The leaf webber, also known as the semi-looper or inchworm, is a common pest that infests green gram crops. This pest belongs to the order Lepidoptera and the family Noctuidae. The adult moth has a wing of about 20-25 mm and is light brown in color. The larvae are pale green with a darker head capsule and can grow up to 25 mm in length.
They feed on the leaves and pods of green gram, creating a characteristic webbed appearance. It takes the leaf webber 30 to 40 days to complete its life cycle. The female moth deposits her eggs on the lower part of green gram leaves. After a few days, the larvae emerge and feed on the leaves. As they expand, they build protective webs around themselves. Before pupating in the ground, the larvae go through several molts.
The adult moth emerges after roughly 10 to 14 days, and the cycle repeats. Green gram crop leaf webber infestations can be managed in several ways. Crop rotation, intercropping with non-host plants, and timely sowing reduces pest populations. Predatory insects and parasitoids can also be added. Chemical control can be used sparingly with other management strategies.
Leaf Webber Management in Green Gram
Identification of Leaf Webber
Leaf webber, scientifically known as Eucosma critica (Eucosmidae: Lepidoptera), is a common pest of red gram and other pulses in India. This pest is widely distributed throughout the country. The adult moths are pale brown and have a wingspan of about 20 mm. They have golden or yellow-brown forewings, three dark zigzagging lines, and some darker patches. On the hindwings, the number of crossing lines is reduced to two.
Female moths lay eggs singly on the young leaves or shoots of the host plants. The young larvae initially roll the leaves of the host and feed on the tender shoots. Later, they create webs by joining the leaves and feeding from within. This results in stunted growth of the main shoot of the plant.
The Life Cycle of Leaf Webber
The female moth lays eggs on the young green gram and other pulse leaves or shoots. The larvae feed on tender shoots after hatching for 3-4 days. After merging leaves, larvae feed from within webs. They undergo several instars before pupating. After 10–12 days, the adult moth appears. The 20-mm-wingspan adult moth lays eggs singly on host plants to finish the life cycle.
Causes/Conditions Favorable for Leaf Webber Spread in the Field
Hot, dry weather is ideal for leaf webber infestations, particularly when the crop is vegetative and reproductive. Plants may be more vulnerable to infestation due to inadequate moisture, nutrient deficiencies, and bad crop management techniques. Pests may find shelter in weeds and agricultural residue, which may also aid in spreading the pests.