The top 10 things peanut farmers ought to take into consideration when planning a weed control program include:
- Know your weeds. Identification is critical.
- Know all control options available, chemical, mechanical and cultural.
- Know what herbicides can and cannot do.
- Yellow herbicides provide a good foundation.
- Start with a clean seedbed.
- Are additional, soil-applied herbicides needed?
- Properly timed, postemergence herbi cides are most effective when weeds are not under stress.
- Be careful of potential crop injury from herbicides. Know the product.
- Scout for unusual weeds.
- Weed control starts in the fall, espe cially for perennials. Consider a sys temic herbicide in the fall.
Those 10 observations provide the basis for a sound weed control program, said Texas A&M (and Texas Tech) Extension weed specialist Peter Dotray. Dotray offered a weed control primer to West Texas peanut growers recently at a production conference in Brownfield.
Some of the 10 are basic and Dotray didn't expand on them. But he provides a bit more detail on some of the more complex issues. He said a number of yellow herbicides, Prowl, Sonolan and Treflan, for instance, do a good job of getting peanuts off to a good start. “The key is application rate and method of incorporation,” Dotray said.
Mechanical incorporation may be the most effective, but he said some farmers in minimum or reduced tillage system are using irrigation to incorporate.
“Farmers may apply Prowl on the surface and then irrigate to incorporate,” he said. “Higher rates are usually necessary because these herbicides are not very water soluble. And the first water application after herbicide treatment is the most important.”
He recommends an initial rate of from one-half to three-fourths of an inch of water to incorporate yellow herbicides. That's better than several applications of lower water rates, he said.
Dotray said preemergence herbicides, such as Dual Magnum, might be good options for tough weeds such as yellow nutsedge. A postemergence application of Dual Magnum will reduce peanut injury, he said.
He said farmers should make certain which nutsedge (purple or yellow) they have. Herbicide selection will vary depending on the identification.
He said Valor, the newest of the soil-applied herbicides, shows good control of ivyleaf morningglory. “The soil activity following a Valor application will be four to six weeks,” he said. “The label states that valor must be applied within 48 hours after planting, and we have seen injury following delayed applications.”
A heavy rain after application could result in slower peanut emergence, he said.
He's also tested Dual Magnum, Caparol and Staple in fields simulating a cotton stand that was destroyed by hail. In 2004, Staple alone and Staple plus Caparol resulted in some crop injury and significantly reduced yield in peanuts that were tilled after cotton failure. In peanuts that were planted in cotton areas without additional tillage, no significant yield loss was observed.
“In 2003, Dual Magnum also injured peanut. We'll conduct this test again in 2005, thanks to the support of the National Peanut Board.”
Postemergence options include Cadre, Pursuit, Ultra Blazer, Basagran, Storm, 2, 4-DB, Select and Cobra.
“Cutting rates in a cotton rotation and maintaining adequate control is a common question these days,” Dotray said.
Basagran offers a good option for cocklebur and nutsedge, he said. And 2, 4-DB is a good material but Dotray cautions about drift to adjacent crops and the difficulty of proper tank and hose clean-out when 2,4-DB is used.
He said Select is a good option for grasses. “Cobra is the newest material, labeled in 2005 and is similar in mode of action to Ultra Blazer.”
Dotray said Cobra works well on a number of broadleaf weeds, including morningglory and carelessweed. Applications must be delayed until after peanuts achieve six true leaves, but weed size for most effective control is important as well. Also, growers should not apply more than 12.5 ounces at a time and no more than 25 ounces per season. Application is not allowed within 90 days of harvest and should not be applied by air.
He's looking at Aim and ET for weed control options but warns that these herbicides are not currently labeled for use in peanut. “We're not certain what the label may state, so we are looking at lots of rates and timings. Applications made 30 days after planting have caused significant injury and yield loss, he said.