Thrips are tiny insects that can cause serious damage to plants. While some species feed on fungus, most thrips species feed on plant tissues by puncturing the cells and sucking up the contents. This can lead to stippling, discolored flecking, browning, deformities, and even death of the plants they feed on. Thrips may be very small, but they can be a big problem for gardeners and farmers who find them infesting their plants.
What are thrips?
Thrips are very small insects, measuring only 1 to 2 millimeters in length in their adult stage. There are over 6,000 species of thrips identified around the world. Some major thrips pest species include western flower thrips, melon thrips, soybean thrips, and greenhouse thrips.
Thrips have elongated, slender bodies. They have two pairs of narrow wings with fringes of long hairs. The wings are folded along the abdomen at rest. Thrips can be various colors like white, yellow, brown, or blackish. They move very quickly and are hard to spot with the naked eye.
Thrips develop from eggs to larvae to pupae and finally mature winged adults in the process called metamorphosis. The life cycle varies by species and environment, but may be completed in 2-4 weeks. Some thrips species can reproduce without mating.
Thrips feed by piercing plant cells with their mouths and sucking up the contents. The injuries they cause allow plant viruses and fungal infections to take hold.
What damage do thrips cause?
Thrips feed on a wide variety of plants, including fruits, vegetables, grains, and ornamentals. They target leaves, flowers, buds, and fruits. Thrips can cause different types of damage depending on the species and plant host. Some of the main problems caused by thrips include:
- Stippling – Light dots on leaves and petals caused by removal of cell contents
- Discoloration – Silvery-white patches or streaks on leaves where cells are killed
- Distortion – Curling, deformity, or stunting of growing tips and flowers
- Spotting – Small black flecks of excrement on leaves and petals
- Scarring – Scab-like lesions or ring spots on fruits
- Flower loss – Aborted buds, damage to pollen, poor fruit set
- Transmission of viruses – Spread debilitating plant diseases
Thrips damage reduces the vigor and aesthetic value of plants. It can lower crop yields and quality. Severe thrips infestations can kill young plants, seedlings, buds, and developing fruits.
How do you detect thrips?
It can be tricky to spot thrips because of their very small size and quick movements. Here are some signs that may indicate the presence of thrips:
- Stippling damage on leaves
- Black tar-like specks of excrement on leaves
- Distorted growth and discolored patches on plants
- Flowers with streaks, scarring, or discoloration
To confirm thrips are present, gently shake the plants over a white sheet of paper. Look closely to see if any tiny slender insects are dislodged. Use a hand lens to inspect leaves and flowers closely for the insects. Look inside unopened buds which thrips like to feed on.
Blue or yellow sticky cards can be used to monitor for thrips. Hang the cards just above the plant canopy and check weekly for captured thrips.
Early detection is important to prevent population buildup and major damage. Regularly inspect susceptible plants to spot the first signs of infestation.
How to control thrips organically
Here are some effective organic methods to prevent and control thrips:
- Remove weeds – Eliminate alternate weed hosts around gardens and fields to deprive thrips of habitat.
- Use row covers – Cover susceptible plants with fine mesh fabric row covers to exclude thrips.
- Apply kaolin clay – Foliar spray with kaolin clay coats plants and deters feeding.
- Use insecticidal oils – Light horticultural oils smother thrips eggs and larvae.
- Apply neem oil – Neem oil extracts deter feeding and disrupt thrips reproduction.
- Use reflective mulch – Silver reflective mulch repels thrips from reaching plants.
- Release predator insects – Predators like minute pirate bugs, lady beetles, lacewings can control thrips.
- Apply spinosad – Spinosad biological insecticide is effective against thrips larvae.
- Use sticky traps – Blue and yellow sticky cards can capture adult thrips.
- Practice crop rotation – Rotate plant families in each bed from year to year.
Using a combination of methods is the best approach for preventing thrips organically. Focus on exclusion, repelling thrips, and conservation of natural predators.
How to control thrips with insecticides
If natural approaches are not keeping thrips under control, insecticidal sprays may be warranted. Here are some effective insecticide options:
| Insecticide | Mode of Action |
|---|---|
| Spinosad | Microbial disruptor of insect nervous system |
| Pyrethroids | Synthetic insect neurotoxin |
| Neonicotinoids | Synthetic nicotine-like insect neurotoxin |
| Azadirachtin | Botanical growth regulator |
Products containing spinosad, pyrethroids like bifenthrin and zeta-cypermethrin, neonicotinoids like imidacloprid, and azadirachtin extracted from neem oil can offer quick knockdown of thrips. Rotate classes of insecticides to prevent resistance.
Ensure complete coverage of leaf undersides and tight crevices where thrips hide. Use targeted spot sprays instead of broad applications when possible. Follow label directions carefully to avoid plant damage or excessive residues.
How to treat thrips on houseplants
Houseplants grown indoors can also fall victim to thrips infestations, often introduced on new plants. Here are some tips for treating household thrips:
- Isolate and quarantine any infested plants.
- Trim off heavily damaged leaves and flowers.
- Remove dropped plant debris which harbors thrips.
- Wash plants thoroughly with a strong stream of water.
- Treat with insecticidal soap or neem oil spray.
- Apply sticky cards near plants to trap adult thrips.
- Release predatory mites which feed on thrips.
Be vigilant about checking new houseplants closely before introducing them. Promptly isolate and treat any plants showing signs of thrips.
How to prevent thrips from spreading
Here are some ways to help prevent thrips from multiplying and spreading further in your growing area:
- Use sterile growing medium and containers.
- Check transplants carefully for signs of thrips before purchase.
- Quarantine and treat new plants separately for 2 weeks before introducing.
- Disinfect tools and gloves after working with infested plants.
- Remove and destroy seriously infested plants.
- Place discarded plant debris in sealed bags for disposal.
- Avoid moving plants around the growing area to restrict spread.
- Allow adequate spacing between plants for air circulation.
Slowing the spread of thrips requires diligent monitoring, isolation methods, and sanitation practices. It also helps to grow plants as strong and healthy as possible to limit susceptibility.
Conclusion
Thrips may be tiny, but they can be a major nuisance in gardens, landscapes, and farms. These tiny piercing-sucking insects feed on a wide variety of plants. Thrips damage includes stippling, scarring, discolored patches, and distorted growth.
Check susceptible plants often for early signs of infestation like stippled leaves and black specks. Monitor with sticky cards and shake plants over white paper to detect thrips. Use preventative row covers and reflective mulches to block thrips. Apply insecticidal soaps, oils, or targeted insecticides to reduce heavy infestations. Practice isolation, sanitation, and removal of infested material to prevent thrips from multiplying and spreading.
Thrips like to hide in tight places so ensure thorough treatment coverage. Combining multiple organic and chemical control options usually provides the best control of thrips infestations. Paying close attention and taking action at the first signs of thrips will help minimize the damage these tiny pests can cause.