Producers will pay a premium for Bt corn seed, but no additional control expenditures for pheromone traps, scouting or insecticide will be necessary for corn borers. The disadvantage, of course, is that the premium for Bt seed cannot be recouped if infestations are light this year.
Louisiana producers are fortunate to have several well-adapted Bt varieties to chose from. Based on LSU AgCenter research at six locations around the state, nine Bt varieties are recommended for 2004 based on yield performance.
The list includes Pioneer 31B13, DeKalb DKC 68-70, DeKalb DKC 69-70, Terral 2160 Bt, Terral 2155 Bt, Terral 26BR10n, Genesis 3214, Genesis 2A16 and N83-N5. The Bt technology (Yieldgard Corn Borer) in these varieties will control southwestern corn borer, sugarcane borer and European corn borer.
It will also suppress (incomplete control) corn earworm and fall armyworm, but it will not control rootworms or cutworms. Producers should refer to LSU AgCenter Pub. 2827, “Corn Hybrids for 2004”, for other agronomic qualities of these varieties.
To preserve the benefits of Bt corn, producers are required to follow a resistance management program. In Louisiana, producers are required to plant a 50 percent refuge of non-Bt corn on every farm where Bt corn is planted. This refuge should be planted within one-half mile of the Bt corn, and it should be planted at the same time. There are several configuration options in which the refuge acreage can be arranged with the Bt acreage.
First, the refuge can be planted in a separate field. Another way is to plant the refuge acreage as a block or blocks within the Bt field. These blocks of refuge corn should be large enough so that they can be easily treated with insecticide, if necessary. Also, a field can be strip planted by splitting the planter so that four or more rows of refuge corn are alternated with four or more rows of Bt corn.
The disadvantage of this configuration is that the refuge strips cannot be treated with insecticide separately. The advantage to strip planting, theoretically, is that the Bt strips may buffer the refuge strips or dilute the corn borer population in the field. Mixing Bt seed with non-Bt seed is not an allowable refuge option.
Jack Baldwin is an Extension entomologist with the LSU AgCenter.