Greenhouse Vegetable Seedling: Protocol for Managing Thrips and the Tomato Spotted Wilt Virus
The Tomato Spotted Wilt Virus was observed extensively throughout Ontario in 1989 wherever field tomatoes and peppers were grown. The virus and its thrips vector were imported into Ontario with transplants. The virus-thrips complex, if not managed properly can cause serious losses in fruit quality and yield. Consequently, the Ontario vegetable seedling industry must guard against this complex. The industry must also assure their grower customers that an effective control strategy is being followed. The Ontario Seedling Marketing Board recommends the following strategy:
The principle management practices are exclusion of the complex through various cultural and management practices, and disease and insect monitoring with appropriate responses:
Provide a complete break in cropping for at least one month before vegetable seedlings emerge. This break includes the entire greenhouse complex.
Commence monitoring for thrips when the first seeding of vegetables is complete. Hang blue, sticky insect-boards close to the seedling canopy and at 15 m (49 ft.) intervals the length of the bay.
Only plants grown from seed may be produced in greenhouses used for vegetable seedling production. Early production of ornamental crops in these greenhouses is permissible if grown from seed.
Greenhouses for vegetable seedling production should not be in close proximity to houses used for flower production. Situations not meeting this stipulation must be evaluated on a case-by-case basis.
Maintain weed-free greenhouses throughout the seedling production period.
Restrict visitors to prevent the introduction of thrips - post no admission signs at entrances. Anyone who has visited other greenhouses the same day should not be permitted entrance, unless thrips-free coveralls are used.
Avoid introducing bedding plants onto your premises for decorative purposes since many producers of this material have thrips and/or TSWV.
Immediately apply appropriate insecticides if thrips are found on plants or sticky boards, or if feeding scars or virus lesions develop on indicator plants. Insecticides of choice are Malathion alternating with a combination of Thiodan + Cymbush (contact your Horticultural Crops Advisor for pest control updates). The initial 3 sprays should be applied 4 to 5 days apart, and thereafter as recommended.
When infected vegetable seedlings are detected, remove them immediately, bag them, and store the closed bags out-of-doors until they can be disposed of.
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