Photo Gallery:
These images were taken in late June in an eastcentral Indiana first-year corn field (previous crop = soybean.) The corn was planted in late May. Emergence and initial seedling growth were reported to be very rapid and uniform. Variable patterns of yellowing and stunting were first observed by the farmer on approximately 19 June. By 24 June, when I visited the field, the affected plants were severely stunted relative to "normal" plants in the field and many were wilting to the point of death.
The cause of the initial plant injury was determined to be corn rootworm (CRW) larval feeding on the seminal (seed) and initial nodal roots. A major contributing factor that compounded the effects of the CRW injury was a period of very hot and dry conditions beginning in mid-June that rapidly dried the upper two or more inches of surface soil. Further development of subsequent nodal roots of severely affected plants was almost completely restricted by the very dry and hot surface soil.
Rain showers subsequent to my visit on 24 June prevented significant stand losses, but the surviving plants were nonetheless greatly stunted relative to the "normal" plants in the field. See my accompanying article for more details.
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 Variable plant size throughout field. |
 Row-to-row patterns that correspond to equipment tire traffic patterns. |
 Magnitude of variability in plant size. |
 Example of severe plant stunting. |
 Excessively dry upper two inches of soil. |
 Root damage caused by CRW larvae feeding. |
 Root damage caused by CRW larvae feeding. |
 CRW larva exiting a root. |
 CRW larva found within root mass. |
 CRW larva found within root mass. |
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For other
information about corn, take a look at the Corn Growers Guidebook on the World
Wide Web at http://www.kingcorn.org