Tobacco caterpillar is a common pest in tomato, tobacco, brinjal and other varieties of the family Solanaceae. They are found in tropical to subtropical climatic regions where warm weather conditions and good rain occurs.
Identification of tobacco caterpillar
Eggs- the eggs of tobacco caterpillars are greenish in color. They are about 1-1.5 millimetres in diameter. The eggs hatch within 1 to 3 days after oviposition by the adult female on the underside of leaves.
Larva- the larva of the pest are green in color with white markings in a diagonal fashion and small reddish horn-like protrusion on the last abdominal segment. The larvae have five instar stages. The larvae can grow up to 75-80mm in length.
Pupa- after the last instar stage, pupal stage occurs in which the larva changes to pupa. In this stage, the insect forms a hard cuticle which darkens to form a pupa. The pupa is dark reddish-brown in color with a loop like structure at the anterior end. It is found in the leaf litter on the ground. The pupal stage is completed within 3 weeks but the pupa may undergo overwintering for more than 4-6months.
Adult- the adult is known as a sphinx moth. The wingspan of forewings ranges from 9.5 to 12cm. The wings possess a mottled pattern on four wings and a pattern of light-dark bands on the hindwing which help the moth in camouflage while resting. The abdomen of the adult has 6 pairs of yellowish-orange spots. A female produces eggs after three to four days of mating and can produce up to 1000 eggs in her lifetime. The total lifespan of the caterpillar is nearly 60 days.
Host plants- the tobacco Caterpillar feeds mostly on the solanaceous crops such as tobacco, tomato, brinjal, potato etc. It is also found to feed sometimes on chili, cotton, cabbage and some weeds of the nightshade family.
Damage caused by tobacco caterpillar
Larvae- the larvae are voracious feeders and feed on the leaves of Solanaceous plants. They defoliate the plants by eating the entire leaves up to the midrib. The larvae eat the leaves and deposit green to black droppings on the plant. Larvae may also feed on the green unripe fruits by making large holes through which pathogens and other insects also attack and damage the crop.
Adult- adult stages do not damage the crop as adult moths feed on nectar from flowers of various plants of Solanaceae family.
Management and control of tobacco caterpillar.
Ploughing of soil to destroy the pupa by exposing them to sunlight.
- Light traps at the rate 1 per hectare can be installed to trap the adult moths.
- Pheromone traps @ 14-15 per hectare can also be applied to attract male moths and prevent breeding.
- Sometimes destruction of the Caterpillar can be done by their removal through hand picking in smaller areas.
- The defoliated leaves of a plant eaten by caterpillars must be removed and burned.
- Tobacco Caterpillar is controlled by spraying nucleopolyhedrovirus (NPV) which kills the larvae when it feeds on the leaves.
- Bt-Tomato can also be used for planting. This variety contains the fetal endotoxin protein-producing gene of Bacillus thuringiensis which kills the lepidopteran larvae when the leaves are consumed by them.
- Tobacco Caterpillar can also be controlled by harnessing the natural predation mechanism. The natural enemies such as lacewing and lady beetle larvae which consume the eggs and early instars are introduced which feed on the host and eventually reduce their population.
- Introduction of Braconid wasps which lay eggs in the body of caterpillars. The larvae of wasp feed inside the body of the caterpillar and their cocoons emerge from the live caterpillar, eventually killing it.