Gypsy Mothocalypse Continued… Was This Winter Sufficiently Cold to Wipe Out Our Infestation?
As the weather is warming up, I’m sure many of you will be wondering, what is going to happen when all those gypsy moth egg masses that are covering our trees hatch this spring? How many caterpillars are we going to be seeing?? The math is kind of intimidating. Say each egg cluster has between 100-1000 eggs, and heavily infested trees can be covered in more than 100 egg masses. That’s > 100,000 hungry hungry caterpillars!! We all know what they’re capable of…
In Tim’s previous blog entry, Gypsy Mothocalypse, he suggested we pray for cold. So, the question is, did we get enough cold weather? We spent the winter in Mansfield, where infestation levels are quite high. Every time the temperature dipped down below -20 C, we celebrated! There were some weeks in February where the temperature remained below -20 C for more than 2 days. Was it enough??
This is a question that can be answered using the scientific method. Our budding junior scientists were keen to help! After reading some papers on the evaluation of cold weather effects on gypsy moth caterpillar emergence, we figured the easiest way to determine what effect this winter had on the gypsy moth eggs would be to collect the eggs and see how many would hatch.
We picked a day about mid-way through March and scraped some eggs off about 5 or 6 different trees. Now I realize that to make it a proper scientific experiment we should have chosen 3 different locations, and at least 3 different trees per location, with all egg masses collected at the same height (or at 3 different heights, keeping these results separate to determine if height of egg mass on the tree had an effect on winter survival). However, as our question was really quite simple, being “Did they survive, yes or no?”, we kept our experiment simple.
Leif scraping some gypsy moth egg masses off of the tree.
After collecting the eggs, we had a look at some under the microscope to see whether we could determine egg viability prior to hatching. We even crushed some to see what kind of goop came out! The microscope told us very little, other than the eggs are covered in a furry coating that likely offers protection from the elements. The eggs themselves are quite hard, it takes a bit of force to crush them. All this is kind of discouraging. They do seem quite hardy.
A gypsy moth egg under 40X magnification.
We then separated some eggs from the masses, counting out 100 and putting them in a container with holes. Again, I meant to do 3 samples of 100, but in the interest of time I did 2. We kept these 2 samples of 100 eggs inside at approximately room temperature, checking on them about twice a week to see when/if they hatched.
Since we had no proper control, if we saw 0 caterpillars emerge it would be difficult to determine whether this was due to cold effecting egg viability or if it had to do with the way our eggs were kept inside in the dark. However, if we saw 100 caterpillars emerge, we would determine that likely the cold did not impact the caterpillar eggs and we are going to be up to our eyeballs in gypsy moth caterpillars this year!
So as not to keep anyone in suspense, I will let you know what we found. After 2 weeks of not seeing anything hatching, I thought maybe they were not viable. Then I checked one of our containers again this morning and counted 25 newly hatched gypsy moth caterpillars! Nooooo!!!!!! Well, I thought, maybe that’s all we’ll get… maybe ¼ of the eggs got destroyed by the cold. Then I checked on April 4, and there was an additional 60! So far that’s 85% survival, not good.
Photo 1: Tiny gypsy moth caterpillars. Photo 2: Riel examining hatching gypsy moth caterpillars under the dissecting scope. Photo 3: Gypsy moth caterpillars under 10X magnification.
What does this mean?? Well, we’d better look into those control measures again. We’ve also armed the boys with squirt guns filled with soapy water. They have been enjoying soaking the eggs, and it is satisfying to watch! However, having not tested this method I can’t guarantee it will work. Likely, it will have to be Bt.
Leif and Fawkes spraying gypsy moth egg masses with soap and water.
By guest blogger Cathy St. Germain