Rearing Xyleborus volvulus (Coleoptera: Curculionidae) on media containing sawdust from avocado or silkbay, with or without Raffaelea lauricola (Ophiostomatales: Ophiostomataceae)

Authors: MENOCAL, OCTAVIO - University Of Florida; CRUZ, LUISA - University Of Florida; Kendra, Paul; CRANE, JONATHAN - University Of Florida; PLOETZ, RANDY - University Of Florida; CARRILLO, DANIEL - University Of Florida

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2017
Publication Date: 12/8/2017
Citation: Menocal, O., Cruz, L.F., Kendra, P.E., Crane, J.H., Ploetz, R.C., Carrillo, D. 2017. Rearing Xyleborus volvulus (Coleoptera: Curculionidae) on media containing sawdust from avocado or silkbay, with or without Raffaelea lauricola (Ophiostomatales: Ophiostomataceae). Environmental Entomology. 46(6):1275-1283.

Interpretive Summary: Xyleborus volvulus is an ambrosia beetle found in Florida and other tropical/subtropical regions worldwide. Like all ambrosia beetles, X. volvulus is a wood borer that feeds on symbiotic fungi which it introduces into host trees. Until recently, X. volvulus was not considered a pest, and none of its symbionts were known plant pathogens. However, since the establishment of redbay ambrosia beetle and its symbiont Raffaelea lauricola (the cause of laurel wilt disease in avocado and other US Lauraceae), it has been shown that X. volvulus can pick up the R. lauricola pathogen if it breeds in trees with laurel wilt. To better study this beetle and its potential as a vector of laurel wilt, scientists from the University of Florida (Homestead, FL) and the USDA-ARS (Miami, FL) conducted research to evaluate laboratory diets for rearing X. volvulus. Diets varied in moisture content, sawdust from different hosts, and incorporation of R. lauricola. A diet low in sawdust and intermediate in moisture was found to be the best medium for rearing X. volvulus. If R. lauricola was present in the medium, beetles did incorporate it into their mycangia (spore storage organs), but at very low levels. This suggests that X. volvulus can vector the laurel wilt pathogen, but much less efficiently than redbay ambrosia beetle. These results benefit scientists and action agencies by increasing our understanding of the epidemiology of laurel wilt, and the role of secondary beetle vectors in disease transmission.

Technical Abstract: Like other ambrosia beetles, Xyleborus volvulus Fabricius (Coleoptera: Curculionidae) lives in a mutualistic symbiotic relationship with fungi that serve as food source. Until recently, X. volvulus was not considered a pest, and none of its symbionts were considered plant pathogens. However, recent reports of an association between X. volvulus and Raffaelea lauricola T.C. Harr. Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), the cause of the laurel wilt disease of avocado (Persea americana Mill.), and its potential role as vector of the pathogen merit further investigation. The objective of this study was to evaluate three artificial media containing sawdust obtained from avocado or silkbay (Persea humilis Nash) for laboratory rearing of X. volvulus. The effect of R. lauricola in the media on the beetle’s reproduction was also evaluated. Of the three media, the one with the lowest content of sawdust and intermediate water content provided the best conditions for rearing X. volvulus. Reproduction on this medium was not affected by the sawdust species or the presence of R. lauricola. On the other two media, there was a significant interaction between sawdust species and R. lauricola. The presence of R. lauricola generally had a negative effect on brood production. There was limited colonization of the mycangia of X. volvulus by R. lauricola on media inoculated with the pathogen. From galleries formed within the best medium, there was 50% recovery of R. lauricola, but recovery was much less from the other two media. Here we report the best artificial substrate currently known for X. volvulus.