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The gypsy moth (Lymantria dispar) develops through a series of stages, from larvae to adult. Newly hatched larvae are black and feature long, hair-like setae, or bristles, while older larvae display raised blue and red spots along their backs. The larvae enter the pupation stage in mid-summer, usually mid-June to July.

Pest of the Month: Gypsy Moth

What does it look like?


The gypsy moth (Lymantria dispar) develops through a series of stages, from larvae to adult. Newly hatched larvae are black and feature long, hair-like setae, or bristles, while older larvae display raised blue and red spots along their backs. The larvae enter the pupation stage in mid-summer, usually mid-June to July.


Adult male gypsy moths are brown and the adult female moths are white. Although most moth species are nocturnal, the gypsy moth is active throughout the day and night.



 


Host material and range


The gypsy moth originated in Europe and Asia and was introduced to the United States in the late 1800s near Boston. It has since spread throughout the Northeast and into Virginia, West Virginia and the Midwestern states.


The gypsy moth feeds on hundreds of plant species, most commonly oaks and aspen.


 


Current threat


The gypsy moth is the cause of massive defoliation, at an estimated rate of more than one million acres each year. The larvae feed on the leaves in the crown or top branches of host trees. Early-stage larvae chew small holes in the leaves, while later-stage larvae feed on the entire leaf — from the outside edge to the center.


Gypsy moth larvae will feed almost continuously until the host is completely stripped, then they will move on in search of a new host.


 


Prevention tips


There are several steps that can be taken to prevent gypsy moth infestation. Preventative insecticide and fertilizer applications can ensure tree health and keep outbreaks at bay. In addition, avoiding pure stands of shade trees or thinning tree groups can lower stress on the trees and maximize tree health.


Deer mice are a natural predator of the gypsy moth and can help keep the population at bay.


 


Treatment Tips


When treating for gypsy moth infestation, there are many factors to consider, including the density of egg masses, host density within a stand of mixed trees and the amount of defoliation that has already occurred. 


One of the most popular and effective treatments is application of Bacillus thuringiensis (BT). BT is a bacterium that, when ingested by gyspsy moths, literally eats the pests’ stomach cell layer causing infection and death. BT is usually applied by an aerial spray application.


In addition, micro-infusion applications of Bidrin have been found effective in preventing and controlling gypsy moth outbreaks. Current trials with micro-infused abamectin materials are also showing outstanding results.


Treating affected or at-risk trees with a fertilizer application including chelated minerals, magnesium and calcium will also stimulate foliar and root growth, increasing vigor in defoliated trees.


 


What can you do?


Programs are currently in place to help control gypsy moth populations and outbreaks and include aerial pesticide application of several millions of acres. If you’d like more information on these programs in your area, contact your local extension service.


 


Jesse Lee is with Epic Creative, Wis. Article provided by Mauget a leader in micro-injection and microinfusion tree care. Contact your Mauget representative, or visit www.Mauget.com, to learn more about the gypsy moth, steps taken to prevent and control it, and proper pesticide application and use.

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