dorsalis Hood & Thrips tabaci Lind
It is one of the important spices crop cultivated practically all over the State. This crop is infested by pests like thrips, aphids, mites, cutworms, root grubs etc. of these, thrips is regarded as the most destructive pest.
The adults are minute delicate insects, less than 1mm long and are light yellow in colour. Their wings are fringed with hairs. The younger stages are still more minute but wingless.
It is a polyphagous species recorded on cotton mango, tondli, bottle gourd, guava, bhendi, brinjal, onion etc.
Female lays fertilized or unfertilized eggs inside the leaf tissues, generally on the lower side of the leaf. A female can lay 40 to 60 eggs at the rate of 4-6 days. Ramchndran (1950) reported average incubation, larval, pre-pupal and pupal periods to be 8 to 9.4 to 6,2 and 3 days respectively. Prepupal and pupal stages are generally found in soil at a depth of 2.5 to 5cm. The pest is more active during later part of monsoon season especially during a dry spell.
The pest can be effectively controlled by spraying with 0.05% endosulfan, 0.03% dimethoate, 0.02% phosphamidon or 0.05% monocrotophos. Addition of sulphur in chlorinated hydrocarbon insecticides in equal proportion would control mites also.
Aphids are tiny yellowish soft-bodied insects, the adult is along 1mm long and has two projections called cornicles on the dorsal side of abdomen.
Aphids are found in large colonies on underside o leaves and tender shoots. The nymphs and adults suck the sap. Therefore, the affected leaves turn yellow, get wrinkled and destorted. The insect also exude honeydew on which fungus develops, rapidly covers the plant with sooty mould that interferes with the photosynthetic activity of the plant. As a result, the growth of plant is stunted and yield is affected adversely. Besides, they act as a vector for transmitting by aphids. The loss caused on this account is far more severe than by their feeding and devitalising the plant.
Adults and apterous forms reproduce parthenogenitically. Single female produces 8-22 nymphs/day. The nymphs are completed in 7 to 9 days and several generations are completed in a season.
It is a polyphagous species have been recorded on cabbage, brinjal, radish, chilly, tomato, tobacco, sanhemp, sweet potato etc.
Spraying with 0.05% endosulfan, 0.02% phosphamidon, 0.03% dimethoate, methyl demeton or thiometon control the pest effectively.
Leyranychus telarius L.
Mites are not insects as they have four pair of legs and belong to the class – Arachnida. They are extremely minute with variable colour.
They suck the cell sap from leaves. Badly attacked leaves show a peculiar bronzy and shiny appearance, ultimately wither and dry up.
Chillies, cotton, cluster bean, brinjal, bhendi etc.
(1) Spray 0.2% sulphur or 0.03% dicofol (2) Sulphur dusting at the rate of 20-25 kg/ha also gives satisfactory control of the pest.