Predicting Termite Swarms
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Termite swarm season mostly occurs from February to June for the native Reticulitermes species including the damaging Eastern Subterranean Termite with southern areas occurring earliest. Swarms usually happen on a warm spring day after some precipitation. A study was conducted by Furman and Gold (2002) in Texas that looked at predicting swarming based on environmental cues including heat units (also called Degree days) and precipitation. They found that a minimum of 602 heat units accumulated after Dec 21 was required before swarming occurred the following spring and the majority of swarms occurred after accumulations between 640 – 680 heat units within 3 days of an initial rainfall event. Heat units for termites were calculated above a base temperature of 4o C = approximately 39o F which is the temperature for termites where growth is pretty much halted. The formula used to calculate the daily heat units is the (maximum temperature (°C) plus the minimum temperature (°C) divided by 2 minus the base temperature (4°C). Therefore, if you can calculate the heat units based on daily temperatures you may be able to predict when swarming will take place shortly after a rain event in a given area based on this Texas study.
Furman B. D., Gold, R. E. 2002. Prediction of spring subterranean termite swarms in Texas with relation to temperature and precipitation, pp: 303–318. In Jones, S. C., Zhai, J., Robinson, W. H.(eds.), Proceedings of the 4th International Conference on Urban Pests, 7–10 July 2002, Charleston, SC. Pocahontas Press, Inc. Blacksburg, VA.