Pupation behavior and larval and pupal biocontrol of Drosophila suzukii in the field

Authors: WOLTZ, MEGAN - Oregon State University; Lee, Jana

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2017
Publication Date: 4/9/2017
Citation: Woltz, M.J., Lee, J.C. 2017. Pupation behavior and larval and pupal biocontrol of Drosophila suzukii in the field. Biological Control. 110:62-69. doi: 10.1016/j.biocontrol.2017.04.007.

Interpretive Summary: The spotted wing drosophila (SWD) is a worldwide pest of fruit crops. Biological control may play an important role in SWD IPM, and suppressing pests in unmanaged areas. While predators of SWD have been observed in the field, nothing is known about the extent these predators may suppress populations. Additionally, the larval and pupal stage of SWD make up a substantial proportion of the pest population, and control measures should target these juvenile stages as well. The first objective of this study was to measure naturally-occurring levels of predation on SWD larvae and pupae. The second objective of this study was to determine the proportion of SWD that pupate in the fruit versus soil. Knowing the location of pupae can be important for developing biological and cultural control programs to target them. Fewer SWD larvae were extracted from fruits exposed to predators, representing a reduction in larval survival of 19–49%. Fewer SWD pupae were recovered from soil exposed to predators, representing a 61–91% decrease in pupae. In the pupation behavior experiment, 82–93% of pupae were found in soil, significantly more than were found in fruit. Ants and spiders were commonly observed in a variety of sampling methods, including video, vacuum samples, and inside of infested fruits. Ants were observed on video to dig pupae out of soil and carry them off.

Technical Abstract: Drosophila suzukii is a worldwide pest of fruit crops. Biological control may play an important role in D. suzukii IPM, and suppressing populations in unmanaged areas. While predation has been observed in the field, nothing is known about the potential for natural enemies to reduce D. suzukii populations. Additionally, juveniles make up a large proportion of D. suzukii populations, thus targeting juveniles may be more effective than targeting adults for reducing population sizes. The first objective of this study was to measure naturally-occurring levels of biocontrol on D. suzukii larvae and pupae. Furthermore, D. suzukii may either pupate inside of fruit or emerge from to pupate in the surrounding medium. Knowing the location of pupae can be important for developing biological and cultural control programs to target them. Thus, the second objective of this study was to determine the proportion of D. suzukii that pupate in the fruit versus soil. Predator exclusion experiments were conducted to measure the ability of natural enemies to reduce D. suzukii larvae in strawberry and blueberry fruits, and pupae in the soil in strawberry, blueberry, and blackberry plantings. Funnels were used to direct larvae dropping from infested blueberry and raspberry fruits into soil-filled containers, enabling a measure of the number of pupae found in the soil and in the fruit. Significantly fewer D. suzukii larvae were extracted from fruits exposed to predators, representing a reduction in larval survival of 19–49%. Significantly fewer D. suzukii pupae were recovered from soil exposed to predators, representing a 61–91% decrease in pupae. In the pupation behavior experiment, 82–93% of pupae were found in soil, significantly more than were found in fruit. Ants and spiders were commonly observed in a variety of sampling methods, including video, vacuum samples, and inside of infested fruits. Ants were observed on video to dig pupae out of soil and carry them off.