The willow flea weevil is a type of snout beetle. Adults are small (approximately 2.3 mm), black in color, with red/yellow legs. Adults are broad in shape, with large eyes, elbowed antennae, and thick hind femurs for jumping. It is known to occur in Massachusetts and other cooler areas of North America (Johnson and Lyon, 1991). Adults overwinter in sheltered areas, such as the leaflitter and under debris. Adults emerge as spring temperatures warm and feed on host plant buds, and eventually on the tips of new shoots and host plant foliage. Adult weevils chew tiny, circular pits in the host plant parts that it feeds on. In Southern Quebec and Maine, flights of the willow flea weevil were frequent in June and July following adult emergence in May. Adults also mated in early June with new generation adults in August (Levesque and Levesque, 1995). Eggs are white in color and tiny (0.3-0.4 mm in size). Following egg laying, larvae emerge in early summer. They feed in small blotch mines in willow leaves. Leaf mines eventually turn dark brown and dry out. Once mature, the larvae pupate within their leaf mines. Pupae change from whitish in color to black as they mature within their leaf mines. Adults from the current season's generation emerge by August and begin feeding on host plant leaves. Adults will gather in large groups on the sides of buildings as cool fall weather approaches.
Larvae create blotch type mines in the upper surface of willow foliage. Mines may cause the leaves to brown or drop prematurely from the host plant by August or September. The adults chew holes/small pits in the foliage in late summer upon emergence and again in the spring after they overwinter and when warm spring temperatures allow. Adult feeding may be enough to kill new shoots in the spring. Pit-like feeding in host plant leaves becomes a hole after the surrounding foliage browns and drops from the leaf. Holes are less than 1 mm in diameter. Historically reported as an important forest pest (Craighead, 1950).
Visually search for the circular pits on the upper surface of host plant foliage created by the adults any time between May and August. Search for blotch mines in host plant leaves approximately in June.
Large, otherwise healthy host plants are likely to sustain willow flea weevil feeding. Proper planting and maintenance to promote tree health can help reduce the impact of insect feeding.
Natural enemies of the willow flea weevil are not readily discussed in the scientific literature. Parasites, predators, and fungal pathogens of other weevil species exist, so it is likely that this native insect also has natural enemies that help keep their populations below outbreak levels.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Clothianidin (NL)
Cyantraniliprole (NL)
Dinotefuran (NL)
Emamectin benzoate (L)
Flonicamid+cyclaniliprole (N)
Gamma-cyhalothrin (adults) (L)
Horticultural oil (L)
Imidacloprid (L)
Lambda-cyhalothrin (adults) (L)
Neem oil (NL)
Permethrin (L)
Pyrethrin+sulfur (NL)
Spinosad (NL)
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), emamectin benzoate (injection), imidacloprid (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.
