Al Wrather recommends a “six-pack” of procedures for managing seedling disease, and it doesn't involve a trip to the nearest package store. The professor of plant pathology at the University of Missouri, Delta Center in Portageville, suggests:
- Plant only when soil temperature at the 4-inch depth is warm, about 65 degrees. Watch the weather. “If it's cool in the morning, if it's supposed to warm up that afternoon and there are five to seven days of warm weather ahead, you can start planting. This is especially helpful for growers who have a lot of territory to cover.”
- Plant only high quality seed. “Look at the warm germination results on the bag. But also ask the dealer for the results of the cold germination tests. Those results are not normally on the bag label, but they are available. Anything above an 80-percent warm germ and a 50-percent cold germ is considered quality seed.
- Plant in fertile soil. Make sure that the soil pH and phosphate and potash levels are adequate for good plant growth.
- Plant on high beds. “A high bed helps drainage. It also enhances soil temperature since dry soil warms up more quickly,” Wrather said. “Make sure that field drainage is adequate to eliminate excess pools of water. And break up hardpans to enhance internal drainage.”
- When planting no-till, equip your planter to move trash away from the row so the sun can warm the soil around the seed faster. Residue on the soil surface blocks solar radiation.
- Use an in-furrow fungicide when cotton is planted early in the season on poorly drained fields or in clay soils and in fields where seedling diseases have been a problem in previous years.
Wrather added that fields where seedling disease generally does not occur have some common characteristics. “Drainage is a key. Fields that have soils which allow good internal drainage and are precision graded so they have excellent surface drainage have fewer problems.
“Organisms that cause seedling diseases will do more damage when the soil is moist, or soggy,” he explained. “On many fields, seedling disease problems are rare when the soil is dry and cold. The problems will be somewhat minor when the soil is warm but wet. But when it's cold and wet, you get the problems. Most people are planting early these days into those types of conditions. So having the drainage helps.”
Yield losses due to seedling disease in Missouri have been on the decline in recent years, according to Wrather. “One reason is that our cotton acreage in heavy clay soils is declining. Growers are beginning to learn that that type of ground is best suited for rice and soybeans. Cotton is being planted on soils with higher sand content and that are precision-graded.”
The Delta Center conducts annual evaluations to determine how products and practices fight seedling disease. “In our tests, hopper-box treatments are seldom if ever are effective on seedling disease. So use an in-furrow fungicide.”
In southeast Missouri, most seedling disease problems are due to the Rhizoctonia fungus, according to Wrather. “We have a few areas in the very northern part of the cotton-growing region of Missouri where Pythium can be problem.”