Much of the US is under an early heat wave right now. I know where I am, temperatures are much higher than normal for this early in the season. With all that heat, insects outside are thriving. There are a number of aspects to think about when it comes to heat and insects.
First, most of them like it. Until it gets really warm, many of the native insects are more active, develop faster, and reproduce quicker in the 90oF/32oC range. However, higher temps can result in dryer conditions; the heat evaporates water faster and water sources may dry out. This can push many pests closer to structures. The structures are still watering their lawns and plants, they still have water fountains, and they may have small ponds or other water features that are kept running. Insects will start migrating to those areas potentially getting into structures. In my area, I’ve noticed a few millipedes getting into my home and quickly drying out and dying. Springtails will do this as well, following the moisture in soils. Ants may also move their colonies closer to structures.
Heat waves will stress out plants and many can wither and die. Plants close to structures that are watered often, provide a shaded area (a little bit cooler) and a potential food source (plant feeding insects). An increase in plant feeding insects close to structures will attract the predators like spiders closer to structures.
Insects, like many animals, will find a way to avoid the worst of the heat. Many insects will be active in the morning and evening (called crepuscular), and will be inactive in sheltered areas during the heat of mid-day. Of course, humans will do the same thing: I know I try to take a walk first thing in the morning when it is cooler. This means people who are out in the early morning and evenings are going to have more insects swarming near them.
Another way they avoid the worst of the heat is some will go dormant. Clover mites are a good example of this. There is typically a spring “explosion” and people will see thousands all over their structures and on their plants. As temperatures rise, they go dormant for the summer and will re-emerge (usually in smaller numbers) in the fall.
Finally, heat can be used as a control method. Heat has been used for years to treat structures for stored product pests, bed bugs, wood destroying insects, and more. Each insect has a slightly different upper limit of the temperatures they can survive, but a general rule is about 120oF/49oC, most insects start dying in minutes. Remember earlier I said they will find a way to avoid the heat? The same thing can happen during heat treatments. The heat has to be uniform throughout the area. Bed bugs may hide under a mattress that doesn’t quite get to the right temp in the middle. Flour beetles may hide inside equipment with product in it that will insulate them against the worst of the heat. Wood insects are already buried in the wood so if the temperature at the center doesn’t get to that magic number, they can survive. The insects won’t just sit there and die, they will seek out cooler spots.
To bring this hot mess together: insects can take the heat...to a point. Outside insects will move close to structures to use what people give them (moisture, shade). And heat treatments can be effective...if all areas get to the target temperature. If you have been dealing with increased pest issues lately (maybe due to the heatwave), contact me to see how I can help you reduce those issues and plan for future influxes due to weather.
Lagniappe – There are some REALLY cool adaptations that desert insects have to deal with extreme heat, check these out!
360 PFCS – your urban pest control consultants.