videoman40
Well-Known Member
Description
Thrips are small (~1/8” long) and narrow-bodied insects commonly found feeding on leaves and stems. Greenhouse thrips (Heliothrips femoralis) and western flower thrips (Frankliniella tritici) are plant pests commonly found in Minnesota greenhouses and on flowering plants kept indoors. Adult greenhouse thrips are dark and western flower thrips adults are straw yellow to light brown. Greenhouse thrips nymphs are pale green and can resemble small aphids without cornicles. The larval form of flower thrips appear wormlike and range from pale yellow to light orange.
Since thrips are quite small and their pale-colored nymphs are difficult to detect, using magnification when scouting is recommended. The presence of thrips gives a splotchy appearance to leaves.
Life Cycle
Female thrips deposit barely visible eggs under the surface of leaves. The following are the life stages and their approximate duration*:
Damage
Using rasping-sucking mouthparts, both larvae and adult thrips cause a distinct splotchy appearance on leaves. Because they feed on woody stems as well as leaves, greenhouse thrips have a wider host range than flower thrips and are considered more destructive. Typical thrips damage includes structural damage to foliage: rolling, blistering, discoloration, splotches, and occasionally leaf drop. A few thrips species are also known vectors of certain plant viruses.
Control Strategies
Monitor regularly. Trapping adults with sticky cards and inspecting crops on a regular basis will help identify an infestation in its early stages. Blue and neon pink sticky cards are recommended and should be placed near the top of crop canopy at a frequency of 1-3 cards per 1000 square feet. Indicator plants can help detect plant viruses caused by thrips.
Physical and cultural controls. Keep growing areas as weed-free as possible by pulling and bagging weeds that may harbor pests. Use of herbicides is not recommended because pests may survive and relocate to other crop plants. Develop a weed-free zone around the perimeter of the greenhouse to discourage thrips and other pests. Avoid wearing brightly colored clothing that may attract thrips and give them a free ride to uninfested locations. Try installing insect screens on intake vents. Keep greenhouse fallow at temperatures of 104 degrees F or higher for 14-21 days to kill thrips before planting.
Chemical controls. Neem oil, horticultural oil, hot pepper wax, insecticidal soaps, and garlic extracts are biorational pesticides that may provide some relief from thrips. Consult your local distributor to see which products are recommended for your situation and whether they are compatible with biological agents.
Biological Control. Several beneficial insects, mites, and nematodes are available from suppliers of biological control agents (BCA). Keep in mind that certain BCA are better suited for some crops than others; some BCA are only effective on the larval stages of thrips. Consult a supplier of BCA to see which organisms best fit your particular crop, budget, schedule, and growing situation. If foliar pesticides are used, waiting about two weeks and/or a minimum of two waterings before releasing biological control agents is advised.
Predators. Green lacewing species (Genus: Chrysoperla), minute pirate bugs (Orius insidiosus), pinkspotted ladybeetle (Coleomegilla maculata), Neoseiulus cucumeris, Hypoaspis miles and others are available from suppliers.
Parasitoids. Thripobius semiluteus parasitizes nymphs of greenhouse thrips.
Nematodes. Steinernema spp. attack the soil stages of thrips that pupate in the soil. Consult with a supplier of beneficial nematodes to find out how to apply nematodes and other beneficials can be used in conjunction with nematodes for additional control.
(One method I've heard is to use plain ol' tap water and 1 drop of natural pine oil in your water bottle which you mist your plants daily with. Bugs, pests and pets stick their noses up at the pine smell.
Another alternative method is a weak solution of dish soap and water.)
Peace
Of the more than 6,000 thrips species known in the world, the following five are common pests of greenhouse crops: Greenhouse thrips (Heliothrips haemorroidalis), Banded greenhouse thrips (Hercinothrips femoralis), Flower thrips (Frankliniella tritici), Western flower thrips (Frankliniella occidentalis), and Onion or tobacco thrips (Thrips tabaci).
Since thrips are quite small and their pale-colored nymphs are difficult to detect, using magnification when scouting is recommended. The presence of thrips gives a splotchy appearance to leaves.
Life Cycle
Female thrips deposit barely visible eggs under the surface of leaves. The following are the life stages and their approximate duration*:
- Egg (2-4 days)
- 1st larval instar (1-2 days)
- 2nd larval instar (2-3 days)
- Pre-pupa (1-2 days)
- Pupa (1-3 days)
- Adult (can live up to 45 days)
Damage
Using rasping-sucking mouthparts, both larvae and adult thrips cause a distinct splotchy appearance on leaves. Because they feed on woody stems as well as leaves, greenhouse thrips have a wider host range than flower thrips and are considered more destructive. Typical thrips damage includes structural damage to foliage: rolling, blistering, discoloration, splotches, and occasionally leaf drop. A few thrips species are also known vectors of certain plant viruses.
Monitor regularly. Trapping adults with sticky cards and inspecting crops on a regular basis will help identify an infestation in its early stages. Blue and neon pink sticky cards are recommended and should be placed near the top of crop canopy at a frequency of 1-3 cards per 1000 square feet. Indicator plants can help detect plant viruses caused by thrips.
Physical and cultural controls. Keep growing areas as weed-free as possible by pulling and bagging weeds that may harbor pests. Use of herbicides is not recommended because pests may survive and relocate to other crop plants. Develop a weed-free zone around the perimeter of the greenhouse to discourage thrips and other pests. Avoid wearing brightly colored clothing that may attract thrips and give them a free ride to uninfested locations. Try installing insect screens on intake vents. Keep greenhouse fallow at temperatures of 104 degrees F or higher for 14-21 days to kill thrips before planting.
Chemical controls. Neem oil, horticultural oil, hot pepper wax, insecticidal soaps, and garlic extracts are biorational pesticides that may provide some relief from thrips. Consult your local distributor to see which products are recommended for your situation and whether they are compatible with biological agents.
Biological Control. Several beneficial insects, mites, and nematodes are available from suppliers of biological control agents (BCA). Keep in mind that certain BCA are better suited for some crops than others; some BCA are only effective on the larval stages of thrips. Consult a supplier of BCA to see which organisms best fit your particular crop, budget, schedule, and growing situation. If foliar pesticides are used, waiting about two weeks and/or a minimum of two waterings before releasing biological control agents is advised.
Predators. Green lacewing species (Genus: Chrysoperla), minute pirate bugs (Orius insidiosus), pinkspotted ladybeetle (Coleomegilla maculata), Neoseiulus cucumeris, Hypoaspis miles and others are available from suppliers.
Parasitoids. Thripobius semiluteus parasitizes nymphs of greenhouse thrips.
Nematodes. Steinernema spp. attack the soil stages of thrips that pupate in the soil. Consult with a supplier of beneficial nematodes to find out how to apply nematodes and other beneficials can be used in conjunction with nematodes for additional control.
(One method I've heard is to use plain ol' tap water and 1 drop of natural pine oil in your water bottle which you mist your plants daily with. Bugs, pests and pets stick their noses up at the pine smell.
Another alternative method is a weak solution of dish soap and water.)
Peace
