Key Features
- Distorted leaves and flowers
- Discolored flowers
- White scrapes on leaves
Symptoms
Thrips discolor the surfaces of fully developed flowers and leaves when they feed by scraping plant tissue. Feeding on expanding buds of flowers and leaves can cause them to twist and distort. When on leaves, thrips leave black fecal spots in scraped leaf portions. One species, the western flower thrips, transfers impatiens necrotic spot virus and tomato spotted wilt virus. See entries on managing these diseases.
Biology
Several species of thrips attack ornamental plants. Many species (like greenhouse and western flower thrips) do not overwinter in the landscape and enter the garden as hitchhikers on infested plants grown in the greenhouse. Other species, such as daylily thrips winter in the landscape and can be a recurring problem. Many thrips are omnivores. For this reason, thrips will often hide from their hungry brothers and sisters in cracks and crevices.
Management Recommendations
Thrips are usually more of a problem when plants are grown inside structures. With the exception of daylilies, thrips on infested plants tend to die off during heavy rains, or when consumed by predatory insects. If daylilies are infested or if thrips problems persist, apply one of the insecticides below. Of these products, spinosad is most effective because it can penetrate leaf and flower buds where thrips hide. Use of oil or insecticidal soap kills many adults and nymphs and lets natural enemies and rain take care of the rest.
Effective Pesticides
Active Ingredients include: Acephate, Acetamiprid, Azadirachtin, Bifenthrin, Cyantraniliprole, Dinotefuran, Horticultural oil (Paraffinic or superior oil) , Insecticidal soap (Potassium salt of fatty acid), Neem oil, Permethrin, Resmethrin, Spinosad
Resources
