Greenhouse Rearing Methods for Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) on Live Cowpea Plants.

Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a pest of concern that must be controlled for market access of host material and regulated articles to certain countries. This work outlines a rearing system for BMSB on live cowpea plants, Vigna unguiculata (L.) Walp. (Fabales: Fabaceae), including methods to induce adults to both enter and exit diapause. This scalable system affords continuous access to >600 specimens per week of each life stage and/or age group, which is particularly advantageous when developing treatment efficacy data.

Assessment of Nymphal Ecology and Adult Xylella fastidiosa Transmission Biology of Aphrophora nr. permutata (Hemiptera: Aphrophoridae) in California Vineyards.

Although Aphrophora nr. permutata (Hemiptera: Aphrophoridae) is a reported vector of the plant pathogen Xylella fastidiosa (Wells) (Xanthomonadales: Xanthomonadaceae), its ecology and role in Pierce's disease dynamics in coastal California vineyards are poorly understood. From 2016 to 2020, we surveyed the abundance of A. nr. permutata nymphs among potential host plants along the vineyard floor, the vineyard edges, and adjacent vegetation in vineyards in Napa and Sonoma county. In 2019 and 2020, vineyards adjacent to woodland habitat hosted larger A. nr. permutata populations than those next to riparian habitat, while in 2017 and 2018, the nymphal populations were similar among riparian and woodland sites. Among 2020 plant cover taxa, nymph abundance was positively associated with Helminthotheca echioides, Vicia sativa, and Daucus carota cover and negatively associated with Taraxacum officinale cover. In 2018 and 2019, we also tracked early-season occurrence and development of A. nr. permutata nymphs among potential host plants. Analyses showed a significant effect of site, year, and plant taxa on the first detection of nymphs and a significant effect of site and year on the estimated development time between first and fifth instars. In 2019, we conducted grapevine to grapevine X. fastidiosa transmission experiments with individuals and groups of five A. nr. permutata adults. In the transmission experiment, 5% (3 of 60) individual A. nr. permutata and 7.7% (1 of 13) of groups successfully transmitted X. fastidiosa. This study provides preliminary evidence of potential host plant associations with A. nr. permutata abundance and phenology that should be explored further with field and greenhouse-based approaches.

Spissistilus festinus (Hemiptera: Membracidae) susceptibility to six generalist predators.

Spissistilus festinus (Say) (Hemiptera: Membracidae) was shown to transmit Grapevine red blotch virus (GRBV) in a greenhouse study. Grapevines infected with GRBV exhibit reduced sugar accumulation, altered secondary metabolite production and delayed berry maturation that negatively impacts wine quality and economics. Augmentative biocontrol may be a useful integrated pest management (IPM) tool for suppressing S. festinus populations in vineyards, but minimal research has been conducted on testing potential predators against the different life stages of S. festinus. The susceptibility of S. festinus adults and nymphs (1st through 5th instar) to predation by six commercially available biocontrol agents in petri dish and bell bean plant arenas was determined under greenhouse conditions. No significant mortality of S. festinus nymphs or adults occurred when exposed to Cryptolaemus montrouzieri adults, C. montrouzieri larvae and Sympherobius barberi adults in petri dish or bell bean plant arenas. Significant mortality of 1st and 2nd instar nymphs of S. festinus in the presence of Zelus renardii nymphs was observed in petri dish but not in bell bean arenas. Hippodamia convergens adults and Chrysoperla rufilabris larvae both consumed a significant number of S. festinus nymphs in petri dish and bell bean arenas. No significant predation of S. festinus adults was documented in this experiment. Results of this study aid in identifying predators that may be suitable candidates for additional field testing to determine their potential efficacy as biocontrol agents of S. festinus in a vineyard setting.

Timing the Implementation of Cultural Practices for Spissistilus festinus (Hemiptera: Membracidae) in California Vineyards Using a Stage-Structured Degree-Day Model.

The three-cornered alfalfa hopper, Spissistilus festinus (Say), was shown to transmit Grapevine red blotch virus (GRBV), the causative agent for Grapevine red blotch disease, in a greenhouse study on grapes. GRBV is a major concern of wine grape growers due to its economic impact on wine quality. Plants in the family Fabaceae are preferred hosts of S. festinus and are commonly planted as cover crops or present in a vineyard's native vegetation. In late winter, during grapevine dormancy, S. festinus migrate into vineyards to feed and reproduce on these cover crop and weed hosts. Tilling vineyard floor vegetation provides growers an opportunity to disrupt the life cycle of early instars that are relatively immobile, reducing the S. festinus first-generation population. Nymphal presence is difficult to detect. First through third instars were not detected in sweep net samples in a 2-yr weekly sampling study, whereas fourth and fifth instars were first found on the same sample date as emerging adults. A degree-day model was developed and successfully predicted when early S. festinus instars are present in the vineyard to aid in exploiting the time period when S. festinus is most susceptible to cultural control measures.