In 1999 we may have encountered some of the worst infestations of wireworms we have witnessed in several years. We have received numerous reports of significant infestations in cornfields in several areas of the state. Replanting has been necessary in several instances, and some growers currently are debating whether a plant population of 17,000 plants per acre (down from an initial 28,000 plants per acre) is sufficient. The main question on many growers' minds is, "How much longer will the wireworms cause damage in the fields?"|
The answer to that question is not known, even by experts. We know that wireworm larvae move downward in the soil when soil temperatures warm up; however, we are not certain when the soil temperatures will exceed the threshold temperature (approximately 70°F). The recent cool conditions likely will not force wireworms deeper into the soil any time soon. Therefore, we strongly recommend that fields infested with wireworms be monitored daily to determine if plant populations continue to decrease. One individual I spoke to indicated that newly wilted plants in one field were evident from one day to the next. Wireworms were still active in that field, and plants were continuing to die. The field was heavily infested, so the likelihood for more stand reduction was high.
Refer to issue no. 8 (May 14, 1999) of the Bulletin for suggestions for seed treatments or soil insecticides for replanted corn.--Kevin Steffey