Residual Effect of Rimon on Plum Curculio in Highbush Blueberries, 2015

This experiment tested the residual effects of a prebloom treatment with Rimon 8.3EC on plum curculio (PC) in highbush blueberries in New Jersey. The experiment included exposure to Rimon residues on treated foliage in mid-season blueberry field var. ‘Bluecrop’ located in a commercial farm in Hammonton, New Jersey. The field was treated with Rimon 8.3EC at 30 fl oz/acre (50 gal/acre volume) before bloom on 24 Apr 2015. Applications were made via a model 2200HT Nitro (Miller Inc., St. Nazianz, WI) with 74 nozzles (nozzle model: TDXL11008-8/16), range 50–60 psi (self-adjusting Raven sprayer controller, Miller Inc.). Five PC adults were placed inside 50-cm long fabric sleeves enclosing branches of treated blueberry bushes. The fabric sleeves (Temkin International, Payson, UT) enclosed approximately 20 cm (8 inches) of terminal branch including multiple foliar buds; however, all flower/berry clusters were removed to prevent oviposition. Each week, there were a total of five sleeves, e.g., 25 PC. For three consecutive weeks, five new fabric sleeves containing five PC adults each were added to treated bushes. The dates of initial exposure were 1 May, 8 May, and 15 May 2015, to test for residues 7, 14, and 21 DAT, respectively. Additionally, fabric sleeves and PC adults placed out in previous weeks were moved to new branches each week to provide fresh foliage for PC feeding. The length of time each PC-exposed group was in the field varied such as the 7-DAT, 14-DAT, and 21-DAT groups spent 3, 2, and 1 wk in the field, respectively. Adult PC used in the experiment were collected from pheromone-baited pyramid traps (Great Lakes IPM, Vestaburg, MI) deployed from 20 Apr until 22 May 2015 on untreated organic blueberry fields located in Hammonton, New Jersey.

All branches enclosed in fabric sleeves were removed from the field on 22 May (week 4), with all PC adults collected from each sleeve and kept in separate groups. Each group of five PC was placed in ventilated 32-oz deli containers and provided with 200 green blueberry fruit (~20 clusters) for feeding and oviposition. Fruit provided to PC adults were obtained from an untreated block of the blueberry var. ‘Bluecrop’ located at the Rutgers P.E. Marucci Center in Chatsworth, New Jersey. Fruit from oviposition containers were examined five times on 26 May, 1 Jun, 4 Jun, 9 Jun, and 15 Jun, representing 4, 10, 13, 18, and 24 days after fruit was exposed to PC, respectively. On each evaluation date, all damaged fruit and surviving PC were counted. Following, the total number of berries was brought back to 200 before the adults were released back into the container. Collected berries were placed on clean moist playsand in 5.5-oz cups (Dixie, Atlanta, GA) and capped with ventilated lids. Cups were kept for at least 10 days in a 25°C incubator on a 15:9 (L:D) h cycle to allow any larvae to develop and emerge. To check for PC larvae, the sand was washed through a fine sieve and the remaining berries were dissected on 25 Jun to ensure no developing larvae were overlooked. The number of PC larvae resulting from berry samples on each evaluation date was summed and percent emergence per date was calculated based on the original number of scarred fruit in the respective sample. Total damaged fruit and number of larvae from the five evaluation dates were summed for the overall ‘season total per exposure group’, and the overall percent emerged larvae was calculated. Data were analyzed using ANOVA and means separation by Fisher’s LSD test at P = 0.05. Count data were ln(x + 0.1)-transformed and percent data were arcsine square-root transformed prior to analysis.

The number of surviving PC did not change among treatments (Table 1). Numerically (but not always statistically different), the number of scared fruit, number of larval emergence, and percent of scared fruit resulting in emerged larvae were lower in the 7- and 14-DAT residual treatments (Tables 2 and 3). These two treatments provided best (60–80%) PC control (Table 4). Results also show that Rimon lost efficacy after adults were exposed to untreated fruit (10–24 days postexposure), indicating that constant exposure to Rimon is needed to maintain efficacy. In summary, Rimon residues of less than 2 wk provide best protection against PC in blueberries: Rimon reduced number of scared fruit (oviposition) and number of emerged larvae.

This research was supported by industry gifts of pesticide and/or research funding.