Despite its name, Western bean cutworm is a corn pest in northern New York.
Adult Western bean cutworm moths are able to overwinter in the North Country and also arrive on weather fronts during the season.
Peak moth numbers occur in late July and early August. Cornell Cooperative Extension installs a network of WBC traps across the region and the rest of the state to monitor population size.
Female moths emerge and look for pretassel corn fields to lay eggs. This year, tasseling will be later than normal, so WBC damage may be partly avoided.
Fields at the greatest risk are those in pretassel to full-tassel stage during and shortly after peak flight, which lasts about three weeks.
WBC eggs hatch and growing larvae eat tassels and make their way down the plant to the ear where they eat silks and, eventually, the developing kernels underneath the husks.
There are two ways to control WBC in the field: Bt traits in the seed or chemical application at the time of larvae hatching. The window of opportunity for chemically controlling this pest occurs between egg hatching and larvae’s arrival inside the ear, a span of only a few days. Once the larvae are inside the ear, chemicals are not effective.
Some Bt traits are no longer providing adequate control of WBC, so some Bt fields must be scouted and sprayed similar to non-Bt corn.
Two Bt traits, Cry1F and Vip3A, have been advertised to have activity against WBC. However, the Cry1F trait found in Herculex and SmartStax corn hybrids has provided incomplete control of the WBC in northern New York.
Results from our 2016 research trials to evaluate these traits side by side showed failure of the Cry1F trait to adequately control WBC. The Vip3A trait has continued to work well in the region though its effectiveness is beginning to be questioned in the Midwest.
Report any WBC damage to your seed dealer, agronomist or Extension agent so the field can be checked.
Northern Corn Leaf Blight
Impact of Northern corn leaf blight may be more serious this year.
Northern corn leaf blight is caused by a fungal pathogen and can cause significant yield losses in corn. Impacts from the pathogen are worsened by cool, wet weather; susceptible varieties; and development of lesions early in the season, before tasseling.
Cool, wet and humid conditions have been prevalent this season, so infections are likely. Spores are windblown and are also present in corn residues on the soil surface. Rain splashes spores up onto the plant from the residues and from previously developed lesions low on the plant.
Wet, overcast days and humid nights ensure periods of several hours of water on leaf surfaces, perfect for the fungus to start an infection. Lesions are often observed after periods of rainy weather, heavy dews, and along shaded or low portions of fields where leaves remain wet all night and into the morning hours. Often, symptoms don’t develop until late in the season when days become cooler.
This year’s weather will probably allow infections to occur early. Lesions will appear seven to 12 days after infection when leaf tissues begin to die. The greater the upper leaves’ surface area is lost to lesions, the less photosynthetic capacity the plant has for ear and grain development.
Hot, dry weather restricts disease development.
There are a number of fungicides that can help reduce losses when disease develops. This may be a year when those treatments can help your fields if you’ve scouted and found lesions on leaves at or above the ear leaf, and it’s early enough in the season. These fungicides have been shown to have no effect in the absence of disease symptoms on upper leaves or late in the season.
Fungicides should be applied at disease onset and when conditions for disease are expected to continue. A sprayer that can apply over tall corn is needed to apply these fungicides or they can be flown on.
For more information on field crop and soil management, contact your local Cornell Extension office.
Editor’s Note: Kitty O’Neil and Michael Hunter are field crops and soils educators with the North Country Regional Ag Team.