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Dynasty Seed Treatment Adjusted

Friday, December 15, 2006
filed under: Disease

Syngenta recently announced a milligram per seed rate for the Dynasty® fungicide component of the company’s CruiserMaxx™ sunflower seed treatment, which will result in more uniform treatment coverage across seed size.

Measuring rate in milligrams per seed can improve performance by offering consistent maximum dosing across variable sunflower seed sizes, and brings Dynasty (azoxystrobin) in-step with the other fungicides and insecticide in the combination, says Cliff Watrin, technical manager for Syngenta Seed Care.

“A per-seed application rate helps seed treaters deliver more accurate dosing and more uniform coverage,” Watrin explains. “In the past, larger seed sizes received a higher effective dose of active ingredient and smaller seed, commonly found with many oil seed hybrids, received a lower dose of active ingredient. Now when that treated seed arrives on the farm, each seed in the bag is uniformly protected, even if a grower purchases different seed sizes.”

The new rate for the Dynasty component of the CruiserMaxx sunflower combination is 0.025 mg per seed. The suggested grower price for CruiserMaxx delivered on the seed is $70 per 200,000 seeds.

CruiserMaxx is a combination of separately registered products, including Cruiser® seed treatment insecticide (still available as a stand-alone treatment) to protect seed against wireworm, sunflower beetle and flea beetle. The Apron® XL and Maxim® 4FS seed treatment fungicides available in CruiserMaxx, combined with the Dynasty component, offers protection against a broad-spectrum of fungal diseases including Pythium, Rhizoctonia, Fusarium, damping off, seedling blight and suppression of seedling downy mildew.

Seed treated with CruiserMaxx Sunflower demonstrates better stand establishment, more vigor, faster early-season growth and higher yield potential, notes Watrin, and because CruiserMaxx Sunflower is applied by seed companies, growers don’t have to handle product or make hopper box treatments.

Three conditions needed for DM outbreak

Downy mildew has generally been a seedling disease found in the northern producing region, although it was not a significant problem this year. While the pathogen has been found in soils all the way to Texas, the spring weather is generally not conducive for the disease in the drier and warmer southern region.

As with most crop diseases, downy mildew needs three conditions to be met for a disease outbreak to occur:

1) the presence of a crop host;

2) a pathogen strain or strains specific to the crop host; and

3) the right environment for infection to proliferate – if there is enough soil moisture for seeds to germinate, but not excessive rain, seedlings will escape infection even if the DM fungus is present.

The occurrence and severity of systemic DM infection is dependent upon water-logged soils occurring soon after planting, which facilitates mildew spore movement through the soil and subsequent root infection.

USDA-ARS plant pathologist Tom Gulya notes that while a seed treatment like CruiserMaxx which includes the fungicide Dynasty will suppress downy mildew, the surefire way to control this disease is to plant a hybrid that is genetically resistant to downy mildew, and a number of DM resistant hybrids are now available on the market.

While there are several DM races or strains in the U.S., most of the genetically resistant commercial hybrids derive their resistance from USDA lines which have proven resistant to all known DM strains for the last 20 years. A combination of a genetically resistant hybrid plus CruiserMaxx, says Gulya, will offer broad protection against downy mildew, other seedling diseases and insects. – Tracy Sayler

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