Understand Insects and Winter Survival
Harsh winter? Black cutworms say ‘Who cares?’
by Tom J. Bechman
The same question arises every winter. Will it get cold enough to knock out insects? It’s often posed as a blanket question. Truth is that while only a few insects are prone to significant damage by winter weather in Indiana. Know your insects before making decisions for 2015.
That’s the message from the panel of Indiana Certified Crop Advisers that tackle tough insect questions.
Question: My neighbor had problems with black cutworms in 2014. He’s going back to corn and thinks the bugs will over winter. Is that true?
Jeff Nagel, Ceres Solutions, Lafayette: No, black cutworms do not overwinter in Indiana. They overwinter in Texas and Mexico as moths, and migrate northward on southerly wind currents in the spring. The migrating moths look for attractive places to lay eggs, such as in weedy fields. Once eggs hatch small larvae climb corn plants and cause minor defoliation. As larvae develop they grow large enough to cut plants. Damage from black cutworm feeding is very sporadic.
Purdue Entomology tracks spring moth migration with cooperating partners to monitor for arrival and ‘intense’ captures. Weekly results are published in the Purdue University Pest & Crop Newsletter.
Intense captures doesn’t necessarily translate into widespread damage, but it’s a tool used to establish where CCAs and farmers should begin monitoring for feeding damage.
Greg Kneubuhler, owner, G & K Concepts, Harlan: As Jeff noted black cutworms don’t overwinter in Indiana, so whether the Indiana winter is harsh or mild doesn’t impact this insect. Larvae feed on young corn plants that have one to four leaves.
The bottom line with this insect is that black cutworms are difficult to predict each season. It depends on how weather fronts carry moths to our fields. The southern half of Indiana carries a higher likelihood of damage than the northern half of the state. However, until the season begins there’s no way to predict it.
Darrell Shemwell, Posey County Co-op: Weedy fields or fields with permanent vegetation are the most likely targets for black cutworm moths. Corn that was planted into fields with a lot of winter annual growth that was burned down should be monitored closely for black cutworm moths. The same applies for fields that weren’t weedy or covered with vegetation, but which are adjacent to fields which were.
Ugly adult- You don’t want to see this critter in your fields this spring. Black cutworms are sporadic, but can damage plants. There is no way to predict black cutworm pressure now. (Photo courtesy Purdue University Entomology Extension)
Facts about black cutworm
Description: Larva have greasy appearance, color varies from light gray to nearly black. When disturbed, larvae curl up.
Time of attack: April to June, or stages VE through V8, or eight-leaf, corn
Damage: Leaf feeding (early), notched and damaged plants, cut and wilting plants, dead plants
Economic threshold: If 3 to 5% of plants show damage, and two or more larvae, 4th to 6th instar stage, are found per 100 plants.
(Source: Purdue Corn & Soybean Field Guide)