A Future for Broad Spectrum Weed Control?
It’s great to have Clearfield sunflower hybrids – tolerant to the imazamox herbicide, Beyond – available now, with Express (tribenuron)-tolerant sunflower hybrids expected within another year or two. But wouldn’t it be interesting to have hybrids tolerant to both herbicides, and maybe another, for even broader spectrum post-emerge weed control?
USDA research geneticist Jerry Miller and Richard Zollinger, North Dakota State University extension weed specialist, think so. At the Northern Crop Science Lab in Fargo, N.D., Miller and Zollinger are experimenting with creating hybrids that could be cross tolerant to imazamox, tribenuron, and thifensulfuron (Harmony GT, formerly Pinnacle).
“The idea is that the sunflower grower some day could look at what weeds are becoming a problem, then determine what herbicide he needs to apply,” says Miller, who also had a role in developing imazamox-tolerant sunflower hybrids.
Whether Miller’s and Zollinger’s research is commercially feasible is far from being determined. In presenting an overview of the research at the NSA’s annual Sunflower Research Forum, held earlier this year in Fargo, Miller points out that their first year of research on the project concentrated primarily on determining if breeding cross resistance to more than one of the herbicides is even possible.
Initial experiments are encouraging, and Miller and Zollinger plan to conduct more tests this summer. They are using classical means of cross breeding, not genetic engineering, the same as how NuSun and imazamox-resistant hybrids were developed.
The NSA’s Sunflower Research Forum features reports and summaries of research funded in part by the National Sunflower Association. Other notes from the forum:
Beyond, Express poor on ALS resistant weeds – Curtis Thompson, crops specialist, Southwest Research Extension Center, Garden City, Kans., summarized research which showed that while herbicides used on Clearfield and Express tolerant sunflower exhibit good weed control of a number of weeds, with good crop safety, both did not exhibit good control of ALS resistant weeds. According to the International Survey of Herbicide Resistant Weeds (http://www.weedscience.org), ALS resistant weeds reported in various locations and crop situations in the U.S. include kochia, palmer amaranth, redroot pigweed, common waterhemp, common ragweed, and wild oats. Thus manage the chemistries accordingly, alternating herbicides with different modes of action. Also, where applicable, use sequential or tank-mix partner herbicides with multiple modes-of-action on target weed species in the sunflower crop and in rotational crops.
Foliar fungicides for Sclerotinia – Khalid Rashid, research scientist, Agriculture/Agri-Food Canada, Morden, Man., has been analyzing several fungicides for their effectiveness in controlling Sclerotinia in sunflower. Results from one year of data show that one product from BASF, Endura, experimentally named BAS 510, was effective in reducing the incidence of head rot. BAS 510 also has activity on Alternaria, Cercospora, and Septoria leaf spot, powdery mildew, and rust. Another BASF product, experimentally called BAS 500 (Headline), has demonstrated activity on Sclerotinia, phomopsis, and rust. The products will be evaluated in the field again in 2004, and at least one of the products may be labeled and commercially available in 2005.
Strategically irrigating sunflower – Craig Alford and Stephen Miller, crop scientists at the University of Wyoming, have been conducting research on irrigation timing of sunflower for the past three years. They compared sunflower watered every 1) seven days (starting five to six weeks after planting, ending post-bloom); 2) every 14 days; 3) every 21 days; 4) watering just at early bud (R-1) or early bud; 5) watering at early bud (R-1) and again at seed fill (R-6); and 6) unwatered check. Each watering provided about two inches of water. Not surprisingly, the sunflower watered every seven days yielded best, but the sunflower watered at early bud and at seed fill yielded similar to that of sunflower watered every 14 days. They also found little difference in yield between sunflower with a plant population of 20,000, and a 30,000-plant population. There was a slight increase in oil with the higher population.
Economics of Cruiser seed treatment – According to results of eight trial locations last year in the Dakotas, sunflower seed (SF187 from Mycogen Seeds) treated with Cruiser™ yielded 96 lbs/ac or about 5% more than the untreated check. Bruce Due, area agronomist with Mycogen, says the sunflower plots treated with Cruiser clearly had an advantage over the untreated checks in control of early-season insects. The treated sunflower also had better plant stand and vigor, blooming several days earlier then the untreated.
Average yield over the eight plots planted to Cruiser-treated sunflower seed was 1,914 lbs/acre, while the average yield for untreated plots was 1,818 lbs. Assuming a price of $12/cwt and 40% oil, the Cruiser-treated sunflower had an $11.52/ac advantage in return over the untreated plots.
Due says estimating the economic return of a Cruiser seed treatment can vary, since cost is determined by the number of treated seeds planted per acre. However, assuming a treatment cost of about 27.5 cents per 1,000 seeds, one can estimate the economic return by comparing plant population with expected return from (price and oil). Thus, a grower would need 47 lbs/ac in extra yield to breakeven with a sunflower crop planted at 20,000 plants/ac, with a return assuming $11/cwt and 43% oil (see table).
Cruiser provides systemic early-season protection in both germinating seed and young plants from damage and stand loss caused by wireworm, pale striped flea beetle, sunflower beetle, and other secondary soil pests in sunflower. The product is compatible with registered seed treatment fungicides such as Apron® XL and Maxim 4FS to help control seedling diseases. Analysis indicates the product has a negligible effect on seed germination (see table). See complete article on Cruiser online at www.sunflowernsa.com. Click on the link “Sunflower Magazine” then “View Archives” and then “insects.”
More detailed reports and proceedings from the 2004 Sunflower Research Forum can be found online at www.sunflowernsa.com. Click on the “Research” link. —Tracy Sayler
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