Although some insects thrive in moist conditions, heat and drought can be the ultimate survival conditions for others. Some of the most common insects that cause problems during periods of heat and drought include:
Aphids. According to an article in the Southeast Farm Press by Alabama Extension Entomologist Ron Smith, aphids are the insect of most concern in such conditions because their populations build and cause increased stress on plants already stressed by heat and drought. In addition, growers often delay treatment, awaiting rainfall or natural disease, enabling the aphid populations to continue to build. Aphids feed on plants for their sap. Although one or two aphids that are quickly eliminated may cause little to no damage, high and quickly developing populations can cause significant damage: Their feeding causes leaves to curl and yellow, and shoots to become stunted. (See Non-Chemical Control of Plant Pests: Aphids for a number of control methods.
Kudzu bugs. Smith also notes that kudzu bugs can be a significant problem in row crops in such weather conditions. The bugs feed on soybeans and can dramatically impact crop production. For control, Smith recommends "scouting" for the bugs, mid-season spraying of crops, and additional late season spraying.
Spider mites. Spider mites appear as tiny dots moving around plant surfaces. It sucks the fluids out of plants in order to feed. With colonies containing hundreds of mites, a single colony can be of significant damage to a plant. These mites can be controlled by increasing the moisture in the area, when possible, and washing small plants with a soap/water mixture.
Potato Leafhopper. Because alfalfa has a long tap root, it will stay greener and more succulent during a drought than other grasses or crops. A major pest of alfalfa that is often overlooked is the potato leafhopper. This is primarily because its initial damage, a wedge-shaped yellowing on leaftips, may be misidentified as plant disease or lack of nutrition. As noted in a University of Kentucky (UKy)publication, plants at greatest risk are those that have been left in the field for more than a month, and postponing harvest can also enable the insect populations to build. Once harvest, the UKy publication continues, after harvest, an insecticide application may be needed if the insect populations remain high.
Grasshoppers. Grasshoppers also feed on alfalfa, as well as tobacco and vegetables, and when heat and drought reduce available food, the grasshoppers can fly relatively far to find a food source. As cited in the UKy publication, Lee Townsend, extension entomologist in College of Agriculture said that grasshoppers become abundant in such conditions, "because the bacteria and fungi that normally provide natural control are not very effective under hot, dry conditions." He recommended that the edges of fields be watched for grasshopper activity to identify and control it before extensive damage is caused.
Stink Bugs. Stink bugs can be active in hot, dry conditions and can cause significant damage to trees, shrubs, and vines, as well as numerous agricultural products such as tree fruits, blackberries, corn, beans, tomatoes, peppers, and soybeans. Although they have a preference for wild plants, they are known to feed on more than 52 different vegetation varieties. Unfortunately, according to Rutgers University Extension Service, "there are no viable strategies for control of the Brown Marmorated Stink Bug. The use of insecticides has very short-lived effect and there is evidence of resistance development. Even where insecticide is effective, repopulation occurs through migration from non-treated areas."
Crickets. Like grasshoppers, cricket populations are kept at a lower level in wet, humid conditions because of the fungi in the soil. But extended heat and drought conditions keeps this fungi from building, thus allowing cricket populations to build instead. Crickets will eat vegetation, particularly the seeds and small fruits of plants, and will eat live and dead insects. Once populations build, crickets often move into homes to annoy residents and potentially cause damage through their chewing. Insect baits labeled for crickets can be purchased at retail stores for control; be sure to follow all label directions and keep out of reach of children and pests.