Effect of different rates, application timing, and combination of non-fumigant nematicides in control of Meloidogyne incognita in watermelon in plasticulture

The use of plasticulture systems, which consist of raised beds, plastic mulch, and drip irrigation for watermelon production, has increased in the Southern United States in recent decades. The root-knot nematode (RKN), Meloidogyne incognita, is a significant pathogen of watermelon production in plasticulture systems and can cause varying levels of yield loss depending on the nematode population density if not properly controlled. Few new non-fumigant nematicides (fluensulfone, fluazaindolizine, and fluopyram) have emerged in the last decade to help manage RKNs. A two-year field study was conducted to examine the impact of different rates, application timing (i.e., days before transplanting [DBT], at transplanting [AT], and days after transplanting [DAT]), and combination of these new nematicides and an older one (oxamyl) in control of RKN in watermelon cv. ‘Fascination’. The nematicide treatments, except for a single-time application of oxamyl in 2019 and 2020, significantly reduced root galling compared to the untreated check. Similarly, all treatments, except a single application of oxamyl in 2020, resulted in a lower soil population level of M. incognita than the untreated check. All nematicide treatments, except a single application of fluensulfone and a two-time application of fluopyram at a half-recommended rate, increased fruit yields when compared to the untreated check. Overall, the drip application of new chemistries, known as 3-F nematicides, shows to be a useful option for RKN management in watermelon. At planting application of fluazaindolizine or fluopyram and two-time applications of oxamyl based on the manufacturer's recommended rate show potential to prevent the crop loss.