Spraying for LDD/Spongy Moth CaterpillarsSpring 2022 with Late Summer Update

High Park was sprayed for LDD Moth caterpillars (also known as Spongy Moth, previously called Gypsy Moth) in spring 2022. The first application took place on Saturday, May 28, the second one on Tuesday, May 31 and the final one on Friday, June 3, all very early in the morning. No special precautions were required for people visiting the park, but people were given advance notice in case they wished to avoid the actual spraying period.

LDD (gypsy) moth caterpillar. Photo: Karen Yukich

High Park is an Environmentally Significant Area (ESA) with high biodiversity and a high oak tree population that is susceptible to LDD moth defoliation. The City used a new product in High Park this year: BoVir. This pesticide contains baculovirus, Lymantria dispar Nucleopolyhedrovirus (LdMNPV), and it is highly selective to LDD moth alone. This means it will not affect other types of caterpillars that may be feeding at the same time. BoVir will not impact other insects, mammals, birds, amphibians or other moth or butterfly species.

City staff will continue to monitor the treatment areas over the season to evaluate the effectiveness of the spray program. Some degree of LDD moth larvae activity is to be expected throughout the season. Park visitors are encouraged to use the LDD moth Online Reporting Tool or call 3-1-1 if they are noticing caterpillars later in the summer. This information will help staff coordinate egg mass surveys in the fall and winter months.

UPDATE August 2022

Naturally present parasites, fungus and NPV virus were all definitely at work this season in addition to the BoVir applications.  A healthy population of LDD moth successfully hatched this spring and were beginning to do some defoliation damage prior to the first round of spraying. They were still noticed a few days after the first round of spray, but after the second round there was a serious drop in LDD numbers.

It is known that BoVir requires a longer time to build and knock back the population and is not as effective as Btk. The main reason for using BoVir in High Park was to ensure that other moths and butterfly caterpillars were not affected by the spray. That being said, BoVir combined with some build-up of natural controls appears to have seriously brought down the LDD moth numbers in High Park. Only a small number of adults were evident.

BoVir is expected to have a lingering effect into next season. However, the severe defoliation in the last two previous seasons may still contribute to oak decline in the upcoming years since energy stores to re-foliate would have been depleted.

For more information visit the City’s website. View the Interactive Treatment map for the 2022 LDD Moth Treatment Program.

Read more about Moths of Concern to Tree Health in High Park.








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