Effect of Eupatorium buniifolium, a varroacide essential oil, on survival and pheromone production in Nosema-infected honeybees.

UMPIERREZ, M.L.; RODRIGO, F; DAVYT, B; GARRIDO P. M.; PORRINI M.P.; EGUARAS M, J.; GONZALEZ, A.; ROSSINI C.

Valparaíso

Congreso; 5th Congress of the Latin American Association of Chemical Ecology; 2018

Latin American Association of Chemical Ecology

Homeostasis inhoneybee colonies depend, among other factors, on semiochemicals such ascuticular hydrocarbons (CHC), which are involved in social recognition, andethyl oleate (EO) which plays a role as primer pheromone in honeybees. Thosesemiochemicals could be affected by many factors including in-hive acaricidesand the gut parasite, Nosema ceranae.We have shown that the essential oil from Eupatoriumbuniifolium (Asteraceae) had activity against Varroa destructor (Mesostigmata: Varroidae), without chroniceffects on survival, EO and CHC production in healthy honeybees. In this work,the effect of the essential oil ingestion on the above variables on Nosema-infested honeybees are reported.Essential oil was offered to 2-day old honeybees for 12 days in bioassaysfollowing the guidelines recommended by The Coloss Beebook. Healthy honey beesfed on E. buniifolium essential oildid not change their EO levels compared to control bees (ANOVA, GLM, p = 0.02).On the other hand, N. ceranaeinfection not only decreased, as expected, the survival of honey bees (Survivalanalysis Kaplan-Mayer) but also EO levels (ANOVA, GLM, p = 0.04). However, Nosema-infected bees fed on E. buniifolium essential oil exhibited asimilar EO level to the one in healthy control honeybees (ANOVA, GLM, p >0.05, Tukey post-hoc comparisons). In the case of CHC, variations were foundfor linear alkanes (ANOVA, GLM, p = 0.03), and not for the other CHC classes(ANOVA, GLM p > 0.05). Considering all these results together, we came up tothe conclusion that E. buniifoliumessential oil can be used in concentrations below 3000 ppm to treat Varroa-infested honeybees withoutaffecting neither their survival nor their EO or CHC levels in healthy hives.When Nosema-infested honeybees arefed on E. buniifolium essential oil,the decrease of EO level produced by the infection is counteracted by theessential oil consumption.