Southern corn leaf beetle
Authors: Buyung Hadi, Phillip E. Sloderbeck and Robert J. Whitworth
The southern corn leaf beetle (Myochorus denticollis) is small (0.19 in or 5 mm), dark brown in color and often found covered with dried soil. This beetle is only infrequently reported in the US. In the 1990s, southern corn leaf beetle damage on corn was reported from Illinois. Sightings of southern corn leaf beetle in corn fields were also reported from southern Iowa, northeastern and northcentral Kansas, Missouri, and southeastern Nebraska.
Life Cycle and Seasonal History
The beetles survive the winter as adults in the field under plant debris or in the clumps of some weeds. The adults emerge early in the spring and begin to feed on early planted corn. The adult beetles are also attracted to feed on Cocklebur (Xanthium sp.), a common weed genus, and fields with cockleburs may have higher risks of southern corn leaf beetle infestation. The mated female beetles lay eggs in the soil near corn plants or in plant debris. The eggs hatch in 6-10 days and the resulting larvae feed on corn roots. The larvae pupate in the soil and adult beetles emerge during summer. Emerging adult beetles feed on corn leaves for a short time before seeking overwintering shelter. There is one generation per year.
Plant Injury and Damage
When present in the field, adult beetles feeding on corn seedlings poses the highest risk. The beetles feed on leaves, producing notched holes and leaving the plants appear ragged. High levels of infestation may result in seedling death and stand loss.
Scouting and Threshold
The economic threshold for black cutworms should be used for this pest.
Controlling cocklebur in the field should help to reduce the southern corn leaf beetle populations.