ABOVE: Western Bean Cutworm Larva (Iowa State University)
The Western Bean Cutworm (WBC) has moved into Iowa — and the rest of the Midwest — and it’s making itself at home. The insect first appeared in Iowa in 2000, and has been confirmed in all 99 counties, according to Ag extension experts. Not only are the insects in Iowa, they’re marching east with confirmed cases in Michigan and Ohio.
It is possible to control the pests, but it will take careful scouting and well timed insecticide application. There is no doubt that Western Bean Cutworm is here, and we are going to have to deal with it long-term.
While scouting your fields this season, follow these tips for dealing with Western Bean Cutworm:
- Plants are most vulnerable to cutworm damage just prior to pollination.
- These cutworms feed on silks, tassels, and ears depending on the time of emergence.
- Cutworm feedings cause direct effects on yield, but it also allows other pests to invade wounded plants. Yield losses can reach up to 30-40 percent.
- WBC’s over-winter in the larval stage and emerge in the pupil stage in May and June.
- In mid-July, the pest will be fully developed as an adult. During this time, farmers should scout for moths both in the air and lying in the upper third of the plant.
- Adults will invade during the late whorl stage to begin laying their eggs.
- Scout for clusters of eggs on the upper-third of the plant. Eggs may also be found on the underside of leaves.
- Eggs hatch five days later and WBC larvae begin to feed for the following 3 to 5 weeks.
- In September, the pests return to the soil and begin to prepare for the wintering stage.
- Farmers should follow these general rules of thumb when scouting and determining WBC thresholds in their fields this season. Treat if…
- Eight percent of plants show presence of egg masses or larvae, and 90-95% of tassels has emerged.
- If tassels are already emerged at the time of diagnosis, 70-90% of the eggs should be hatched before application of insecticide.
- Timing of insecticide application is critical for control of the WBC. Once the insect tunnels into the silk channel, treatment by insecticide is almost-impossible.
ABOVE: Western Bean Cutworm Moth (Iowa State University)
ABOVE: Western Bean Cutworm eggs (Iowa State University)
With late plantings and a wet spring, this year has created disease conditions in areas with:
- Wet, humid soils combined with recent high temperatures
- Fields with high residue
- Reduced or no-till ground
Anthracnose is among the diseases that thrive in these conditions. It’s caused by a fungus and can affect the plant at any stage of growth. Look for these symptoms: leaf blight, stalk rot, top-kill of the stalk, and kernel rot. The disease causes the most problems at the leaf blight and stalk rot stages.
ABOVE: Anthracnose leaf blight (Ohio State University)
ABOVE: Anthracnose stalk rot (Ohio State University)
Grey Leaf Spot can be easily confused with other types of disease in its first stages of development. The tell-tale sign for this disease is small lesions surrounded by yellow rings or halos. The fungus will begin in the lower leaves and move to the top of the plant. Lesions travel through the tissues in the leaf, elongating and eventually merging together. The plants then become much more susceptible to other disease such as stalk rot.
ABOVE: Gray Leaf Spot
Northern Leaf Spot is a fungal disease that, like Grey Leaf Spot (GLS), is identifiable by its narrow elongated shaped lesions surrounded by a pigmented border. The disease will spread to all parts of the plant including leaves, sheaths, husks, and ears. Spores are released and are capable of traveling and infecting neighboring fields.
ABOVE: Northern leaf spot (Ohio State University)
For each of these specific diseases, I recommend control methods of fungicides or resistant/tolerant hybrids. For more information on these and other mid-season corn diseases, Purdue University’s Desktop Reference link is a great resource.
For those of you who made the investment in YieldGard-stacked-trait products this year, this information is good news for you! With rising concerns about Western Bean Cutworm problems in fields this year, Monsanto has come out with a Western Bean Cutworm Reassurance Program that will provide financial support in the event of an infestation.
Here’s how the program works.
Farmers must have purchased, and planted, YieldGardVT Triple, YieldGard Corn Borer with Roundup Ready Corn 2, YieldGard Plus or YieldGard Plus with Roundup Ready Corn 2 products between September 1, 2007 and May 31, 2008. At any time in the growing season, if a producer believes an infestation is present and is above the economic threshold, that infestation must be verified. A Crop Scout Log Sheet must be completed by one of the qualified crop scouts including Seed Dealers, Extension Agents, Crop Consultants or Ag-Chem Retailers.
If treatment for the Western Bean Cutworm is necessary, Monsanto will support growers with up to $7 per acre reimbursement to defray the cost of treatment with an approved insecticide. Qualifying insecticides include: Asana, Baythroid, Fury, Capture, Lorsban, Mustang, Mustang Mex, Pounce, ProAxis, Respect, and Warrior. To make a claim, contact your local Latham Dealer to have your claim verified and log sheets completed.