Effects of Reduced-Risk Nematicides on Target and Non-Target Nematodes In Low Desert Vegetable Cropping System
Root-knot nematodes (Meloidogyne spp.) are the most economically important nematodes ranking at the top among ≈4,300 plant-parasitic nematode species described. In southern desert valleys of California, M. incognita and M. javanica are predominantly found to be infecting vegetable crops. Management of Meloidogyne spp. depends on the use of EPA Restricted-Use Pesticides or California Restricted Materials, which are high-risk nematicides. Considering the current global paradigm shift in favoring the use of environmentally conscious approaches, high-risk pesticides are either banned or their use is restricted. The use of reduced-risk nematicides with selective mode of action including fluazaindolizine (Salibro™) and fluopyram (Velum® One) would not impact non-target nematodes. The objectives of this study were to examine the effects of Salibro and Velum on Meloidogyne spp., and to determine the non-target effects on beneficial nematodes. A field experiment was conducted in a grower’s field in Coachella Valley, California during the summer of 2022. Four treatments were tested including Salibro I (one application at 31 fl oz/ac 2 weeks post-plant), Salibro II (two applications each at 15.5 fl oz/ac 2- and 6-weeks post-plant), Velum (2 applications each at 6.8 fl oz/ac 4- and 6-weeks post-plant), and untreated control. Each treatment was replicated 4 times and arranged in a randomized complete block design. Okra was directly seeded on 36-inch beds. The nematicide treatments were delivered by chemigation through single driplines buried 2-3 inches deep per bed. Soil samples were collected before chemigation and at monthly intervals thereafter for the duration of the okra crop to extract nematodes. Salibro discriminately suppressed only the target root-knot nematodes but not the non-target beneficial nematodes. Especially, Salibro II suppressed Meloidogyne population because a second application was critical to maintaining a lethal dose in the rhizosphere to control juveniles that hatch from surviving eggs in response to host root exudates. This demonstrated Salibro’s selective activity against target nematodes, which suggests its compatibility with beneficial nematodes or soil health. In contrast, Velum suppressed both target and non-target nematodes alike. The findings reiterated the selective nature of Salibro targeting only plant-parasitic nematodes. Salibro can be an important IPM option for sustainable nematode management.
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Authors: Philip Waisen
Waisen, P. Vegetable Crops Advisor, University of California Cooperative Extension, California, 92211