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Opening weed control options for sunflowers

Clearfield sunflowers may be available for the spring of 2007.

January 22, 2008  By Top Crop Manager

Add another potential crop to the Clearfield family. Clearfield sunflowers were given the go-ahead for testing in Canada in September of 2005 by the Canadian Food Inspection Agency (CFIA) and Health Canada. That is not to say Clearfield sunflowers will be available for 2007. Rather, it was one hurdle for BASF to clear along the way to commercialization.

“Whether Clearfield sunflowers is available depends on variety and herbicide registrations,” explains Robert Hornford. “There are varieties in registration trials and those have been submitted for registration, but we still need to get Minor Use registration of Solo herbicide on Clearfield sunflowers. At this point, we’re not sure if everything will fall in place in time for seeding; it is not something growers should plan on for the coming spring.”

Clearfield sunflowers would bring an improved herbicide package to sunflower growers. Currently, registered post-emergence grassy weed herbicides include Centurion, Select, Poast Ultra and Venture.


Eptam also gives post-emergence grassy weed control, along with a few broadleaf weeds. Pre-emergence trifluralin and Edge provide a broader spectrum grassy and broadleaf weed control, but these products must be incorporated, a practice that is not compatible with reduced till, narrow row cropping systems.

Assert is registered for in-crop broadleaf weed control, as is Muster Toss-N-Go through a Minor Use registration.

Solo herbicide, on the other hand, provides grassy and broadleaf weed control. The grassy weed spectrum includes wild oats, green foxtail and volunteer wheat (non-Clearfield) and barley, and barnyard grass. In the broadleaf category, weeds controlled include cow cockle, green smartweed, lamb’s quarters, redroot pigweed, shepherd’s purse, stinkweed, wild mustard and non-Clearfield volunteer canola. Solo also suppresses cleavers, kochia and wild buckwheat.

“Right now the main issues with sunflowers are weed control and white mould. The Clearfield technology can help with the weed control issue,” explains Hornford.

Varieties submitted for approval
Brian Jack, farm production advisor with Manitoba Agriculture, Food and Rural Initiatives (MAFRI) at Altona, is the chair of the Manitoba Regional Sunflower Performance Tests. He says the committee recently recommended several Clearfield sunflower varieties to CFIA for registration approval. These varieties include two oilseed hybrids from Seeds 2000, Viper and X9765, and a Mycogen seed variety called 8N386CL. One confectionary type, Jaguar from Seeds 2000, was also recommended.

“These varieties received a one year interim registration recommendation from the committee,” explains Jack.

“We have requested approval from CFIA for the sale of these varieties, but it is hard to say if this approval, as well as the approval from PMRA for the herbicide will come through in time for spring.”

The Manitoba trials only included one year of performance data, conducted in 2006. In the oilseed trials, the mean yield for the two checks (hybrids 6111 and 63M52) was 3602kg/ha. Viper had an average yield of 2812kg/ha, X9765 at 2540 and 8N386CL at 2716. (Multiply kg/ha by 0.89 to get lb/ac).

In the confectionary category, the average yield for Jaguar was 2983kg/ha, compared to two different mean yields in the trials. The mean yield for the hybrids 6946 and 9338 was 3162kg/ha, and was 3110kg/ha for hybrids 6946 and IS8048.

Currently, these Clearfield sunflower varieties are being marketed across the border in the US. Sunflower growers are advised to contact their seed suppliers to line up seed supplies in order to try out these Clearfield hybrids on their own farm, should they become registered. “The US is several years ahead of us in the use of the Clearfield technology. Growers there have had good experience with it,” says Hornford.
Hornford says that even with Clearfield technology, some growers, especially those in row cropping situations, may still choose to use pre-emergence herbicides, particularly if they have kochia. Edge controls kochia, while Solo provides suppression. He also says that Group 2 kochia resistance must be acknowledged when using Solo, as these resistant bio-types would not be controlled by Solo.

“Clearfield sunflowers will probably appeal the most to those farmers who are in a narrow row seeding situation and who don’t have access to row crop equipment. They are the ones most likely to try the technology, since they generally don’t use pre-emergence herbicides,” says Hornford. For row croppers, Hornford also sees a fit, but it depends on the weed spectrum and whether they want to continue with the pre-emergence approach. n


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