Evaluation of the Green Lacewing (Mallada signatus) as a biological control agent for the invasive Tomato Potato Psyllid (Bactericera cockerelli)

Natasha Zhou

The tomato potato psyllid Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), is a sap-sucking insect pest originating from North and Central America. It was first reported to have invaded and established in Western Australia (WA) in February 2017. Its arrival threatens WA’s two most produced vegetable crops (in volume) - tomato and potato. These two crops combined, made up over 25% of Australia’s total vegetable production value in 2021. This highlights the importance of successfully controlling B. cockerelli’s damage and spread in Australia. Globally, lacewing species have shown potential to be used as biological control agents for the management of B. cockerelli. Using tomato plants (Solanum lycopersicum L.) as a model species, we focused on the native and commercially available green lacewing (Mallada signatus) (Schneider) (Neuroptera: Chrysopidae) and evaluated its potential, at different growth stages, as a biological control agent for B. cockerelli. We also studied the effect of feeding on B. cockerelli on the developmental time, survival and oviposition of M. signatus. Then, greenhouse study was conducted to determine at what density level M. signatus larvae should be released to reduce an established B. cockerelli population on tomato plants. This study indicates M. signatus larvae, specifically in the 3rd larval instar stage, are voracious predators with the capacity to prey on a large number of B. cockerelli in the late instar stages (> 75 per 24-hour period). Feeding on B. cockerelli nymphs decreased the pre-adult development time, in days, of M. signatus larval instars (M = 25.2, SE = 0.3) compared to when fed on a control diet of green peach aphids (Myzus persicae) (Hemiptera: Aphididae) (M = 26.8, SE = 0.2). When fed on a diet of B. cockerelli nymph, M. signatus adults laid a similar number of eggs per day (M = 17.3, SE = 1.1) compared to when fed on a M. persicae diet (M = 18.1, SE = 0.85). This suggests that there is little or no negative impact of a diet of B. cockerelli on the developmental cycle and oviposition of M. signatus. Following the introduction of 1st instar M. signatus larvae to a closed environment containing established tomato plants at the 10 to 12 leaf stage, and a known population of B. cockerelli, it was found that eight larval instars per plant were effective at reducing the B. cockerelli population by 81%, which was 31% greater than the control where no M. signatus larvae were introduced. These results indicate M. signatus larvae, particularly at the 3rd instar stage, are an effective biological control option for B. cockerelli. These findings prove to be effective in Australia's horticultural industry and could provide a viable alternative to traditional control methods which heavily rely on chemical pesticides.

Evaluation of the Green Lacewing (Mallada signatus) as a biological control agent for the invasive Tomato Potato Psyllid (Bactericera cockerelli)

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