Efficacy of Attract-and-Kill Formulations Using the Adjuvant Acttra SWD TD for the Management of Spotted-Wing Drosophila in Blueberries, 2020

A laboratory bioassay was conducted to assess the efficacy of attract-and-kill formulations prepared by incorporating selected commercial (conventional and organic) insecticides into a SPLAT adjuvant (ACTTRA SWD TD) for managing spotted-wing drosophila (SWD) in rabbiteye blueberry. SPLAT (Specialized Pheromone and Lure Application Technology, ISCA Technologies, Inc.), ISCA’s rain fast slow-release matrix was used to formulate two proprietary attractive blends, ACTTRA SWD TD and ACTTRA SWD OR1, that contain phagostimulants, and a pink dye, and are specifically developed for SWD management. The ACTTRA SWD adjuvants are designed to be mixed with an insecticide at low doses, usually at 0.25 A.I. (%v/v), to serve as an attract-and-kill formulation where the ACTTRA SWD attracts SWD adults and upon interacting with the formulation, the deleterious effects of the insecticide incorporated into the formulation reduces the insects’ vitality, and eventual insect mortality. The objective of this laboratory bioassay was to determine the efficacy of nine insecticides incorporated into ACTTRA SWD TD for controlling SWD in comparison with two SPLAT adjuvants that lack an insecticide (positive check) and an untreated check.

The laboratory bioassay consisted of 12 treatments, including nine formulations of insecticide + ACTTRA SWD TD, two blank SPLAT adjuvants (ACTTRA SWD TD check and ACTTRA SWD OR1 check), and an untreated check (Table 1). The bioassay arena consisted of a 946-ml clear plastic container (Fabri-Kal, Kalamazoo, MI) with a matching lid, and with a single 5–7 cm long blueberry terminal with 4–5 leaves inserted into a water pick (DL 3805, Diamond Line, Akron, OH), filled with distilled water, which was then fitted through a circular hole in the bottom center of the arena. Each assay container was supplied with 15 ripe organic blueberries (Simple Truth Organic, Kroger Co. Cincinnati, OH), as SWD food source and an oviposition substrate. A floral tube (Juvale, Juvo Plus Inc. Monrovia, CA) filled with distilled water and with its opening plugged with moist cotton was provided as a water source. Each container, except the untreated check, received a single 0.2 ml drop of one ACTTRA SWD treatment, applied to the adaxial surface of the topmost leaf. Bioassay containers were then arranged in an RCBD design and were replicated eight times. Five male and five female adult SWD (5–7 d old), reared from a laboratory colony, and starved for ≈2 h, were released into the bioassay containers approx. 2 h after treatment application. After the flies were released, the containers were kept in a lab maintained at 21°C, 14:10 (L:D) h and ≈80% RH for 6 d. On the 6 DAT, blueberries were removed from the bioassay containers and transferred to a ventilated 237 mL deli container (Fabri-Kal) with a cotton round (Swisspers, Gastonia, NC) in the bottom, and incubated in same lab environment for 14 d for adult progeny emergence. Treatment efficacy was determined based on the adult SWD mortality and number of adult progenies developed from the blueberry fruits. Experiment was initiated on 29 Oct, and posttreatment male and female SWD mortality counts were taken on 30 Oct, 1 Nov, and 4 Nov (1, 3, and 6 DAT, respectively). Additionally, number of male and female adults that emerged from the blueberries were counted on 19 Nov (20 DAT). Data were subjected to ANOVA (PROC GLIMMIX, SAS v. 9.4) with data fitted to a normal distribution, and the mean (LSMEAN option) separation were carried out using Tukey–Kramer method (P ≤ 0.05, Table 1).

No significant interaction of treatments with sex was observed for adult mortality in any of the observation dates (1 DAT, P = 0.374; 3 DAT, P = 0.756; 6 DAT, P = 0.970). However, significantly higher male mortality was observed in 1 DAT (male = 18.9%, female = 12.2%; P = 0.004). A significant difference in SWD adult mortality was observed among the treatments on 1, 3, and 6 DAT (Table 1). At 1, 3, and 6 DAT, ACTTRA SWD TD with Danitol 2.4EC, Exirel 0.83SE, Gowan Malathion 8F, and Mustang Maxx 0.8SC resulted in significantly higher SWD mortality compared with the untreated check (Table 1). Additionally, on 3 and 6 DAT, Entrust 2SC Naturalyte, and on 6 DAT, Azera 0.21SL and Venerate XC also resulted in significantly higher mortality than untreated check. At 6 DAT, among the OMRI-approved insecticides tested, only Entrust 2SC Naturalyte incorporated into ACTTRA SWD TD caused more than 80% mortality.

Similar to adult mortality data, no significant interaction of treatments with sex was observed for adult progeny emergence (P = 0.197). However, averaged across the treatments, 25% more adult female progenies were produced than male progenies (male = 18.1, female = 22.7; P < 0.0001). A significant difference in SWD adult emergence was observed among the treatments (Table 1), and compared with untreated check, application of the ACTTRA SWD TD formulation with Danitol 2.4 EC and Mustang Maxx 0.8SC resulted in significantly reduced SWD adult emergence.¹

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