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Aphids
The main species attacking lentil are the cowpea aphid, Aphis craccivora Koch, and the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae). Both species are cosmopolitan and found in America, Europe, Africa and Asia.
A. craccivora is small (2 mm long), soft-bodied, shiny and black (Fig. 56). A. pisum is 3-4 mm long, green and has long legs (Fig. 57).
Winged females (alatae) are carried by the wind to the plants. They reproduce parthenogenetically (females produce offspring without mating); viviparous colonies of wingless females (apterae), and later also winged forms, are further dispersed.
Type of injury: Aphids feed by sucking the plant sap from the phloem. They can infest leaves, stems and pods and mostly colonize the young leaves and growing points, which become characteristically deformed (Fig. 58). Yield can be drastically reduced, and if infestations are early and severe, plants can be killed. Aphids also transmit several virus diseases.
Control: In case of severe infestations before or at flowering, foliar application of Rogor or Roxion (dimethoate), Pirimor (pirimicarb) or other insecticides will provide adequate control. If reinfestation occurs before pod maturity, a second spray may be needed. Often aphids infest lentil fields only at a later stage of crop development (podding); in such cases no spray would be necessary.
Aphids are attacked by a number of natural enemies, especially coccinellids (Fig. 59). Although the larvae and adults feed on aphids, the extremely fast reproduction rate of the aphids prevents the coccinellids from reducing infestation levels sufficiently.
Thrips
Several species of thrips, such as Kakothrips robustus (Uzel), Thrips angusticeps Uzel and Frankiniella spp. and others (Thysanoptera: Thripidae), infest lentil in most lentil-growing areas, but rarely cause severe damage.
Thrips are minute (1-2 mm), elongate insects with four extremely slender wings with a fringe of hairs on the hind margin. The developmental stages resemble the adults but are lighter in color and wingless.
Type of injury: Thrips attack leaves, flowers and pods. They puncture the leaves and suck up the sap, causing silvery blotches and dashes (Fig. 60). As the attack increases the leaves become distorted. High numbers of thrips often are present in the flowers, but apparently do not cause severe damage.
Control: Control measures are not necessary in the field. Under greenhouse conditions, however, thrips often appear in high numbers and cause severe damage on lentil plants grown for experimental purposes. Application of an insecticide for sucking insects (e.g., deltamethrin, malathion, dimethoate or endosulfan) will provide good control.
Bud weevil
Several species of Apion (Coleoptera: Apionidae) have been recorded infesting leguminous crops such as lentil. Apion arrogans Wenck. has been reported from the eastern Mediterranean and Apion trifolii (L.) from Europe, the former USSR and Southwest Asia.
The adult A. arrogans weevils are 3-3.5 mm long and convex (Fig. 61). The snout is very long in comparison with the body and the legs also are long. The elytra are dark blue and the head, thorax, legs and abdomen are black. Larvae are yellow and legless.
There is no published information on the life cycle of A. arrogans.
Type of injury: The adult weevils feed on lentil leaves, making small holes (Fig. 62). The main damage is caused by the larvae feeding in the buds and flowers, which destroys the ovules. Thus buds and flowers dry up and drop off (Fig. 63). Inside the buds the yellow larvae of A. arrogans can be found. Larvae of A. trifolii feed on the developing seeds.
Control: Infestation levels usually are not high enough to necessitate control measures. However, in some years localized high population densities might occur. Insecticides such as SupracideR (methidathion 0.5 kg a.i./ha) and NuvacronR (monocrotophos) at 2 ml/L can provide adequate control.
Pea moth
The pea moth [Laspeyresia nigricana (Stephens)] (Lepidoptera: Tortricidae) is mainly a pest of field pea in North America, Europe and the Mediterranean, but it also attacks lentil in these areas.
The adult moth is small (15 mm wingspan) and delicate; it is generally brown with short, oblique, black and white lines along the front margins of the
forewings. The larva is yellowish white with small dark spots and short hairs scattered over the body. It reaches about 13 mm in length.
The larvae overwinter in a silken cocoon below the soil surface and pupate in spring. Adults appear at the time of flowering. Eggs are laid on plants and the hatching larvae bore into the pods. Fully grown larvae drop to the soil to aestivate/hibernate.
Type of injury: The larvae attack the seeds inside the pods, eating irregular cavities out of half seed (Fig. 64). They are only detected when the pods are opened. Larva feeding results in spoilage of partially filled pods with excrement and silk of the larvae (Fig. 65).
Control: In most cases infestations are not severe enough to require control measures. However, since this insect directly affects the seeds and thus yield, insecticide application might be necessary sometimes. Sprays of methidathion (SupracideR 0.5 kg a.i./ha), deltamethrin (Decis 38 g a.i./ha), endosulfan (Thiodan 35, 6 ml/L) and others at the time of flowering/early pod-setting can provide adequate control.
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