For more than 100 years, cotton root rot (CRR) has limited cotton yields and lowered quality across the states of Texas, New Mexico and Arizona.
“Over the last five-year period, we estimate Texas cotton farmers have lost an average of $29 million a year in revenue from lost cotton lint and cottonseed to CRR,” says Dr. Bob Nichols, senior director of agricultural research for Cotton Incorporated.
Not only does CRR kill cotton in patches and thereby lowers cotton yields, but plants that are affected late in the production season may develop hardlock. Such late-season infection leads to a reduction in fiber quality, which can lead to additional grade discounts because cotton’s lint picks up bark from dead stalks after CRR has taken its toll on the plant.
“Both grass and bark cause significant discounts because to a gin and/or yarn mill, they both behave like the cotton fiber – the equipment can’t discriminate between the two,” explains David Clapp, Director of Fiber Proces-sing for Cotton Incorporated.
CRR is a persistent soil-borne fungus. Control options were few and far between over the past 100 years, and all efforts have met with very limited success – until now. On Feb. 2, 2012, the Environmental Protection Agency granted a Section 18 for flutriafol, commercially sold by Cheminova as the fungicide Topguard.
Cotton Incorporated’s core research budget and the producer committee steering the Texas State Support Program have funded root rot research projects since 2005. In the course of this research, Tom Isakeit and Rick Minzenmayer with the Texas AgriLife Extension Service – part of the Texas A&M University System – identified flutriafol as an effective fungicide against root rot.
“Topguard was originally brought into the United States as a fungicide for use against soybean rust,” says Nichols. Based on field data from Texas AgriLife Extension Service and health environment safety data from Cheminova, the Texas Department of Agriculture petitioned the Environ-mental Protection Agency (EPA) for an exemption from full registration to use flutriafol in the counties where CRR was observed.
The label for Topguard calls for 16 ounces to 32 ounces of formulated product to be applied in a five-inch T-band at planting.
In support of this effort and to estimate the economic impact of the disease, Gaylon Morgan, Texas AgriLife Extension cotton specialist, conducted a survey of county and IPM agents to determine the percent of infestation of fields and counties affected, as well as the economic impact of CRR on cotton yields at the county level.
Based on the survey responses, CRR is present in both irrigated and non-irrigated fields in South, Central and East Texas.
“The total cotton production area represented in the survey was 1.93 million harvested acres over a five-year average,” says Morgan.
Of the 1.27 million non-irrigated acres covered by the survey responses, an average of more than 21 percent was reported to have CRR, with the range of incidence going from 0 percent to 90 percent.
For irrigated acres, an average of more than 19 percent of the 0.66 million acres was reported to have CRR with the same 0 percent to 90 percent range of incidence.
“CRR is estimated to occur on more than 40 percent of the acres in several counties of the Southern Rolling Plains where the CRR incidence is estimated to be more than 80 percent of the combined irrigated/non-irrigated acres,” says Morgan.
“The funding from Cotton Incor-porated really gave this entire project the critical mass that led us to much more expeditiously bringing this product to cotton because we were able to expand the locations of our trials,” concludes Isakeit.
The Cotton Board, which administers Cotton Incorporated’s Research and Promotion Program, contributed information for this report.