The life history and biology of the privet thrips is not completely understood. Adult females lay their eggs on host plant leaves late in the spring, with several generations per year possible through the summer. The number of generations on a single plant may depend upon the food quality of the plant for the thrips following so many generations of feeding. Immature thrips (larvae) are slender and wingless and found with magnification primarily on leaf undersides. Adults are also tiny, 1 mm in length, with wings. The larvae and adults feed and cause chlorosis on host plant leaves, which may be visible to the naked eye as a dusty/gray color. When populations are high, 20-30 privet thrips may be found per leaf. Adult privet thrips are active fliers. Note that the word "thrips" refers to both the singular and plural of the insect. The privet thrips is non-native to North America, and was introduced. This insect is native to parts of Europe, Asia, and Russia.
Leaves and twigs of privet are fed upon by the privet thrips. Attacked leaves will appear grayish in color, made up of chlorotic spots. Immature (nymphal) thrips are found on the underside of the foliage. Magnification is required to view the insect. Pests of nursery and greenhouse production.
Scout for graying or chlorotic leaves and visually inspect for long, tiny insects. Magnification will be required to help view them. Check leaf undersides. Visual scouting can occur regularly through the growing season in nursery production, and is aided by tapping symptomatic material over a white sheet of paper or placing blue or yellow sticky cards near plants. Search for the insects on paper or sticky cards.
Sanitation can help in certain circumstances to reduce thrips activity. This may be particularly helpful in nursery settings. Remove weeds, old planting materials and debris, and keep the area clean. Screening can also help exclude insects from greenhouses. Screens less than 0.88 mm. may be necessary to exclude thrips, but make sure the small screen size isn't impacting airflow quality in these settings.
Predators, nematodes, and entomopathogenic fungi have been used to successfully manage certain species of thrips, particularly in greenhouse production. These methods are understood for western flower thrips and chilli thrips, but the efficacy of the different species of natural enemies available for use on privet thrips may not be currently fully understood.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Carbaryl (L)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Clothianidin (NL)
Cyantraniliprole (NL)
Cyfluthrin (NL)
Dinotefuran (NL)
Fenpropathrin (NL)
Flonicamid+cyclaniliprole (N)
Tau-fluvalinate (NL)
Gamma-cyhalothrin (L)
Lambda-cyhalothrin (L)
Malathion (L)
Metarhizium anisopliae (robertii) (NL)
Neem oil (NL)
Pyrethrin+sulfur (NL)
Spinetoram+sulfoxaflor (N)
Spinosad (NL)
While imidacloprid products are often labelled for thrips management, and are registered for use in Massachusetts, this active ingredient may not be the best option for managing thrips. Unlike dinotefuran (another neonicotinoid), imidacloprid often does not provide satisfactory results when used to manage thrips. For example, some research suggests that imidacloprid causes insecticide resistance and resurgence in western flower thrips post application (Cao et al., 2019).
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), Metarhizium anisopliae (robertii) (soil drench), and neem oil (soil drench).
When used in a nursery setting, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
