More Power with Flower for the Pupal Parasitoid Trichopria drosophilae: A Candidate for Biological Control of the Spotted Wing Drosophila

Abstract

Parasitoids are currently considered for biological control of the spotted wing drosophila (SWD) in berry crops. Releases of mass-reared parasitoids require the presence of all resources necessary to ensure their effectiveness in the crop system. The use of floral resources to feed Trichopria drosophilae, one of the candidate species, was investigated in a laboratory study. The life expectancy of males and females increased by three to four times when they had access to flowers of buckwheat or of two cultivars of sweet alyssum. Female realized lifetime fecundity increased from 27 offspring/female exposed to water only to 69 offspring/female exposed to buckwheat flowers. According to this almost threefold increase in parasitoid fitness, it is advisable to introduce flowering plants into the crop system, when parasitoid releases are carried out. Sweet alyssum offers the advantage of not growing too tall in combination with an extended blooming. However, adult SWD were also able to feed on flowers of both plants and survived for at least 27 days, much longer than starving flies. The introduction of flowering plants to promote natural enemies therefore requires further consideration of the risk–benefit balance under field conditions to prevent unintended reinforcement of this pest.

Aromatic border plants in early season berries do not increase parasitism of spotted wing drosophila, Drosophila suzukii

“…[28][29][30] It has been demonstrated that D. suzukii survival is enhanced when they had access to alyssum, as the proboscis is sufficiently long to reach the nectaries and feed on the nectar they contain. 13 Although the nectaries of the buckwheat control mix may have been more readily accessible to D. suzukii, clearly alyssum provides supplemental resources as well. 13 Another possible explanation for our results is phenological mismatches between early season berry crops, D. suzukii, and its associated parasitoids.…”

“…13 Although the nectaries of the buckwheat control mix may have been more readily accessible to D. suzukii, clearly alyssum provides supplemental resources as well. 13 Another possible explanation for our results is phenological mismatches between early season berry crops, D. suzukii, and its associated parasitoids. Studies that have monitored D. suzukii populations across growing seasons have found that populations peak depending on the climate of the area sampled, but generally occur around July or August.…”

“…Various qualities of sweet alyssum make it a desirable intercrop for berries, including its ease of nectar access to parasitic wasps, ease of sowing, heat resistance, and ability to grow without impeding berry crop growth. 13 In the laboratory, it has been demonstrated that the volatile compounds found in sweet alyssum reduced both attraction and infestation rates of D. suzukii in raspberries. 14 In the field, alyssum has shown promise as an attractant to various natural enemies, both predaceous 15 and parasitic.…”

“…An intercrop of particular interest in the control of D. suzukii is sweet alyssum ( Lobularia maritima) . Various qualities of sweet alyssum make it a desirable intercrop for berries, including its ease of nectar access to parasitic wasps, ease of sowing, heat resistance, and ability to grow without impeding berry crop growth 13 . In the laboratory, it has been demonstrated that the volatile compounds found in sweet alyssum reduced both attraction and infestation rates of D. suzukii in raspberries 14 .…”

“…In the laboratory, it has been demonstrated that the volatile compounds found in sweet alyssum reduced both attraction and infestation rates of D. suzukii in raspberries 14 . In the field, alyssum has shown promise as an attractant to various natural enemies, both predaceous 15 and parasitic 13,16,17 . Given the evidence pointing to sweet alyssum's potential as both a repellent to D. suzukii 14 and attractant to its natural enemies, 15 there is a strong impetus to investigate whether intercropping can lower strawberry infestation rates in the field.…”