PEST OF ONION :: MAJOR PESTS :: ONION THRIPS

1. Onion thrips: Thrips tabaci  (Thysanoptera: Thripidae)
Distribution and status:  Found world-wide and is found throughout India as a major pest of onion and garlic (Allium fistulosum).
Host range: Onion, garlic, cotton (Gossypium spp.), cabbage, cauliflower, potato, tobacco, tomato, cucumber (Cucumis sativus L.), brinjal, tea, pear, pine apple, chillies, tomato, radish, grapes etc.
Damage symptoms : Adults as well as by nymphs lacerate the leaf tissue and feed on the plant juice. The insects are just visible to the unaided eye and are seen moving briskly on the flowers and leaves of onion and garlic plants. They usually congregate at the base of a leaf or in the flower.  Leaves of attacked plants turn silvery white, curl, wrinkle and gradually dry from tip downwards. The plants do not form bulbs nor do the flowers set seed. Leaf  tip  discoloration and drying is the main symptom.

Thrips tabaci	Thrips tabaci

Thrips tabaci

Bionomics : The adults are slender, yellowish brown and measure about 1 mm in length. Males wingless; females have long, narrow strap-like wings. Nymphs resemble the adults in shape and colour but are wingless and slightly smaller. This pest is active throughout the year and breeds on onion and garlic from November to May, migrates to cotton and other summer host plants and breeds till September. In October, it is found on cabbage and cauliflower. The adult female 'lives for 2-4 weeks and lays 50-60 kidney-shaped eggs singly in slits made in leaf tissue with its sharp ovipositors. Egg period 4-9 days· Nymphs pass through four stages and are full-fed in 4-6 days, after which they descend to the ground and pupate at a depth of about 25 mm. The pre-pupal and pupal stages last 1-2 and 2-4 days, respectively. Several generations are completed in a year.

Management

• Grow resistant varieties viz., White Persian, Grano, Sweet Spanish and Crystal Wax.
• Use neem coated urea to reduce the infestation of the pest.
• Install sky blue colour sticky traps@ 25/ha        
• Spray 625 ml of malathion 50 EC or methy demeton 25 EC or dimethoate 30 EC or moncrotphos  36 SL 500 ml- 750 ml   in 500 - 750 L of water per ha as soon as the pest appears. A waiting period of 7 days should be observed, before harvest.
• Conserve predators like Scymnus nubilis,Orius albidipenis, Chrysopa sp,and predatory thrips vis., Aelothrips collartris