Efficacy of Indoxacarb Insecticide on Lygus Bug in Strawberry, 2015

The efficacy of indoxacarb (Avaunt) on Western tarnished plant bug (WTPB) was compared to a grower standard (Danitol + Actara) and a non-treated check in late-season strawberries. WTPB feeds on strawberry achenes and results in deformation of the fruit, known as cat-facing. Annual losses in the California strawberry industry are estimated at $200 million. There is great need for improved control of WTPB in strawberry as many products have been rendered ineffective through resistance. While indoxacarb is registered for use against WTPB in other crops, efficacy data is lacking for strawberry.

The experiment was conducted at Field 25, block 3 at the Cal Poly Horticultural Crops farm (GPS coordinates: N35°18'19.06″; W120°40'33.44″) in San Luis Obispo, CA. Bare root strawberry transplants (Albion) were set in the field on 10 Nov 2014. WTPB was managed during the season using standard industry insecticides in rotation. The final insecticide was applied on 7 Aug 2015 and the WTPB population was allowed to increase for 11 weeks without further insecticide applications. Plots were 10 beds wide (5.3 ft/bed) × 75 ft long, arranged in a RCB design with 4 replicates. Insecticides were applied on 15 and 22 Oct using a tractor-mounted boom that is 5 beds wide with 18 nozzles per bed (2 hollow cone, Albuz 80 ATR nozzles every 6 in.,), operating at 150 psi, traveling at 2.7 mph and delivering 150 gpa. Danitol and Actara were applied at the maximum recommended rate for WTPB and Avaunt was applied at the manufacturer’s recommended rate (personal communication) (Table 1).

WTPB adults, large nymphs and small nymphs as well as beneficial arthropods (i.e., spiders, lady beetle, and lacewing) were counted using the “beat box” method. Two individuals sampled 20 plants from the middle two rows of each plot and the average count is reported. Pre-treatment counts were made immediately prior to the first and second applications. Post-treatment counts were made 1, 7, 14, and 21 d following applications. Beneficial arthropod counts began 7 d after the first application. Data were subjected to ANOVA and Tukey's HSD mean separation procedure using ARM 2016 (Brookings, SD).

Treatments showed no significant difference in the number of adults, large nymphs, and small nymphs prior to the first application (Tables 1–3). Plots treated with Avaunt and Danitol + Actara had significantly fewer adult WTPB beginning 1 DAT-A and remained low throughout the study with a few exceptions (Table 1). In many cases, both treatments also reduced the number of large nymphs beginning 1 DAT-B (Table 2). However, plots treated with Avaunt had significantly fewer large nymphs than the non-treated beginning 1 DAT-B; plots treated with Danitol + Actara had fewer large nymphs beginning 7 DAT-B (Table 2). There were also significantly fewer small nymphs in plots treated with Avaunt 1 DAT-A and 7 DAT-A for Danitol + Actara (Table 3). Small nymph counts in the treated plots tended to remain low thereafter with the exception of 1 DAT-B in the Avaunt plots and 14 DAT-B where no small nymphs were found in any plots (Table 3). Lygus bug counts generally declined over time in the non-treated check, likely due to decreasing temperatures. Weekly maximum/minimum temperatures for the weeks of 11, 18, 25 Oct, and 1 and 8 Nov were 83.6/61.4, 78.3/52.6, 82.3/54.7, 72.0/46.9, and 68.9/44.1 F, respectively.

Avaunt reduced WTPB populations similar to Danitol + Actara. Avaunt also had less impact on beneficial arthropods, especially spiders (Table 4).

Disclosure of Potential Conflicts of Interest

Avaunt, Actara and Danitol insecticides were donated by E.I. DuPont de Nemours and Company, Syngenta Crop Protection and Valent USA Corporation, respectively.

Author notes