Onion crop Insect Pests and their control Insect Pests:The onion is attacked by a number of pests some of them are described as under.

1. Onion thrips: The thrips are very small (1-2 mm long) in size, elongated and creamy yellow in colour. The nymphs and adults both suck the cell sap of the seed stalk and young leaves. The central leaves become curled while the outer leaves turn brown at the tips. The insect causes more damage during dry weather.

Control: i.Spray the crop with Thiodan @ 2 ml per litre of water. ii. Spray Rogar @ 1 litre per hectare for 2-3 times at 10 days interval kills the insect. iii. Remove the grasses and weeds from the field to destroy the alternate hosts. iv. Grow fairly resistant varieties like Grano, Sweet Spanish, Crystal Wax etc.

2. Onion maggot: The adult lays eggs on the plants near the base or in cracks of the soil. The adult maggot measures about one third inch long and is translucent white in colour. The maggots crawl on the plants behind the leaf sheath and enters the bulb. For about 14-21 days it feeds then bore through underground stem portion into the bulb. The bulb becomes watery and turn brown from the tip to downwards. The infested plants turn yellowish brown and ultimately dry up.

Control: i. Infected bulbs should be buried in pits and covered with soil about 30 cm in early spring before the adult emerges out. ii. Dust the bulbs with 10% DDT at the rate of 25 kg per hectare. iii. Use Heptachlor @ 1 kg per 250 kg of seed bulb. iv. Adopt crop rotation.

3. Tobacco caterpillar: The moths are greyish in colour. The caterpillars feed gregariously on leaves in nursery and fields. They are found everywhere and breed throughout the year. They eat the young foliage leaves which results in very less bulb formation.

Control: Dust the crop with BHC 10 @ 25-30 kg/hectare and adopt crop rotation.