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Broomrape (Orobanche)
Orobanche species are important root parasites of lentil and are especially prevalent in Eastern Europe, the Mediterranean basin, the Middle East, Asia and parts of the former USSR. Orobanche infestation may cause severe yield losses (5-100%) and even result in complete crop failure. Yield reduction is positively correlated with the number of parasites per host plant and the earliness of attack. Lentil cultivation was abandoned in Andalucia, southern Spain, because of broomrape.
Three major Orobanche species are known to occur on lentil in the Mediterranean basin: O. aegyptiaca Pers., O. crenata Forsk. and O. Ramosa L.
Orobanche seeds can remain viable in the soil for more than 12 years. The life cycle consists of two phases: (i) the induction of seed germination and formation of the unconnected seedling, and (ii) the attachment of the seedling to the host. The parasite then derives its nutrition from the host. Dissemination is achieved in different ways (through handling, by surface water, by carrying seeds, or by winds). Heavy parasite infection usually occurs in the early sown lentil.
Symptoms: The appearance of the parasite itself is the most diagnostic feature of infestation (Fig. 32).
The parasite has erect, branched or unbranched aerial flowering shoots. The leaves are reduced to scales and are disposed alternatively. The shoots bear bisexual tubular flowers in a spike (Fig. 33).
The tiny seeds are produced in enormous numbers in capsules.
Control: Hand weed shoots prior to their seed formation to reduce inoculum levels. This is recommended in minor infestations only.
Sow the crop late to help plants escape the worst effects of infection.
Plow deep to bury Orobanche seeds into deeper soil layers to reduce infestation.
Use selective herbicides such as imazaquin (10-15 ml a.i./ha).
Use soil solarization to reduce soil-borne inoculum.
Use resistant varieties, if available.
Dodder (Cuscuta)
Dodder is a problem in some areas of the Middle East, and is a threat to lentil in certain locations. Dodder affects the growth and yield of infected plants and causes slight to complete destruction of the crop in heavily infested areas.
The most important species is Cuscuta campestris. Another species, Cuscuta hyalina, has been observed on lentil in India. The stem of the parasite is tough, curling, leafless and bears only minute scales in place of leaves. Gray to reddish brown seeds are produced in abundance and mature within a few weeks from bloom, Seeds may germinate immediately after they fall to the ground, or may remain dormant until the following season.
Symptoms: The appearance of the parasite itself is the best diagnostic symptom. It has fine, yellow or orange, thread-like branches which grow and entwine around the stems and other aboveground parts of the host (Fig. 34).
Dodder-infected areas appear as patches in the field and continue to enlarge during the growing season. In late spring and early summer, dodder produces a massed cluster of white flowers (Fig, 35).
Infected host plants become weakened, decline in vigor and produce poor yields.
Several patches might coalesce to form large areas that can be easily recognized by the yellowish color of the parasite strands.
Control: Use dodder-free seed,
Clean the infested equipment before and after using it.
Limit the movement of domestic animals from infested to dodder-free areas.
Cut and bum dodder patches to prevent spreading and production.
Spray scattered patches early in the season with contact herbicides.
Till frequently to help reduce the parasite.
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