Grapevine red blotch-associated virus (GRBaV) is a single-stranded DNA virus, proposed to be a member of the family Geminiviridae, and is associated with grapevines showing red blotch symptoms in North America. The existence of the virus was reported in 2012, and subsequently detected in grapevines in major grape production regions. We investigated if a vector exists that can transmit GRBaV in vineyards. Phylogenetic analysis of the predicted amino acid sequence of coat protein (CP) of GRBaV with the CP of 23 geminiviruses representing all seven genera of the family Geminiviridae revealed that GRBaV-CP was most similar to that of Tomato pseudo-curly top virus, a geminivirus known to be transmitted by a treehopper (Membracidae), a family that is closely related to leafhoppers (Cicadellidae). To identify vectors of GRBaV, hemipteran species within and nearby wine grape vineyards where virus spread was suspected were collected and transmission assays were conducted. Among the species tested, the three-cornered alfalfa hopper Spissistilus festinus (Hemiptera: Membracidae) was able to both acquire the virus from a grapevine infected with GRBaV and transmit the virus to healthy grapevines in the laboratory. In commercial vineyards, lateral shoots of grapevines girdled due to feeding injury by the adult three-cornered alfalfa hopper also tested positive for the virus using digital PCR. These findings represent an important step in understanding the biology of GRBaV and develop management guidelines.

Grapevine red blotch-associated virus (GRBaV) is a recently discovered virus of concern to wine grape production in North America. While the vector of this virus is unknown, other elements of virus epidemiology are essential to develop guidelines for the management of the virus as well as to assist in the search for its vector. The objective of this study was to evaluate vegetation within and surrounding GRBaV-infected vineyards to identify potential virus reservoirs that may serve as sources of inoculum. In this study, 13 plant species were sampled throughout the year and were tested for the presence of GRBaV. Of the 13 species tested, two species, Rubus armeniacus and wild grapes (Vitis californica × V. vinifera), tested positive by quantitative PCR. Of these two species, only wild grapes were determined to be a true host. This study documents the first time GRBaV has been confirmed in an alternative host or in a species outside of a commercial vineyard and suggests that a mechanism exists by which GRBaV moves between plant species that is not human-mediated. The precise role that wild grapes play in the epidemiology of GRBaV remains unknown.

The olive fly, Bactrocera oleae, is the most devastating pest of cultivated olives. Its control has been traditionally based on insecticides, mainly organophosphates and pyrethroids. In recent years, the naturalyte spinosad is used against the olive fly. As with other insecticides, spinosad is subject to selection pressures that have led to resistance development. Mutations in the α6 subunit of the nicotinic acetylcholine receptor (nAChR) have been implicated in spinosad resistance in several species (e.g., Drosophila melanogaster) but excluded in others (e.g., Musca domestica). Yet, additional mechanisms involving enhanced metabolism of detoxification enzymes (such as P450 monooxygenases or mixed function oxidases) have also been reported. In order to clarify the spinosad resistance mechanisms in the olive fly, we searched for mutations in the α6-subunit of the nAChR and for up-regulated genes in the entire transcriptome of spinosad resistant olive flies. The olive fly α6-subunit of the nAChR was cloned from the laboratory sensitive strain and a spinosad selected resistant line. The differences reflected silent nucleotide substitutions or conserved amino acid changes. Additionally, whole transcriptome analysis was performed in the two strains in order to reveal any underlying resistance mechanisms. Comparison of over 13,000 genes showed that in spinosad resistant flies nine genes were significantly over-expressed, whereas ~40 were under-expressed. Further functional analyses of the nine over-expressed and eleven under-expressed loci were performed. Four of these loci (Yolk protein 2, ATP Synthase FO subunit 6, Low affinity cationic amino acid transporter 2 and Serine protease 6) showed consistently higher expression both in the spinosad resistant strain and in wild flies from a resistant California population. On the other side, two storage protein genes (HexL1 and Lsp1) and two heat-shock protein genes (Hsp70 and Hsp23) were unfailingly under-expressed in resistant flies. The observed nucleotide differences in the nAChR-α6 subunit between the sensitive and spinosad resistant olive fly strains did not advocate for the involvement of receptor mutations in spinosad resistance. Instead, the transcriptome comparison between the two strains indicated that several immune system loci as well as elevated energy requirements of the resistant flies might be necessary to lever the detoxification process.

The olive fruit fly (Bactrocera oleae Rossi) is the primary insect pest in all olive-growing regions worldwide. New integrated pest management (IPM) techniques are needed for B. oleae to mitigate reliance on pesticides used for its control which can result in negative environmental impacts. More effective lures for monitoring olive flies would help to know when and where direct chemical applications are required. The aim of this research was to find new, more effective methods for B. oleae detection and monitoring. Twelve insect-associated yeasts were selected and tested as living cultures in McPhail traps for the attraction of olive flies. Certain yeasts were more attractive than others to B. oleae; specifically, Kuraishia capsulata, Lachancea thermotolerans, Peterozyma xylosa, Scheffersomyces ergatensis, and Nakazawae ernobii, than the industry-standard dried torula yeast (Cyberlindnera jadinii; syn. Candida utilis). The attractiveness of dry, inactive (i.e., non-living) formulations of these five yeasts was also tested in the field. Inactive formulations of K. capsulata, P. xylosa, N. ernobii, and L. thermotolerans were significantly more attractive to B. oleae than commercially available torula yeast. Green lacewing, Chrysoperla comanche (Stephens) (Neuroptera: Chrysopidae), adults were incidentally caught in traps baited with the live yeast cultures. This is the first field study that compares olive fly attraction to yeast species other than torula yeast. Commercialization of yeasts that are more attractive than the torula standard would improve monitoring and associated control of the olive fruit fly.