A two-part study was initiated in 2019 to identify the most effective management tools, focusing on cotton varieties and nematicides. This is a brief summary of results from the first year at three diverse locations across the state with known reniform nematode infestations: Damon, Wall, and College Station.
The cotton varieties tested have a varying range of nematode resistance, mostly to root-knot nematode, and are shown in Table 1. These varieties were planted with, or without a nematicide, fluopyram and prothioconazole (Propulse at 13.6 oz/acre in-furrow).
At all three locations, lint yield was influenced by variety, with PHY EXP W3FE, a variety with reniform nematode resistance that is not yet on the market, had the highest ranking at all three sites (Figure 2). DP 18R628 was also a high-yielding variety at Damon and College Station. The additional application of fluopyram and prothioconazole increased yield only at the Wall location.
The second study compared 3 different nematicides, applied individually and in combination (Table 2), using two varieties.
The nematicide treatments did not affect yield and showed no partial net return at all three locations. At College Station, final reniform nematode populations in the susceptible variety were reduced by the combination of Aldicarb 15G + Oxamyl and the combination of Fluopyram and Prothioconazole + Oxamyl (mean=12), compared to other treatments and the control (mean=45). Nematicides did not affect reniform nematode populations at Damon or Wall.
The data from 2019 suggests that genetic resistance is likely a better option for reniform nematode management in cotton than nematicides. As weather conditions can influence yield loss from nematodes, these experiments will be repeated in 2020, to determine if the observed trends are consistent from year to year. The experimental lines tested in this research are not commercially available yet but do offer hope for effective reniform nematode management in the future. In the meantime, growers need to be aware of reniform nematode infestations in their fields and prevent new infestations by movement of contaminated soil on implements. Soil samples can be analyzed for nematodes at the Texas Plant Disease Diagnostic Lab in College Station (https://plantclinic.tamu.edu/).