The Canadian Bt Corn Trait Tables have been updated for April 2021. The tables list information about trade names, Bt proteins, refuge requirements, and more for products approved in Canada. 

In Iowa, the species of corn rootworm (CRW) that are of economic importance include western corn rootworm Diabrotica virgifera virgifera LeConte and northern corn rootworm D. barberi Smith and Lawrence, and these two species are the most damaging pests of corn, Zea mays, in the United States Corn Belt. Eggs are laid in the soil during the summer and hatch the following spring. Larval feeding on corn roots in June may diminish yield by reducing plant growth and drought tolerance, and by imposing harvest losses due to plant lodging. Adult emergence from the soil is underway by early July, with most adult emergence completed by mid-August. Additional crop losses may be caused by adult beetles feeding on corn silk and soft doughy kernels. In Iowa, crop rotation, where it fits cropping practices, remains the preferred method of management.

The Handy Bt Trait Table provides a helpful list of trait names (below) and details of trait packages (over) to make it easier to understand company seed guides, sales materials, and bag tags.

A monitoring network was established this year to monitor corn rootworm adults in Iowa cornfields, similar to the moth trapping network we manage in the spring each year. The goal was to help farmers and agronomic professionals monitor populations of northern corn rootworm (NCR) and western corn rootworm (WCR) in their fields and assess management decisions. A secondary goal was to estimate the ratio of NCR to WCR throughout the state and describe changing ratios into the future. The sampling protocol used is detailed at the end of the article.

With several severe weather events in Iowa this month, reports of lodged corn are coming our way. Often times, a small part of the field is flattened and would be difficult to see from the edge. I encourage you to get out into cornfields and see how your stands look this month. In some cases, using a UAV camera to scan large fields is helpful. Evaluating root injury and adult activity is helpful for determining future management decisions.

Corn rootworm egg hatch in Iowa occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2020, the expected hatching date will be behind the average due to cool spring temperatures. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50% of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa will reach peak corn rootworm egg hatch in 5-7 days (Figure 1).

Today, with Ashley Dean and Angie Rieck-Hinz, I met Warren Pierson at FEEL to look for corn rootworm larvae. I predicted peak corn rootworm egg hatch for central Iowa this week based on accumulating degree days. We had no trouble finding larvae in refuge corn, ranging from ¼ to ½ inches in length. They were very active (wiggly) today.

The latest version of the table is always posted at https://www.texasinsects.org/bt-corn-trait-table.html For questions & corrections: Ben Phillips, Michigan State University (phill406@msu.edu) Contributor: Pat Porter, Texas A&M University (web site host)