Environmental Entomology最新文献

Temperate-zone Geometridae moths, active across seasons, offer an excellent model for investigating how related species respond to varying environmental conditions, particularly photoperiod-a major Zeitgeber regulating biological oscillators. In this study, we examined the daily cycle of sperm release from the testes in 9 geometer moth species, including univoltine and bivoltine taxa, as well as diurnal and nocturnal species. We found that sperm release into the upper vasa deferentia differs consistently between day-flying and night-flying species. Moreover, we observed marked differences in the diel regulation of sperm release between spring and summer generations of the same species. Experimental evidence suggests that these intergenerational differences are photoperiod-dependent. Further manipulation confirmed that a long photoperiod not only abolishes rhythmic sperm release but also significantly reduces the number of eupyrene sperm bundles transferred into the vasa deferentia. This is the first demonstration, under near-natural conditions, of photoperiodic regulation of a physiological rhythm in a peripheral organ via its suppression. These findings underscore the importance of environmental timing cues in reproductive physiology and provide new insights into the temporal plasticity of insect reproductive systems. Importantly, they also highlight the potential for integrating agro-chronobiological knowledge with mechanistic studies of temporal regulation in insect pests. Finally, this work adds to our understanding of how peripheral oscillators may be shaped by selective pressures in closely related species occupying distinct ecological niches, where differences in the timing of life-history processes serve as key axes of divergence.

Osmia lignaria Say, the blue orchard bee is a native managed bee used to pollinate almond orchards and other early-blooming fruit crops. While this pollinator has proven effective for almond pollination, in-orchard propagation of this species has proven difficult. This study analyzed the usefulness of planting early blooming annuals within orchards to enhance on-site propagation of O. lignaria during pollination. Three native species were established between rows (inter-row flower strips, IRFS) in an isolated almond orchard in California's southern Central Valley. Pollination by O. lignaria was provided as a supplement to that provided by recommended levels of honey bee (Apis mellifera) hives. Proportion of supplemental pollen within brood provisions collected during the almond bloom period was analyzed with respect to the distance of nesting domiciles from IRFS and time interval. Maximal use of supplemental pollen occurred within a proximity of 0 to 40 m between th nest box and the IRFS. Activity levels of O. lignaria in the IRFS increased through the almond bloom period, peaking during the last third of the IRFS bloom. At the end of almond bloom, O. lignaria numbers sharply declined as honey bee numbers increased on the IRFS. Other native bee species also utilized the IRFS. This study reveals that 40 m or less between in-orchard floral plantings and nest boxes for O. lignaria optimized IRFS utilization, providing a pathway for determining nest box placement relative to IRFS plantings. Comments are made on practical considerations with respect to orchard management.

Why and how herbivorous insects choose to feed on some plant species and not others can be influenced by many factors; however, it is not always clear why herbivorous insects will choose to lay their eggs on some plants over others. The Hopkins' host selection principle (hereafter HHSP) hypothesizes that female insects prefer to lay eggs on host plants upon which they fed as larvae, but there are studies that both support and refute the hypothesis. Here, we test HHSP in a dietary generalist moth, fall webworm (Hyphantria cunea, hereafter FW). Previously, local host plant abundance has been the only factor found to determine FW host plant use; whether FW exhibit individual host plant preferences is unknown. We conducted preference tests with females of the two FW morphotypes (red-head and black-head), presenting females with four host plants: their one natal host plant, two other potential host plants, and one non-host plant for that morphotype that is a host plant for the other morphotype. Overwhelmingly, females of both morphotypes oviposited on a non-plant surface in the choice arena and those that did oviposit on a plant did not distinguish between host plants and non-host plants. Of the few FW females that oviposited on a host plant, only red-head females showed preference for their natal hosts. Our results support previous findings that HHSP is not a strong driver of host plant selection, suggesting that female FW are not selective in their choice of host plants, which may facilitate generalism in this species.

The use of native plant cultivars in pollinator plantings is somewhat controversial. Although some cultivars originate from wild populations, others are bred for novel ornamental traits, which may have unintended impacts on floral rewards, such as nectar and pollen. It is unclear whether changes in floral displays and/or rewards may alter plant-pollinator relationships. We established an experimental garden of Pacific Northwest native plants and native cultivars to evaluate differences in their floral traits and bee communities. We used a combination of methodologies to quantify variation in plant traits that could influence pollinator foraging, including those associated with floral displays (eg petal color, corolla morphology) and floral rewards (pollen and nectar). We also measured changes in bee community composition (eg species associations, functional diversity) across plant groups. We found that cultivars varied significantly from native plants across multiple floral display or reward traits. No plants were bred for nectar or pollen traits, thus changes in rewards were likely pleiotropic. Nine out of 10 tested cultivars had dissimilar bee communities to their native plant counterpart, though minimally developed cultivars were associated with similar bee species and functional traits. Our results suggest that the development of native plant cultivars can come at the cost of pollinator functional richness, though some variation in bee composition may be expected among wild plant populations with diverse phenotypes. Plants with phenotypes consistent with wild-type plants tended to support functionally rich bee communities and should be emphasized in plantings to maximize potential benefits to pollinators.

Bactericera maculipennis (Crawford) and Bactericera cockerelli (Šulc) (Hemiptera: Triozidae) share hosts within the Solanaceae and Convolvulaceae (Solanales), and both are associated with "Candidatus Liberibacter solanacearum" (Lso). Lso, transmitted by B. cockerelli, causes diseases in solanaceous crops including zebra chip disease of potato. Up to 50% of B. maculipennis adults also harbor Lso, but transmission of Lso to plants by this psyllid has not been confirmed yet. The only documented field host of B. maculipennis in the Pacific Northwest is Convolvulus arvensis L. (Convolvulaceae) but diagnostic methods fail to detect Lso in leaves of this plant. It is therefore unclear how Lso persists within B. maculipennis populations. We surveyed species of Convolvulaceae and Solanaceae for B. maculipennis and report a widespread association between B. maculipennis and Lso throughout the western United States. Diagnostic polymerase chain reaction failed to detect Lso from leaves of C. arvensis yet readily detected Lso from stems where B. maculipennis nymphs tend to feed. Bactericera maculipennis transmitted Lso to species of Convolvulaceae in greenhouse experiments, confirming vector competency. We report high rates of Lso infection in populations of both B. maculipennis and B. cockerelli occurring on C. arvensis, but occurrence of B. cockerelli on C. arvensis was limited to autumn months only and with very low populations. Results suggest C. arvensis is a non-crop reservoir of Lso but do not suggest that B. maculipennis is a direct threat to solanaceous crops or that C. arvensis is a major source of Lso-infected B. cockerelli colonizing potato fields.

Elongate hemlock scale, Fiorinia externa Ferris (Hemiptera: Diaspididae), is an invasive pest of eastern hemlock, Tsuga canadensis, and other Pinaceae such as Fraser fir, Abies fraseri. Cut Fraser firs (ie for Christmas trees and other holiday greenery) with F. externa have been intercepted in US states beyond where the insect is known to be established and, in some cases, where exposure to freezing temperatures might be prolonged. This study measures the effect of constant low temperatures (3, -10, or -20 °C) on survival of overwintering F. externa females from eastern hemlock in Michigan and from eastern hemlock and Fraser fir in North Carolina. Survival was determined with biochemical viability testing, which assesses the presence of metabolically active cells, and changes in survivorship through time were quantified with Kaplan-Meier methods and beta regression. Collection date and host occasionally affected survival rate but not in a consistent pattern. Survival rates generally decreased as temperature decreased. At 3 °C, F. externa maintained high survival (>75%). At -10 °C, survival was projected to fall to 50% within 22 to 92 d and 10% by 45 to 195 d. At -20 °C, survival typically declined to 50% by 1 to 27 d and 10% by 6 to 52 d. We used survival durations at -20 °C to map how often F. externa might experience 50 or 90% mortality from prolonged cold exposure. Temperatures in recent winters have not been below -20 °C for long enough to stop F. externa from spreading throughout the ranges of eastern hemlock or other hosts in Canada and the continental United States.

When sap-feeding insects invade ecosystems, they create novel resource subsidies by exposing previously unavailable resources to resident consumers. Spotted lanternfly, Lycorma delicatula (White), is an invasive phloem-feeding planthopper native to Asia that has spread across multiple US states since its 2014 detection in Pennsylvania. It heavily feeds on tree-of-heaven, Ailanthus altissima (Mill.) Swingle, an invasive tree naturalized across the United States that previously lacked sap-feeders. During feeding, L. delicatula excretes honeydew and creates sap-exuding wounds, providing carbohydrate resources. Here, we document invertebrates consuming these subsidies in southeastern Pennsylvania from June to October 2021. At 43 sites sampled 3 times, we measured L. delicatula biomass via circle trunk traps and recorded 1,576 feeding observations through visual surveys. These observations were made up predominantly of Hymenoptera (78.0%) and Diptera (19.5%), with smaller proportions of Coleoptera (0.76%), Lepidoptera (0.44%), Hemiptera (0.44%), Orthoptera (0.38%), Opiliones (0.38%), and Stylommatophora (0.06%). Among Hymenoptera, we identified 33 species (29 native, 4 introduced) from 13 families, including key pollinators and parasitoids. The invasive wasp, Vespa crabro, was abundant and exhibited aggressive behaviors toward native consumers, including pollinators. Using redundancy analysis, we tested whether spatiotemporal variation in L. delicatula biomass explained the composition of honeydew-feeding Hymenoptera compared to other environmental factors. Lycorma delicatula biomass was the strongest predictor of Hymenoptera community composition, with temperature, landscape-scale impervious surface, and site-scale vegetation structure also contributing. The L. delicatula invasion has created novel resource subsidies for many invertebrates and altered temporal dynamics of Hymenoptera, with potential cascading effects on pollination and biocontrol ecosystem services.

The planthopper Lycorma delicatula (White) (spotted lanternfly; SLF) was introduced to North America from Asia. It was first found in southeastern Pennsylvania in 2014 and now, a decade later, has increased in abundance and spread into 18 eastern US states. To study naturally occurring fungal pathogens infecting SLF, eastern Pennsylvania sites were sampled every 1 to 2 wk in 2020 and 2021 during the adult life stage of L. delicatula to detect prevalence of infections by the fungi Batkoa major (Thaxt.) Humber (Entomophthorales: Batkoaceae) and Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae). To sample, living adult SLF were collected and reared and cause of death was diagnosed. In 2020, at the site hosting a co-epizootic of these 2 generalist pathogens in 2018, an epizootic caused by B. major was documented from 30 September to 21 October. Low levels of infection by both pathogens were detected at an additional 2020 site and both 2021 sites. Overall, there was a negative association of B. major infection with SLF density and no association with density for B. bassiana. Co-infections in individual SLF by both fungi were never documented, and there was an inverse relationship between prevalence of B. major and B. bassiana infections in the sampled populations. At the time that SLF for rearing were sampled, adult cadavers were also sampled. For B. major, infection rates of sampled cadavers and reared individuals were positively correlated, but higher infection rates were observed in cadavers than among reared SLF. For B. bassiana, no such pattern occurred.

Multivoltine insects, those having more than one generation per year, often use daylength as a cue for terminating reproduction and entering diapause prior to the onset of winter. In a common garden experiment in Corvallis, Oregon, USA (44.6°), we compared voltinism and impacts of the loosestrife leaf beetle Galerucella calmariensis, a classical biological control agent for the wetland weed purple loosestrife (Lythrum salicaria), sourced from 6 locations in their introduced range (39.4 to 48.8° N). The populations were known to have diverged in their critical daylength for diapause since introduction in 1992. After rearing the populations in similar conditions for a generation, and overwintering the adult beetles outdoors, we followed cohorts of eggs on size-matched potted plants as they developed with natural timing through 2 generations in a randomized complete block design. Adult beetles from both the first and second generations were sampled to determine their reproductive status and voltinism. We harvested, dried, and weighed inflorescences and roots of the plants to measure agent impact. The 6 beetle populations were found to differ significantly in both voltinism and impacts, with a higher voltinism corresponding with greater impact. We also showed that voltinism in the introduced location was, to some extent, predictable based on laboratory determined photoperiod response curves, but other factors including plant quality also appeared to be influential. These results show that the efficacy of a biological control agent varies by geographic source and that this can be at least partially predicted by the population's diapause response to photoperiod.