Early, but maybe not often, describes an ideal program for weed control in corn.
“Early-season control is the key,” says Paul Baumann, Texas Extension weed specialist.
“We have a number of good herbicides and techniques available to control weeds in corn,” Baumann said during the Stiles Farm Field day earlier this summer.
The annual field day, near Thrall, features production research and demonstrations for corn, cotton and other crops important to the Texas Blacklands.
“In corn, we have to keep the crop from having to compete with weeds early,” Baumann said. “Week one through twelve is a critical period. If we have a significant weed population at five to six weeks we're already badly hurt. We can come in with Roundup to get weeds such as Johnsongrass or pigweed but by then we've already delayed the crop and hurt harvest potential.”
Baumann recommends growers “control weeds early after planting. In fact, we can band pre-emergence herbicides at planting. That's a big insurance policy since weather may prevent growers from getting back in time to use a post-emergence material effectively.”
He says an early pre-emergence treatment with a reduced rate of Dual II Magnum, atrazine or similar products will help to hold weed infestations in check for a while, then a clean-up treatment with any of the appropriate postemergence herbicides will finish the job. He says that reducing rates may reduce weed control.
“If we use a half-rate that does not mean we get good control for half as long as with a full rate. We will get reduced control and will see that right off the bat. Still, that reduced rate will take the edge off early season competition and may push 70 percent control.”
Baumann says farmers have some new materials to look forward to in the near future.
“We looked at Callisto from Syngenta as an experimental product for several years before it came on the market. We recommend it for postemergence broadleaf weed control, although it has some soil residual activity.”
Cinch is a new metolachlor product from DuPont and with their product Steadfast makes a nice pre- and post-emerge program. Syngenta also has Expert, containing the same active ingredients as in Touchdown, Dual II and Aatrex, providing knockdown and residual control of weeds and grasses. Bayer's Equip, also a postemergence product, also looks good on broadleaf weeds and grasses, Baumann said.
He said options for sorghum are more limited. “Sorghum always gets the short end of the stick with herbicides,” he said.
He mentioned Aim from FMC for morningglory control. “It's a good burndown product and the earlier it's used the better. It has no residual activity.” Roundup also may be used through a hooded sprayer between the rows after sorghum is 12 inches tall. But keep the spray or mist from Roundup off the sorghum.”
Baumann said he's also looking at Liberty applied with a hooded sprayer. “It's a broad spectrum product with no residual activity. We've seen minor injury to sorghum but there is little translocation so we see only slight leaf burn and no injury inside the plant. We're still not certain of label support.”