With the unusually wet, cold weather Louisiana has been experiencing this spring , soil borne insect issues are becoming increasingly evident as the field season progresses. One such issue that I looked at this week was a corn field with severe wireworm damage.
Wireworms are slender, hard bodied, wire like insects that are the immature stage of click beetles. They are shiny brown
in color and typically ½ inch to 1 ½ inches in length. Wireworms can injure cotton, corn and soybeans during the early stages of seedling growth. Adverse conditions such as cool temperatures and excessive moisture resulting in stalled seedling growth leaves plants more susceptible to injury. Insecticide seed treatments will typically provide adequate protection against wireworms; however, excessive moisture may cause the insecticide to move out of the root zone leaving seedlings susceptible. Of the three neonicotinoid insecticides available for use on agronomic seed, imidacloprid is the most water soluble at 0.61 g/l of water, followed by thiamethoxam and clothianidin at 0.41 and 0.33 g/l, respectively. These values represent the degree of leachability but are highly dependent on soil type.
Wireworms will typically build large populations in reduced tillage, sandy fields that have not been have not been rotated (ie. corn behind corn). Wireworm damage will often result in stunted plants, dead hearts in corn, and irregularly shaped holes that become more pronounced as the crop grows. There are no rescue treatments for wireworms and crops become less susceptible as the season progress. Warm temperatures cause these insects to move deeper into the soil where they are no longer a threat to growing crops.
For more information or if you have any questions or concerns please contact Sebe Brown, or Drs. David Kerns or Julien Beuzelin.
Sebe Brown Cell: 318-498-1283 Office: 318-435-2903
Dr. David Kerns Cell: 318-439-4844 Office: 318-435-2157
Dr. Julien Beuzelin Cell: 337-501-7087 Office: 318-473-6523