Planting methods add layer of defense against seedling diseases

FAYETTEVILLE, Ark. – According to best estimates, some 30,000 acres of Arkansas soybeans had to be replanted in 2004 because of fungal seedling diseases, says Chris Tingle, Arkansas Extension soybean specialist.

"Each year, growers are trying to plant earlier. With Arkansas' climate, such early crops face the potential for cool, rainy weather that stimulates seed diseases."

Ongoing research is showing the effectiveness of using broad-spectrum fungicide seed treatments as a line of defense against soil borne pathogens like Pythium that attack soybean seed.

Plant pathologist John Rupe is also studying the use of varying planting methods to improve disease management. In research supported by the Arkansas Soybean Promotion Board, Rupe, Tingle and plant pathologists Rick Cartwright and Craig Rothrock are determining whether raised seedbeds offer advantages.

In test plots at research and Extension centers, treated and untreated soybean seed has been planted on both raised beds and conventional fields at varying row widths and planting dates. Both high- and low-quality seed are used with planters, drills and broadcast. In the first year of a three-year study, raised beds are showing promise.

"The advantage of raised beds is that they get the seeds above water in wet planting seasons," says Rupe. "Also, the beds are warmer, which helps provide better emergence than planting in flat ground, especially in early-planted soybeans."

Rupe has also seen some differences in the type of equipment used for planting. "The fields seeded with a planter had better stand counts than those where a drill or broadcast were used, because the planter provided better soil contact.”

Rupe is looking at nine different seed treatments used with high- and low-quality seed at three planting dates (April, May, June) and at three locations (Keiser, Stuttgart and Hope). "Four of these treatments showed significant differences in effectiveness in initial tests.”

With rising costs of seed, fuel and other inputs, replanting fields because of losses from seed diseases has a big economic impact on the state and makes the research critically important to growers, Tingle says. "The key for Arkansas producers is to determine the most productive method and what reduces risk of diseases.”

Rupe is also researching cultivar resistance to fungal diseases. "Originally, resistance was found in Archer, a Group 1 cultivar that is not adapted to Arkansas. Now we're looking at four commercial varieties adapted to Arkansas, two of which appear to have resistance. We're testing them with and without a Pythium fungicide."

Seed treatments have limited effectiveness and wear off with time. Natural resistance is always there.

"We want to see if we can identify resistance and see how effective it is," says Rupe. "We will take these to yield and see how they perform."

e-mail: [email protected]

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