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Thursday, April 1, 1999
filed under: Weeds

Some refer to common cocklebur as "nature's Velcro." Cocklebur might also be called the "hitchhiker of weeds," with prickly, football-shaped burs that seem to attach to almost anything. This weed can also be troublesome for confection sunflower producers and


"No one wants to chomp down onto a cocklebur when eating sunflower seeds," affirms Tim Petry, confection field production manager for Dahlgren and Company, Crookston, Minn.

Petry says cocklebur and Sclerotinia are two of the most significant foreign material problems for confection sunflower processors. "That's because they're hardest to separate. Sclerotinia comes in every shape, form and weight imaginable. Some can be easy to remove, but some are exactly the same size and shape of a sunflower seed," he explains. "Same for cocklebur. Larger cocklebur can be removed, but a good percentage are the same size as sunflower."

Cocklebur (which, incidentally, is a member of the same botanical family as sunflower) has not been a major problem in confection sunflower in recent years, Petry says. Cocklebur that does infest confection sunflower shipped from the farm is classified as foreign material and is

included in dockage. Foreign material including cocklebur can result in price discounts, and in some cases, may devalue food-grade confection sunflower to birdseed - resulting in a substantial market discount.

Processors commonly clean cocklebur from confection sunflower using a "deburring machine" - a revolving barrel or drum to which carpet is attached. As the sunflower seeds are moved by a conveyor over the deburring machine, cocklebur seeds become stuck to the carpet on the drum. The burs collect on the machine until they are automatically scrapped off, in preparation for the next batch of sunflower to be cleaned.

Some deburring machines that are more technically advanced are entering the market. They electronically detect the presence of cocklebur seeds and use a blast of air to remove cockleburs from the product stream.

From the processor's standpoint, cocklebur seed can be removed during cleaning. But it's always better to fight the battle in the field, and not in the processing plant," says Steve Edwardson, director of research and development, Minn-Dak Growers Ltd., Grand Forks, N.D.

Cocklebur plants typically grow short enough so that they are not harvested with the sunflower seed. The exception is with all-crop headers, says Edwardson. When the header is cutting closer to the ground, there is a greater potential for cocklebur seeds to be collected

during harvest. "Those who use traditional sunflower pans and a sickle bar don't seem to have as much of a problem, because the header is operated high enough to avoid the cocklebur," he observes.

Petry and other processors agree that the use of all-crop headers and cutting low to pick up hanging or downed sunflower heads increases the potential for cocklebur infestations. John Donnelly, vice president of trading and purchasing for Red River Commodities, Fargo, N.D., suggests that growers raise the header height of their combines if they come across a patch of cocklebur in a field at harvest- hopefully while still taking in the sunflower heads. If there's a real problem spot, he suggests keeping that load of sunflower separate from the rest of the crop from the field. Don't blend it in with the rest of the crop if there's a lot of cocklebur, Donnelly states.

Tolna, N.D., farmer Myron Halvorson says cocklebur has been an occasional problem in his confection sunflower crops over the years. When it is, he borrows a cleaner from a grain shipper he knows to remove the cockleburs before his confection 'flowers go to market. He also tries not to plant confection sunflower where cocklebur is a problem.

"We can get a pretty decent contract for confectionery sunflower," Halvorson remarks. "And with farming the way it is, we're putting sunflower on as much ground as we can. But then you end up with closer rotations and less time to clean up ground."

The potential for cocklebur and other weed problems isn't helped by the fact that there are so few chemical control options. "We've got some big holes for weed control in sunflower," says Richard Zollinger, extension weed specialist with North Dakota State University. "Not only cocklebur, but absinth wormwood, perennial sow-thistle, Canada thistle, common ragweed, wild buckwheat and velvetleaf in the High Plains. Even our kochia control is erratic. That's a good list of weeds for which there are few options."

Trifluralin, Sonalan and Prowl - grass herbicides that offer some broadleaf weed control - are among the few chemical options available to sunflower growers for cocklebur management. Shielded-sprayer postemergence applications of Roundup can be risky, and they obviously cannot be used to control broadleaf weed problems within the sunflower

rows themselves.

Spartan is a new product that may receive a Section 18 or temporary label registration in time for use on sunflower during the 1999 growing season. Pre-emergent, residual weed control without incorporation in no-till or conventional till production systems is the product's

strength - and at rates with less carryover concern and better crop safety than other products, says Zollinger.

Spartan has better activity on small-seeded broadleaf weeds. Common weeds in North Dakota that Spartan will control include redroot pigweed, common lambsquarter, kochia, Russian thistle, nightshade, marshelder and smartweed. It also offers suppression of wild buckwheat and wild mustard and has slight activity on cocklebur.

Crop scientists are developing imazamox- (Raptor) tolerant sunflower that will help improve broadleaf weed control, says Zollinger, but that won't be available to producers for at least a few years.

Rotating sunflower with small grains will help manage cocklebur and other broadleaf weed problems. So will cultivation. For no-till producers where cultivation is not an option, Zollinger advises planting confection sunflower in their cleanest fields - and, if chemical

control is needed, applying at higher-end rates for as much control from available chemicals as possible. - Tracy Sayler

For more information on weed control and other information relating to

sunflower production, visit the National Sunflower Association's

"Producer Primer" online:

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