Examining spray-induced gene silencing for pollen beetle control

Pollen beetles are a transcontinental threat to oilseed rape cultivation. Conventional insecticide use has resulted in resistance development, and can furthermore lead to losses of non-target organisms, including those that contribute to natural biological control of pollen beetle populations. Biosafe alternatives to synthetic pesticides must be explored. Double-stranded RNA (dsRNA) targeting pollen beetle, by the RNA interference (RNAi) mode of action, has been previously demonstrated under laboratory conditions. The present study examined, under a whole plant context, the potential for spray-induced gene silencing (SIGS) in pollen beetle. We confirmed translocation of sprayed dsRNA to later-emerging, non-sprayed dietary tissues of oilseed rape, as well as infiltration of sprayed dsRNA to the inner tissues of reproductive buds (pollen beetle's food source). No effect on survival was observed. The inefficacy of SIGS observed here highlights the requirement for more effective SIGS approaches to pollen beetle management. The translocation of sprayed dsRNA within oilseed rape plants, and the non-significant yet detectable effect on target mRNA downregulation, together suggest potential for future optimization of a SIGS approach against pollen beetle.