Foliar insecticide treatments in bell pepper for pepper weevil control, 2020

Abstract

Land preparations for plastic mulch began on 4 February 2020 with a total of 500 lbs of 10-10-10 per acre incorporated into Tift pebbly clay loam 6 ft beds. Bell pepper plants, hybrid “Vanguard,” were transplanted into 2 rows per black plastic mulch bed on 18 August 2020 and maintained with standard cultural practices at the Lang-Rigdon Farm, Georgia Coastal Plain Experiment Station in Tifton, GA. Weekly drip irrigation occurred with 30 gal/acre early of 7-0-7 liquid fertilizer injected every biweekly. An Anthonomus eugenii-infested row of jalapeno pepper was established along the entire length of the test, and the plots were seeded with A. eugenii-infested pods in late August to ensure maximum weevil pressure. Treatment plots were laid out in a randomized complete block design with 4 replicates per treatment. Whole plant sampling began on 25 August and continued through 22 October. Four insecticide applications were made on the following days, 1, 8, 22 September, and 13 October 2020, using a volume of 53 gal/acre per treatment via a tractor-mounted tank with 5 TX-18 hollow cone nozzles per row at 60 psi with no adjuvant added. Plots were ~80 plants across 44 ft. All mature bell peppers were picked on 27 October 2020, regardless of damage. Peppers, damaged or undamaged, were ranked, with ranking prioritizing pepper weevil damage (lepidopteran damage was not ranked). Fallen pods were also collected for ranking due to severe pepper weevil damage. The total number and weight of pepper pods (Table 1) included these fallen pods. Poor fruit set limited our ability to determine pepper weevil mortality due to insecticide treatments in field tests when GLM and LSD analyses were conducted. A separate lab bioassay was conducted to rank the insecticides of this study relative to adult pepper weevil control. The insecticides evaluated were BAS 450 (06 I 100 SC), Vydate (L), Actara (25 WG), Belay (2.13 SC), Exirel (0.83 SC), Assail (30 SG), Torac (1.29 EC), and Dibrom (8 E) against a water check. The high labeled rates of insecticides were diluted to the equivalent of 100 gal/acre. That concentration was used to dip slices of pepper pods before placing the slices into test Petri dishes with 5 pepper weevil adults. The Petri dishes were left at ambient temperature (25 ± 2 °C) on a countertop for the duration of the experiment. Mortality was assessed at 24 and 72 h as the amount of dead or unresponsive weevils at these intervals. Mortality was also calculated as a percentage, that is, (the total number of insects used at the beginning − the total dead after a time period) × 100. Each treatment was replicated four times in an RCB design. Data were analyzed using GLM and LSD tests to separate means. aMeans within columns followed by the same letter are not significantly different (LSD, P < 0.05). bOriginal treatment followed by insecticide rotations. coz wt/acre. This test was heavily preinfested to test the insecticide efficacy against the pepper weevil; unfortunately, heavy infestation resulted in the loss of fruiting structures in the untreated plots. Regarding pepper yield response, the BAS 450 high rate and Vydate rotations performed the best. Dropping the first bloom application resulted in a yield as low as the check (Table 1). Despite the few available fruits, pepper weevil per damaged fruit was highest in the untreated plots (Table 2). Based on the bioassay, BAS 450 and Vydate provided the greatest mortality at 24 h (Table 3). Mortality at 72 h for Actara and Belay was similar, with intermediate response seen with Assail, Torac, and Dibrom treatments.1 aMeans within columns followed by the same letter are not significantly different (LSD, P < 0.05). bOriginal treatment followed by insecticide rotations. coz wt/acre. aMeans within columns followed by the same letter are not significantly different (LSD, P < 0.05). boz wt/acre.

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