Tuesday, April 03, 2007

Gypsy moth coming - get ready to do battle

Over the winter, as I walked the golf course across the road I saw lots and lots of gypsy moth egg masses - so many that I began to scrape them off the trees. Beautiful old burr oaks had dozens of egg masses, most of them so high I couldn't reach them. So I wasn't too surprised to see this headline in the local paper today: Gypsy moth invasion predicted.

I had noticed the gypsy moth caterpillar population building up over the past several years. We've managed to keep them from doing too much damage to our trees by getting rid of the egg masses and killing the caterpillars (mostly squishing them - rubber gloves help!).

The map shows the area of gypsy moth infestation in eastern North America. The gypsy moth caterpillars build over a number of years to the point where they can defoliate entire forests. I remember this happening in the late '80s and the early '90s. The infestation usually isn't fatal, but the trees then have to use up a lot of energy to grow a second set of leaves, and if they're stressed by heat and drought as well, they can die. (So, if you can, do water your trees during drought to keep them healthy.)

After a massive infestation, predator populations rise, and the gypsy moth population collapses. Then we can breathe a sigh of relief for a few years - usually about a decade.

Here's what you can do to control gypsy moth on your property:
• Right now, look at all of your trees, scrape and destroy egg masses to reduce the number of caterpillars during the season. Don't just scrape onto the ground, instead burn them or soak them in kerosene or soapy water. The picture at the right shows you what they look like.

• Watch for small caterpillars in late spring. A garden hose has enough water pressure to knock them off the leaves and tree trunks and kill them, especially when they are very small.

• Wrap a piece of burlap cloth that's folded in half lengthwise around tree trunks. Caterpillars feed at night and they crawl into the burlap fold to escape the heat during the day. Collect and destroy caterpillars each afternoon. An insecticidal soap spray also kills them. You can squish them if you're not too squeamish, or hand pick and drown them in a bucket of soapy water.

• Trap male moths by hanging pheromone (sex hormone) traps on the trees. These traps act as decoys and prevent male moths from mating with female moths.

• In severe infestations, apply the biological insecticide Bacillus thurigiensis kurtsaki (Btk). This kills the caterpillars, but is only effective when they're quite small. The best time to apply Btk is when the bridal wreath spirea shrub is in bloom.
For more information: The U.S. Department of Agriculture Forest Service has an informative and well illustrated website about gypsy moth and a list of trees that are most affected.

6 comments:

  1. We live close to Princeton NJ and I read in the newspaper that they were arguing about whether to aerial spray with BT because it looks like they will have an very heavy infestation this year. I think an entomologist walked through the woods to determine the likelyhood and severity of the infestation. I was wondering if we would be affected too but there aren't many large trees around as the land has been heavily infested with people, um, subdivided into suburbia.

    Thanks for posting pictures on how the egg masses look. Will definitely keep an eye out for them.

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  2. Sweden seems to be safe... My experience with pests in general is that mechanical treatment (ie. squishing to death) is the best - as long as you can stand the boring work.

    Oh, and I agree; rubber gloves help.

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  3. Anonymous4:47 PM

    We live in the Poconos in Northeastern PA. These discusting 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 DT 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

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  4. Anonymous5:33 PM

    I too live in the Poconos Area. I did an experiment by spraying the bottom of the tree with an insecticide, then putting tin foil around the tree leaving it open on the bottom for the caterpillar to crawl under- It seemed to work really well on the bigger caterpillar. I also used the BT spray but it only seemed to work near the creek and a marshy area. I also heard thinning the trees out helps too.

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  5. Anonymous5:19 PM

    I´m also in the Pocono area and completely understand the frustration. As for stepping on them, I wish there were so few to actually even attempt such a suggestion...we´re talking thousands and thousands of these guys. And, the lovely lime green guts all over isn´t pleasant either. Unfortunately, the trees are too close together to try to stop them from crawling up, they move from tree to tree. I even saw one swinging from its silk like Tarzan and moved from one tree to another. The area should´ve been sprayed. I´m all for the environment taking care of itself, but this will be overkill this year.

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  6. Anonymous9:36 AM

    I LIVE IN MICHIGAN, WE ARE BOMBARDED WITH GYPSY MOTH CATERPILLARS. I HAVE LOST 5 OAK TRESS. I AM HOPING THEY COME BACK IN A MONTH. DOES ANYONE KNOW THE BEST OVER THE COUNTER PRODUCT TO KILL THE LARGER CATERPILLARS?? I AM HAVING MY TREES SPRAYED WITH BT TO KILL THE EXSISTING SMALL ONES.
    PLEASE HELP !!! I TOO AM STUCK INDOORS, THEY HAVE INVADED MY DECK, PORCH AND POOL.

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