Washington State University
Mount Vernon Northwestern Research and Extension Center
Mount Vernon, WA 98273-4768
Black vine weevil (BVW), Otiorhynchus sulcatus (F.) field trial.
Sprench treatments of two experimental insecticides were compared with three registered weevilcides and an untreated check in a 3 year-old ‘Totem’ planting in Burlington, WA. Each treatment was applied to five replicates separated by 5’ buffers and arranged in a randomized complete block. A single row separated each block and blocks were composed of three, 30’ row plots. Treatments consisted of chlorotraniliprole (DPX-E2745 1.67 lb/gal SC, 0.09 lb(AI)/acre); metaflumizone (BAS 320 I, 0.178 and 0.25 lb(AI)/acre + Penetrator Plus 0.25% v/v); thiamethoxam (Actara™, 0.047 lb(AI)/acre); bifenthrin (Discipline™, 0.1 lb(AI)/acre; zeta-cypermethrin (Mustang™, 0.05 lb(AI)/acre and an untreated check.
The treatments were applied between 9:30 to 10:30 pm on 16 July 2008, with a tractor mounted plot sprayer equipped with three Spray Systems™ row application units. Each unit was equipped with 3 twin fan spray tips (TJ60-8006) mounted on a row boom to deliver 150 gal/acre at 45 psi at 1.8 mph. Black vine weevil (BVW) density per plot was determined from 3 minute, timed counts of adult weevils on strawberry foliage after 10 pm with the aid of flashlights at 1, 5 and 9 days posttreatment.
Both rates of metaflumizone performed comparably and there was no significant difference in adult BVW mortality with our standard bifenthrin at 5 to 9 days posttreatment (Table 1). At 5 DAT, the strawberry rows in each metaflumizone plot were littered with BVW adults in a state of relaxed paralysis. All were lying on their backs with weak leg and mouthpart movements. These symptoms fit those described by BASF for their sodium channel blocker insecticide, with death delayed 1-72 hours after ingestion. Although chlorotraniliprole’s mode of action is very different from that of metaflumizone, affected insects exhibit very similar symptoms including paralysis, cessation of feeding and ultimately death. Pending their registrations, these data indicate both new chemistries could be rotated with registered weevilcides, thus ensuring their long-term use and sustainability in small fruit IPM programs.
Rough strawberry root weevil (RSRW), Otiorhynchus rugosostriatus (Goeze) lab bioassay.
Rough strawberry root weevils (RSRW) were collected from ‘Totem’ strawberry located in Burlington, WA, 27 August 2008. Individual trifoliate strawberry leaves were inserted into water-filled vials, plugged with a cotton dental roll, dipped in respective deionized water-insecticide solutions for approximately 5 seconds, placed into 5-inch diameter Petri dishes and allowed to air-dry before four weevils were placed into each arena. Each treatment tested a total of twenty weevils, divided equally among five Petri dish leaf arenas, held at room temperature.After 1 day posttreatment, Discipline and two rates of experimental BAS 320 I, provided complete mortality of RSRW through contact and ingestion under lab conditions. BAS 320 I represents a new class of chemistry (Group 22) that controls insects by ingestion, blocks the flow of sodium ions and does not require metabolic bio-activation to become insecticidal. RSRW exposed to BAS 320 I were in a moribund state after 1 day posttreatment. Symptoms observed were cessation of feeding, metabolic stress (e.g., diarrhea) and uncoordinated movements that resulted in prolonged morbidity and death.
Clay colored root weevil, Otiorhynchus singularis (L.) lab bioassay.
These same post exposure responses were also observed for our clay colored root weevil (CCW) bioassay conducted in June for the same two rates of BAS 320 I on red raspberry. Though the target site of BAS 320 I differs from Discipline, population mortality upon exposure to bifenthrin often is variably prolonged for 2-3 days as well in adult root weevils. Moribund RSRW were scored as dead because they were incapable of pest status and population survival under field conditions was unlikely, given their responses in the laboratory. The insecticidal effect on root weevils is irreversible like pyrethroids and neonicotinoids and slower acting compared with the modes of action of the earlier carbamate and OP chemistries. BAS 320 I is pending registration in blueberry and we will recommend it as an ‘A’ priority for 2009 for strawberry and caneberry IR-4 residue projects.