Plant pathologist Melvin Newman planted his seedling disease plots at the first opportunity this year. Luckily, most west Tennessee cotton producers didn’t experience such a timely planting.
The result is that west Tennessee may have avoided large losses to seedling disease in cotton in 2005, according to Newman at the University of Tennessee Experiment Station, Jackson, Tenn.
Newman planted his research plots April 18-19, and the weeks that followed were rainy and cool. His plots showed lots of disease pressure and, not surprisingly, “that an in-furrow, soil treatment is still the very best insurance against seedling disease.”
But the rainy weather that was so good for disease pressure in Newman’s plots kept west Tennessee cotton producers out of fields and pushed them into early-May planting. Then in May, “we had such warm weather you’re probably not going to see much difference between seed treatments and in-furrow fungicides in grower fields. That’s what you would expect, and that’s good.”
West Tennessee typically has significant annual losses to seedling disease, according to the Cotton Disease Council, mostly due to its northern latitudes and large percentage of no-till acreage. In 2002 and 2003, west Tennessee growers lost 20 percent and 22 percent, respectively, of their potential yield to seedling disease. In 2004, the percentage dropped to 8 percent.
The losses have not deterred west Tennessee cotton producers from a trend toward seed treatments over an in-furrow treatment to combat disease, despite research that shows a higher return for in-furrow fungicides.
Newman noted that the percentage of west Tennessee cotton producers using in-furrow fungicides has slipped from about 50 percent to about 25 percent. Meanwhile, the percentage of growers using seed treatments and overcoats has grown from about 25 percent to 50 percent.
Seed treatments have certainly taken hold here, and as Newman says, “It’s going to take more than a couple of years of disease pressure to make them put nozzles and spray tanks back on the tractors.”
The big reasons for the shift are speed and efficiency of seed treatments. “I don’t think the cost factor is keeping people from using in-furrow fungicides. It’s just the convenience of a seed treatment. Farmers really love not having the tanks on there. They can see what they’re doing, and they don’t have to fill up with chemicals and water. They just plant as fast as they can.”
Trends directly responsible for farmers wanting to plant faster include bigger farms and farmers trying to get by with less labor. “They can plant a lot faster using treated seed versus a machine with tanks for in-furrow treatments,” Newman said. “This, plus the Roundup Ready technology, no-till, bigger and better tractors, allows some producers to do everything themselves.”
In addition, “when we compare today to the 1970s and 1980s, we have more vigorous cotton and better machinery that does a better job of placing the seed in a firm, no-till seedbed.”
Of course, seed treatments have come a long way, too, “especially with the development of the strobilurin-type materials. A lot of overcoat and seed treatments are doing a good job. Definitely, times are changing. We are headed more toward seed treatments for seedling disease, nematodes, everything right on the seed.
“All the technology advances and the chemical advances also make the cost of the seed that much higher, noted Newman. “That does worry me a little bit.”
Another thing to consider is that in west Tennessee, when seedling disease is at its worst, there’s not much a farmer can do to stop it, including an in-furrow treatment. “The weather still holds the high card in seedling disease control. We can help it some with in-furrow fungicides and good seed treatments, but if the weather gets too bad, there’s not much we can do about it.”
Other factors that appear to be indirectly driving the move toward seed treatments include the introduction of longer-season varieties, which can compensate for early season stresses with a longer fruiting period.
Longer-season varieties are making a comeback, thanks to Bt cotton and boll weevil eradication, which have eliminated much of the risk to late-season insects, although there is still the risk of late-season rains.
Roundup Ready cotton has also helped the move to seed treatments — giving cotton a healthier start “by not having as much pre-emerge in the soil.”