This year one of the worries was a heavy gypsy moth caterpillar infestation. These beasties are voracious eaters that can defoliate entire forests, something we experienced in the early '90s, when we spent a lot of time in Ontario cottage country.
In previous years, we kept them under control by removing them from tree trunks, but this season, the caterpillar population has exploded.
Since we've been gardening here, we must have planted something in the range of 40 to 50 deciduous trees, mostly maples, oaks and ashes. When we checked the trees last week, there were so many caterpillars that we had to make a decision: to spray or not to spray.
The spray in question is the biological insecticide Bacillus thuringiensis subspecies kurstaki (Btk), a natural bacterial insecticide that works against gypsy moths.
The key thing is that Btk must be eaten by the caterpillars when they're very young, just as they start to feed. After they take it in, they get sick, stop feeding and eventually die. The great thing about Btk is that spiders, birds and bees are not affected at all, and neither are people or pets.
The indicator plant for the right time to apply Btk is bridal wreath spirea in bloom. If you don't spray at the right time, you may as well not bother. Btk isn't effective when the caterpillars are big (like the ones in the picture, above).
So we sprayed early last week with a backpack sprayer. It's hard work holding the spray nozzle above your head. Luckily, our trees are still young - 15 to 20 feet tall - and the spray reached the leaves of the lower part branches where most of the caterpillars were. My husband had to spell me off halfway through when my arm got sore.
Today, I looked at all of the trees and, tada, there were very few caterpillars. The ones I found I scraped off and killed if I could reach them. So the upshot of our spraying is that our trees get to keep their leaves this season. My arm was sore for a day or two after the effort, but it was worth it.
If you have gypsy moth caterpillars and the Btk spray window has closed, there are still things you can do:
• pick caterpillars off leaves and soak them in a pail of soapy water
• place sticky bands on tree trunks, where the caterpillers rest during the day (they feed mostly at night)
• tie burlap wraps around tree trunks and then collect and destroy the caterpillars
More information about gypsy moth caterpillars.
We live in the Poconos in Northeastern PA. These disgusting gypsy moth caterpillars have literally invaded our area. Our houses are "moving/crawling structures". The caterpillars have even eaten the evergreens down to sticks. Our brilliant politicians have decided it was expensive to spray the BT and comments were "they will be gone in a few weeks". We are hostages in our own homes. Backyard picnics, graduation parties, swimming in pools, none existent in our area.
Our beautiful landscape has been eaten alive and hopefully will recover. Our area is known for the beauty, which is now nonexistent.
Thanks PA politicians for keeping our area safe. Spending our tax dollars wisely isn't a concern of yours.
Creepy-Crawly Disgusted Pennsylvanian