Early Spring? Be Aware

Mild temperatures, strong southerly winds, weedy fields and certain cover crops in April and May provide an environment conducive for economic infestations of True Armyworm (TA) and Black Cutworm (BCW).

BCW predominately migrate to our region from our southern states in the spring. BCW adult populations in our region depend on the frequency and intensity of southerly winds depositing them here for another season of potential economic injury. Upon arrival adult BCW seek out weedy fields, especially chickweed, to lay eggs, hatch and feed on corn or soybeans. Yes, BCW will feed on both corn and soybeans if egg laying is successful, weeds are killed and there is nothing else for the young larva to feed on.

There is however, some things you can do to reduce the risk and control BCW.

1.) The most convenient and effective control is to plant “Herculex I”, ” Herculex Xtra” or “SmartStax” insect resistant traited corn hybrids. Refuge must be scouted and treated if thresholds have been reached.

 

2.) Burndown or till weeds prior to BCW adult arrival.

 

3.) If you are not certain of the timing of moth arrival adding “Lorsban” or “Cobalt” insecticides to the burndown herbicide will provide good protection from emerging larva. Scouting is important, since adult arrivals may occur over a long period of time.

 

4.) “Lorsban” and “Cobalt” insecticides are effective for both corn and soybeans if a rescue treatment is warranted after scouting indicates threshold has been reached.

Economic threshold for BCW in corn is when larva are ¾” or less and 3% of the plants are cut or 1″ larva are found and 5%+ of plants are cut. If BCW is found in soybeans, stand counts and size of larva will have to be used in determining whether or not treatment is justified.

TA as well, predominately migrates from our southern states, hitching a ride on strong southerly winds to our region, but seeks out small grains and grasses as their ideal egg laying sites. TA will hatch and feed on small grains and grasses until the small grains or grasses begin to mature or are killed with burndown herbicides. As the small grains and grasses become less desirable TA will also migrate into neighboring corn fields to feed. Scout corn planted into grass cover crops closely for TA. Currently, there are no insect resistant traited corn hybrids available to control True Armyworm.

What can you do to reduce the risk and control TA in corn?

1.) Burndown or till cover crops prior to TA adult arrival.

 

2.) If you are not certain of the timing of TA adult arrival, the addition of “Lorsban” or” Cobalt” insecticide to the burndown herbicide may provide some control from larva. Scouting is important since timing of egg laying occurs over a period of time.

 

3.) Scout corn, especially planted into or neighboring small grains and grasses and treat if thresholds are reached with “Lorsban” or “Cobalt” insecticides.

Economic thresholds for TA in corn is when 20-25% of the corn shows leaf feeding and larva are are less than 1-1/4″ long.

As previously mentioned environmental conditions may indicate a potential for economic thresholds of TA in wheat. Economic threshold for TA in wheat is an average of 6 larva/ foot of row and larva are less than 1-1/4″ long.

If you have any questions or concerns please contact:

Terry Jones CPAg, Regional Agronomist @ 419.346.7786 or

or

Rod King CCA, Regional Agronomist @ 574.596.6721 or