Corn borer infestation has been associated with stalk rot but probably not in the same way that some have inferred. Second brood larva of the European corn borer makes a hole through rind and then a tunnel in the pith. Some have conjectured that this allows fungi to enter the stalk but actually the fungi associated with stalk rot are restricted by living pith cells, regardless of how the fungus gets into the tissue.
The borer can weaken the stalk causing it to break. If it lodges below the ear, then the remaining stalk will not be rotten. However, if the breakage is above the ear before completion of grain fill, the lower stalk will be brown and rotting. The borer did not cause stalk rot by allowing the fungus to enter the stalk but instead is associated with stalk rot by preventing, after lodging, photosynthesis in the upper leaves. Consequently, insufficient carbohydrates are available to fill the kernels and keep the roots alive. The plant wilts as the root tissue dies and stalk rot fungi invade the wilted stalk tissue. This affect can be produced artificially by cutting the leaves off the corn. The more leaves cut above the ear after pollination. the higher the percentage of plants with stalk rot. If the stalk is cut below the ear node, there is no yield but also no stalk rot.
The same phenomenon is involved with corn borer damage and occurrence of stalk rot.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.