Gypsy Moth (GM), Lymantria dispar, is one of the most destructive pests to ever be introduced to the US. Although oak is preferred, caterpillars feed on over 300 species of tree and shrub species such as apple, birches, pines, and spruces, among others. Infestations are cyclic and regional. Effective management strategies can be used to slow the spread of gypsy moth movement into suitable, uninfested areas or reduce the risk of tree mortality from repeated defoliation. Strategies include physical removal of egg masses, tree banding for caterpillars, insecticide use, and traps baited with a pheromone lure that attracts male gypsy moths. Effective programs utilize early detection through monitoring followed with well timed applications of insecticides targeting specific life stages.
Caterpillars hatch from egg masses in spring, first appearing dark and hairy, then developing characteristic markings as they increase in size. They defoliate trees as they feed; however most broadleaf trees produce new foliage in response to defoliation of less than 50%. Defoliation leaves trees vulnerable to diseases and other pests that can eventually kill the tree.
Suppression strategies include Bacillus thuringiensis var. kurstaki (Btk), a naturally occurring soil bacterium that has been formulated into a commercial biological insecticide targeting foliar-feeding, early instar larvae. It is favored in many large-scale treatment programs because it is effective against high-density populations and has limited non-target effects. Btk is typically applied from an aircraft but can also be applied to the canopy from the ground. Application of broad-spectrum insecticides to the tree crown can also be used to target larvae. Immediate and persistent toxicity of these products may benefit homeowners, but non-target effects make them unfavorable for use in larger treatment programs.
Pheromone-baited delta traps can be used to detect low abundance of gypsy moth populations, providing the opportunity to manage new infestations before they reach outbreak numbers and cause detrimental effects. Additionally, pheromone traps can monitor population spread and evaluate the success of treatment programs. The PHEROCON® IIID Trap is the preferred trap used in survey and detection programs.
Adults are usually present from mid- to late-June through mid- to late-September depending on location. PHEROCON IIID Traps should be set up in a trapping grid to ensure appropriate distribution of traps throughout the survey area. The distance between traps will depend on the density of traps used and the objectives of the program. Proper traps placement is on host trees, 4-5 feet high, on woodland edges, and on the windward side so prevailing winds carry the pheromone into the woods.
Trécé has time tested monitoring products that are frequently the choice of government research and quarantine programs like USDA APHIS and Forest Service. And the good news is that these are readily available from your local supplier, Great Lakes IPM. Visit their website and webstore to learn more about available gypsy moth traps and lures.
Always contact local extension authorities and consultants for regional advice. For additional information regarding PHEROCON GM insect monitoring traps and lures, please visit the Trécé IPM Partner® Guidelines for Use or contact a Trécé Rep.
Danielle Kirkpatrick, Ph.D.
Global Technical Support Coordinator
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