Efficacy, systemicity, and placement of non-fumigant nematicides for management of root-knot nematode in cucumber
Morris, Kelly Andrew
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Root-knot nematodes (RKN), Meloidogyne spp., are the most damaging plant-parasitic nematode to vegetable crops. Upon infection, RKN cause large galls to form on plant roots that inhibit the uptake of water and nutrients leading to yield decline. In addition, a RKN infection may predispose plants to secondary pathogens. Traditionally RKN have been managed by soil fumigation; however, the recent ban of methyl bromide coupled with increasingly stringent fumigant regulations has increased the interest in non-fumigant alternatives for nematode control. Fluensulfone is a non-fumigant nematicide that received EPA registration in 2014 for use in cucurbits and fruiting vegetables. Field trials conducted from 2011-2014 indicate that fluensulfone manages RKN when applied to soil before planting tomato or cucumber. A pre-plant incorporation or drip application of fluensulfone consistently managed RKN compared to an untreated control. Foliar applications of fluensulfone were evaluated on eggplant, tomato, squash, and cucumber to determine if systemic activity was present on these crops. Fluensulfone demonstrated systemic activity in tomato, but no other crop. Foliar applications of fluensulfone were phototoxic to cucumber and eggplant. A growth chamber experiment and a field trial in 2012 produced evidence that a disease complex could exist between Meloidogyne incognita and Pythium aphanidermatum on cucumber. An experiment was designed and conducted twice to evaluate this potential complex. In both trials, a significant statistical synergistic interaction occurred when pots were inoculated with both pathogens than pots inoculated with either pathogen alone (P=0.015 for trial 1 and P=0.0002 for trial 2). This synergistic interaction is the first report of a disease complex involving a plant-parasitic nematode on a cucurbit crop. The adsorption-desorption and mobility of fluensulfone was evaluated on different soils. Soil organic matter and clay content significantly contribute to fluensulfone adsorption. However, these are not the only parameters that determine soil adsorption as fluensulfone adsorbed strongly to some soils with low organic matter and clay content. Mobility of fluensulfone differed among the soils tested. Fluensulfone distributed evenly through Tifton loamy sand and Greenville sandy clay loam, but was not evenly distributed through an Arredondo sand or a Chualar sandy loam.