Diamond back moth: pest on vegetable crops
It is a major pest of all cruciferous vegetable crops and cabbage and cauliflower are major host crops. The adult is a small, slender, grey brown moth. It is a weak flier. However, they are easily carried by the wind.
The eggs are oval and flattened yellow or pale green in colour, and are deposited singly or in small groups of two to eight eggs in depressions on the surface of leaves.
Development time
Larva has four instars. Throughout their development, larvae remain quite small and active. Initially, the feeding habit of first instars larvae is leaf mining, although they are so small that the mines are difficult to notice.
The larvae emerge from their mines at the conclusion of the first instars, molt beneath the leaf, and thereafter feed on the lower surface of the leaf. Their chewing results in irregular patches of damage, and the upper leaf epidermis is often left intact. Larval periods last for 14-21 days.
Pupation occurs in a loose silk cocoon, usually formed on the lower or outer leaves. The duration of the cocoon is 7-11 days.
Plant damage is caused by larval feeding. This is particularly damaging to seedlings, and may disrupt head formation in cabbage, broccoli, and cauliflower. The presence of larvae in florets can result in complete rejection of produce.
Management
— Remove and destroy all debris and stubbles after harvest of crop and plough the field.
— Grow 20 days old mustard seedlings as intercrop at the time of cabbage or cauliflower planting at 1:20 ration to attract diamond back moths for oviposition. Periodically spray mustard crop with Dichlorvos 0.75 per cent at 10 or 15 days interval to avoid dispersal of larvae.
— Instal pheromone traps at 12/ha spray Cartap hydrochloride 0.5 per cent or Bacillus thuringiensis 2 g/l or Carbosulfan 0.225 per cent or Quinalphos 0.5 per cent at primordial stage or head initiation stage.
— Spray NSKE 5 per cent along with Teepol or Sandovit 0.5 ml/I after primordial stage
— Release parasitoids such as Diadegma semiclausum in hills or Cotesia plutellae in plains. Release of 10,0000 adults/ha at 20,000 adults/release commencing from 20 days after planting reduces the damage.
Sunitha N.D.
& Jagginavar S.B.
Department of Entomology, College of
Agriculture, Bijapur
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