What is in this article?:
- Research efforts solve century-old problem
- Grower responses are positive
- Aerial imagery plots root rot progression.
- New fungicide gets good reviews after first year with emergency label.
- IPM philosophy till critical with cotton production.
CHENGHAI YANG, with the USDA Agricultural Research Service, discusses he role aerial imagery may play in controlling cotton root rot in Texas.
Grower responses are positive
Grower reports from the first year of use have been positive. “They say control looked good. We have had some issues with lack of experience with the product. But responses also show that control more than made up for the cost of the fungicide. Also, we had reports that cotton strippers did not clog up during harvest. That is a valuable benefit.”
Isakeit said Texas AgriLife testing in the Lower Rio Grande Valley has not panned out in recent years because of extended drought. “Other tests in the area have shown efficacy, however. The most effective way to monitor Topguard is under conditions that are conducive to disease—wet weather.”
He reminds growers, however, that the decision on Topguard use must be made long before they know what weather will be like. Current label permits only at-planting applications.
Modifications for Topguard application this year include a narrower T-band width, as well as in-furrow application. The label says the material should have no direct contact with the seed. Also, application through irrigation is not allowed, and a 365-day plant-back restriction applies to crops except cotton, corn, peanuts or soybeans. Recommended rate is 1 to 2 pints per acre at planting.
Persistence in the soil should not be a problem at labeled rates, he said, with the caveat that using the higher rate could be problematic in a monoculture.
“We also recommend an IPM strategy,” Isakeit said. “Crop rotation is still important since fungicide resistance is possible. But resistance is likely to occur slowly if the fungicide is not constantly used.”
Monoculture production creates other problems as well. “Monoculture can lead to other problems that are much more difficult to deal with.” Root knot and reniform nematodes are possibilities that “build up in monocultures.”
Future research will include the possibility of a more concentrated liquid formulation from the manufacturer, Cheminova, and the possibility of adding application through subsurface drip irrigation to the label.
Isakeit said the things that keep him up at night now are the possibilities that things will go awry through off-label use on other crops—partly because of the soil stability of the fungicide.
Also a concern is that farmers may abandon the product if it doesn’t live up to standards—if it’s inconsistent or inefficient—issues that do not seem to be occurring in initial applications. Phytotoxicity is another concern. “The product is not perfect, and we still need to tweak it some,” he said. “But we know enough to understand what causes phytotoxicity. Seedling damage is possible if the product comes in direct contact with the seed.”
He said tests that looked at Topguard use on other plants and other diseases have not been successful. “Soilborne diseases are tougher to deal with.”
A graduate student has been looking at soil conditions as a possible predictor of root rot infection. “He’s studied electro-conductivity, texture, pH and other properties, but he has not found anything,” Isakeit said.
“We want to use an in-season plant sensor to monitor changes in leaf reflectance. But we still go back to needing a map. That’s where Yang’s efforts will pay dividends.”
“Root rot has been a destructive disease for Texas cotton growers for the past 100 years,” Yang said. “And they have had no effective control until recently.”
Isakeit said research back in the 1920s found formaldehyde to be somewhat effective in knocking back root rot infections. “But it is a nasty application,” he said.
“A lot of farmers used Topguard in 2012,” Yang added.
And, based on reports, success was noteworthy. With that start, Isakeit’s continued efforts to make the product even more efficient and Yang’s ability to plot progress of the disease, efficacy of the fungicide and target hot spots in the field, farmers may now have the solution that has eluded them for the past 100 years.