Xyleborus bispinatus reared on artificial media using sawdust from avocado or silkbay in presence or absence of the laurel wilt pathogen (Raffaelea lauricola)

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

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2018
Publication Date: 2/28/2018
Citation: Menocal, O., Cruz, L., Kendra, P.E., Crane, J., Cooperband, M.F., Ploetz, R., Carrillo, D. 2018. Xyleborus bispinatus reared on artificial media using sawdust from avocado or silkbay in presence or absence of the laurel wilt pathogen (Raffaelea lauricola). Insects. 9(1):30.

Interpretive Summary: Xyleborus bispinatus is an ambrosia beetle first detected in Florida in 2013. Like all ambrosia beetles, it is a wood borer that feeds on symbiotic fungi which it introduces into host trees. Until recently, X. bispinatus 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. bispinatus 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), USDA-APHIS (Buzzards Bay, MA) and the USDA-ARS (Miami, FL) conducted research to evaluate laboratory diets for rearing X. bispinatus. Diets varied in moisture content, sawdust from different hosts, and incorporation of R. lauricola. In general, diets containing avocado saw dust and low moisture content were found to be the best media for rearing X. bispinatus. 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. bispinatus 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: Xyleborus bispinatus Eichhoff (Coleoptera: Curculionidae: Scolytinae) was reported in Florida for the first time in 2013. Previously, it was unrecognized and not distinguished from the morphologically similar Xyleborus ferrugineus (F.). Like other members of the tribe Xyleborini, X. ferrugineus (and possibly X. bispinatus) can cause economic damage in lowland areas of the Neotropics. In addition, when breeding in a host infected with laurel wilt, X. bispinatus has been found to incorporate the laurel wilt pathogen, Raffaelea lauricola T. C Harr., Fraedrich & Aghayeva; Ophiostomatales: Ophiostomataceae) into its mycangia and may potentially function as a vector of the disease in avocado (Persea americana Mill.; Laurales: Lauraceae). The main objective of this study was to evaluate three artificial media containing sawdust from avocado or silkbay (Persea humilis Nash; Laurales: Lauraceae) for rearing X. bispinatus under laboratory conditions. In addition, the media was inoculated with R. lauricola to evaluate its effect on the biological parameters of X. bispinatus. There was a significant interaction between sawdust species and R. lauricola for all three media. Two of the media supported prolific reproduction of X. bispinatus, but generally the avocado-based medium was better than the silkbay-based medium either inoculated or not with the fungus. The presence of R. lauricola had a neutral or enhancing effect on beetle reproduction. The pathogen was recovered from few individuals reared in inoculated media and showed limited colonization of the beetle's mycangia. Raffaelea lauricola was frequently recovered from beetle galleries. The two media with lower water content were best for rearing X. bispinatus under laboratory conditions.