Is it ice or insects?

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

In past years, I’ve visited fields with tattered and ripped leaves attributed to insect feeding, only to find hail damage. With the recent thunderstorm activity, I am reprinting this list of tips that point towards hail rather than insects.

Distribution of damage in space. Is the damage found at a constant level across the entire field? If so, this points to an environmental cause such as hail. In contrast, insect damage is often patchy, worse in some areas than others, or concentrated along edges or in areas of poor crop growth.

Distribution of damage in time. Leaves with damage are of a similar age (hit at same time with hail), while new growth is not affected. In contrast, with a recent or on-going insect infestation, you expect at least some new growth to be affected.

Damage to neighboring crops, weeds. The same type of damage is found on larger weeds in the field, on plants along the edge of the field, and in neighboring, especially different, crops. This indicates a widespread event affecting many plants, i.e., hail.

Lack of consumption. Leaves may be tattered, torn and ripped, but leaf tissue itself is not necessarily missing. The tattered leaf can often be “reconstructed” by aligning the tears. In contrast, feeding by defoliating insects removes leaf tissue.

Lack of insects or signs of insects. No insects are found, or at least consistently found, associated with the damage. There is also a lack of cast skins, frass (bug droppings), slime trails or other signs that insects were present.

Coffee talk. The talk in the coffee shop is about recent thunderstorms, not about armyworms and beetles.

Dr. DiFonzo’s work is funded in part by MSU‘s AgBioResearch.

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