Environmental Entomology最新文献

Pesticide drift into sensitive habitats is an increasing concern in agricultural landscapes due to negative impacts on non-target animals including wild bees and other beneficial insects. Creating buffer zones between the crop and sensitive habitats has been commonly proposed as a mitigation measure for reducing off-target pesticide deposition. Given prior evidence of significant pesticide deposition in wildflower plantings adjacent to highbush blueberry farms in Michigan, the aim of this study was to determine the buffer zone needed to significantly reduce pesticide deposition in these plantings. We used silicone bands as passive pesticide samplers placed at varying distances between 0 and 32 m from the crop at conventionally managed blueberry farms during the fruit ripening period when insecticide applications are common. We found there was no significant reduction in number of active ingredients detected in samples at any measured distance from the crop. There was also no significant reduction in pesticide concentration (summed mass of all active ingredients) until 24 m from the field border, and this change was driven by reductions in concentrations of fungicides as there was no significant reduction in total insecticide or herbicide deposition at any of the tested distances. Drift reduction measures, such as installation of windbreaks and use of precision application methods are recommended to reduce off-target pesticide movement.

Cold winter temperatures affect the distribution and abundance of the mountain pine beetle, Dendroctonus ponderosae Hopkins, an eruptive tree-killing bark beetle native to pine forests of western North America. The cold-tolerant larval stage often overwinters but adults also enter winter in some regions or years yet little is known about their ability to survive winter. Here we report on experiments to assess the cold tolerance of mature, brood adults. Adult mountain pine beetles exhibited a strong cold-hardening response over a period of weeks to months that intensified at colder temperatures; however, adult beetles from Cranbrook, which experiences cold winters, were more cold hardy than adults from Victoria, which has mild winters. These results are consistent with a seasonal cold-hardening response that is affected by both environmental factors and local adaptation to climate. The lowest mean and minimum lethal temperatures recorded for preconditioned adults during the study were ‒26.8 and ‒32.2 °C, respectively. Preconditioned adults from Cranbrook and Victoria challenged with prolonged exposure to a cold temperature (‒18 °C) suffered negligible mortality after 8 d; almost half of the Victoria adults and three-quarters of the Cranbrook population were still alive after 28 d. Adults had a limited ability to rapidly cold harden but possessed substantial basal cold tolerance. Our results on the cold tolerance of the adult stage of the mountain pine beetle are expected to contribute to models of forest disturbances that incorporate the population dynamics and climatic suitability of forests for tree-killing bark beetles.

Tracking individual insects with harmonic radar (HR) allows observations of insect movement behavior under wild and semi-wild conditions. However, attaching tags to insects has the potential to alter natural behavior. Quantifying the negative effects of tag attachment may allow researchers to correct movement parameters to account for deviations from natural movements, thus producing more accurate estimates of insect behavior. Using two HR tag sizes, ~350 (small) and ~570 μg (large), the movements of Ceratitis capitata and Bactrocera dorsalis were investigated in flight tubes and an outdoor field cage. Bactrocera dorsalis with small tags attached did not perform differently than untagged flies in flight tubes, while flies with large tags took longer to exit the tubes. Time to exit did not vary with B. dorsalis body size, wing area, or wing length for any tagged status (untagged, small, or large). However, B. dorsalis exit times did vary with rearing and irradiation status but not with sex. For C. capitata, negative impacts were observed on both the time to exit and the failure to exit rate. Field cage experiments revealed differences in movement parameters among tested groups. For instance, female, colony-reared, non-irradiated, B. dorsalis showed the greatest bias in (pseudo) turning angles; male, wild, non-irradiated, B. dorsalis showed the weakest correlation between flight and wind direction (β); and colony-reared C. capitata showed random movement directions (other groups showed directional biases). This study shows the feasibility of tracking tephritids as small as C. capitata and demonstrates the advantages of using the smallest possible tags.

As an emerging forestry pest characterized by rapid spread, wide distribution, and significant damage, Euwallacea interjectus necessitates comprehensive and scientifically validated chemical control measures. Currently, there is a lack of large-scale and precise experimental data on the efficacy of insecticides and fungicides for chemical control. Even for closely related ambrosia beetles, existing chemical control methods have unresolved aspects. Given the high dependency of E. interjectus life cycle on its symbiotic fungi, this study employed fungicides as a pivotal control strategy. Additionally, to mitigate potential secondary environmental hazards associated with broad-spectrum insecticides, detailed toxicity tests were conducted in laboratory settings, followed by field spray experiments. An organosilicon compound was utilized to examine the synergistic effects of insecticides, and liquid chromatography was employed to quantify insecticide residues in the xylem of host trees. In the laboratory, beta-cyfluthrin exhibited the lowest LC50 value (8.989 mg/L), achieving an 80.6% reduction in beetle infestations after 30 d. The addition of adjuvants increased residue levels by 2.5%, thereby enhancing control efficacy. Among the tested fungicides, a 4:1 mixture of fludioxonil and prochloraz-manganese chloride complex demonstrated the highest efficacy, with an EC50 value of 2.669 mg/L. In field experiments, spraying at a concentration of 2000 mg/L resulted in a 58.7% reduction in beetle infestations after 60 d. The findings provide a scientific basis for the control of E. interjectus and the judicious application of chemical pesticides, offering technical support for the management of wood-boring pests in forestry production.

Cornegenapsylla sinica is a devastating pest of longan that vectors the longan pathogen witches' broom virus (LgWB), leading to significant agricultural losses. Efficient control strategies targeting this pest are imperative for sustainable longan production. However, the genetic research on C. sinica is relatively limited, which may hinder the discovery of effective control strategies. Accurate gene expression analysis under various conditions using RT-qPCR is essential for advancing our understanding of this pest and for identifying potential targets for management. In this study, a comprehensive array of specific algorithms, including geNorm, Normfinder, BestKeeper, and the ΔCt method, was applied to assess the stability of 8 candidate reference genes under 4 distinct experimental conditions: developmental stages, sex, tissue, and temperature. Through the application of RefFinder software, a ranking of expression stability among the candidate genes was established. The results indicated that RPL13 and RPL6 were the most stable reference genes under varying developmental stages and temperatures, ATPB and RPL13 were the top choices for different sexes, and RPL13 and EF1α were the most stable in different tissues. Additionally, heat shock protein 70 (Hsp70) served as a reporter gene to validate the selected reference genes. This study is the first to report detailed data on comprehensive reference genes suitable for RT-qPCR in C. sinica, laying the groundwork for biological control and functional target gene research in this species, which is crucial for preventing the spread of longan witches' broom virus in longan trees.

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), is a polyphagous woodboring beetle that infests and damages hardwood host trees in Asia, Europe, and North America. Native to China and the Korean peninsula, ALB is invasive in both North America and Europe. Due to the large environmental and economic impacts associated with ALB, much effort has been placed on its management and eradication from invaded areas. Eradication programs consist of visual surveys, regulatory quarantines, host removal, public outreach and education, and in some cases, insecticides. Host removal is effective but is laborious and costly, and while insecticides have been useful as a component of some eradication programs, they can be expensive, ineffective, and environmentally detrimental. Thus, several arthropod biological control agents (BCAs) have been evaluated which could support a more environmentally friendly management strategy to supplement traditional ALB management tactics. Here, we review the biological control strategy for ALB, including the exploration within the native and invaded ranges of the pest, to find potential arthropod BCAs. We discuss the ecological premise behind the method as well as the potential for its success, and we identify knowledge gaps and future considerations for the enactment of this method. While biological control shows promise, care will be needed in utilizing this method, and further research must explore the success of BCAs in field settings.

Understanding the demography of Xyleborini ambrosia beetles and accurately estimating their optimal growth temperatures remains a challenge due to their cryptic behavior and complex reproductive habits. In this study, we reared the ambrosia beetle Xyleborus bispinatus at five distinct temperatures (17 °C, 20 °C, 26 °C, 29 °C, and 35 °C) over a 36-d period. Population dynamics, growth rates, and life cycle durations were assessed through destructive sampling every 4 d for each temperature treatment. To analyze temperature-dependent growth and development, a nonlinear model was fitted to the intrinsic growth rate values at each temperature, allowing us to determine the species' optimal temperature and corresponding maximum growth rate. In the laboratory, X. bispinatus exhibited optimal growth rates between 26 °C and 29 °C, with rates of 0.10 and 0.12, individuals/individuals/day, and life cycle durations of 20 and 16 d, respectively. However, based on the fitted growth curve, the thermal optimum was estimated at 26.2 °C, where the maximum intrinsic growth rate reached 0.13 individuals/individuals/day. Given its potential to transmit Harringtonia lauricola, these findings provide valuable insights into the thermal effects on X. bispinatus throughout its life cycle and offer a practical approach for estimating growth rates and thresholds in species with cryptic behavior or where cohort tracking is challenging for demographic assessments.

Symbiotic nitrogen-fixing plants such as Russian olive can significantly impact soil chemistry and invertebrate biodiversity in riparian ecosystems. Here, the effects of Russian olive on soil chemical properties and invertebrate communities in riparian zones of the southwestern United States were investigated. Russian olive stands were compared to native cottonwood stands and restoration sites by analyzing soil nitrogen (N), phosphorus (P), and moisture levels, and arthropod diversity and abundance. Sites where Russian olive is present led to a net increase in soil nitrogen, a decrease in soil phosphorus, and greater soil moisture compared to both native cottonwood stands and restoration sites. Native cottonwood stands showed lower soil N and higher P levels, as well as higher arthropod diversity. This increased diversity could be linked to the soil's nutrient stoichiometry, as there is a negative correlation between taxonomic diversity and the soil N:P ratio. Moreover, there was a greater abundance of detritivorous arthropods in Russian olive stands compared to native vegetation. Soil nitrate (NO3-) levels showed a strong positive correlation with detritivorous arthropod abundance (r2 = 0.98), but only a moderate correlation with herbivores (r2 = 0.38), and NO3- was unrelated to predator abundance (r2 = 0.01). These results suggest that Russian olive stands can alter soil chemistry in ways that disproportionately benefit detritivores, potentially disrupting the balance of arthropod communities and reducing overall biodiversity in riparian ecosystems. The study underscores the need for careful management of invasive, symbiotic N2-fixing plant species to preserve the ecological integrity of riparian habitats.

During the eradication program undertaken against Anoplophora glabripennis (Motschulsky) in the Greater Toronto Area, information was collected on the numerous signs of injury found on wounded trees. Herein, we used a portion of this information to assess the characteristics of logs with signs of oviposition (i.e., pits). Specifically, we related the basal diameter, type (log bole vs. log branch), height above ground, and branch hierarchy level of logs with pits to tree size (i.e., height and diameter at breast height) and level of infestation intensity. In general, pits were concentrated on logs from the bole and branches that were 8-14 cm in diameter in the lower 8 m of the bole and in the first 2 levels of the branching hierarchy. Oviposition pit location was strongly influenced by tree size-both height and diameter at breast height, with more pits on the lower bole in small trees and then higher on the bole and into the branches as tree size increased. As tree-level infestation intensity increased, pits were found on both larger and smaller diameter portions of the trees, presumably as preferred oviposition sites became saturated. These findings can improve the efficacy of surveillance activities for A. glabripennis.

This study addresses how gut symbiont, Caballeronia insecticola, could change reproductive capacity, mating behaviors, and copulation success of host insect, Riptortus pedestris (Fabricius) (Hemiptera: Alydidae). First, we evaluated symbiotic effects on the female reproductive capacity with varying numbers of males available to a female. Overall, symbiotic females displayed on average a 1.8-fold increase in egg production compared to aposymbiotic individuals. However, eggs from symbiotic females were on average 42% less viable, compared to those from the aposymbiotic, when paired with single male. The decrease in the hatchability was alleviated to 12% when paired with 3 males. Consequently, this yielded significant increase in the number of viable offspring by symbiotic females when multiple males were available. Second, we evaluated symbiotic effects on male morphometric characteristics including hind legs used as weapon, and found significant increases in hind leg sizes associated with symbiosis. Finally, we investigated mating behaviors between a female and 2 males of different symbiotic status. Symbiotic females displayed on average a 1.4-fold increase in the number of copulations compared to the aposymbiotic. From both female types, however, no significant difference was observed in their mate choice and copulation success rate between aposymbiotic and symbiotic males. However, symbiotic females exhibited on average 17% reduction in copulation duration compared to the aposymbiotic. Copulation failure was caused more frequently by female's rejection than by intruder male's disruption for both female types. Our study demonstrates that symbiotic females benefit from the symbiosis increasing their reproductive capacity and copulation frequency.