With the bitterly cold temperatures we have experienced this winter, producers may be wondering if overwintering insect pests could be killed and their populations reduced?
Cold temperatures are probably not the most significant influencer on insect demise. The reason temperature has little effect on their survival is related to their life cycle. Depending on the species, insects overwinter in all life stages – from adults to eggs, larvae or in chrysalis and cocoons. Some insects will avoid the cold altogether and migrate to warmer temperatures such as the monarch butterfly, armyworms, potato leafhopper and corn earworm, to name a few. Some literally will freeze to death (sorghum aphid) but the next generation will migrate in from the south.
Insects have survived for millions of years and evolve with the climate. Insects are cold-blooded, which means they do not generate heat. Their body temperatures fluctuate with the weather patterns, which gives many of them the ability to withstand just about any extreme weather nature brings their way. As cold-blooded insects, they go dormant or inactive when the temperatures drop below 50 degrees.
Insects that overwinter in more exposed areas have additional cold adaptations. For example, soybean aphids overwinter as eggs and supercool to temperatures as low as -29 degrees, while European corn borer larvae can produce glycerol, a substance which acts as a biological antifreeze.
Insects overwinter in protected areas, sheltered from the extremes. They spend the winter deep in the soil, buried in plant debris, inside plants and even in our homes. These locations insulate and protect the developing stages ensuring emergence and survival.
Species that overwinter as eggs are usually very winter hardy. The eggs exist in tough shells, often in egg clusters. Grasshopper eggs are laid in the ground and if the ground is undisturbed, they can freeze over winter and still hatch out just fine. Praying mantis lay very tough and resilient egg cases on tree bark, sides of buildings, almost anywhere that they can. If left alone, these will survive to hatch in spring. Bagworms survive as eggs tucked inside a densely woven silken bag protected from the harshest elements.
Even though insect pest populations will undoubtedly survive extreme cold, remember that beneficial insects like parasitoids and natural predators will survive too.
Mentioning insects there is a program coming up concerning livestock insects. Dr. Cassandra Olds, Professor of Entomology at KSU is presenting a program. “Insect control for livestock” on Tuesday, March 4th. It will be held at the Cottonwood Extension office at 601 Main St. in Hays. The program will start at 4 p.m. with light refreshments and run about an hour.
Dr. Olds is an expert in control of common livestock pests including flies, and ticks among others. Topics covered during the program include: Determining which flies your livestock have a problem with, why flies develop resistance to insecticides, what can you do to slow the spread of resistance within fly populations and developing an effective/integrated pest management program for your operation.
RSVP is appreciated, but not necessary for the refreshments. Please email Alicia Boor at aboor@ksu.edu or call 785-628-9430 to RSVP. We hope to see you there!
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.eduor call the Hays office, 785-628-9430.
