A long period of cold, wet weather this planting season created what the University of Tennessee plant pathologist described as “the worst year for seedling disease I’ve seen in 28 years of research.”
It was a year when a $15 or less in-furrow fungicide produced dramatic results in Newman’s seedling disease research plots and on farms in west Tennessee. For the most part, cotton plots treated with an in-furrow fungicide came up to a viable stand. Plots with seed or hopper-box treatments only, didn’t.
Yield losses from replanting, planting late or damage from seedling disease in the north Delta could be significant when the dust from harvest settles this fall, according to Newman, who planted the plots on April 19-20.
While a longer season could help the 2002 cotton crop regain some of its lost yield potential, cotton plants permanently damaged by seedling disease often cannot support an average boll load, he added.
Newman also noted that seed and hopper box treatments can provide a cotton seedling with protection against disease. “But it’s not enough in bad weather or where you don’t follow good management practices.”
Newman stressed that “you can’t throw a fungicide at bad management practices. You’ve got to get it right the first time.”
Here are 10 things to consider for good seedling disease control:
- Use high quality seed. Newman’s tests indicated that variety and seed quality can play a big role in the effectiveness of fungicide seed treatments. You should also know the cold germination test score of the seed you’re planting. Locate the lot number on the seed bag, then call the seed company for cold test information.
- Land selection. Make sure land is well-drained.
- Tillage system. No-till’s firm seedbed is good for seed and you can get in the field quicker. But it could be colder and you may need to plant slower.
- Planting depth. Set at 1 inch or less.
- In-furrow fungicides. West Tennessee cotton growers use a point system developed by the University of Tennessee to determine when you should use an in-furrow fungicide. Environmental conditions should also tell you whether you need a product for both Pythium and Rhizoctonia. When weather warms up, consider going with a Rhizoctonia-only product.
- Seeding rate. Growers looking to cut costs are lowering seedling rates on Bt and herbicide-resistant varieties. This makes disease control all the more important.
- Check your fertility. Low potassium and low pH can lead to more seedling disease.
- Soil temperature. Before you plant, make sure conditions are warming up, i.e., a 5-day forecast for a warming trend.
- Protect plants on fields with a history of seedling disease. And remember, if you are replanting into a field where you just lost a stand due to seedling disease, chances are the disease is present in the soil. Take extra precautions to make sure you don’t have to replant for a third time.
- Weed control. With seedling disease and replanting comes variance in height of plants. In this situation, post-directed sprays have to be timed to the smallest cotton plant, meaning weeds have more time to grow and compete with larger cotton for nutrients. This also creates timing problems with Pix and defoliation.