The canola canopy is very thick, making it difficult to penetrate with an insecticide spray unless gallonage is increased. This is his best guess, as we don't have any data to really go on. I figured that it was similar in size and appetite to a variegated cutworm so after doing some quick math, (18 moths per square yard ÷ 9 square feet per square yard) I suggest we use 2 or more cutworms per square foot as a treatment threshold. I did find a suggested threshold from North Dakota for bertha armyworm that states their threshold is ca. Royer says he has combed the literature for any suggestions for a treatment threshold for variegated cutworms, and have not found anything I can rely on. It is very important to check the field before deciding to spray and check several locations in the field to get an accurate assessment of the infestation because only two of the five fields we checked had cutworm problems.ĭr. They typically prefer to feed at night and like to hide underneath leaf material and dirt clods during the day. Look for damage signs (damaged pods) as well as the caterpillars themselves. It literally climbs up the canola plant and feeds on the developing pods (Figure 2), cleaning out the seeds within them (Figure 3a) and stripping the green material from the raceme (Figure 3b). This climbing characteristic is why it is now causing problems in canola. Unlike most cutworms, the variegated cutworm is a "climbing cutworm" and is much less subterranean than its relatives. Variegated cutworm populations go through 3 to 4 generations per year in Oklahoma. The larva grows through 7 instars in 4-6 weeks. The caterpillar can be recognized by the 4 to 7 diamond shaped white/yellow spots on the top center of their back (Figure 1). It winters as a pupa in the soil, but can be active year-around in warmer climates. The variegated cutworm is a common cutworm pest of alfalfa and vegetable crops. Similar reports are coming out of SW Oklahoma as well. What they found in two of the five fields we checked was unsettling seed pods being consumed by variegated cutworm caterpillars. After receiving phone calls from several people about caterpillars infesting canola, Royer traveled with Heath Sanders of Producers Cooperative Oil Mill and Josh Bushong, OSU Canola Extension Specialist to look at some canola fields in Kingfisher County around the Okarche area.
This year is no exception on the insect front. Tom Royer says he heard Heath Sanders say "we learn something new about canola every year". Scout for Cutworms/Armyworms and Spray When You Find Them in Your Canola Sun, 06:16:00 CDTĭuring the Oklahoma canola field days last week, at every stop Dr.
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