Environmental Entomology最新文献

The east Asian ambrosia beetle Xylosandrus germanus (Blanford) was first detected in the United States in 1932. It now occurs across much of eastern North America and parts of the Pacific Northwest. It attacks a broad range of stressed, woody hosts including ornamental and orchard species. The foundress tunnels into the sapwood of hosts where it cultures a symbiotic fungus as food for its offspring. A few other ambrosia beetles have been shown to possess a facultatively eusocial structure among gallery members, but this has not been described for Xylosandrus spp. Using a novel artificial diet arena, we quantified the behaviors of X. germanus larvae and adults (foundress and mature offspring) over 10 wk inside their galleries. Foundresses were responsible for constructing the gallery. They also initially tended the fungal garden and brood but eventually spent most of their time blocking the gallery entrance. Larvae were mainly observed to feed, crawl, or be inactive within the gallery, regardless of the absence or presence of adult siblings. Adult female offspring were primarily inactive, likely due to dormancy. Adult male offspring actively crawled and attempted to mate with their sisters before eventually dispersing out of the gallery. Cooperative hygienic behaviors (removal of frass, cannibalism of dead nest mates, grooming siblings) were observed but a division of labor among offspring was not clear. Rather, foundress behaviors were mostly distinct from offspring behaviors, particularly as the gallery aged. Because no overlap in generations occurred, X. germanus displays a quasisocial structure.

Several protected troglobitic invertebrate species are known to occur in caves on Joint Base San Antonio-Camp Bullis, Bexar County, Texas, United States. The United States Fish and Wildlife Service (USFWS) identified red-imported fire ant Solenopsis invicta (hereafter RIFA) (Buren 1972) as the primary threat to cave species' nutrient sources, cave crickets, Ceuthophilus secretus (Scudder 1894). Per the service's recommendations, Joint Base San Antonio-Camp Bullis currently implements boiling water mound injections with digging for RIFA control. However, treatment effectiveness is highly variable and largely dependent on the time of day, weather, and personnel diligence. Toxicants have been used for RIFA treatment throughout the world, but concerns exist that traditional applications of toxicant bait around caves might be accessible and inadvertently affect nontarget arthropods, including cricket populations. To mitigate this accessibility, physically limiting access to the toxicant from crickets may be an option. Our objectives were to (i) compare and evaluate the effectiveness of Amdro (Hydramethylnon) and Advion (Indoxacarb) granular baits housed in Ants-No-More Bait Stations (Kness MFG. Inc., Albia, IA) and (ii) evaluate the distance of effectiveness of each bait within a bait station. Ultimately, we observed a 98% reduction in RIFA mound abundance from both baits. Additionally, RIFA mounds within 10 m of the containerized toxicant were reduced by 70%. Our pilot study suggested that Ants-No-More Bait Stations are an effective way to reduce RIFA mounds by 70% if placed 10 m from each other. In practice, this could include bait stations completely covering a particular distance to a cave entrance or fewer bait stations in a ring barrier at a single radial distance to a cave entrance. Containerized toxicants may be a cost-effective and safe RIFA control option around protected cave environments, but further studies are needed to determine potential effects on nontarget arthropods, optimal bait station configuration, and potential effects of biomagnification.

The beet leafhopper, Circulifer tenellus (Baker 1896), is the sole vector of beet curly top virus (BCTV). Both the virus and the vector have very wide host ranges, including many crops and weeds. Industrial hemp (Cannabis sativa L.) has been reported as a host for both the virus and leafhopper in the past few years with the legal cultivation of the crop in the United States. This research assessed the interactions of the beet leafhopper and hemp in New Mexico by determining the natural infection of hemp with BCTV in 3 field plots in 2021 and 2022 and monitoring the numbers of leafhoppers using yellow sticky traps. The relative preference of beet leafhopper for hemp types and varieties of hemp was assessed using cafeteria-style choice tests. Higher numbers of beet leafhoppers were trapped in and around hemp fields in 2022 than in 2021 in all 3 locations. BCTV was found to infect all 3 types of hemp (cannabidiol or CBD, fiber, and grain) in 2022 in 1 location and only a single CBD variety of hemp in the other 2 locations. Two BCTV strains were identified in CBD hemp, while an additional BCTV strain was found infecting chile pepper grown at the same location.

Harvester ants create habitats along nest rims, which some plants use as refugia. These refugia can enhance ecosystem stability to disturbances like drought and grazing, but their potential role in invasion ecology is not yet tested. Here we examine the effects of drought and grazing on nest-rim refugia of 2 harvester ant species: Pogonomyrmex occidentals and P. rugosus. We selected 4 rangeland sites with high harvester ant nest densities in northern Arizona, USA, with pre-existing grazing exclosures adjacent to heavily grazed habitat. Our objective was to determine whether nest refugia were used by native or exotic plant species for each site and scenario of drought and grazing. We measured vegetation cover on nest surfaces, on nest rims, and at 3 distances (3, 5, and 10 m) from nests. At each site, we sampled 2 treatments (grazed/excluded) during 2 seasons (drought/monsoon). We found that nest rims increased vegetation cover compared with background levels at all sites and in almost all scenarios of treatment and season, indicating that nest rims provide important refugia for plants from drought and cattle grazing. In some cases, plants enhanced on nest rims were native grasses such as blue gramma (Bouteloua gracilis) or forbs such as sunflowers (Helianthus petiolaris). However, nest rims at all sites enhanced exotic species, particularly Russian thistle (Salsola tragus), purslane (Portulaca oleracea), and bull thistle (Cirsium vulgare). These results suggest that harvester ants play important roles in invasion ecology and restoration. We discuss potential mechanisms for why certain plant species use nest-rim refugia and how harvester ant nests contribute to plant community dynamics.

We examine consequences of climate-induced range expansion on community composition and diversity within trees attacked by the southern pine beetle (Dendroctonus frontalis Zimmermann). At the northernmost limit of the southern pine beetle range where populations have persisted for multiple years (currently Long Island, NY), we collected and reared bark samples and placed emergence traps on southern pine beetle-attacked pitch pine, Pinus rigida Mill. (Pinales: Pinaceae). From these samples, we quantified southern pine beetle gallery length and emergence as well as the diversity and abundance of all associated insects including known and suspected competitors, predators, and parasitoids. We compared our results to that of historic sampling data (1975-1997) in the core of southern pine beetle's range in the southern United States. Key community members were present in both the northern and southern regions; composition and relative abundances differed markedly. A key predator, the clerid beetle Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), was present in similar densities in both regions. Southern pine beetle infested a greater proportion of the length of the tree bole in the North. This increased tree utilization may be a consequence of a lack of resource competition by Ips De Geer (Coleoptera: Curculionidae) engraver beetles, which we found only in very low abundance in the northern sites. We discuss the implications of these results in the context of southern pine beetle range expansion. Continued study of the southern pine beetle community and temporal southern pine beetle dynamics in the North will add to our current knowledge base and aid preservation of rare and ecologically valuable pine barrens of New England.

For herbivorous insects with a broad diet breadth, host plant identity can influence larval development by either accelerating or delaying growth. For some species of Lepidoptera, the number of larval instars varies depending on the host plant's identity. Fall webworm (Hyphantria cunea, Drury) is a polyphagous herbivore that feeds on over 450 host plants worldwide. Of the 2 morphotypes (red- and black-head) of fall webworm, the number of instars for the red-head fall webworms has not been characterized. Given its broad diet breadth, fall webworm developmental stages may vary with plant identity. We investigated whether host plant identity affected the number of instars observed during red-head fall webworm development. We measured the head capsules of over 6,000 fall webworm larvae reared on 6 different plants commonly eaten by fall webworms in Colorado. We modeled head capsule widths as Gaussian mixture models, with a Gaussian distribution that corresponded to each instar. We show that our red-head fall webworms varied in number of instars depending on the identity of their host plant upon which they fed. We found that red-head fall webworm exhibited 7 instars on 5 of the host plants and 8 instars on 1 host plant that we studied. Our results for the number of instars for red-head fall webworm are consistent with reports of the number of instars for black-head fall webworm. Our research provides insight into the influence of host plant identity on fall webworm development, which can be used to advance lab and field research of this species.

Cannabis sativa or hemp, defined as <0.3% total tetrahydrocannabinol (THC), is a specialty crop in the United States, of particular interest among growers in the southeastern United States to replace tobacco production. Tetranychus urticae (twospotted spider mite), Aculops cannabicola (hemp russet mite), Polyphagotarsonemus latus (broad mites), and Phorodon cannabis (cannabis aphids) are considered the most significant pests in greenhouse grown hemp. Mite and aphid injury can cause cupping and yellowing of leaves, resulting in leaf drop, and reduced flower and resin production. We sought to understand the effects of feeding by T. urticae and Myzus persicae (green peach aphid), as a proxy for P. cannabis, on the concentration of economically significant cannabinoids through a series of experiments on greenhouse grown plants. First, we compared the variability of chemical concentrations in samples collected from individual plants versus pooled samples from 5 plants, and found that chemical concentrations in single plants were similar to those in pooled plant samples. Next, we compared chemical concentrations prior to arthropod infestation and post infestation. When evaluating the mite feeding damage in 2020, cannabinoids in plants infested with high densities of T. urticae increased more slowly than in uninfested control plants or plants infested with low T. urticae densities. In 2021, the concentration of tetrahydrocannabinol did not differ significantly between treatments. Cannabidiol increased more slowly in plants with low T. urticae densities when compared to uninfested controls but did not differ from the high T. urticae densities 14 days after infestation.

Hemp russet mite, Aculops cannibicola Farkas (Acari: Eriophyidae), is one of the key pests of hemp, Cannabis sativa L. (Rosales: Cannabaceae). Hemp russet mite feeds primarily on new growth and can reach high densities, frequently exceeding a thousand mites per leaf, and leading to a decrease in yield and quality of cannabinoids. The objective of this experiment was to determine the efficacy of reduced-risk pesticides used in organic crop protection as well as conventional insecticides in managing hemp russet mites in a greenhouse and field. Hemp (var. Unicorn) was exposed to leaves heavily infested with hemp russet mites, and once mite densities reached an average of 50 mites per leaf, the following insecticides were applied to the plants: abamectin, etoxazole, fenpyroximate, rosemary oil, and 2 concentrations of a mineral oil. An application of sulfur was also included in the field experiment. Treatments were replicated 9 times in the greenhouse and 6 times in the field. Each of the pesticides significantly reduced hemp russet mite densities in the greenhouse, with all treatments resulting in significant decrease in mite populations 10 days after the initial treatment that persisted until the end of the experiment. On the other hand, only fenpyroximate, sulfur, and rosemary oil provided strong and effective suppression of the mites in the field. This is the first study to test these products against hemp russet mites in hemp, and our outcomes indicate that several pesticides available for organic crop production can provide effective control of the pest.

Arthropods use a variety of environmental cues to navigate between and locate hosts. In agricultural systems, clarifying the relevant cues and their effects on arthropod behavior can inform management practices to reduce or inhibit the activity of arthropod pests. The lesser mealworm Alphitobius diaperinus (Panzer) is a ubiquitous arthropod pest of broiler house chicken production, and while the patterns of movement and behavior of A. diaperinus are well documented, the specific environmental factors that govern these patterns are not known. We conducted behavioral assays testing the response of A. diaperinus adults and larvae to different wavelengths of light and to the presence of water. Alphitobius diaperinus displayed a significant repulsion from white, green, red, and blue light, while larvae consistently sought shelter and displayed no behavioral change in response to light. Dehydrated adult beetles displayed an attraction to water while hydrated beetles displayed a repulsion to water. Regardless of the availability of water, dehydrated beetles displayed a reduced repulsion from light. Taken together, these results indicate that A. diaperinus will hide from sources of light unless they are dehydrated. Knowledge of the environmental cues that influence the behavior of A. diaperinus could be used to improve methods of trapping, monitoring, and controlling populations of A. diaperinus in experimental and commercial settings.

Of the many arthropod species affecting hemp (Cannabis sativa L.) cultivation in the United States, one species of particular importance is the hemp russet mite (Aculops cannabicola, HRM). Hemp russet mite is a microscopic arthropod which feeds on all parts of hemp plants. Due to its minute size, HRM can proliferate undetected for a long time, complicating management efforts and causing serious economic losses. DNA sequencing and PCR assays can facilitate accurate identification and early detection of HRM in infested-plants. Therefore, a real-time SYBR Green based species-specific PCR assay (quantitative PCR, qPCR) was developed for the identification of HRM DNA by amplification of a 104 bp Internal Transcribed Spacer 1 (ITS1) sequence. The detection limit was estimated to be approximately 48 copies of the HRM marker gene sequence. The real-time-PCR assay is rapid, detects all life stages of mite under 2 hours. A 10-fold serial dilution of the plasmid DNA containing the ITS1 insert were used as standards in the real-time PCR assay. The quantification cycle (Cq) value of the assay showed a strong linear relationship with HRM DNA with R2 of 0.96. The assay was tested against several commonly found hemp pests including two-spotted spider mite and western flower thrips to determine specificity of the assay and to show that no non-target species DNA was amplified. The outcomes of this research will have important applications for agricultural biosecurity through accurate identification of HRM, early detection and timely deployment of management tactics to manage and prevent pest outbreaks.