%.

-The leaf-hopper (dubas bug) Ommatissus lybicus (family Tropiduchidae)

This insect has two distinct generations per year; spring and summer, each lasting for about 3 ½ months. At the end of each generation (April-May and October-November) the female lays its eggs inserting them singly into holes it pierces in the tissue of the rachis of the date palm frond. The eggs remain dormant for about 3 months and when they hatch the resulting nymphs continue living on the fronds of the same palm – drawing the sap and excreting copious honeydew which covers the fronds making them glistening. In heavy infestation the droplets of the honeydew coalesce to give a thin film on the frond on which sooty moulds grow to block the stomata of the pinnae causing partial or complete suffocation to the palm; this will dramatically reduce its crop. The honeydew secreted by the autumn generation drops on the dates making them unpalatable. The date palm is the only host for this pest.

No biological control is taking place on this pest in UAE, but it is mentioned in the Iraqi, Saudi and Iranian literature, more than a quarter of a century ago, of the presence of an ‘egg parasitoid’ and some coccinellid predators on the dubas bug, but no work has been done to encourage the development of such important relationships. Chemical control is the only answer, at present; but to be successful it has to be properly timed; there is a short and critical period of only two weeks for that when the oldest nymphs reach the 5^th instar and before any of them develop to adults.

Some cultural operations help greatly in preventing the attack in the first place. The most important is the proper spacing of the palms. Well-spaced palms never get infested with this pest.

The Scale Insects

(i) - The Green Scale Insect Palmaspis phoenicis (family Asterolecaniidae)

Because of its importance as a serious and damaging pest, mention was made for the green scale, with examples from the Sudan. This pest was introduced to Sudan date palm farms circa 1985 with planting material imported by two farmers from the Kingdom of Saudi Arabia.

 (ii) - The white Scale Insect Parlatoria blanchardi (family Diaspididae)

This is perhaps the oldest and most widespread pest on the date palms; it is found on them where-ever they grow – spreading on the fronds but sometimes it is found on the fruits making them in-edible. The degree of infestation of this pest is markedly variable it is sometimes thickest on 1-3 palms in a farm whereas other palms do not show any symptoms; even in the affected palm only few fronds are infested. In UAE this pest rarely reached a serious stage; when that happened it was usually concentrated on few of the old fronds of the palm. Cutting of these infested fronds is one of the effective means of control.

 There is a good biological control taking place in nature by a number of predators and few parasitoids. No chemical control was ever needed.

(iii) - “The Long Scale Insect” Fiorinia phoenicis; (family Diaspididae) -

This is a new introduction to UAE farms (introduced circa 1984); it rarely reached a serious stage because of some effective natural enemies, particularly a Nitidulid (Cybocephalus sp.) larva and the predatory mite Cydnoseius negevi. No chemical control was ever needed.

(iv) “The Red Scale Insect” Phoenicococcus marlatti; (family- Diaspididae) -

A widespread scale insect found on all date palms, where-ever the date palm grows; but because its colonies are usually concealed between the overlapping frond bases of the palm it is never noticed until deep pruning of the fronds is done. It will then be seen as white powdery material on the surface of the inner base of a frond, with the red scale embedded inside.

 No natural enemies can reach this insect in its hideout, but the deep pruning of the palm will expose it to the sun to be killed by its light.

Chemical control is not feasible.

 - The ‘giant” mealy bug  Pseudaspidoproctus hypheniacus - (family Margaro- didae)

This mealy bug is occasionally found on the outside of the bases of the fronds of the palm. In UAE it never reached a serious stage and no apparent damage was noticed of its presence. It has a close association of symbiosis with a black ant, the latter usually cleans the bug and its surrounding from its secretions and wards off parasitoids and predators from reaching it.

An effective method of control is to prevent the ants from climbing the palm to reach the bugs; this will leave the door open to its many natural enemies.

Chemical control may be resorted to in the very rare cases of high infestation.

2- Order Coleoptera

This Order contains the most destructive pests of the date palm that threaten its existence; mostly borers either in the trunk of the palm, eg. the Red Weevil and the longhorn beetle – or in the roots and fronds, eg. the rhinoceros beetles, or more recently the inflorescence beetle.

The Red Palm Weevil Rhynchophorus ferrugineus (family Curculionidae)

As is well known, this serious pest is a newcomer to the region. Its occurrence in UAE was discovered in 1985; from then it spread, in the same way in planting material imported from the Indian Subcontinent, to all other Gulf Region countries and then to Egypt and Jordan, to become a most important pest of the century. Its importance lies in being a fast killer to the palm, unlike the cerambycid trunk borer which is a very slow killer; un-noticed to a layperson.

The adult weevil measures about 40mm in length, with an about 10mm long snout; the male is a little smaller than the female; otherwise there are no morphological differences (dimorphism) between the two sexes, except for a narrow strip of red hairs on the dorsal surface of the male snout (a beard in reverse).

The larva is the trunk borer and the damaging stage of the weevil. When hatched, it starts burrowing on the site of the wound on which the eggs are laid; then it gradually enters into the palm’s trunk, digging upwards intricate tunnels, feeding on the sap for 2-3 months. Upon completion of its development the larva directs its tunneling towards the surface of the palm trunk till it reaches a base of a frond; there it collects the fibrous strands to wrap them around itself; building the pupation cocoon. An effective method of control is to remove all the fibrous strands from the palm.

Control there is a number of, methods; no chemicals are involved in any of them -

Early detection of infestation in a palm and then performing surgery to remove the eroded tissue of the palm at the site of entry of the larvae into the trunk together with all development stages of the weevil, which are mostly larvae. Aluminium phosphide tablets are placed in the resulting opening, usually at the base of the trunk and then the opening is tightly closed. This is the most important method of control.

Proper use of the pheromone trap; the traps at present are not properly used and they are doing some damage themselves.

Control of the rhinoceros beetles, especially Oryctes agamemnon, because they cause wounds, which pave the way for the entry of the weevil into the palm trunk.

Best of all is to prevent the infestation from taking place; here a good extension service is vital, not for this pest but for all pests and for all cultural operations.

The longhorn trunk borer Jebusaea hammerschmidtii (family Cerambycidae)

This is the oldest and now the most widespread pest of the date palm; gaining importance over the red weevil; in UAE it is becoming more important than the red weevil, but because it is a slow killer its occurrence is usually un-noticed until it is too late. It attacks a palm under stress due to neglect or high salinity in the irrigation water.

The infested palm with a riddled trunk due to the boring of the larvae (sometimes there will be more than 500 larvae inside a trunk) and the contamination of the trunk with saprophytic fungi and bacteria that follow, will remain standing for years until an external force, eg. wind breaks it at midpoint and makes it kneel and then fall.

The larvae bore inside the trunk for nearly a year, pupation takes place inside the trunk, and emergence of the adult commences in the month of May till early June. Exit holes of the adult (made by the larva before pupation) are a good sign of an attack.

Control Beside improving the growing condition of the palm to prevent the infestation, a light trap is the only means of control – it is very effective if properly managed, it should be used regularly from the month of April till the month of July only.

Research is needed in the use of entomopathogenic fungi for killing the larvae inside the trunk.

The rhinoceros beetles Oryctes spp (family Scarabaeidae)

It was noticed from the different country reports that this group of beetles is referred to as “trunk-borers” without differentiation into species; that is not right. Each species of this group should be regarded as an independent entity. Moreover, none of the different species of the group is a trunk-borer.

In UAE there are three species of rhinoceros beetles and none of them is a trunk-borer; the most important and most widespread is Oryctes agamemnon which is a root-borer in its larval stage and a frond borer in the adult stage. There is also O. elegans which may be referred to as fruit stalk-borer; it can also act as a root-borer. There is O. rhinoceros, a newcomer from the Far East, where it causes considerable damage to coconut and oil palms, there and in the Pacific Region.

These beetles breed in organic manure pits and dung heaps; the tremendous increase in their numbers is mainly due to the mishandling of these manures in the farms – sometimes they develop on the palm itself, particularly the neglected uncleaned ones

Control a) Better handling and proper application of organic manures

 b) The regular use of light traps from the month of April till the Month of November

 c) Use of aggregation pheromone traps for O. rhinoceros .

The inflorescence beetle Macrocoma sp (family Chrysomelidae)

This is a new pest to the date palm and also a new species to science. At present, it is only confined to few farms in the Emirate of Fujeira.

A small beetle of about 5mm in length. The adults, which come in big numbers to invade a spathe,  nib the small female flowers of the date palm to completely damage the crop. Its biology is centered in one palm; larvae and pupation in the soil of the irrigation basin of the palm attacked by the adults

Control

1.                 Digging the top 10cm of the soil in the irrigation basin of the date palm that was attacked in the previous flowering season and removal of larvae and pupae; this should be done in the month of November when larvae attain a large enough size to be spotted.

2.                 Failure to do (1) in time, use of chemical insecticides for the adults as soon as they are seen around the inflorescence in the next flowering season.

The dried fruits beetle Carpophilus dimidiatus (family Nitidulidae)

A small beetle of about 3mm in length; originally a pest of dried stored fruits, but because of neglect in farm hygiene and neglect in collecting and destroying rotting fruits (mainly damaged by fruit flies) on which these beetles breed, this pest has become a regular resident of farms, attacking and destroying ripe dates at the “rutab” stage.

Chemical control is not allowed when the dates are at the rutab stage. Here hygiene of the farm is very important; regular (better daily) removal of rotting fruits (citrus, mango, guava, dates, etc.) should be part of the farm labour force duties.

3- Order Lepidoptera

The Dates Moth (Humeira) Batrachedra amydraula (family Cosmoptery- gidae)

This is one of the most important pests of the date palm in UAE that may cause more than 50% loss of the crop if not properly managed. It has three generations a year; the first larvae appear in April to start the damage on the newly formed fruits.

The larva has a period of dormancy August till March of the next year between the bases of the terminal fronds. Pupation takes place in March and adults of the new cycle emerge in April, giving more larvae in 3 overlapping generations to damage different growth stages of dates.

Control - At present chemical control is the only possible option, but research is needed in (1) the use of pheromone traps is the right answer for the control of the dates moth; it saves much of the annual costs of chemical control and it is more accurate and more reliable. Preparation of the pheromone itself is not a big problem and any sticky trap will do the job properly. (2) The use of parasitoids – there is mention in the Iraqi literature of naturally occurring parasitoids on this pest.

The inflorescence Moth Aphomia sabella (family Pyralidae)

Adult Moth about 20mm in length and the larva is about 22mm in length, fast moving and wriggly. Unlike the Dates Moth this moth is not an important pest of the date palm in UAE, at present; its infestations are sporadic. Its occurrence starts after fruit setting; it is becoming similar to the Dates Moth in damage caused.

Because of the nature of its infestations, at present, chemical control of this pest is inevitable.

4- Order Hymenoptera

The Oriental Wasp Vespa orientalis (family Vespidae)

This wasp, which builds its mud nests in the rock cracks of the mountains, is an important pest of the date palm in the farms of the mountainous east coast of UAE. Attacking, sometimes in big numbers, the ripe dates, nibbling bits to eat and to take to feed the larvae in the nests.

Chemical control is not feasible at the “rutab” stage of the dates, but some farmers now use special nets to cover the date bunches from the wasp attacks.

5- The Mites- Order Acari

The “Dates Mite” Oligonychus afrasiaticus (family Tetranychidae)

An important pest of the date palm, particularly in the last four years. It attacks the dates from their early stages of development, spinning its webs around the dates bunches and multiplies in big numbers. Dust collects in the webs plus the exuviae of the different development stages of the mite thus making the dates bunches look dusty. It feeds on the juices it sucks from the dates rendering them unfit for human consumption.

Chemical control by the use of acaricides mixed with adjuvants, is inevitable, at present. Research is needed into the possibility of other and safer methods of control.

The “Scarlet Mite” Raoiella indica (family Tetranychidae)

A common mite living on the pinnae of the date palm fronds, usually forming circular patches, with scarlet coloured mites, their eggs and nymphs to the inside surrounded by white exuviae. There is a natural biological control on this mite, but in the rare occasions of high densities chemical acaricides may be used.

Fungal Diseases

Fungal diseases on date palms never reached epidemic statges; occurring only in sporadic cases that need individual attention. In UAE, the following are the important diseases that may lead to the death of the palm or to the loss of its produce.

1- The Terminal Bud Rot Ceratocystis paradoxa (Theilaviopsis paradoxa) – Moniliales

This fungus causes the rot of the terminal fronds of the date palm; if not properly controlled it usually spread and kills the palm. At some stage of  its prognosis the fronds of the  infected palm take different directions giving the phenomenon of “al-majnoona”, followed by the death of the palm.

There are some effective fungicides that will stop the disease from spreading in the palm; the latter will then develop side shoots at the top to replace the damaged terminal shoot.

Research is needed for the proper study of this important disease.

2- The inflorescence Rot  Mauginiella scaettae  - Moniliales

An uncommon fungal disease that causes the inflorescence rot. It is slightly prevalent during high humidities, particularly in rainy seasons. Its spores usually persist in an infested palm till the following flowering season to infect the new inflorescence.

Control at present depends on chemical fungicides.

3- Another “Terminal Bud Rot” Phytophthora sp. (Phycomycetes)

In the late eighties, there was, in UAE, a mini-epidemic of this fungal disease on small date palms wrongly planted deep in deep irrigation basins, allowing the entry of the irrigation water to the center of the terminal fronds bases. The irrigation water usually carries the motile zoospores of Phytophthora spp. (contaminants in the soil) which adhere to the tender fronds to germinate and spread. Symptoms appear after about three years terminal fronds rot in a way very much similar to that caused by Ceratocystis paradoxa – ie. another  “majnoona”.

4- Leaf-spotting fungi

There are four species of leaf-spotting fungi on a very high percentage of date palms. They are just known by names, without any further studies. Research is essential to find out their effect on the palm and its produce.

5- Pathogenic fungi appearing in very rare individual cases

Graphiola phoenicis  - a smut producing tufts of mycelia, which drop to leave behind leaf spots on the infected pinnae; very few cases were seen particularly in old farms.

Mycosphaerella tissana  (Ascomycetes) – a frond spotting fungus, which in very rare cases caused slow decline to the date palm.

Ganoderma sp. (Basidiomycetes) – a shelf fungus seen to infect one small palm only; leading to its death.

Discussion on the control of the Pests of the Date Palm

Successful control of the pests of plantations depends to a great extent on the standard of the agricultural extension service. It is the duty of the extension officers, who should be well trained themselves, to train the farmers and steer them away from the continuous use of chemical pesticides towards safer and more effective alternative agents of control. There should also be in the different countries a cadre of plant protection officers whose main duty is to carry out surveys and studies of the pests of the date palm (and other crops), to send unidentified arthropod pests to identification centers and to have access to identification laboratories for the isolation of fungi. They should be able to take part in the training of  farmers in the different components of pest control, including  the knowledge of the life cycles of the important pests like the “dubas bug”.

As seen in this brief account of “The Pests of the Date Palm”, very little mention was made for the use of chemical pesticides, not only for the toxicity of these chemicals, but because there are better and more effective alternatives. Chemical insecticides are never used for the control of scale insects, because they usually kill the natural enemies while the scale insect is protected by its scale.

Improvements in some cultural practices, like the right spacing in planting the trees, hygiene of the farm, proper handling of organic manures in the farm, proper and correct use of pheromone and light traps, etc. are all important measures in the reduction and management of pests. Because most farmers are not convinced of the importance and effectiveness of  pheromone and light traps in the control of the important pests of the date palm, the only way out is to use communal traps to be run by  official agricultural establishment or by tendered private establishments. The traps do not need to be placed inside farms. That will be much cheaper to run and more effective than what is being done at present.

Training of farmers, training and refresher courses for the extension and crop protection officers are vital for a better health and  plentiful production of plantations.

Al wijam

This disease of unknown aetiology needs to be properly investigated; if caused by a phytoplasma, as is suggested it might have some serious and difficult to handle repercussion in the future.

Opportunities for Development and Use of Enteropathogenic Fungi

Michael Brownbridge, Margaret Skinner & Bruce L. Parker.

University of Vermont Entomology Research Laboratory,661 Spear Street

Burlington ,Vermont 05405

USA.

Abstract

Modern agricultural systems and trade in agricultural commodities has created conditions favoring the rapid establishment and spread of various noxious insects.  This has promoted a heavy reliance on synthetic insecticides to control, limit, and contain the spread of these insects.  Concerns over environmental pollution, human-health risks, and insect resistance have stimulated the search for alternative control strategies and their use within integrated pest management (IPM) programs.  This approach emphasizes population monitoring to guide pest management decisions, use of cultural and biological controls, and limited insecticide usage.  Biological control is considered a major component of IPM, but is frequently under-utilized.  Microbial biocontrol agents, and fungi in particular, can play a significant role in the regulation of many insect pests; mycopathogens  such as Beauveria bassiana and Metarhizium anisopliae infect many insects over a wide range of environmental conditions.  Some notable successes have been achieved using fungi to control major pests such as desert locusts, tsetse flies, and Colorado potato beetle, under what may be considered less-than-favorable conditions.  Novel delivery systems have also met with success in the control of pests that have been hard to contact with conventional sprays.  To achieve similar progress against pests of date palm, a progressive series of steps need to be taken.  First, to obtain candidate strains for testing, an extensive survey of the pest population throughout its range is likely to yield indigenous pathogens from infected adult and larval stages, and from soils in date palm groves; isolates recovered from or known to be active against related pests found in similar climatic/agroenvironmental zones can also be acquired.  Whatever the source of the fungi, the same considerations are then required for their further development as effective and reliable pest management tools.  Many pests live in cryptic environments, so pathogenicity trials should initially be directed against developmental stages that can be realistically targeted with fungi.  Assays should be run at temperatures replicating those experienced at the time of insect activity to identify strains capable of infecting and killing the pest under these conditions.  But virulence should not be the sole criterion for selection; active strains need to be characterized according to their spore production capacity (for mass-production purposes), and environmental competence (i.e., their ability to persist, germinate, grow, and infect insects in the environment in which they will be used).  These are essential to the selection of the most suitable strains, and must be followed by the development of efficient mass production and delivery systems, and effective use strategies.  The ability to produce and formulate large quantities of stable, virulent inoculum of consistent quality in a cost-effective manner is vital, but the complexity of the process is often underestimated; critical issues relevant to mass-production and formulation will be covered in this presentation.  Compatibility of the fungi with other IPM components and non-target organisms must also be ensured.  Field efficacy has to be demonstrated through scale-up trials, and the technology refined into a form that can be readily implemented and (with appropriate support and guidance) transferred to the farming community.  Fungi have great potential for development as effective microbial control products, but their successful development depends upon these factors being addressed.

Introduction

Extensive monoculture plantings create conditions that favor the rapid growth of insect pest populations, and regional trade in agricultural commodities has resulted in the transportation of pests far beyond their natural borders.  Heavy reliance is placed on the use of synthetic pesticides to regulate such species, but, this is neither sustainable nor desirable from an economic, human-health, or environmental perspective (Pimental et al. 1999, Harris 2000, Wesseling et al. 2001, Fenske 2002).  The goal of maintaining high levels of agricultural productivity and profitability while reducing pesticide use, though, presents a significant challenge.  Research and outreach efforts must focus on increasing the implementation of integrated pest management (IPM) practices on all crops, emphasizing the use of cultural and biological controls as the first line of defense against pests. 

By definition, biological control entails the utilization of natural enemies – predators, parasitoids and pathogens – for the management of pests.  Fungi are the predominant pathogens found in insect populations, and are unique in their ability to infect their hosts through the external cuticle; thus they are capable of infecting both soft- and hard-bodied insects (Hajek 1997).  But how can we capitalize on this unique potential?  Environmental conditions can be manipulated to enhance their natural incidence and activity (Pell et al. 2001); pathogens may be introduced into a pest population with the goal of their becoming established and exerting a suppressive effect on population over the long-term, e.g., Entomophaga maimaiga, Neozyygites fresenii (Reardon & Hajek 1998, Steinkraus et al. 1999); or, microbes may be used as biological insecticides, requiring their cost-effective mass production and efficient delivery to the target pest.  Most attempts to exploit insect-killing fungi commercially have focused on the development of selected strains of Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii and Paecilomyces fumosoroseus as biopesticides. 

Fungi have many desirable traits – they leave no toxic residues on crops, and are generally harmless to beneficial insects and other non-targets (Waage 1997, Hajek et al. 2000, Goettel et al. 2001).  Furthermore, they pose minimal risk to humans and the environment (Dent 1999).  In fact, their host-specific nature enhances their potential role in IPM, as it preserves natural enemies which then make a greater contribution to the overall regulation of pests; maintaining biodiversity and capitalizing on existing preventative pest control measures are increasingly recognized as being critical to the long-term viability of agricultural production systems (Lewis et al. 1997, Waage 1997).

Insect Infection

All fungi have the same basic mode of action (see Hajek & St. Leger 1994, Hajek 1997, Goettel et al. 2000).  Insect infection begins when a viable spore, or conidium, becomes attached to a susceptible host (Fig. 1).  The spore germinates, puts out a germ tube, and generally produces a specialized infection structure or appresorium; penetration hyphae are produced by the appresorium, and using a combination of mechanical forces and enzymatic action, grow through the cuticle.  In the haemocoel, the fungus proliferates and insect death results from a combination of nutrient depletion, invasion of organs, and toxicosis.  The fungus will grow back out of the insect, and sporulate on the cadaver under conditions of high relative humidity.

In most cases, spore dispersal is passive, and they are carried on wind currents or via rain to new sites on leaves or in the soil; transmission can also occur as susceptible insects contact infected individuals, or conidia can be distributed on the bodies of other arthropods (Goettel et al. 2000, Rath 2002, Wraight 2002).  Entomophthoralean fungi can contact new hosts by actively ejecting conidia, and by producing specialized structures that elevate conidia above, say, a leaf surface, thereby increasing the chances of contact with a moving host (Hajek 1997, Wraight 2002).  Entomophthoralean fungi are highly sensitive to desiccation, but are able to rapidly sporulate and infect a susceptible insect to exploit short periods of high humidity.  In contrast, Hyphomycetes such as B. bassiana and M. anisopliae produce large quantities of conidia that are tolerant of dry conditions.  Although they do not infect as rapidly as entomophthoralean fungi, they can survive repeated intervals of low humidity, renewing development (infection) when favorable conditions return (Fargues & Luz 2000).  In addition, these fungi appear to be able to infect insects even under conditions of low ambient humidity; attachment of the small conidia at infection sites within intersegmental folds where humidity levels are high may account for this (Charnley at al. 1997, Wraight 2002).

Successful Utilization of Fungi in Insect Pest Management

Entomophthorales

Forest and Field Crops.  Entomophthoralean fungi often cause spectacular epizootics when ambient conditions are favorable (Hajek 1997, Steinkraus et al. 1999, Pell et al. 2001).  Such has been the impact of E. maimaiga in gypsy moth populations in the Northeast, that pest numbers have been suppressed to the point that the insect’s population dynamics may have been irrevocably altered.  The fungus has been introduced into new areas by transportation of soils and bark  contaminated with resting spores, expanding the range of the disease, and increasing the rate at which it has become established and spread within the pest population (Hajek et al 1998a, b, Reardon & Hajek 1998).  N. fresenii has provided natural control of cotton aphids for 11 consecutive years in commercial plantations in Arkansas (USA).  Neozygites appear to function best in hot weather, when aphid populations are increasing rapidly, and epizootics occur even under hot, dry conditions; epizootic development is apparently promoted by the high night-time humidity that occurs within the cotton canopy (Steinkraus & Slaymaker 1994, Steinkraus et al. 1995, 1999).  This fungus saves cotton growers thousands of dollars by eliminating the need for pesticide sprays, concurrently reducing environmental and human health risks.   However, opportunities for commercialization of entomophthoralean fungi in the existing industrial paradigm are limited as they cannot be mass-produced in vitro.  Instead, modification of agricultural practices to provide ecological conditions that promote their incidence, or augmenting populations through introductions, can increase their impact (Hajek et al. 1998a, Hajek & Webb 1999, Pell et al. 2001).

Hyphomycetes

Development of commercial microbial control products has instead focused on species that are relatively easy to mass produce on simple substrates, e.g., B. bassiana, M. anisopliae, V. lecanii, and P. fumosoroseus.  These pathogens have relatively broad host ranges and have been successfully used against insects in a wide variety of environments; several fungal-based products are now available (Table 1).  The examples given below will provide information on fungal use in different crop/pest ecosystems.

Protected Agriculture.  Greenhouses are often viewed as providing ideal conditions for use of entomognous fungi.  Crops are high value, and are protected from environmental extremes; potential also exists to manipulate the environment to one that favors fungal infection (e.g., by elevating humidity levels).  However, care must be taken with the latter approach as plant diseases can also flourish under such conditions.  Interest in the use of fungi has been further promoted by the rapid development of insecticide resistance by major greenhouse pests such as thrips, aphids and whiteflies (Prabhaker et al. 1985, Broadbent & Pree 1997).   Commercial and experimental products based on B. bassiana, M. anisopliae and V. lecanii have significantly reduced thrips populations in greenhouse vegetable and floral crops (Butt & Brownbridge 1997, Bradley et al. 1998, Ludwig & Oetting 2002, Shipp et al. 2002).  Similarly, laboratory and field trials have confirmed the suitability of B. bassiana, P. fumosoroseus and V. lecanii as viable control agents for whiteflies (Negasi et al. 1998, Gindin et al. 2000, Wraight et al. 2000, Faria & Wraight 2001, Jazar & Hammad 2004).  Aphids too, have been satisfactorily controlled on a variety of greenhouse crops with these fungi (Helyer 1993, Fournier & Brodeur 2000).  Several commercial products are currently available for use in protected crops, formulated as wettable powders or in emulsifiable oils for high or low volume spray application (Table 1).

Field Crops.  Use of fungi in field crops presents a greater challenge.  Sunlight, rain and temperature strongly influence fungal efficacy and persistence (Goettel et al. 2000, Inglis et al. 2000, 2001, Wraight 2002, McCoy et al. 2003).  Nevertheless, good control of a variety of pests has been achieved on a commercial scale, including Colorado potato beetle, cotton boll weevil, diamondback moth, European corn borer, and whitefly (Bemisia spp.) (Wright 1993, Shelton et al. 1998, Fernandez et al. 2001, Vandenberg et al. 1998, Wraight & Carruthers 1999, Long et al. 2000, Wraight et al. 2000, Inglis et al. 2001).  Control has been achieved even in hot, dry (desert) regions in irrigated crops such as potatoes and cotton (Wright 1993, Lacey & Horton 2003).  Oil-based and wettable powder formulations are commercially available for high volume spray application (Table 1).

Locusts and Grasshoppers.  These are pests of global significance, capable of decimating cultivated crops, grassland and rangeland.  Their feeding activity on staple crops frequently leads to food shortages in Africa, and can deplete grasses from pastureland in many countries, severely impacting livestock production.  The need to develop more environmentally benign methods for their control stimulated the search for natural enemies, and led to the development of highly effective fungal-based products and strategies (Inglis et al. 2000).  B. bassiana has been extensively studied for control of locusts and grasshoppers, and promising results have been obtained in West Africa and Canada (Johnson et al. 1992, Delgado et al. 1997, Jaronski & Goettel 1997).  Effects of sunlight (uv degradation of conidia), and the ability of locusts and grasshoppers to thermoregulate (and ‘cure’ themselves of fungal infection), however, were identified as factors limiting the activity and potential widespread use of this pathogen in hot and sunny conditions (Inglis et al. 1996, 1997b).  M. anisopliae var. acridum has a higher temperature tolerance, and has been commercially developed for use against acridids in Africa, Australia and Brazil (Lomer et al. 1997, Magãlhaes et al. 1997, Milner 1997, Langewald et al. 1999, Blanford & Thomas 2001).  Probably one of the best-known fungal products today, M. a. var. acridum conidia are produced and sold for locust control in Africa as Green Muscle®.  Conidia are formulated in paraffinic oils; this enhances field efficacy against locusts at low humidities and permits application at ultra-low volumes, an important consideration in regions where water is in short supply and large areas need to be treated (Bateman et al. 1993, Bateman 1997).  Efficacy is enhanced by the secondary acquisition of conidia from sprayed vegetation, and the horizontal transfer of infection within the locust population (Bateman et al. 1998, Thomas et al. 1998, Langewald et al. 1999).  Application of a combination of Beauveria and Metarhizium has been considered as a means of overcoming the temperature constraints (high/low, respectively) of these pathogens against grasshoppers, especially in areas where temperatures can oscillate between cool or hot for extended periods (Inglis et al. 1997a, 1999).

Pests in Soil and Cryptic/Protected Environments.  Many pests spend at least part of their life cycle in soil.  It is an attractive environment in which to target microbial control efforts as it is protected from environmental extremes of temperature and moisture, and is a natural habitat for fungi such as M. anisopliae and B. bassiana.  Yet soil is a highly complex environment, and fungal activity against soil-inhabiting insects is affected by many biotic and abiotic factors (Jackson 1999, Rath 2002, Ekesi et al. 2003).  Fungi have been effectively used against several subterranean pests, though, and commercial products based on B. brogniartii and M. anisopliae are available for their control.  B. brogniartii, for example, is used to control the European cockchafer in grassland regions of Austria, Italy and Switzerland.  Adults of this insect feed on forest and fruit tree leaves, and the larvae are polyphagous feeders, attacking the roots of trees, cereals and root crops.  Formulated on colonized barley kernels, the fungus is applied to the soil (pastures, grasslands, forests, orchards, etc.) via a modified seed drill, and will suppress cockchafer populations for several years (Inglis et al. 2001).

The red-headed pasture cockchafer, Adoryphorus coulani, is an important root-feeding pest of pasture and field crops in Australia and New Zealand.  The insect has been controlled with M. anisopliae.  Grains impregnated with the fungus are applied to the soil using a seed drill at the time of pasture renovation (Rath et al. 1995, Rath 2002).  The pathogen shows excellent persistence in the soil, and has effectively suppressed chafer populations in treated soils for several years.  A commercial product – BioGreen® – based on a strain of M. anisopliae specifically selected for its activity at cooler temperatures, is now marketed in Australia for use against this pest.

Some insects cause no crop damage during the soil phase of their life cycle, but the soil provides an inviting target for application of fungal controls; these include pests such as western flower thrips and fruit flies.  Experimental trials have clearly demonstrated the potential for using fungal drenches to suppress soil-dwelling life stages of these pests (Brownbridge et al. 1994, Helyer et al. 1995, Ekesi et al. 2003).   Fungi may also be formulated in granules for control of soil insects, which can incorporate nutrients to support growth and sporulation of the fungus in the pest’s habitat (Wraight et al. 2001).

Many pests occupy cryptic habitats, where they are protected from direct contact with fungal sprays, or their behavior/biology precludes the widespread application of fungi for their control.  In such situations, novel means of disseminating fungal conidia need to be found.  Pollen beetles, for example, are widespread pests of oilseed rape and other important cruciferous crops in Europe.  The adults and larvae feed on pollen in buds and open flowers, causing buds and stamens to drop which affects seed set and thereby affects yield.  In this protected environment, they are very difficult to reach using conventional sprays.  Honey-bees are frequent visitors to flowers in oilseed crops as they forage for nectar and pollen.  They are known to carry fungal and bacterial spores on their hairy bodies, prompting investigations into their potential utilization for dissemination of biocontrol agents.  They have been used to carry antagonistic fungi, e.g., Trichoderma harzianum, to flowers for control of  diseases such as Botrytis (Kovach et al. 2000), and to disseminate bacterial and viral pathogens (Gross et al. 1994).  Their potential as carriers of entomopathogenic fungi has also been assessed, and bees were successfully used to deliver dry M. anisopliae conidia to flowers of oilseed rape.  Bees picked up conidia via an inoculum dispenser as they left the hive, and transferred it to the flowers, where it was acquired by the pollen beetles (Butt et al. 1998).  High levels of beetle mortality and mycosis were obtained, particularly during times of peak flowering when feeding activity of both bees and beetles was maximal.  No evidence of adverse effects on the honey bee colonies was observed; pathogen safety for honey bees has been similarly demonstrated by other investigators (see Goettel et al. 2001).

The coconut palm rhinoceros beetle, Oryctes rhinoceros, is a major pest of many oil- and food-palms.  Adults bore into the axils of palm fronds, destroying leaf tissue; immatures occupy the soil and litter underneath palm trees.  The beetles are highly susceptible to M. anisopliae, which is considered to be a significant natural mortality factor (Inglis et al. 2001).  Attempts to utilize this fungus in control programs have so far met with mixed success, although recent approaches suggest that M. anisopliae can play a greater role when used within an IPM program together with other pathogens such as baculoviruses.  With refinements in formulation, application and use strategies, it is likely that the fungus will become an important component in future bio-based IPM strategies for this insect.

Capable of transmitting protozoan parasites that affect humans and livestock, the tsetse fly is a major impediment to rural development in many African countries.  Previous control attempts have focused on habitat manipulation and widespread application of insecticides (Maniania 1998).  The long-term efficacy of these approaches is poor, however, and the high cost and environmental contamination resulting from widespread insecticide applications provided impetus to develop alternative management approaches.  Tsetse are known to be susceptible to fungi, and contaminated flies can transmit an infection to healthy ones during mating (Maniania 1998).  Area-wide spray applications of fungi are impractical; instead, fungi may be introduced into the target pest population via devices that attract pests to a focal point where they are then contaminated, so-called auto-dissemination or auto-inoculation devices (Vega et al. 2000).  Various traps have been devised which are highly attractive to tsetse, e.g., biconical traps baited with cow urine (Dransfield et al. 1990); by combining this technology with an inexpensive trap-and-release inoculation device, an efficient and low-cost method of delivering lethal doses of M. anisopliae conidia to adult tsetse has been developed in Kenya (Maniania 2002).  Trials were carried out in hot, semi-arid areas, but the conidia used in the device retained their activity for >30 days, and activity against tsetse was not affected.  The fact that conidia can be transmitted from exposed to non-exposed individuals also means that the overall impact on the pest population is greater than could be achieved by simply using the trap alone.  A similar approach has been taken to the development of an auto-dissemination device for control of adult fruit flies (Dimbi et al. 2003).

Such novel and relatively inexpensive approaches to the dissemination of fungi are often needed for pests in cryptic habitats.  Knowledge of the pest’s biology is an essential component in this developmental process, but the products arising from such research can be highly effective, and sustainable.

Potential use of Fungi in the Management of Date Palm Pests

There is a clear and demonstrated potential for using fungi successfully in insect pest management.  Fungal efficacy has been shown in a diverse range of environments, including ones that may be thought of as being hostile to fungal infection processes due to high temperature extremes and conditions of low humidity.  Not all date pests will be suitable targets, but through a progressive series of steps fungal strains exhibiting desirable characteristics can be identified and efficient methods of producing, formulating and delivering the pathogen to the target pest developed.  Briefly, the following stages in the development of viable fungal products for insect pests in date palm may be envisioned

1.  Obtain candidate strains for testing.  These may be derived from the target pest directly, or from its environment. Collection of adult and larval stages of the pest from sites throughout its range, and baiting of soils collected from infestation sites (with wax moth larvae), are likely to yield a variety of indigenous isolates (see Goettel & Inglis 1997 for isolation methods).  Alternatively, isolates may be acquired from culture collections; selection of strains recovered from the target pest or close relatives found in similar climatic or agroenvironmental zones, or those already known to be active against these insects, are also likely to make the best candidates.  It is essential that the identity of all isolates obtained is confirmed prior to testing to ensure that they are insect pathogens, and not contaminants which are potential human or plant pathogens, e.g., Aspergillus, Fusarium.  Pure cultures of all isolates need to be maintained, and stock cultures preserved to prevent attenuation.

2. Bioassay against the target pest.  Pathogenicity tests should be carried out against developmental stages that can be realistically targeted with a fungal treatment.  Different developmental stages are known to vary in their sensitivity to fungi.  Ideally, assays should be carried out using lab-reared insects for consistency, although this is not always feasible.  Assay conditions should be standardized and mimic those experienced in the field at the proposed time of application, so that isolates best suited to work at temperatures and humidities prevailing at that time can be identified.  A discriminating single- and/or multi-dose series of assays should be undertaken to select the most virulent isolates (using time from exposure to death, and dose – the number of conidia required to kill a proportion of the test population – as discriminating factors).

3. Selection for other desirable characteristics.  Virulence, environmental competence and biological fitness all need to be considered in the selection of strain(s) for further evaluation (Jackson 1999).  In vitro definition of germination, growth and sporulation characteristics of active strains will provide relevant information on their ecological fitness, their suitability for mass-production, and their genetic stability (Varela & Morales 1996, Brownbridge et al. 2001).  Steps 1-3 are, essentially, laboratory-based, and will allow strains that are well suited to field conditions and commercialization to be identified.

4. Mass production.  The ability to mass produce and preserve large quantities of stable, virulent inoculum of consistent quality, and in a cost-effective manner, is a critical step in the development process.  Yet the complexity of the process, and the influence of minor changes in media constituents and production conditions on the quality and performance of the inoculum produced is frequently underestimated, especially when making the transition from small- to large-scale production.  Temperature, pH, and substrate components all influence conidial yield, viability, and virulence.  A well-defined production system, with in-built quality-controls, is essential to the commercialization of a fungal biocontrol agent (Jenkins & Grzywacz 2000, Wraight et al. 2001).

5. Formulation and delivery.  Formulation directly affects the stability of fungi in storage, and efficacy and persistence in the field (Goettel et al. 2000, Wraight et al. 2001).  Fungi can be formulated in a variety of ways, using dried conidia or mycelia, and formulations must be tailored to meet the needs of the delivery system.  Application strategies have a major impact on efficacy, and conventional pesticide application techniques, i.e., sprays, may not be the most effective method of delivering inoculum to the target pest.  Knowledge of the pest’s biology is essential to the identification of a suitable target stage, and cooperation with entomologists, formulation and application specialists will enhance the development process.  Use strategies need to be rigorously tested and refined to devise a system that not only provides consistent levels of control, but can be readily implemented at the farm level without the need for specialized equipment.  The influence of the host plant on the pest and the fungus efficacy must also be considered, as fungal activity can be affected (Maniania et al. 1998, Poprawski et al. 2000).

6. Compatibility with other IPM tactics and safety.  Simple compatibility with agrochemicals is required whenever fungi will be used together with pesticides.  Beneficial interactions can also occur.  For example, use of fungi together with sub-lethal doses of imidacloprid has led to enhanced levels of infection and mortality in several pest insects (Quintela & McCoy 1998, Kaakeh et al. 1997).  The field efficacy of B. bassiana was increased against grasshoppers when used with diflubenzuron (Dimilin®) (Delgado et al. 1999).

We tend to automatically assume that biological control agents are compatible. Although safe for a wide variety of beneficials, interactions between fungi and natural enemies should be evaluated prior to their concurrent use (Parker et al. 1997, Roy & Pell 2000, Jacobsen et al. 2001, Goettel et al. 2001, Ivie et al. 2002); the sensitivity of some predatory beetles (Poprawski et al. 1998) highlights the need to proactively assess such interactions.  Some natural enemies, i.e., predators and parasites cause agitation in pest populations, leading to increased movement over plant surfaces and enhanced pick-up of fungal inoculum (Roy & Pell 2000); synergistic interactions may thus also occur if fungi are used together with other natural enemies in IPM.

Pathogen safety for both humans and non-target invertebrates must be demonstrated prior to their widespread use (Goettel et al. 2001, Jaronski et al. 2003).  Allergic reactions can occur in people exposed to conidia, and precautions should be taken during the mass production process.  Testing is also required to ensure there are no adverse effects on the ecosystem in which the pathogens will be used.

7. Technology transfer.  This stage is vital to promote the adoption and effective use of fungal-based control products.  Education and outreach programs are needed to ensure that products are used correctly to achieve maximum efficacy, and to refine farmers’ expectations.  Biological products perform very differently from chemicals, and it is important that the end-users understand these differences and modify their expectations and farming practices accordingly.  Continued training and support of extension personnel and farmers will be important.

Conclusion

Fungi have a demonstrated capacity to regulate pest populations.  Our ability to capitalize on this potential, and develop products and strategies that exploit their unique characteristics presents a significant challenge.  We must recognize the strengths and weaknesses of fungal controls, and not simply try to replace chemical insecticides with biologically-derived materials.  With appropriate collective effort and investment of resources, though, fungal biocontrols can become integral components of future date palm production systems.

References

Bateman, R.P. 1997. Methods of application of microbial pesticide formulations for the control of grasshoppers and locusts. Memoirs Ent. Soc. Can. 171 69-81.

Bateman, R.P., M. Carey, D. Moore & C. Prior. 1993. The enhanced infectivity of Metarhizium flavoviride in oil formulations to desert locusts at low humidities. Ann. Appl. Biol. 122 145-152.

Bateman, R.P., O.K. Douro-Kpindou, C. Kooyman, C. Lomer & Z. Ouambama. 1998. Some observations on the dose transfer of mycoinsecticide sprays to desert locusts. Crop Protec. 17 151-158.

Blanford, S. & M.B. Thomas. 2001. Adult survival, maturation, and reproduction of the desert locust Schistocerca gregaria infected with the fungus Metarhizium anisopliae var. acridum. J. Invertebr. Pathol. 78 1-8.

Bradley, C.A., J.C. Lord, S.T. Jaronski, S.A. Gill, A.J. Dreves & B.C. Murphy. 1998. Mycoinsecticides in thrips management. Proc. BCPC-Pests and Diseases 35 177-181.

Broadbent, A.B. & D.J. Pree. 1997. Resistance to insecticides in populations of Frankliniella occidentalis (Pergande) (Thysanoptera Thripidae) from greenhouses in the Niagara region of Ontario. Can. Entomologist 129 907-913.

Brownbridge, M., S. Costa & S.T. Jaronski. 2001. Effects of in vitro passage of Beauveria bassiana on virulence to Bemisia argentifolii. J. Invertebr. Pathol. 77 280-283.

Brownbridge, M., D.L. McLean, B.L. Parker & M. Skinner 1994. Use of fungal pathogens for insect control in greenhouses, pp. 7-20 In Robb, K. [ed.] Proc. Tenth Conference on Insect and Disease Management, 19-21 Feb. 1994, Dallas, Texas.

Butt, T. & Brownbridge, M. 1997. Fungal pathogens of thrips, pp. 399-476 In Lewis, T. [ed.] Thrips as Crop Pests. CAB International, Wallingford, UK.

Butt, T.M., N.L. Carreck, L. Ibrahim & I.H. Williams. 1998. Honey-bee-mediated infection of plooen beetle (Meligethes aeneus Fab.) by the insect-pathogenic fungus, Metarhizium anisopliae. Biocontrol Sci. Technol. 8 533-538.

Charnley, A.K., B. Cobb & J.M. Clarkson. 1997. Towards the improvement of fungal insecticides, pp. 115-126. In H.F. Evans [ed.], Microbial insecticides novelty or necessity? Proc. 1997 BCPC Symposium (No. 68). BCPC, UK.

Delgado, F.X., M.L. Lobo-Lima, C. Bradley, J.H. Britton, J.E. Henry & W. Swearingen. 1997. Laboratory and field evaluations of Beauveria bassiana (Balsamo) Vuillemin against grasshoppers and locusts in Africa. Memoirs Ent. Soc. Canada 171 239-251.

Delgado, F.X., J.H. Britton, J.A. Onsager & W. Swearingen. 1999. Field assessment of Beauveria bassiana (Balsamo) Vuillemin and potential synergism with diflubenzuron for control of Savanna grasshopper complex (Orthoptera) in Mali. J. Invertebr. Pathol. 73 34-39.

Dent, D. 1999. Biopesticides as alternatives to chemical pesticides. CABI Bioscience Biopesticides Programme Briefing Paper 2/99, 3 pp.

Dimbi, S., N.K. Maniania, S.A. Lux, S. Ekesi & J.K. Mueke. 2003. Pathogenicity of Metarhizium anisopliae (Metsch.) Sorokin and Beauveria bassiana (Balsamo) Vuillemin, to three adult fruit fly species Ceratitis capitata (Weidemann), C. rosai var. fasciventris Karsch and C. cosyra (Walker) (Diptera Tephritidae). Mycopathalogia 156 375-382.

Dransfield, R.D., R. Brightwell, C. Kyorku & B. Williams. 1990.Control of tsetse fly (Diptera Glossinidae) populations using traps at Nguruman, south-west Kenya. Bull. Ent. Res. 80 265-276.

Ekesei, S., N.K. Maniania & S.A. Lux. 2003. Effect of soil temperature and moisture on survival and infectivity of Metarhizium anisopliae to four tephritid fruit fly puparia. J. Invertebr. Pathol. 83 157-167.

Fargues, J. & C. Luz. 2000. Effects of fluctuating moisture and temperature regimes on the infection potential of Beauveria bassiana for Rhodnius prolixus. J. Invertebr. Pathol. 75 202-211.

Faria, M.F. & S.P. Wraight. 2001. Biological control of Bemisia tabaci with fungi. Crop Protec. 20 767-778.

Fenske, R.A. 2002. Incorporating health and ecologic costs into agricultural production. Environ. Health Perspect. 110 228-229.

Fernandez, S., E. Groden, J.D. Vandenberg & M.J. Furlong. 2001. The effect of mode of exposure to Beauveria bassiana on conidia acquisition and host mortality of Colorado potato beetle, Leptinotara decemlineata. J. Invertebr. Pathol. 77 217-226.

Fournier, V. & J. Brodeur. 2000.  Dose-response susceptibility of pest aphids (Homoptera Aphididae) and their control on hydroponically grown lettuse wth the entomopathogenic fungus Verticillium lecanii, azadirachtin, and insecticidal soap. Environ. Entomol. 29 568-578.

Gindin, G., N.U. Geschtovt, B. Raccah & I. Barash. 2000. Pathogenicity of Verticillium lecanii to different developmental stages of the silverleaf whitefly, Bemisia argentifolii. Phytoparasitica 28 1-11.

Goettel, M.S. & G.D. Inglis. 1997. Fungi Hyphomycetes, pp. 213-250 In Lacey, L.A. [ed.] Manual of techniques in insect pathology.  Academic Press, Inc., San Diego, USA.

Goettel, M.S., A.E. Hajek, J.P. Siegel & H.C. Evans. 2001. Safety of fungal biocontrol agents, pp. 347-375 In Butt, T.M., C. Jackson & N. Magan [eds.] Fungi as biocontrol agents progress, problems and potential. CAB International, UK.

Goettel, M.S., G.D. Inglis & S.P. Wraight. 2000. Fungi, pp. 255-282 In Lacey, L.A. & H.K. Kaya [eds.] Field manual of techniques in invertebrate pathology. Kluwer Academic Publishers, Netherlands.

Gross, H.R., J.J. Hamm & J.E. Carpenter. 1994. Design and application of a hive mounted device that uses honey bees (Hymenoptera Apidae) to disseminate Heliothis nuclear polyhedrosis virus. Environ. Entomol. 23 493-501.

Hajek, A.E. 1997. Ecology of terrestrial fungal entomopathogens. Adv. Microbial. Ecol. 15 193-249.

Hajek, A.E. & R.J. St. Leger. 1994. Interactions between fungal pathogens and insect hosts. Annu. Rev. Entomol. 39 293-322.

Hajek, A.E. & R.E. Webb. 1999. Inoculative augmentation of the fungal entomopathogen Entomophaga maimaiga as a homeowner tactic to control gypsy moth (Lepidoptera Lymantriidae). Biol. Contr. 14 11-18.

Hajek, A.E., L. Bauer, M.L. McManus & M.M. Wheeler. 1998a. Distribution of resting spores of the Lymantria dispar pathogen Entomophaga maimaiga in soil and on bark. BioControl 43 189-200.

Hajek, A.E., K.M. Tatman, P.H. Wanner & M.M. Wheeler. 1998b. Location and persistence of cadavers of gypsy moth, Lymantria dispar, containing Entomophaga maimaiga azygospores. Mycologia 90 754-760.

Hajek, A.E., L. Butler, J.K. Liebherr & M.M. Wheeler. 2000. Risk of infection by the fungal pathogen Entomophaga maimaiga among Lepidoptera on the forest floor. Environ. Entomol. 29 645-650.

Harris, J. 2000. Chemical pesticide markets, health risks and residues. Biopesticide Series No. 1, CAB International, Wallingford, UK.

Helyer, N. 1993. Verticillium lecanii for control of aphids and thrips on cucumber. IOBC/WPRS Bull. 16 63-66.

Helyer, N.L., P.J. Brobyn, P.N. Richardson & R.N. Edmondson. 1995. Control of western flower thrips (Frankliniella occidentalis Pergande) pupae in compost. Ann. Appl. Biol. 127 405-412.

Inglis, G.D., G.M. Duke, L.M. Kawchuck & M.S. Goettel. 1999. Influence of oscillating temperatures on the competitive infection and colonization of the migratory grasshopper by Beauveria bassiana and Metarhizium flavoviridae. Biol. Contr. 14 111-120.

Inglis, G.D., M.S. Goettel, T.M. Butt & H. Strasser. 2001. Use of hyphomycetous fungi for managing insect pests, pp. 23-70 In Butt, T.M., C. Jackson & N. Magan [eds.] Fungi as biocontrol agents progress, problems and potential. CAB International, UK.

Inglis, G.D., M.S. Goettel, M.A. Erlandson & D.K. Weaver. 2000. Grasshoppers and locusts, pp. 651-679 In Lacey, L.A. & H.K. Kaya [eds.] Field manual of techniques in invertebrate pathology. Kluwer Academic Publishers, Netherlands.

Inglis, G.D., T.J. Ivie, G.M. Duke & M.S. Goettel. 2000. Influence of rain and conidia formulation on persistence of Beauveria bassiana on potato leaves and Colorado potato beetle larvae. Biol. Contr. 18 55-64.

Inglis, G.D., D.L. Johnson, K.-J. Cheng & M.S. Goettel. 1997a. Use of pathogen combinations to overcome constraints of temperature on entomopathogenic Hyphomycetes against grasshoppers. Biol. Contr. 8 143-152.

Inglis, G.D., D.L. Johnson & M.S. Goettel. 1997b. Effects of temperature and sunlight on mycosis (Beauveria bassiana) (Hyphomycetes Sympodulosporae) of grasshoppers under field conditions. Environ. Entomol. 26 400-409.

Inglis, G.D., D.L. Johnson & M.S. Goettel. 1996. Effects of temperature and thermoregulation on mycosis by Beauveria bassiana in grasshoppers. Biol. Contr. 7 131-139.

Ivie, M.A., D.A. Pollock, D.G. Gustafson, J. Rasolomandimby, L.L. Ivie & W.D. Swearingen. 2002. Field-based evaluation of biopesticide impacts on native biodiversity Malagasy Coleoptera and anti-locust entomopathogenic fungi. J. Econ. Entomol. 95 651-660.

Jackson, T.A. 1999. Factors in the success and failure of microbial control agents for soil dwelling pests. Integrated Pest Man. Rev. 4 281-285.

Jacobson, R.J., D. Chandler, J. Fenlon & K.M. Russel. 2001. Compatibility of Beauveria bassiana (Balsamo) Vuillemin with Amblyseius cucumeris (Acarina Phytoseiidae) to control Frankliniella occidentalis Pergande (Thysanoptera Thripidae) on cucumber plants. Biocontrol Sci. Technol. 11 391-400.

Jaronski, S.T. & M.S. Goettel. 1997. Development of Beauveria bassiana for control of grasshoppers and locusts. Memoirs Ent. Soc. Canada 171 225-237.

Jaronski, S.T., M.A. Goettel & C. Lomer. 2003. Regulatory requirements for ecotoxicological assessments of microbial insecticides – how relevant are they? pp. 237-260 In Hokkanen, H. & A.E. Hajek [eds.] Assessment of environmental safety of biological insecticides, Kluwer Academic Publishers, Netherlands.

Jazzar, C. & E.A.-F. Hammad. 2004. Efficacy of multiple biocontrol agents against the sweet potato whitefly Bemisia tabaci (Gennadius) (Homoptera Aleyrodidae) on tomato. J. Appl. Ent. 128 188-194.

Jenkins, N.E. & D. Grzywacz. 2000. Quality control of fungal and viral biocontrol agents assurance of product performance. Biocontrol Sci. Technol. 10 753-777.

Johnson, D.L., M.S. Goettel, C. Bradley, H. van der Paauw & B. Maiga. 1992. Field trials with the entomopathogenic fungus Beauveria bassiana against grasshoppers in Mali, West Africa, July 1990, pp. 296-310 In Lomer, C.J. & C. Prior [eds.] Biological control of locusts and grasshoppers, CAB International, UK.

Kaakeh, W., B.L. Reid, T.J. Bohnert & G.W. Bennett. 1997. Toxixity of imidacloprid in the German cockroach (Dictyoptera Blattellidae), and the synergism between imidacloprid and Metarhizium anisopliae (Imperfect Fungi Hyphomycetes). J. Econ. Entomol. 90 473-452.

Kovach, J., R. Petzoldt & G.E. Harman. 2000. Use of honey bees and bumble bees to disseminate Trichoderma harzianum 1295-22 to strawberries for Botrytis control. Biol. Contr. 18 235-242.

Lacey, L.A. & D. Horton. 2003. Microbial control of Colorado potato beetle in irrigated desert combinations and alterations of Bacillus thuringiensis and Beauveria bassiana, pp. 59 In Abstracts, 36th Ann. Mtg. of the Soc. for Invertebr. Pathol., 26-30 July 2003, Burlington, VT.

Langewald, J. et al. (9 others). 1999. Comparison of an organophosphate insecticide with a mycoinsecticide for control of Oedaleus senegalensis (Orthoptera Acrididae) and other Sahelian grasshoppers at an operational level. Biocontrol Sci. Technol. 9 199-214.

Lewis, W.J., J.C. van Lenteren, S.C. Phatak & J.H. Tumlinson. 1997. A total system approach to sustainable pest management. Proc. Natl. Acad. Sci. 94 12243-12248.

Lomer, C..J., C. Prior & C. Kooyman. 1997. Development of Metarhizium spp. for the control of grasshoppers and locusts. Memoirs Ent. Soc. Can. 171 265-286.

Long, D.W., E. Groden & F.A. Drummond. 2000. Horizontal transmission of Beauveria bassiana (Bals.) Vuill. Agricultural and Forest Entomol. 2 11-17.

Ludwig, S.W. & R.D. Oetting. 2002. Efficacy of Beuveria bassiana plus insect attractants for enhanced control of Frankliniella occidentalis (Thysanoptera Thripidae). Fla. Entomol. 85 270-272.

Magalhães, B., M. Faria, M.S. Tigano & B.W.S. Sobral. 1997. Characterization and virulence of a Brazilian isolate of Metarhizium flavoviride Gams & Rozsypal (Hyphomycetes). Memoirs Ent. Soc. Can. 171 313-321.

Maniania, N.K. 1998. A device for infecting adult tsetse flies, Glossina spp., with an entomopathogenic fungus in the field. Biol. Contr. 11 248-254.

Maniania, N.K. 2002. A low-cost contamination device for infecting adult tsetse, Glossina spp., with the entomopathogenic fungus Metarhizium anisopliae in the field. Biocontrol Sci. Technol. 12 59-66.

Maniania, N.K., K.N. Saxena & A. Odulaja. 1998. Influence of three sorghum cultivars on the activity of the fungus Metarhizium anisopliae (Metsch.) Sorok. against Chilo partellus (Swinhoe). Insect S