Western Flower Thrips
Class: Insects
Common Name
Western flower thrips, californian thrips
Scientific name
Frankliniella occidentalis
Potential Hosts
Pepper, grapes, melon, chrysanthemum, strawberry, peas, peanuts, watermelon, plums, nectarines, peach, cotton, tomato, cucumber, basil, eggplant, cabbage, cauliflower, beans, and a large group of ornamental plants
Who am I?
Western flower thrips are small, polyphagous insects (adults are 1.2 mm in length). They are a major pest in the world of agriculture with several hundred different host plants. They can usually be found on the upper parts of plants, especially inside the flowers, where they feed on pollen. Western flower thrips undergo partial metamorphosis, developing through several distinct stages, including egg, larva, pupa and adult-which can fly only weekly.
They can cause damage to crops directly from scarring of fruits (as a result of feeding or laying eggs in the plant's tissue) and indirect damage from the role it plays as a vector of viruses, responsible for TSWV (tomato spotted wilt virus; the most economically important), TCSV (tomato chlorotic spot virus), INSV (impatiens necrotic spot virus), GRSV (groundnut ringspot virus) transmission.
Control measures
Cultural
Growing inside structures: The most effective way to protect your crop from thrips is simply (but costly) growing it inside a greenhouse or a dense (50 Mesh) net structure.
Monitor the field regularly, and gently shake foliage or flowers onto a bright colored sheet of cardboard occasionally. Count the number of thrips that fall onto the sheet and make an estimation for levels of infestation.
Thrips are attracted to bright floral colors; take advantage of this and use sticky traps that lure and capture, which can help with monitoring.
Sanitation: Try keeping your crop’s close surroundings and environmental conditions as neat as you can by removing weeds that thrips are especially attracted such as sinapis arvensis (“wild mustard”).
Conventional (chemical)
It’s hard to manage thrips effectively with insecticides. They have high maneuverability skills and their egg and pupa stages are protected, which makes it difficult. Another common issue that greatly reduces effectiveness of treatments is inadequate coverage when spraying contact insecticides.
Try to avoid using organophosphate, carbamates, or pyrethroids insecticides; they will effectively eliminate natural enemies and pollinators, while leaving most of the thrips population intact and unharmed.
Organic
Spinosad-based products are not cheap, but possibly the best insecticides available today that effectively combat thrips. Spinosad-based insecticide are fermented products of a naturally occurring bacterium, and certain formulations are organically acceptable. Keep in mind that combining horticultural oil with each spray application is essential and will increase overall effectiveness.
Biological
A successful commercially available natural enemies of thrips are of the genus Orius (“minute pirate bug”), omnivorous bugs in the Anthocoridae family.
Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.