In last week's issue of the Bulletin (no. 5, April 28, 2000), I presented an article about southern corn leaf beetles because they had been "discovered" causing injury in western counties again. Within the past week, I received several additional reports of these insects causing damage, some of it severe enough to require insecticide application. Most reports were from western Illinois, but as I indicated in a previous article, these pests were relatively common in Randolph and Monroe counties, too. Illustrations of this insect and the injury it causes were provided in last week's issue of the Bulletin. |
What more can I tell you about this pest ,which seemingly remained silent for decades, until the 1990s? I've indicated many times that the only source of information about this insect I can locate is "The Southern Corn Leaf-Beetle" by E. O. G. Kelly, Bulletin No. 221, USDA, June 16, 1915. Kelly indicated in his article that the first time he witnessed these beetles' destructive habits was "in the summer of 1905, while investigating insects injurious to corn in southern Illinois." He observed them, over time, near Wellington, Kansas, in 1910 and 1913, in northern Texas in 1910, and in eastern Arkansas in 1913 and 1914. However, the earliest report of injury was in 1887, and the earliest report of severe damage was in 1900 in Ohio.
Other observations that Kelly made included the following:
· Adults overwinter, and when they come out of "hibernation," they feed on seedling corn plants.
· Early-planted corn is more seriously affected than late-planted corn.
· Adults begin laying eggs in the soil around young corn plants as soon as the plants are available.
· Egg laying occurs over a relatively long period of time.
· The larval period ranges from May 1 to July 15 at latitude 37° (approximately southern Illinois). No observations regarding length of the larval stage were offered from more northern latitudes.
· The pupal stage lasts about 15 days.
· The adults emerge around early August at latitude 37°.
· The adults are strong fliers and were "observed in fields long distances from where they originated."
It's obvious that we need considerably more information about this pest if growers have to deal with it annually, or every other year, as one grower informed me. However, I have learned at least one other bit of news that contributes to the management picture. I had stated that no insecticide was labeled for control of southern corn leaf beetles. Recently I was informed by an FMC representative that Capture 2EC is labeled for control of southern corn leaf beetles. The recommended rate of application is 2.1 to 6.4 ounces per acre. The label indicates that Capture 2EC should be applied in a minimum of 10 gallons of finished spray per acre with ground equipment. However, some of the FMC folks' experience in southern Missouri suggests that 15 gallons per acre provide better results. So at least one insecticide is labeled for control of this recently rediscovered pest, and I suspect that more will follow in the future if the problems continue to occur.--Kevin Steffey