Thrips

Thrips are tiny flying insects, measuring about 1-1.5 mm in length when fully grown. They are characterized by their long, slender bodies and two pairs of narrow wings fringed with hairs. These insects thrive by feeding on the plant juices found in the upper leaf and flower cells, which can create distinct silver-grey spots and brown dots on the plants. If left unchecked, their feeding can cause significant damage.

To effectively manage thrips, it's important to understand their environmental preferences. They typically flourish in warm, dry conditions, especially when plants are stressed. When a plant is under stress, it sends out signals that attract adult thrips looking for vulnerable hosts. Interestingly, thrips avoid colder temperatures and tend to hide in sheltered areas when it's chilly.

In North America, there are hundreds of thrips species, but the onion thrips and western flower thrips are particularly problematic for vegetables. Together, these species can affect a wide variety of plants, including winter wheat, alfalfa, legumes, onions, beans, cucumbers, peppers, potatoes, garlic, cabbage, leeks, asparagus, and cauliflower.

To manage thrips effectively in small gardens, one constructive approach is to use a forceful spray of cold water early in the morning. Using a nozzle that creates a fine mist, make sure to wash the undersides of affected leaves thoroughly. This method is most effective when done at least three times, either daily or every other day.

Additionally, keeping plants well irrigated and misted can create an environment less favorable to thrips. Pruning and removing any injured or infested plants is also critical; make sure not to compost these plants.

For immediate control, you can use insecticidal soaps to reduce thrips populations temporarily. Just be sure to follow the instructions on the label carefully. Neem oil is another option, but it’s best to apply it in the early morning or late evening to avoid damage during the hottest part of the day.

You can also attract beneficial insects such as ladybugs, lacewings, predatory mites, and minute pirate bugs, which are natural enemies of thrips. Nematodes can also play a role in control. Consider using pyrethrin-based insecticides and sticky traps (in yellow or blue) for additional management. Remember to be patient and ready to repeat treatments as necessary to achieve the best results in controlling thrips.