Courtesy Bruce Willmer via KAPOA on Facebook
A recent article on gypsy moth cold temperature survival rates got one of our local residents to thinking about what the implications are mathematically.
The pertinent extract from the referenced abstract is: “Although eggs of the gypsy moth Lymantria dispar (L.) supercool, a steady and substantial portion freezes and dies at a steady temperature below −26°C. The rate of freezing at steady temperature is about 1% per min at −27°C and changes about tenfold per degree. The freezing of the eggs at varying temperature is predicted by integration of the rates observed at steady temperature.”
This area registered a temperature of –30C on the morning of January 11th, 2022. Suggesting that we experienced a temperature of less than –27 C for a period of 10 hours. So, taking a conservative steady –27 C (as opposed to an average of –28.5 C, say), we can derive the following from the article’s assertions: After 1 minute, egg masses still remaining are 0.99 (99%), after 2 minutes we have 0.99 X 0.99 = .9801 (or just above 98% remaining) and so on. So after 10 hours (600 minutes), we get: Eggs remaining of 0.24% of the original population after 10 hours of at or below –27 C. The referenced abstract further indicates that for every degree below –27 C, we can expect a 10-fold increase in egg mortality. So, if we assumed even a 3 hour period of –28 C, using the same calculation based on 10% die-off per minute, we get less than a millionth of a percent survival after 3 hours. To further help in the potential die-off is the fact that we have had a few more sub -27 C nights since January 11th with a few more in the forecast this week. Of course, there may be other variables such as snow cover at the base of trees where many eggs can be found. But there is very little snow this year. So, if, the assertions in the article are valid, it seems we have nothing to worry about this spring. Of course, only time will tell.
Thank you to Anna Dolan and George Zurakowski for giving us some hope to seeing the end of the recent Gypsy Moth infestation in this area.
