Novel nematicides to manage root-knot nematodes in California sweetpotatoes, 2016

摘要

Three novel development nematicides were evaluated in a sweetpotato field trial in California. Rootless sweetpotato stem cuttings ("slips") were planted on 18 May in a root-knot nematode (RKN, Meloidogyne incognita)-infested site on the UC South CoastR&E Center, Irvine, CA (sandy loam, 17% clay, 63% sand, 20% silt, 0.2% OM, pH 7.9). The cultivar used was 'Beauregard', a commercially grown orange-flesh selection that is very susceptible to root knot nematodes. The experiment was designed as a randomized complete block with 5 replications. Plots consisted of 6 m long sections of 1.5 m wide (center to center) beds. Along the beds, plots were seperated by 1 m buffers. In each plot, two rows 50 cm apart of sweetpotato were planted (40 cm plant spacing)resulting in 30 plants per plot. Watering was through drip tubing (drip emitters 2 L/hr., 1 ft. spacing) over the top of the center of the bed. The test products were compared to metam-sodium and an untreated control. Second-stage juvenile root-knot nematodes (J2 RKN) were extracted from soil collected from each plot using Baermann funnels and counted. The pre-treatment average J2 RKN population density was 29 per 100 g soil and not significantly different (P>0.05) among the treatments. Vapam was applied 21 dbp, Nimitz 7 dbp Velum and Salibro 1 dbp. The granular formulation of Salibro was evenly spread over the top of the bed as a 1 m wide band before incorporation by rototilling to 8-10 cm depth. All other products were suspended in 7.5 L water per plot and applied with a watering as a 1 m wide band before incorporation by rototilling to 8-10 cm depth. An additional 30 L wate was then sprinkled over each plot. A second Salibro application was made 21 dap by suspending the product in 7.5 L water per plot and sprinkling in a 1-m-wide band over the top of the bed, followed by an additional 30 L water over the rop of the bed. The temperature at 0.15-m soil depth was 18.6°C on 22 Apr (soil sampling, Vapam application), 20.0 °C on 11 May (Nimitz application) 19.7°C on 17 May (Velum and Salibro application), 20.6°C on 18 May (planting), and 22.6°C on 6 Jun (2nd Salibro application). The trial was fertigated with a total of 617 kg per ha 20-20-20 over 6 applications. At harvest, sweetpotato storage roots in each plot were counted, weighed and divided into three classes: marketable, non-marketable due to RKN damage (surface bumps, cracking), and non-marketable due to other defects (shape, size). Ten roots were randomly collected from each plot and nematode eggs were extracted from these roots and counted. Percentage data were arcsine (sqrt(x/10)) and nematode count data were log10(x+1) transformed before statistica analysis (ANOVA). Means separation was performed by Fisher's protected LSD test at .P=0.05.