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April 5, 1999 Crop Protection Selected Articles
Saving on spraying |
Saving on spraying
Cutting your herbicide rates can cut your costs, but it takes some serious spray savvyBY TOM BUTTON
The average corn grower pays $30 an acre for weed control. Soybean growers pay close to $40. Care to cut that in half?It's called reduced rate weed control and it's going mainstream, based on plot and field evidence that growers sometimes don't need as much herbicide as the labels indicate.
But there are risks associated with cutting rates, especially for growers who cut their spray rates without spending more on management. As well, companies are unlikely to honour warranties for growers who spray below label; receipts are required to prove the grower used recommended rates.
"You don't want to be guessing," says Ailsa Craig-based agronomist Steve Redmond. "If you have heavy weed pressure, or if you aren't really sure, you're probably better off sticking with a pre or spike-stage spray like Marksman with Dual or Frontier.
"If every weed looks like a pigweed to you, whether it's a lamb's-quarters or a nightshade, reducing rates isn't a good idea."
Going below label rates is also out of the question for most growers who rely on custom applicators, as they are often rushed during the post season, he says.
"The key is to identify situations where we don't put the herbicide under so much pressure," says Gabrielle Ferguson, former weed specialist for the Ontario agriculture ministry and now a private consultant. "That comes down to management."
Ferguson has spent much of the last two years working with Al Hamill, weed scientist for Agriculture and Agri-Food Canada at Harrow, on half-rate spraying on a dozen southwestern Ontario soybean fields.
In every case, the half rates of Pursuit and Basagran performed as well - and gave the same soybean yields - as the full rate. But so did the strips without any post-emerge spray, stresses Ferguson.
That doesn't mean these fields will never need in-crop spraying, however. In the last two years, soybeans were planted late, so that many annuals had germinated by the time the burndown went down. In years with earlier planting, more might come up post planting.
"The message is, walk your fields," Ferguson says. "If you're in reduced tillage and you use a non-selective burndown, you may not need anything else."
It's also smart to learn more about herbicides, Ferguson adds. The label rate is the amount needed to control all the weeds on the label. But some weeds are harder to kill than others. A half-rate of Pursuit, for instance, gives excellent control of emerging pigweed. If the field has two-leaf lamb's-quarters, it will need every drop of the full label rate.
Getting information on weed-by-weed control rates will take a visit from one a product rep to work through the reams of data.
Cyanamid tried unsuccessfully to get federal approval for different rates on its Pursuit label, says tech services manager Scott MacDonald: "It may just have been too novel. They had questions about its validity and usefulness."
MacDonald opposes below-label rates, despite the fact that lower rates could allow Cyanamid to sell more product. Having worked with Pursuit for 15 years, he says the product was tested at rates from 50 mls per acre to a much as 350 grams before 125 ml was determined to be the bare minimum needed for consistent control.
"Lower rates are too inconsistent on ragweed, lamb's-quarters and barnyard grass," competitive must-control weeds affecting large acreages, MacDonald says.
Technically, cutting spray rates below the label is illegal. Federal pesticide inspector Ross Pettigrew, however, says growers needn't worry about being hunted down. "We're concerned about actions that create unsafe conditions," Pettigrew says. "I don't see how spraying less of a substance than you're allowed is unsafe."
Ferguson puts the focus on economics: "You really need to think this through. There are a lot of farms where reduced rates will be very effective."
© copyright 1999 Agricultural Publishing Company Limited.
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Your '99 post-emerge primer
Tom Button asked leading agronomists how to get the biggest bang out of your post-emergent spray buck
Post-emerge is where the action is. The hot new sprays are all post-emerge. So are the newest herbicide-resistant programs. Narrowing down the choice
Post-emerge is also user friendly. Growers can focus first on planting, then worry later about putting down their weed control. They don't have to pray for activating rains, and they can actually see their weeds before they spray.
Corn growers, however, must pick their way through a dizzying list of 80 registered post-emerge sprays. For soybean growers, there are 40.
As well, every post spray has its weaknesses and peculiarities, says Bill Deen, weed scientist at Ridgetown College. Despite company claims, every spray is weak on at least a few weeds. Some come with a serious risk of crop injury. Others are expensive, or have tight application windows.
Deen and colleague Peter Sikkema have worked out the following eight questions to help growers narrow down their post-emerge options.
1) How much does it cost?
Standard corn programs range from the low $20s to the high $30s. Soy programs can top $40. And don't forget to add in the cost of surfactants.2) Will it kill weeds that emerge after application?
Pursuit has lots of residual control. Pardner, Roundup and many others have none. In between are several sprays including the new Distinct, Viper and Reliance. Without residual, timing must be precise.3) Will it carry over?
Sprays such as Peak, Striker and Patriot are only some of the herbicides that can prevent you from rotating into crops ranging from sugar beets to vegetables.4) Will it hurt my crop?
Ultim can injure corn in hot weather. Accent is safer, but also more expensive. Herbicide-resistant programs tend to have exceptional crop safety.5) Will it control my weeds?
Every herbicide has a hole. Basagran is weak on tall pigweed. Reliance is weak on nightshade. Find out the details of weed control, including when weeds are most sensitive.6) What's the drift risk?
Some sprays are volatile. Non-selective herbicide resistant programs, such as Roundup Ready and Liberty Link, will kill any crop not protected with their genes.7) Will I get resistant weeds?
Sort the herbicides out by their group number so your herbicide program hits weeds with different modes of action.8) How wide is the application window?
Is the window wide open or narrow? Can you be sure you'll be able to spray when the herbicide must be applied?"It isn't simple," Sikkema says. "It can take a lot of effort to choose the optimum post program for your conditions, but it's worth it."
Two-thirds of Ontario's corn crop is already sprayed post-emerge, says Peter Sikkema, weed scientist at Ridgetown College. He predicts the level will keep growing. New weed killers are mainly post-emerge, and they're providing weed control that was never dreamt of a decade ago. Post-emerge corn pointers
As a first step, Sikkema recommends, split the post-emerge options into chemicals that kill grasses or broadleafs or both.
The "both" category in corn is limited to herbicide-resistant sprays. Liberty will kill broadleafs and annual grasses, plus suppress quackgrass, for $22 an acre. For an extra $5, a pound of atrazine improves control and adds some residual. Crop safety is excellent. Timing is one to eight-leaf.
Roundup Ready will kill most emerged weeds. First to break through may be buckwheat and lady's-thumb. Price is $10 plus the TUA. Supply of resistant hybrids is tight. So far, there aren't any tankmixes on the label to provide residual control, which Sikkema says may be more important in wide-row corn than in drilled soybeans.
Patriot, a pre-blend of the active ingredient in Pursuit together with atrazine, is the third herbicide-resistant package aimed at both grasses and broadleafs. It has a narrower application and must be sprayed by the four-leaf stage of the weeds. On the other hand, it's the only one of the three with effective residual control.
Corn growers can go pre-emerge or early post with material such as Dual and Frontier, Sikkema adds. To get true post-emerge grass control, there are only three choices, however. At about $15 per acre, Elim is cheapest but must also be sprayed earliest: spike to three-leaf stage. Ultim can be sprayed to the six-leaf stage, but is $22 per acre, while for $23, Accent can be sprayed to the eight-leaf stage.
Ultim and Accent offer quackgrass control. Elim doesn't. All three are weak on crabgrass and yellow foxtail. Elim may also miss late-emerging fall panicum. Sikkema likes a tankmix of Elim plus the pre-emerge Prowl. Add in Banvel and he calls it "an excellent combination that's given us very good results."
Ultim can be sprayed with Striker - sold together as Ultimax - and with a range of other broadleaf partners.
More than 90 per cent of Ontario's post acres in recent years have been sprayed with just four broadleaf products: Banvel, Marksman, atrazine and Pardner. A rush of new sprays, however, offers more choice.
For $8 to $16 per acre, Banvel gives broad-spectrum broadleaf control with some residual at the high rate. It can be weak on mustards, however, and may miss late-emerging velvetleaf. For an extra $3 per acre, Marksman adds atrazine to Banvel's active ingredient, sharpening broadleaf control, helping on grasses, and providing some residual. "For my money," Sikkema says, "Marksman is the standard; it's hard to beat." An Ultim tankmix adds more grasses.
Distinct at $10.40 an acre is a related weed killer that adds perennial broadleafs and annual grass suppression to Banvel, although there is some reduction in residual activity.
Sikkema is impressed, too, with Shotgun, a pre-blend of atrazine and 2,4-D, saying Elim plus Shotgun is proving a good choice for early-post application. Shotgun is broad-spectrum, but its 2,4-D can make corn brittle if sprayed beyond the four-leaf stage.
Pardner is effective on a wide range of broadleafs, but is made much better with an atrazine tank-mix. Sikkema likes the Pardner-plus-atrazine with Ultim combination. On its own, Pardner has no residual control, and can be tough on the crop.
Striker is also broad-spectrum: It's the best available in-crop spray for horsetail. Striker offers some residual. Lady's thumb and nightshade control can be weak.
Peak plus Banvel offers a wide spectrum of broadleaf control together with some residual. Crop safety is good, but as with Striker, watch recropping restrictions.
Other broadleaf sprays, ranging from Laddok to MCPA, are either too expensive or have been outclassed by newer chemistry, Sikkema says. "We've made tremendous progress since they were introduced."
Soy growers are spraying half the Ontario crop with post-emerge controls, but weed scientist Bill Deen sees it growing quickly as growers discover how much killing power there is in the new generation of post sprays. Post-emerge soybean pointers
Like Sikkema, Deen recommends starting by looking at grass killers and broadleaf killers, and sprays than can kill both.
Roundup Ready has revolutionized in-crop soybean spraying, offering effective control of annual grasses and most broadleafs, together with quackgrass. Label expansion this year permits spraying to full-flower, plus a two-litre rate for milkweed and nutsedge. Since Roundup has zero residual, it must be carefully timed or it may have to be repeated, Deen cautions.
Pursuit gives a combination of post-emerge and pre-emerge control of both broadleaf and grassy weeds. Basagran sharpens control of emerged broadleafs.
Non-residual grass killers include Assure, Select, Poast, Venture and Excel. Costs typically range from $13 to $26 per acre, with the high end needed for quackgrass control. Venture has a low $8-per-acre rate for volunteer corn.
Assure generally offers control equal to or better than the others. Unlike Select and Poast, it can be tankmixed with a broadleaf spray. Foxtail control may be better than Venture, although Venture is better on wirestem muhly.
While it's been several years since a new post-emergent grass killer for soys (other than Roundup) has been approved in Ontario, the list of broadleaf options is getting longer. Still, there isn't a perfect spray.
Reflex at $17 beats Basagran at $19 to $26 for pigweed and ragweed, although it may let lamb's-quarters and velvetleaf escape. Blazer at $13 to $24 is similar to Reflex. Lamb's-quarters and velvetleaf must be small. Crop injury can be a worry in hot, humid weather.
Pinnacle offers good control of lamb's-quarters, pigweed and mustard, plus other broadleaf weeds, but is weaker on nightshade, ragweed and cocklebur. At $12 per acre, the similarly priced Classic is effective on ragweed, velvetleaf and more, plus nutsedge, milkweed, sowthistle and dandelion. Classic, however, is weak on nightshade and lamb's-quarters, and can cause crop injury.
Also at $12 pre acre, Reliance is a pre-blend of Pinnacle and Classic for use on soybeans that contain the STS resistance gene to prevent injury. It offers the best of the other two chemicals, but like them is weak on nightshade. Like the others, it also needs a grass partner.
New this year is Viper, a one-pass post for the one- to six-leaf stage of weeds. It controls nightshade, pigweed and velvetleaf among other broadleaf and grassy weeds. Price is $34 per acre.
"We have a lot of strong options for post-emerge application in soybeans," Deen says. "There's much more flexibility to select the program that's best for each field...of course, that's also a challenge."
© copyright 1999 Agricultural Publishing Company Limited.
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