Liquid Baits with Oenococcus oeni Increase Captures of Drosophila suzukii

Abstract

The spotted-wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), native to Eastern Asia, is an invasive alien species in Europe and the Americas, where it is a severe pest of horticultural crops, including soft fruits and wine grapes. The conventional approach to controlling infestations of SWD involves the use of insecticides, but the frequency of application for population management is undesirable. Consequently, alternative strategies are urgently needed. Effective and improved trapping is important as an early risk detection tool. This study aimed to improve Droskidrink^® (DD), a commercially available attractant for SWD. We focused on the chemical and behavioral effects of adding the bacterium Oenococcus oeni (Garvie) to DD and used a new trap design to enhance the effects of attractive lures. We demonstrate that microbial volatile compounds produced by O. oeni are responsible for the increase in the attractiveness of the bait and could be later utilized for the development of a better trapping system. Our results showed that the attractiveness of DD was increased up to two-fold by the addition of commercially available O. oeni when combined with an innovative trap design. The new trap-bait combination increased the number of male and especially female catches at low population densities.

Keywords: feeding attractant; fruit fly lure; insect trapping; invasive species; lactic acid bacteria; spotted-wing drosophila; volatile organic compounds.

Figure 1

For each treatment in trials 1–3: Mean Drosophila suzukii (SWD) total catches per trap at each assessment (a,d,g); dot plots of mean total catch/trap/day with 95% confidence limits (as error bars), sorted by the means, with dotted vertical line at the mean for Treatment A (control) (b,e,h); and percentage of the total catch that was female (blue) or male (red) (c,f,i). Note that for h, the upper confidence limit for a mean of 0 is not shown as it is difficult to obtain. For a description of treatments, see Table 1: Traps are: C = cup with a lid; Δ= delta trap; IB = insulated bottle; UB = uninsulated bottle. Delta traps without a bottle had a cup without a lid and supplied with two cotton balls. Liquid components are: K = KOH added; α= Alpha; β = Beta; 2 = rate 0.2; 5 = rate 0.5; CA = citric acid added. n = no liquid replacement; w = liquid replaced weekly.