Most of the best article ideas come from observations in the field. Recently, a crop consultant recently contacted us with questions about about what was causing damage, shown below, that included corn leaves appearing to have been dragged down into burrows where they were presumably fed upon. The damage was not estimated to be at economically significant levels, but interesting all the same.
Note the uppermost leaves have been dragged or pulled down into holes in the ground. See video below for the appearance of the leaves below the surface.
Common early season pests like cutworms and armyworms typically don’t cause this type of damage. The consultant hypothesized that this may be due to earthworm feeding, which at first sounded unlikely… earthworms don’t eat living, healthy plants, do they? They are widely viewed as soil building organic material recyclers, beloved by farmers, gardeners, fishermen and the many birds that eat them.
I’ll admit I had never read about what earthworms actually eat, so I consulted the literature and found a few good references, including this one, that points out that earthworms (particularly the large nightcrawlers, Lumbricus terristris) will eat just about anything under the right conditions. While living, healthy plant tissues are not preferred and are likely more difficult for them to digest than the partially decomposed leaf litter and crop residues they prefer, it’s a whole lot better than nothing. Like most animals, they will make do with what’s available.
Adding to this particular story, this field was subjected to the dust storm conditions of about 2 weeks ago that damaged corn foliage and completely destroyed some soybean fields in the area. That may have may these leaves even more accessible and palatable. Perhaps also partially as a result of those high winds, you can see the soil surface of this field is almost completely barren – there’s not much material for earthworms, or anything else, to get nutrition from aside from corn.
Does this mean earthworms should be considered pests? Certainly not. But it’s an interesting story about how opportunistic and variable animal behavior can be and the value of getting into the field and keeping your eyes open!
