Vegetable Insect Pest Updates

Sweet Corn-- All is quiet on the “Minnesota ECB Front,” so far. The European corn borer (ECB) 1st generation flight should soon be winding down with a whimper. A combination of low numbers, plus less-than-ideal weather for mating and egg-lay, have contributed to what should be a low infestation for much of southern Minnesota. Zero to very low counts in Corn Earworm (CEW) pheromone traps indicates that we should not have a significant early CEW infestation this year (compared to last year).

For more information on ECB flights, via the “Light trap Network” on the web, go to the MAP at the following web site
(then click on the location of your choice). For rapid access in the future, you may want to bookmark this page with the map. http://www.mnipm.umn.edu/Bugweb/bugbase/flight/reporting/find-a-siteMN.htm

Minn. Dept. of Agric. (MDA) surveys, provided by Mark Abrahamson and staff, show that, although we have a few “hot spots” of armyworm, cutworms, common stalk borer and grasshoppers, much of the corn has little insect feeding damage. Primary concerns for many growers are stand loss from late frosts or flooding. MDA surveys, as of June 16th, show that for much of the state feeding damage by all corn pests was between 0-10%, with a few locations in southeastern and west central MN showing 10-25% feeding damage. Although armyworm trap catches were up last week, larvae/sweep were averaging zero to a max of 0.6/sweep

Alert: Despite the low sweep counts at this time, armyworm trap catches increased this past week (6/18) in the following counties: Cottonwood (43/night), Sibley (16/night), LeSueur (56/night), and Faribault (75/night). Corn in these areas should be scouted carefully for possible infestations.

Alert: One exception to the trend for light insect feeding, is a Black cutworm infestation on 2-3-leaf stage corn at Rosemount (Dakota Co.). This is very heavy (30-40% of plants infested) on some of our sweet corn; most larvae are in the 4-5th instar and actively cutting plants, below and above the surface. Any fields still in these early growth stages should be checked carefully for cutworms. Cutworms are primarily active at night. However, they can be located during the day, by inspecting damaged plants just below the soil surface. When disturbed they will curl up in a “C-shape.”Most growers do not want to accept more than a 10% stand loss. If 5-10% of the stand (high-value vegetable crops) is lost or damaged, an insecticide treatment is warranted. Even if the plant is not been completely killed, damaged plant regrowth (e.g., cut above the soil surface) could result in a delay in maturity, and subsequent uneven maturity at harvest. The pyrethroids labeled for sweet corn (e.g., Asana, Baythroid, Warrior, Ambush, Pounce, Capture) as well as Lorsban should all be effective. For Lorsban, however, shallow incorporation is recommended if the soil is dry. See Midwest Veg. Production Guide-2000 for details.

For more information, and updates on pest activity, view the MDA Pest Report at the following web site. Click on the crop of interest, then click on “Check Notices.” http://www.mda.state.mn.us/pestsurvey/

Snap Beans-- Bean leaf beetle counts, however, have been high in soybeans, and could also be high in snap or lima beans, throughout much of the southern half of the state. MDA surveys indicate many fields had infestations ranging from 25-50% of the plants infested and/or showing some defoliation. The threshold for snap, dry and lima beans is 1 beetle/foot of row; several insecticides are labeled for control. When making a treatment decision, also consider the stage of plant growth (e.g., defoliation concern with young plants in the cotyledon to first true leaf stages.

Peas-- Scout fields for brown stink bugs, which have been relatively high this year. Stink bugs overwinter as adults. These can be a contaminate concern in processing peas. In addition to treating for the larval complex, ca. 10 days before harvest, a pyrethroid may also be needed closer to harvest, as stink bugs can re-infest fields just before harvest.