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The following work was initiated to determine the scope of application methodology and fumigant combinations for increasing efficacy of 1,3-dichloropropene (1,3-D) and metam sodium for management of root-knot nematodes (Meloidogyne spp.) in Florida. A series of five experiments were set up during spring and fall seasons to evaluate the potential of different fumigants, alone or in combination, in polyethylene film tomato production. The most promising chemical alternatives to methyl bromide, in terms of root-knot nematode management, were the combinations 1,3-D-chloropicrin, chloropicrin-proprietary solvent ,and 1,3-D-metam sodium. Sprayed or injected metam sodium generally provided only short-term nematode management and by harvest nematode infection was not different from the nontreated control. Drip-applied metam sodium gave good nematode management under high nematode pressure, but needs further verification to establish (i) the importance of soil moisture and temperature on treatment efficacy and (ii) whether similar management can be obtained with fewer than three drip tubes. Broadcast applications of 1,3-D showed better efficacy as compared to applications on a preformed raised bed. Fumigation did not increase tomato yields in spring when root-knot nematode pressure was low, but during fall all chemical treatments increased yields three to five-fold, as root-knot nematode was a major yield-limiting factor.
The efficacy of the nematicide fenamiphos [ethyl‐3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl) phosphoramidate] often is reduced when applied annually or biannually for extended periods to turfgrasses in Florida. This study was conducted near Gainesville, FL, on a Blichton sand (loamy, siliceous, hyperthermic Arenic Plinthic Paleaquults) to determine whether the degradation of fenamiphos was enhanced by long‐term applications to a turfgrass golf course fairway and putting green. 14C‐fenamiphos was used for determination of mineralization rates, metabolites, and mass balance. Initial mineralization of 14C‐fenamiphos in soil collected from the turfgrass site was more rapid than in soil collected from the rough (untreated). Fenamiphos sulfoxide (FSO) was the main metabolite detected, whereas fenamiphos sulfone (FSO2) was either not detected or only occasionally detected in trace amounts. Half‐life values for total toxic residues (TTR, fenamiphos + FSO + FSO2) in soil samples collected from the site were all small, ranging from 0.9 to 4.2 d, and half‐life values for TTR in soil collected after the fenamiphos application were smaller than in soil collected before the application. Total 14C recovery from 14C‐fenamiphos‐treated surface soil collected 0.7 mo after the annual application was well below 100%. Rapid initial mineralization of fenamiphos was also observed in this sample. Applications of fenamiphos to the same site for prolonged periods appear to increase the potential for enhanced degradation of TTR.
A total of 327 root samples collected from horticultural and agronomic crops, and weeds associated with these crops in Florida crop production regions, were examined. Isozyme phenotypes, esterase (EST) and malate dehydrogenase (MDH) phenotypes were used to characterise and identify the species of Meloidogyne present in these samples. At least 26 females from each sample were examined using polyacrylamide gel electrophoresis. Sixteen major bands of EST activity were found, corresponding to 12 phenotypes. A species-specific EST phenotype was consistently associated with each of the Meloidogyne spp. identified: Meloidogyne arenaria, M. floridensis, M. graminicola, M. hapla, M. incognita, M. javanica, M. mayaguensis and M. partityla. Two unique EST phenotypes, which have not been described, were found associated with three unidentified nematode populations. Five bands of MDH activity and four phenotypes were also found among the populations. During this study, new host records were determined for M. floridensis and M. mayaguensis, two recently reported Meloidogyne spp. in Florida. Plant species found as new hosts of M. floridensis were Cucumis sativus, Phaseolus sp., Solanum melongena and one weed species, Emilia sonchifolia, and the M. incognita-resistant peach rootstock 'Flordaguard'. New hosts for M. mayaguensis were Carica papaya, Capsicum annuum var. Longum, and six weed plants, including Eclipta prostrata, Fatoua villosa, Panicum sp., Poinsettia cyathophora, Solanum americanum and also one unidentified weed species belonging to the family Acanthaceae. To our knowledge, Florida is the only geographic area of North America where M. floridensis and M. mayaguensis have been detected.
Fluensulfone is a new nematicide in the flouroalkenyl chemical group. A field experiment was conducted in 2012 and 2013 to evaluate the efficacy of various application methods of fluensulfone for control of Meloidogyne spp. in cucumber (Cucumis sativus). Treatments of fluensulfone (3.0 kg a.i./ha) were applied either as preplant incorporation (PPI) or via different drip irrigation methods: drip without pulse irrigation (Drip NP), pulse irrigation 1 hr after treatment (Drip +1P), and treatment at the same time as pulse irrigation (Drip =P). The experiment had eight replications per treatment and also included a PPI treatment of oxamyl (22.5 kg a.i./ha) and a nontreated control. Compared to the control, neither the oxamyl nor the fluensulfone PPI treatments reduced root galling by Meloidogyne spp. in cucumber. Among the drip treatments, Drip NP and Drip +1P reduced root galling compared to the control. Cucumber yield was greater in all fluensulfone treatments than in the control. In a growth-chamber experiment, the systemic activity and phytotoxicity of fluensulfone were also evaluated on tomato (Solanum lycopersicum), eggplant (Solanum melongena), cucumber, and squash (Curcurbita pepo). At the seedling stage, foliage of each crop was sprayed with fluensulfone at 3, 6, and 12 g a.i./liter, oxamyl at 4.8 g a.i./liter, or water (nontreated control). Each plant was inoculated with Meloidogyne incognita juveniles 2 d after treatment. There were six replications per treatment and the experiment was conducted twice. Foliar applications of fluensulfone reduced plant vigor and dry weight of eggplant and tomato, but not cucumber or squash; application of oxamyl had no effect on the vigor or weight of any of the crops. Typically, only the highest rate of fluensulfone was phytotoxic to eggplant and tomato. Tomato was the only crop tested in which there was a reduction in the number of nematodes or galls when fluensulfone or oxamyl was applied to the foliage compared to the nontreated control. This study demonstrates that control of Meloidogyne spp. may be obtained by drip and foliar applications of fluensulfone; however, the systemic activity of fluensulfone is crop specific and there is a risk of phytotoxicity with foliar applications.
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