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Gypsy Moth

By City Staff

It is gypsy moth season and the City of Sarnia is aware of a local gypsy moth infestation.


The caterpillars are often a nuisance during the last two weeks of June. The caterpillars can defoliate trees, and if this happens more than a couple of years in a row, it can cause stress to the trees.


The City does not have a formal plan to combat gypsy moth.  It is a seasonal issue with varying degrees of infestations.  Generally, a wet spring will help to deter this pest by encouraging a fungal insect pathogen, Entomophaga maimaiga, which causes collapse of heavy infestations.  Most deciduous trees can withstand defoliation of one year.


This pest generally runs in cycles with two years of light infestation with minimal defoliation, and then a year or two of moderate to heavy infestation, and then a population collapse. 


City staff are monitoring tree health and will make recommendations for control should it be deemed necessary.

This article was posted Friday, June 21, 2019 2:53 PM

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255 North Christina Street,
Sarnia, ON N7T 7N2
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