WHITE GRUBS & WIREWORMS

White grubs and wireworms may cause early-season stand reduction in corn by feeding on the roots and thus killing seedling plants. As with most soil insects, it is difficult to predict when and where true white grubs will be found. An increased incidence may be anticipated in cornfields following pasture or grassy Conservation Reserve Programs. Increased susceptibility and stand reduction are fairly common in both continuous and rotated corn and fields where heavy residue and/or manure are present.

All NuTech hybrids are pre-treated with Cruiser^® Extreme 250, which controls both of these pests.

CORN ROOTWORM

“Extended diapause” northern and/or “soybean variant” western CRW often negate management through crop rotation alone. Since pruned roots are less capable of supplying water and nutrients to the growing plant, yield losses are greatly accentuated under drought stress. Injury also increases susceptibility to root and stalk rot fungi and high adult densities may clip silks. In areas more free from extended diapause or soybean variant, the most cost-effective management strategy is crop rotation. Sequentially, in more problem prone areas, the best solution is to be found with the use of transgenic rootworm resistant hybrids followed by in-furrow granular insecticides and then liquids, followed by high rate seed treatments.

BLACK CUTWORMS

Black cutworm moths migrate northward on southerly spring winds, typically beginning in mid-March and peaking in April through mid-May. If herbicides eliminate weeds one to two weeks before planting, black cutworms that had been present will likely starve. Larger larvae may cut plants above or below ground, reducing plant stands up through V5. A rescue treatment is recommended when greater than 3% of the corn seedlings are cut. NuTech suggests Herculex^® I hybrids for improved control. NuTech corn hybrids are pre-treated with Cruiser^® Extreme 250, which provides good suppression. Therefore, Syngenta provides a Cutworm Assurance Program to address rescue treatment costs. Ask for details.

WESTERN BEAN CUTWORM

Eggs are laid on upper leaf surfaces. After hatching, if corn has not tasseled, larvae move to the whorl to feed on pollen in the developing tassel. If corn has tasseled, larvae feed on silk in the ear. If silk feeding persists during pollen shed, pollination may be poor. Once the ear has formed, it becomes the major feeding site for western bean cutworms. One cutworm per ear results in a loss of about four bushels per acre. Severe infestation can result in the reduction of grain yield by as much as 30-40%. Herculex^® I hybrids give good control. Generally, an insecticide application should be considered when more than 8% of the plants have egg masses or small larvae and 95% of the corn is tasseled.

EUROPEAN CORN BORER

North Dakota and northern Minnesota are subject to yield losses from the first-generation of ECB. More southerly areas of our market are subject to first, second and third-generation ECB. Taller, early-planted corn is more vulnerable to first-flight ECB, while late planted or full-season hybrids are more susceptible to the second and third generation infestations which are closely associated with stalk rot and lodging. Yield losses around 5% from first and 2-3% from second generation ECB are common. Severe losses occur under drought conditions and/or when damage begins before kernel fill. The best, most cost effective control is found with YieldGard^® Corn Borer (Mon810), Agrisure^®CB/LL (Bt11) and Herculex^® I (1507) hybrids.

CORN FLEA BEETLE

Economic damage is caused by over-wintering beetles carrying bacterial wilt of corn (Stewart’s disease). Damage is greatest after a mild winter followed by a cold spring, in which high numbers of beetles survive the winter and attack the slowly-growing corn over a prolonged period. Control by plowing under crop residue and maintaining good weed control to eliminate over-wintering sites. Use wilt resistant hybrids to lessen the chances of excessive loss. All of our NuTech corn hybrids are pre-treated with Cruiser^® Extreme 250, which has shown effective control of flea beetle until the 5-leaf stage, resulting in disease reductions of 23-70%.