Last week I went looking for small new nests in hopes I could find eastern tent caterpillars just as they hatched. What I found were large nests with large caterpillars. March is pretty early for eastern tent caterpillars in Raleigh. This is a result of the warmer than ‘normal’ spring we have had. Based on State Climate Office Growing degree day calculator Raleigh (RDU airport) has accumulated 346 GDD (base 50F) so far in 2017. This is not so different than the 316 GDD accumulated by March 27 in 2016. However, it is almost threes times as many as in 2015 (150 GDD), 2014 (92 GDD), and 2013 (108 GDD).
In 2013 and 2014 we did not reach similar GDD until the third week in April putting us almost a month ahead this year. Interestingly, this matches when Google indicates that most people are looking for information about eastern tent caterpillars. According to Google Trends, ‘eastern tent caterpillar’ as a topic in the Raleigh area has peaked in mid-April (e.g. April 6-12, 2014; April 19-May 9, 2015) each year since 2012. This year we already see a peak March 19-25.
Such large changes in insect phenology is important for many reasons. In some cases phenology of mutualists like pollinators may become unsynchronized. In other cases, predators and prey or parasitoid and host phenology may become unsynchronized leading to loss of biological control. Not many people probably care about eastern tent worm prosperity or that of other pests like cankerworms. However, if these critters hatch before their host plants develop leaves they starve. This means migrating birds and other animals people do care about, and that rely on spring caterpillars for food, also suffer.
Of course monitoring and predicting pest activity is an important part of IPM for caterpillars and other pests. The more pest development varies from year to year, or even from warm to cool spots in a city, the harder IPM becomes. Your state probably has a State Climate Office with a growing degree day calculator. As phenology gets more variable, using these tools rather than relying on previous years to implement IPM tactics will be essential.