April's Ag Advice by April Borders It seems like you barely get your crops harvested and you have to start thinking about what you are going to plant for next year's crop. If you are planning for next year's corn crop there is one thing that you should be considering. According to SDSU Extension Entomologist Mike Catangui, there is no perfect Bt corn.
Producers are being bombarded with advertisements touting the advantages of various types of Bt corn. Farmer should keep in mind that every Bt corn currently available has limitations, Catangui said.
The following is a summary of the Bt corns currently available.
* Herculex I controls European corn borer, western bean cutworm, and black cutworm. But it does not control corn rootworm
* YieldGard Corn Borer controls European corn borer, but it does not control corn rootworm, western bean cutworm, or black cutworm.
* YieldGard Rootworm controls corn rootworm, but does not control European corn borer, western bean cutworm, or black cutworm.
* YieldGard Plus (not yet currently available as of Oct. 14) may control European corn borer and corn rootworm, but may not control western bean cutworm or black cutworm.
Catangui said some seed companies are adding seed treatments to Bt varieties to control corn rootworm, white grub, wireworm, seedcorn maggot and other soil insects but such treatments will not control black cutworm, European corn borer, or western bean cutworm. He reminds producers that they shouldn't overlook an effective, free tool that is available to them for managing insects and that is crop rotation.
Corn rootworms can be especially troublesome, according to Catangui, because they have adapted to corn-soybean rotations by what is called "extended diapause" response. This means that the eggs laid by beetles when corn was on the field do not hatch when soybeans are grown the following season. They hatch when corn is planted again after the one-year interval.
"To date, no economic populations of rootworm eggs ever have been shown to survive in the soil for more than two growing seasons," Catangui said. "Thus, rotating out of corn for at least two seasons will eliminate extended diapause rootworms in the soil."
Larvae of corn rootworms feed almost exclusively on the roots of corn. They cannot normally survive on roots of soybeans, sunflower, wheat, or alfalfa. "Remove corn from the field and the rootworm larvae will starve to death in the spring after they hatch from eggs," Catangui said.
Remember that crop rotation remains the most effective means of managing rootworms and it is free.
Another thing that producers should be on the look out for are weeds. A close check of weeds in fields this fall will give you a sneak preview of what to expect for next year and allow you to plan ahead.
SDSU Extension Weed Specialist Leon Wrage said producers should check during fall harvest or as they inspect fields before freeze-up. "It's the time to spot new weeds or other shifts that escaped this year's control. Weeds like waterhemp, velvetleaf, lambsquarter, or woolly cupgrass are easier to identify in the fall," Wrage said. "Herbicide-resistant weeds such as kochia can be another kind of shift."
One or two plants can start a bigger problem for next year. For example, a common waterhemp plant in a SDSU plot area had more that 1.7 million seeds. Velvetleaf seed can remain viable for more than 50 years in some conditions."Spotting these weeds when they first appear pays off for years ahead," said Wrage.
Watch along field edges and entry points for these weeds. Take note and be prepared for next year. If you find a plant that you can't identify, bring the sample to the Extension office and have it checked.
For more information of these topics contact the Extension Office at 677-7111.