Key Features
- Irregular notching on leaves
- Black beetles with white spots
- Wilted leaves
Symptoms
This weevil can cause extensive damage when grubs feed on roots. Adults sometimes make their way into homes in heavily infested, urban sites. Adults are black, 1/2 inch long with distinct light spots. Adults chew leaves and cause irregular notches (not to be confused with the perfect circles made by leaf cutter bees). Grubs feeding on roots and the base of the stem can cause plants to wilt when they reduce the capacity of the plant to take up water.
Biology
Early and late stage grubs winter in soil and resume feeding in spring. In early June adults begin to emerge from the soil and continue to emerge for several weeks. After 2 or 3 weeks of feeding, adults begin to lay eggs on the soil surface. Adults lay up to 500 eggs over the course of a month. They winter in all stages, but the egg stage.
Management Recommendations
Foliar insecticides, including pyrethroids such as bifenthrin or cyfluthrin, applied when first adults are seen (usually in June when multiflora rose is in bloom) and again 3 weeks later will kill beetles before they lay the bulk of their eggs. Soil drenches of a systemic insecticide (imidacloprid, dinotefuran, and clothianidin) in mid-August will kill young grubs in the soil. Several species of nematodes (Steinernema carpocapsae,Steinernema feltiae,Heterorhabditis bacteriophora) can be purchased and released to control the grubs in the soil in the spring and fall. Soil must be moist and the temperatures above 60 F. To protect bees, do not apply foliar insecticides when bees are flying to flowers and avoid using soil insecticides like acetamiprid, imidacloprid, dinotefuran and clothianidin on plants prior to or during flower production.
Effective Pesticides
Active Ingredients include: Acetamiprid, Bifenthrin, Clothianidin, Cyfluthrin, Dinotefuran, Imidacloprid, Lambda- cyhalothrin, Permethrin, Tebufenozide
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
