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Growers stack deck with fungicides

You don't often get a second chance in cotton production, but west Tennessee growers did in 2002. After the worst seedling disease pressure in 30 years and a flurry of replanting lasting into June, they had a very favorable growing season the rest of the way and in the end harvested excellent yields.

There's no telling what kind of seedling disease pressure this spring will bring, but according to University of Tennessee plant pathologist Melvin Newman, it's best to stack the cards in your favor, rather than hoping you'll dodge a bullet.

Research indicates that such an approach pays.

The use of an in-furrow fungicide produced a $1,200-per-acre increase in profit over an untreated check in a 12-year study conducted at the Milan Experiment Station. “Some years, there was very little savings,” noted Newman. “But some years, there was a lot.”

Here are a few tips on seedling disease for west Tennessee growers:

Certain cultural practices can help considerably in controlling seedling disease. Turning under crop residues as early as possible is suggested. Also, crop rotation with soybeans, corn, or grass will help prevent the buildup of organisms pathogenic to cotton seedlings.

A well-prepared seedbed greatly enhances the chances of a good stand. Planting on beds has been shown to be of considerable value in some seasons by providing better drainage and warmer soil temperatures. Use certified seed or high quality seed with a germination of 80 percent or higher and plant only when soil temperatures reach 65 to 70 degrees and are expected to remain that high or higher for an extended period of time.

The use of soil fungicides should be determined by the presence and intensity of the following factors:

  • Soil temperature

    Low soil temperatures create conditions that will slow seed germination and seedling emergence, thus extending the vulnerable period for infection. Many soilborne pathogens are active at lower temperatures.

  • Five-day forecast

    Environmental conditions during the first week of planting are important to consider. A critical factor to evaluate is the combination of low soil temperatures and high soil moisture. Any condition that slows germination and growth of the seedling favors the seedling disease complex.

  • Seed quality

    Poor quality seeds germinate and emerge slower than good quality seeds under similar conditions. Slow germination and emergence extends the period seeds are vulnerable to infection.

  • Field history

    The history of each field should be evaluated to determine if it has had a stand-establishment problem, which may have been caused by factors including: soil type, drainage, soil pH, and levels of organic matter.

  • Tillage

    A no-till, or stale seed bed has a tendency to be slightly cooler and wetter than a conventional seed bed. This combination may be conducive to a carryover of disease inoculum on the past year's crop debris.

  • Seeding rate

    Recommended seeding rates have gradually declined in most parts of the Cotton Belt. This increased the importance of getting a high percentage of seeds to germinate, emerge, and become established.

  • Insecticide/nematicide use

    Experience shows that the use of a soil fungicide can be a “safening” factory when certain soil-applied insecticides/nematicides are used.

  • Soil moisture

    When soils are saturated with moisture for prolonged periods, seeds and seedlings are adversely affected. These conditions are ideal for the growth of several soil pathogens.

  • Planting date

    A field planted prior to normal planting dates for its area will have conditions that favor greater seedling disease pressure.

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