For more than 100 years cotton root rot (CRR) has been limiting cotton yields and lowering quality across parts 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,” explains 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 hard-lock. 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 a yarn mill, they both behave like the cotton fiber – the equipment can’t discriminate between the two,” explains David Clapp, Director of Fiber Processing for Cotton Incorporated.

CRR is a persistent soil-borne fungus. Control options have been few and far between over the past 100 years, and all efforts have met with very limited success – until now. On February 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 grower committee steering their Texas State Support Program have been funding root rot research projects since 2005. In the course of this research, Tom Isakeit and Rick Minzenmayer, Texas AgriLife Extension Service, 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,” adds Nichols. Based on field data from the Texas AgriLife Extension Service, and health environment safety data from Cheminova, the Texas Department of Agriculture petitioned the Environmental Protection Agency (EPA) for an exemption from full registration to use flutriafol in the counties where CRR has been 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.

Economic Impact

In support of this effort and to estimate the economic impact of the disease, Gaylon Morgan, associate professor and state Extension cotton specialist, conducted a survey of county and IPM agents to determine the percent of infested fields and the counties affected, as well as the economic impact of CRR on cotton yields at the county level. Based on 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 responses, an average of over 21 percent was reported to have CRR, with the range of incidence from zero 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 zero to 90 percent range of incidence.

“CRR is estimated to occur on over 40 percent of the acres in several counties of the Southern Rolling Plains where the CRR incidence is estimated to be over 80 percent of the combined irrigated/non-irrigated acres,” adds Morgan.

“The funding from Cotton Incorporated 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,” says Isakeit.