Pear thrips are tiny insects that are pests of deciduous trees. (Thrips is both the singular and the plural of this word.) They were introduced into California from Europe in 1904. Adult pear thrips are slender, 1.5 mm long, and brownish-black in color with nearly veinless wings fringed with long hairs. In the Northeast, pear thrips adults become active in April and May and feed inside tender, newly developing flower and vegetative buds of their hosts. Winged females fly up to and enter buds. All adult pear thrips in North America are female and reproduce using parthenogenesis (asexually). After feeding, they will lay eggs in flower stems and leaf petioles, with small brown scars developing in the areas where eggs were laid. Eggs hatch, and both the pale white and translucent larvae (immatures) and adults feed on host plant foliage with piercing and rasping mouthparts which allow them to drink up host plant fluids that escape from the wounds they create. Tattered, mottled, distorted, dwarfed foliage can result from pear thrips feeding. With very heavy populations, defoliation can sometimes occur. Feeding is typically complete by early June. Pupation occurs in the soil, and it is the pupal life stage that overwinters. A single generation is reported per year.
Sugar maple is the primary host in Massachusetts, but pear thrips are also found on fruit trees and other maples. Feeding and egg laying in buds can cause severe damage. Tattered, mottled, distorted, dwarfed foliage can result from pear thrips feeding, and in heavy population years, defoliation can also occur. Blister-like scars on leaf veins and petioles may also develop. Although the damage from this insect can periodically be significant and noticeable, chemical management options are limited in their effectiveness because adult pear thrips emerge prior to host plant leaf-out in the spring. Adults enter newly developing buds to feed, which can protect them from contact insecticides. Abiotic conditions can also impact the relative damage caused by this insect. In springs where leaf expansion happens quickly, pear thrips typically cause less damage unless their population is extremely high. The longer the buds remain closed, the more damage may be possible from pear thrips feeding. Synchronization of adult emergence with bud expansion also increases the likelihood of damage from this insect. Maple trees, historically, that lose up to 2/3 of their leaves may be able to refoliate in a few weeks. Hosts that are otherwise healthy (not stressed by other factors) can often withstand repeated years of defoliation by pear thrips. However, consecutive years of heavy defoliation by this insect are not common. Tree vigor may be reduced, but hosts typically recover from the activity of this insect. Pear thrips will also feed on tree pollen.
Pear thrips damage can be monitored for in blooming hosts at the time of bloom. Tap blooms against a yellow surface to look for adult pear thrips. 5 adults (or any larvae) per 50 blooms sampled may indicate a need for treatment options in fruit production, but the threshold for ornamental host plants is likely higher. Because this insect has population outbreak years followed by relatively little damage, occasional outbreaks may be tolerated. Additionally, chemical management options for pear thrips in ornamental settings may be limited in their efficacy.
No effective cultural management options for pear thrips have been noted.
Lecanicillium (previously Verticillium) lecanii, an entomopathogenic fungus that is naturally occuring, has been previously reported to attack pear thrips larvae removed from forest soils (Parker et al., 2011). Paecilomyces farinosus, Beauveria bassiana, Hirsutella spp., and Metarhizium anisopliae have been reported from various life stages of pear thrips in various locations (ex. tree canopy vs. soil) previously (Brownbridge et al., 1999). Depending upon geographic location, some papers discuss predators and parasitoids of pear thrips. However, the exact species present in New England and their overall impact on pear thrips populations may not be fully understood.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (immature) (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 (N)
Gamma-cyhalothrin (L)
Isaria (paecilomyces) fumosoroseus (pupae) (NL)
Lambda-cyhalothrin (L)
Metarhizium anisopliae (robertii) (NL)
Neem oil (NL)
Pyrethrin+sulfur (NL)
Spinetoram+sulfoxaflor (N)
Spinosad (NL)
Some chemical management options cannot be used on sugar maples to be tapped for maple syrup production. As always, consult product labels for all instructions if the host plant being treated is to at all be used for food production. Chemical management of this insect is usually not possible or effective.
While imidacloprid products are often labeled 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.
