Thrips are among the most common and difficult insect pests to manage in commercial ornamental production. Thrips are very small ranging from 1/16 to 1/8 inch in length and can vary in color from yellow to brown to black. Both adults and larval stages feed on plant tissue with rasping-sucking mouthparts. Most thrips feed on leaf tissue but some species can be very damaging to young flower buds causing deformation or failure to open. In addition to direct damage, thrips are capable of transmitting plant viruses making thrips management critical in commercial production settings.
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// What to look for
- The thrip's life cycle includes an egg stage, two mobile feeding larval instars, two pupal stages and an adult stage.
- Adult greenhouse thrips appear dark brown to black with a silver sheen and yellow legs. Often small brownish black specks of excrement can be seen on the leaves.
- Thrips feeding damage causes discoloration of the leaf tissue to appear bronzed to bleached between the lateral veins.
- Thrips infested flower buds often fail to develop or the flowers are deformed. Damaged flowers often have streaks of necrotic or discolored tissue.
- Adult thrips are frequently found in shaded areas of the plants.
Larval stage of chill thrips on a rose leaf. (Photo: Envu)
Symptoms of INSV (thrips transmitted) on rununculus. (Photo: Envu)
// Host Range
- Thrips are most prevalent during the spring when populations are reported to reach their peak. They damage both foliage and flowers of numerous ornamental plants.
- Greenhouse thrips are most problematic on annual bedding plants including begonia, chrysanthemum, dahlia, nasturtium and phlox.
- The type of thrips and the host they occur on depends on geographic location, but the most economically important species of thrips include greenhouse, flower, gladiolus, red-banded, Cuban-laurel and chili thrips.
Thrips feeding damage on a Chrysanthemum flower. (Photo: Envu)
// Cultural Control
- Frequent inspection of plant material is essential to prevent rapid buildup of thrips in nurseries and greenhouses. This includes thorough inspection of new plant material for thrips prior to moving them into production areas.
- The use of yellow or blue sticky cards can be a useful tool for monitoring thrips populations.
- Many weeds are susceptible hosts for thrips and should be removed or controlled with herbicides.
- Remove and dispose of old stock plants. Infested plant hosts and plant debris serve as reservoirs for thrips infesting new plants. Sanitation is an important tactic in managing thrips.
// Insecticide solutions
Preventative insecticide applications are recommended. Altus®, Kontos® and Sevin® can be used on all stages of crop development for effective control of thrips. Refer to product labels for directions.
// More information
Contact your Envu Ornamental Specialist for further assistance.
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