Management of Cotton and Peanut Diseases in the Southern High Plains of Texas
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Diseases of cotton in this region that cause substantial yield losses on a yearly basis are Verticillium wilt and root-knot nematodes. Bacterial blight is capable of causing significant losses sporadically if not managed. Reniform nematode and seedling diseases can also cause losses if not managed. For peanuts, the most important disease problem is pod rot, and the hardest to control is Pythium pod rot. This project is designed to investigate strategies or assist in germplasm development that will minimize losses to these plant pathogens. A large part of the program involves evaluating commercial cotton varieties in multiple producer fields to root-knot nematodes and Verticillium wilt. A field trial is also conducted on cotton variety responses to bacterial blight. The results of these trials are made available to producers, consultants, industry, and university/extension people. In addition, a considerable amount of time is spent in screening germplasm for university cotton breeders and industry in inoculated greenhouse trials. This work provides information to cotton breeders, so that ultimately they bring forward more disease resistance in their releases.Cultural management of soil-borne diseases can have more impact than any varieties or chemicals, however they can also be the most difficult to examine in a research setting. I am fortunate to have two sites where cultural management effects can be studied on large plots over sufficient years to draw sound conclusions. At the Helms farm (infested with Verticillium dahliae), research is conducted on a 120-acre circle which includes crop rotations with cotton, sorghum, and wheat; cover crops versus none; tillage effects (conventional versus minimum); and irrigation rate. This systems trial is typically conducted for at least 4 years before changing the research focus, and involves interactions between scientists specializing in plant pathology, irrigation engineering, cropping systems, and soil nutrients. The effect of crop rotations before disease builds up was previously quantified; the focus is now on the effects of crop rotation after the pathogen is already present in the soil at adequate levels for significant disease. Irrigation rate effects on disease and its consequences for yield are also being studied. The tillage system experiment is fairly recent, and the full impact of the minimum tillage/flat ground system on disease and yield is still to be determined. Prior to 2016, there was a yield detriment to using the flat ground/minimum tillage treatment, however, in 2016, which was very conducive to disease, it appeared to reduce yield losses due to Verticillium wilt, at least in some crop rotations. Our understanding of how all the pieces of crop rotation/minimum tillage/irrigation rate combine to result in yield benefits is still evolving. It will require more years of measuring disease/yield to fully understand the impact and make appropriate recommendations. Similar work is being conducted at the AGCARES circle which is naturally infested with root-knot nematode, though only with crop rotation with cotton and wheat compared to continuous cotton, and irrigation rate. Previous work at this site has investigated crop rotation with sorghum and cotton or peanut and cotton; and also the impact of varieties that are susceptible, partially resistant, or highly resistant to root-knot nematodes..........