Development of a mating disruption program for a mealybug, Planococcus ficus, in vineyards

Authors: DAANE, KENT - University Of California; YOKOTA, GLENN - University Of California; WALTON, VAUGHN - Oregon State University; Hogg, Brian; COOPER, MONICA - University Of California - Cooperative Extension Service; BENTLEY, WALTER - University Of California; MILLAR, JOCELYN - University Of California

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2020
Publication Date: 9/16/2020
Citation: Daane, K.M., Yokota, G.Y., Walton, V.M., Hogg, B.N., Cooper, M.L., Bentley, W.J., Millar, J.G. 2020. Development of a mating disruption program for a mealybug, Planococcus ficus, in vineyards. Insects. 11(9):635. https://doi.org/10.3390/insects11090635.
DOI: https://doi.org/10.3390/insects11090635

Interpretive Summary: The vine mealybug (VMB) is an invasive pest of vineyards that damages grape clusters and can weaken or kill vines in high numbers. Pesticides are often needed to control VMB, but are largely unavailable to organic growers and can kill natural enemies that would otherwise help to control VMB. Sustainable control methods for VMB are needed to meet increasing consumer demand for organically farmed products. One promising option is mating disruption, whereby vineyards are flooded with synthetic sex pheromone to disrupt mating in VMB and reduce VMB populations by preventing male VMB from finding females. In a series of experiments over four years, we tested the effects of mating disruption on VMB populations in California vineyards. Across all trials mating disruption consistently reduced VMB numbers in traps and either numbers on vines and/or damage to grape clusters, regardless of the amount of pheromone that was applied. However, numbers in traps never decreased to zero, possibly because trials were conducted in vineyards with unusually high VMB numbers. Also, VMB numbers peaked in mid-July or August, when an insecticide was needed to help control VMB. Examination of pheromone dispensers showed that the pheromone was either released too early for the late-season peak in VMB numbers or was not completely released during the season. Development of a dispenser that releases the pheromone over the entire season should be a future goal.

Technical Abstract: The vine mealybug (VMB), Planococcus ficus (Hemiptera: Pseudococcidae), is a key insect pest of vineyards. Pesticides are typically needed to suppress Pl. ficus below economically damaging levels, but can disrupt natural enemy populations and are largely unavailable to organic growers. Improvements in sustainable control of Pl. ficus are needed to meet increasing consumer demand for organically farmed products. One promising option is mating disruption, whereby vineyards are flooded with synthetic sex pheromone to reduce or delay mating in Pl. ficus. In a series of experiments conducted from 2003-2007, we tested the effects of mating disruption on trap captures of Pl. ficus males in pheromone-baited traps, on Pl. ficus numbers and age structure on vines, and on damage to grape clusters. From 2004-2005 the effects of dispenser load (mg active ingredient per dispenser) was also assessed, and dispensers were compared to a sprayable formulation. Across all trials from 2004-2007 mating disruption consistently reduced pheromone trap captures, mealybug numbers on vines and/or crop damage, regardless of the pheromone dose that was applied. However, reductions in Pl. ficus densities in mating disruption plots were not accompanied by clear effects on population age structure; production of non-viable ovisacs by unmated females may have obscured any differences in proportional representation of ovisacs in Pl. ficus populations. Complete trap “shut down” was never achieved, possibly because trials were conducted in vineyards with unusually high Pl. ficus densities. Also, trap captures of Pl. ficus resurged in mid-July or August, when a post-harvest insecticide spray was often applied. The release rate of pheromone dispensers was assessed from 2004-2007, showing that the pheromone was either released too early or was not completely released during the season. Thus, season-long coverage or late season coverage may be as or more important than per hectare dose. Development of a dispenser that provides season-long pheromone emission should be a future goal.