Northern Corn Rootworm Damage in First-Year Corn: A Review of the Situation in Iowa

Northern com rootworm larvae occasionally damage fields of first-year com in Iowa. Rootworms typically have a one-year life cycle and rotating com with another crop has been a very successful management strategy to prevent lodging and yield loss from this insect. Unfortunately, some populations of the northern com rootworm have successfully adapted to the com-soybean rotation and now have a two-year life cycle. This two-year life cycle is called extended diapause because some of the eggs remain dormant in the soil for nearly two years before the larvae hatch. For instance, for the eggs that are laid in 1999, some larvae will hatch in 2000, but the remainder will not hatch until2001

When should you be concerned about adult corn rootworm feeding on your corn?

Last week, we were asked when a grower should be concerned about adult corn rootworms feeding on the silks of their corn. The importance of beetle feeding on corn silks is variable and there is not a definitive treatment threshold. The variability is the result of the environmental conditions and the maturity of the corn in relation to surrounding fields. During the 1970s, Purdue University conducted a study to try to identify a treatment threshold for adult rootworm feeding. The resulting threshold was 5 to 15 adult rootworms per plant

Black Cutworm Thresholds: What has Changed with the Price of Corn and New Control Methods?

Black cutworm traps across Iowa have been capturing migrating moths for several weeks. Pheromone traps are valuable tools in integrated pest management, but they have limitations. The traps only tell you that the insects are in your area; they do not report in which fields the insects have laid their eggs. Where moths lay their eggs will be influenced by environmental and agronomic factors such as weed cover, tillage, the date the crop is planted and previous crop residue, etc. The bottom line is that once adult black cutworms are forecast to be in your area, you must scout your fields to determine if there are larvae present and if they are “cutting” your corn plants. If there is sufficient cutting then controls should be applied

Bt rootworm corn failures: Understanding the issues

Genetically engineered corn that produces a Bt toxin effective against corn rootworms is now readily available and was widely planted in Iowa during 2006. Several seed companies have registrations, or will have shortly, and they will add additional Bt events and varieties to the choices for corn rootworm management. Does that mean that our corn rootworm management decisions are over, and we don\u27t have to worry about rootworm injury? No. Bt corn rootworm hybrids are another insect management tool that must be thoughtfully incorporated into corn production practices

Rootworms and YieldGard RW hybrids

It is that time of year when your corn rootworm management strategy should be examined. We are currently digging corn roots in our research plots to evaluate the performance of the seed treatments, soil insecticides, and YieldGard Rootworm (YGRW) hybrids. As you dig corn roots, you might find larvae feeding on the roots of YGRW hybrids or adult beetles in the field. Either of these situations may come as a surprise if you are unfamiliar with the technology

Did northern corn rootworms lay eggs in soybeans?

During the summer of 2005, adult northern corn rootworms were abundant throughout Iowa. They were common in gardens during the midsummer, they frequented lights around buildings at night, and they were still common on early fall flowers such as thistle. But most surprising was the frequency at which large numbers were found in soybean fields

The variant western corn rootworm in Iowa

Corn producers in eastern Iowa should expect to see changes in corn rootworm behavior. The variant of the western corn rootworm has now been confirmed in eight Iowa counties. Their presence may influence corn producer management decisions, especially in corn rotated with soybeans

Corn Rootworms: Elect Problems and Possible Solutions in Iowa Corn

During the past summer, 2001, there was widespread and substantial lodging in central and northwest Iowa first-year cornfields. In many cases, it was determined that the rotated com was susceptible because of root destruction caused by com rootworm larval feeding. In the cases reported, the insect present was the northern com rootworm and the infestation was attributed to extended diapause that allowed the pest to survive in the rotated corn

Corn rootworms and lodged first-year corn

Northern corn rootworm larvae occasionally damage fields of first-year corn in Iowa. Rootworms typically have a 1-year life cycle and rotating corn with another crop has been a very successful management strategy to prevent lodging and yield loss from this insect. Unfortunately, some populations of the northern corn rootworm have successfully adapted to the corn-soybean rotation and now have a 2-year life cycle. This 2-year life cycle is called extended diapause because some of the eggs remain dormant in the soil for nearly 2 years before the larvae hatch. For instance, for the eggs that are laid in 1999, some larvae hatch in 2000, but the remainder will not hatch until 2001