All Cutworms Not Created Equal

All Cutworms Not Created Equal

If you're lucky enough to have corn up, but unlucky enough to have it attacked.

That attacker for corn that emerged last week, what little there was, was likely not the black cutworm. While it gets all the press most of the time, there are actually several types of cutworms, says Christian Krupke and John Obermeyer, Purdue University entomologists.

The black cutworm is the most common, but is the only one that must migrate in because it can't overwinter in Indiana. It generally blows northward from the gulf on winds aloft. What entomologists call 'impressive' numbers of black cutworm moths continue to be found in traps. As a farmer, you might call them scary numbers. After all, how many more strikes do you need beyond soggy soils? Add in the fact that the black cutworm moths will be attracted to fields with vegetation, especially green vegetation. Many fields that weren't fall-sprayed are now getting into that condition since spring tillage of any sort has been delayed or eliminated over most of the state.

The thing about black cutworms, however, the entomologists note, is that their larval development is directly linked to the accumulation of heat units. Since it has been so cool, the development of the cutworms has been slowed down so far. That's why if you're seeing cutworm damage or what appears to be cutworm damage right now, it's probably do to a different species than black cutworm.

Dingy, variegated and claybacked cutworm species do overwinter in Indiana as partially grown larvae. Only the claybacked type typically cuts plants. The other two tend to be more of leaf feeders. But if you're seeing damage on corn emerged now, particularly in the northern half of Indiana. It's likely that the damage is from one of these species, not black cutworm, the entomologists say. They'll be around later unless something changes, based on moth trap counts, but they haven't had enough heat units accumulate to allow them to develop into larvae that would attack plants yet.

Damage can be significant in fields where they develop because these species are not affected vary much by seed-coated insecticides, especially at the lower rates. That's because they may come out of winter as a larva that's already three-fourths inches long, too large to be affected by the light rate of insecticide. They typically overwinter under winter annuals in many situations.

You may need help identifying one species from another. The main distinguishing characteristic is the texture and feeling of the skin.

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