Impact of Cotton Genetics and Nematicides on Reniform Nematode Populations and Yield

Rotylenchulus reniformis, the reniform nematode, is an increasingly important crop pest in Gossypium hirsutum, cotton. Cotton yields have suffered due to the increasing prevalence of this plant-parasitic nematode throughout the United States Cotton Belt. Two field trials were conducted at Damon, College Station, Wall, and Lubbock, Texas to evaluate the efficacy of genetic resistance and nematicides against reniform nematodes in cotton. Cotton cultivars in the genetic resistance trial included Meloidogyne incognita (southern root-knot nematode) and reniform nematode resistant genes and a nematodesusceptible check, each with and without an application of fluopyram (199 g ha⁻¹) and prothioconazole (199 g ha⁻¹). The nematicide trial tested three different pesticide products. A granular in-furrow application of aldicarb 15G, a liquid in-furrow combination of fluopyram and prothioconazole, foliar-applied oxamyl and all applicable combinations of these treatments were applied to two cotton cultivars with differing genetic resistance. In 2019, the reniform nematode resistant (REN) cultivar (PHY 443 W3FE) had 26% greater lint yields than all other cultivars across the Wall and College Station sites. At Damon in 2019, PHY 443 W3FE was among the highest yielding cultivars, but was similar to some of the root-knot nematode resistant (RKN) cultivars. REN cultivars PHY 443 W3FE and PHY 332 W3FE had the highest yields among all locations in 2020. Cultivar only impacted post-harvest nematode populations in 2020. PHY 332 W3FE and DP 18R628NR B3XF (RKN) reduced reniform nematode populations by 45% compared to DP 1747NR B2XF (RKN) (P = 0.001). In the nematicide study, yield, nematode populations, and economic return, were not impacted by the nematicide treatments or cultivar at Damon in 2019 (P > 0.05). In all other site-years combined, the combination of aldicarb and oxamyl increased yield by 14% compared to the untreated check (P = 0.0048). Aldicarb application increased partial net return $245.37 ha⁻¹ (P = 0.02) over the combination of [fluopyram and prothioconazole] and oxamyl (which was both expensive and ineffective). However, none of the nematicide treatments resulted in a net economic gain or loss compared to the untreated check. The findings of this study indicate genetic resistance is a more effective tool than nematicide applications to mitigate negative impacts of reniform nematodes in cotton