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Feb. 23, 2009 11:36 AM


Termite swarm on tree stumpWeather extremes can influence the local populations of almost any insect, even subterranean termites. Over the past seven or so years, termite experts have reported a decreased number of swarms during the spring and fall, as compared to typical averages. While experts cannot confirm one factor that is responsible for this decline in swarm activity, there is some evidence that indicates both lack of rainfall and too much rain can reduce the amount of swarmers that are produced in the colony – thus reducing the number of  swarmers available to swarm. Unfortunately for homeowners, a decline in termite swarms does not mean these insects are less active – it means their infestations are less visible. Homeowners may be unaware of an infestation until damage has occurred. 

While last year was a slow year for termite swarms, experts believe we have just passed the midway point in the weather cycle affecting these insects. Experts report swarms may become more prevalent each year as the weather pattern continues to shift. In the meantime, check out some interesting facts below on the impact of rainfall and temperature on swarms.    
 
Research has shown that floods can reduce the size of termite colonies in the soil below the floodwater. Under normal rainfall conditions, water moves through the soil within a few hours, and termite colonies are unaffected. If the water stays in the soil, then problems can occur. Flooding doesn’t usually kill the colony but it does eliminate some of the workers, which can slow things down for awhile. Colonies do not move to high ground during a flood, but rather shift to a lower level of activity – reduce the amount of foraging. The colony may be back to full strength in 1-2 years. Flooding in New Orleans following Hurricane Katrina did not eliminate the termite colonies in that city. The flooding that has occurred in the South and Midwest in 2008 is not likely to eliminate termite colonies either.

High daytime temperatures can also heat and dry the surface of exposed soil and certainly kill some insects there, but soil covered with mulch or grass is shielded from direct heating. Termites that forage close to the soil surface would be repelled more by the dry conditions than they would be by the heat. High heat conditions are limited to daytime and may be unfavorable for only a few hours. During the thousands of years that termites have been in North America, they have undoubtedly experienced extremes in temperature and rainfall and have adapted to these conditions.

Reference: Subterranean Termite Behavioral Reaction to Water and Survival of Innundation: Implications for Field Populations. 1995. Brian T. Forschler and Gregg Henderson. Environmental Entomology 24: 1592-1597.