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Agricultural plant species differ in susceptibility to herbivores; therefore, identifying natural resistances or tolerances to pests can be leveraged to develop preventative, integrated pest management approaches. While many Citrus species are grown in California, most pest management guidelines are based upon research conducted on navel oranges [ Citrus sinensis (L.) Osbeck; Sapindales: Rutaceae]. A recent study has established European earwigs (Forficula auricularia L.; Dermaptera: Forficulidae) as herbivores of young navel orange fruit, causing damage ranging from small bite marks to large chewed holes. It is unknown whether earwigs damage fruit of other citrus species. We conducted field experiments in which we caged earwigs to branch terminals bearing young fruit to explore potential differences in susceptibility of Citrus species to European earwigs. Specifically, we tested whether three species, navel oranges, clementines (C. clementina hort. ex Tanaka), and true mandarins (C. reticulata Blanco) exhibit differences in: 1) feeding deterrence to earwigs; 2) suitability as food for earwigs; 3) preferential abscission of damaged fruit; and 4) healing of damaged fruit. Earwigs caused heavy damage on navel orange and clementine fruit, whereas heavy damage was rare on true mandarin fruit. There was little evidence of preferential abscission of damaged fruit or healing of seriously damaged fruit. Consequently, several heavily damaged navel orange and one clementine fruit were retained to harvest and developed large scars. Overall, we found that Citrus fruit vary in their susceptibility to earwigs, and pest management strategies for earwigs should be refined to consider their varying effects on different Citrus species. [ABSTRACT FROM AUTHOR]

The role of generalist predators has long been considered an important component of mortality for many agricultural pests but can be difficult to quantify. We present the use of digital imaging as a means of both identifying key stink bug egg predators and measuring their relative impact on egg survivorship. Brown marmorated stink bug (BMSB), Halyomorpha halys and bagrada bug, Bagrada hilaris, two exotic stink bugs new to California, are now widely distributed throughout the state. A survey was conducted to identify resident natural enemies of their eggs. A field camera aided in the identification of arthropods attacking these eggs and their relative impact. Predation of BMSB eggs, which are naturally oviposited onto plant foliage, was less than for eggs of bagrada bug, which oviposit onto and into soil. The top ranked predators of BMSB eggs were the carabid Laemostenus complanatus (Coleoptera) the European earwig Forficula auricularia and ring-legged earwig Euborellia annulipes (Dermaptera), the oriental cockroach Blatta orientalis (Orthoptera), and the spider Trachelas spp. (Araneae). The two most common and important predators of bagrada bug were two ant species (Formicidae), Solenopsis xyloni and Monomorium ergatogyna, and species of Collembola (Entomobryidae). A Predation Index was developed to compare the relative importance of BMSB egg predators. Lastly, two striking, unanticipated results are reported: an apparent synergistic interaction between the spider Trachelas spp. and native ant M. ergatogyna in causing damage to sentinel eggs of BMSB, and the predaceous role for Collembola on bagrada bug sentinel eggs. [ABSTRACT FROM AUTHOR]

The valley elderberry longhorn beetle (VELB), Desmocerus californicus dimorphus (Coleoptera: Cerambycidae), is a federally threatened subspecies endemic to the Central Valley of California. The VELB range partially overlaps with that of its morphologically similar sister taxon, the California elderberry longhorn beetle (CELB), Desmocerus californicus californicus (Coleoptera: Cerambycidae). Current surveying methods are limited to visual identification of larval exit holes in the VELB/CELB host plant, elderberry (Sambucus spp.), into which larvae bore and excavate feeding galleries. Unbiased genetic approaches could provide a much-needed complementary approach that has more precision than relying on visual inspection of exit holes. In this study we developed a DNA sequencing-based method for indirect detection of VELB/CELB from frass (insect fecal matter), which can be easily and non-invasively collected from exit holes. Frass samples were collected from 37 locations and the 12S and 16S mitochondrial genes were partially sequenced using nested PCR amplification. Three frass-derived sequences showed 100% sequence identity to VELB/CELB barcode references from museum specimens sequenced for this study. Database queries of frass-derived sequences also revealed high similarity to common occupants of old VELB feeding galleries, including earwigs, flies, and other beetles. Overall, this non-invasive approach is a first step towards a genetic assay that could augment existing VELB monitoring and accurately discriminate between VELB, CELB, and other insects. Furthermore, a phylogenetic analysis of 12S and 16S data from museum specimens revealed evidence for the existence of a previously unrecognized, genetically distinct CELB subpopulation in southern California. [ABSTRACT FROM AUTHOR]