Journal of Pest Science (2023) 96, 1061-1075

Pamela Bruno, Carla C.M. Arce, Ricardo A.R. Machado, Gaia Besomi, Anna Spescha, Gaétan Glauser, Charlyne Jaccard, Betty Benrey and Ted C.J. Turlings (2023)
Sequestration of cucurbitacins from cucumber plants by Diabrotica balteata larvae provides little protection against biological control agents
Journal of Pest Science 96 (3), 1061-1075
Abstract: Cucurbitaceae plants produce cucurbitacins, bitter triterpenoids, to protect themselves against various insects and pathogens. Adult banded cucumber beetles (Diabrotica balteata), a common pest of maize and cucurbits, sequester cucurbitacins, presumably as a defensive mechanism against their natural enemies, which might reduce the efficacy of biological control agents. Whether the larvae also sequester and are protected by cucurbitacins is unclear. We profiled cucurbitacin levels in four varieties of cucumber, Cucumis sativus, and in larvae fed on these varieties. Then, we evaluated larval growth and resistance against common biocontrol organisms including insect predators, entomopathogenic nematodes, fungi and bacteria. We found considerable qualitative and quantitative differences in the cucurbitacin levels of the four cucumber varieties. While two varieties were fully impaired in their production, the other two accumulated high levels of cucurbitacins. We also observed that D. balteata larvae sequester and metabolize cucurbitacins, and although the larvae fed extensively on both belowground and aboveground tissues, the sequestered cucurbitacins were mainly derived from belowground tissues. Cucurbitacins had no detrimental effects on larval performance and, surprisingly, did not provide protection against any of the natural enemies evaluated. Our results show that D. balteata larvae can indeed sequester and transform cucurbitacins, but sequestered cucurbitacins do not impact the biocontrol potential of common natural enemies used in biocontrol. Hence, this plant trait should be conserved in plant breeding programs, as it has been demonstrated in previous studies that it can provide protection against plant pathogens and generalist insects.
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Database assignments for author(s): Betty Benrey, Ted C.J. Turlings

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Diabrotica balteata	Cucumber (Cucumis sativus)
Chrysoperla carnea (predator)	Diabrotica balteata
Orius laevigatus (predator)	Diabrotica balteata
Dalotia coriaria (predator)	Diabrotica balteata