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K-State Agronomy eUpdates

Department of Agronomy

Kansas State University

1712 Claflin Rd.

2004 Throckmorton PSC

Manhatan, KS 66506

785-532-6101

agronomy@ksu.edu

Extension Agronomy

Special Issue: Army cutworm alert on winter canola in Kansas; Scout wheat and alfalfa fields

With the onset of warmer temperatures, winter canola has broken dormancy and army cutworms are now present in many fields across Kansas. Army cutworms have been found this week from Marquette in McPherson County all the way south to near the Oklahoma border.

The economic threshold for chemical control is 1 to 2 per foot of row. Army cutworms were found Tuesday, March 10, in numbers as high as 6 per foot of row at the South Central Kansas Experiment Field. Agronomists travelling through southern Kansas also found army cutworm populations aboveground as high as 15 per foot of row.

This is unusual because army cutworms behave nocturnally and typically spend the daylight hours belowground. Thus, when scouting it is critical to dig in the soil around individual canola plants to find the larvae. The larvae are greenish-gray and often curl up into a C-shape               

Figure 1. Army cutworm (on blade of knife) in a winter canola field on March 10 at the South Central Kansas Experiment Field. Photos by Mike Stamm, K-State Research and Extension.

 

Figure 2. Army cutworm feeding and damage to winter canola at the South Central Kansas Experiment Field.

 

Army cutworms feed aggressively and significant damage can occur in a short period of time. Canola plants can withstand some damage, but smaller plants are most susceptible. The larvae feed on the leaf tissue, leaving the plants with a fed-on appearance. When minor feeding is observed, you may find leaves severed from the plant and laying on the soil surface. Where infestations are high, army cutworms will remove all leave tissue leaving only the base of the stem.

 

Figure 3. Severe army cutworm damage to winter canola.

 

Insecticides labeled for army cutworm control are quite effective. Carefully read the label for proper application and any restrictions.

Insecticide

Rate per acre

Brigade 2EC

2.1 to 2.6 fl oz

Hero

2.8 to 5.95 fl oz

Mustang MAX EC

4.0 fl oz

Proaxis 0.5 CS

1.92 to 3.84 fl oz

Warrior with Zeon

0.96 to 1.92 fl oz

Source: Management of Insect and Mite Pests in Canola, Oklahoma State University publication CR-7667

As a reminder, if a final herbicide application is planned for the spring, it must be made before bolting or significant crop injury and yield loss can occur. Tank mixing an insecticide and herbicide is a good option.

Producers should also be scouting winter wheat and alfalfa fields that are beginning to green up for army cutworms.

 

Mike Stamm, Canola Breeder
mjstamm@ksu.edu

Gary Cramer, Agronomist-in-Charge, South Central Experiment Field
gcramer@ksu.edu