Environmental Entomology最新文献

Interspecific competition is an important ecological concept which can play a major role in insect population dynamics. In the southeastern United States, a complex of stink bugs (Hemiptera: Pentatomidae), primarily the brown stink bug, Euschistus servus (Say), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), are the 2 most common pests of field corn, Zea mays L. (Poales: Poaceae). Stink bugs have the greatest potential for economic injury during the late stages of vegetative corn development when feeding can result in deformed or "banana-shaped" ears and reduced grain yield. Corn earworm moths lay eggs on corn silks during the first stages of reproductive development. A 2-year field study was conducted to determine the impact of feeding by the brown stink bug during late-vegetative stages on subsequent corn earworm oviposition, larval infestations, and grain yield. Brown stink bug feeding prior to tasseling caused deformed ears and reduced overall grain yield by up to 92%. Across all trials, varying levels of brown stink bug density and injury reduced the number of corn earworm larvae by 29-100% and larval feeding by 46-85%. Averaged across brown stink bug densities, later planted corn experienced a 9-fold increase in number of corn earworm larvae. This is the first study demonstrating a competitive interaction between these major pests in a field corn setting, and these results have potential implications for insect resistance management.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are often the target of insecticide seed treatments commonly used in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production in North America. Nevertheless, there is a lack of knowledge of the species, life history, and economic impact of wireworms present in these agroecosystems. An extensive survey of wireworms was conducted in corn and soybean fields in Ontario, Canada, from 2014 to 2017 to document species distribution and co-occurrence and to identify risk factors related to their abundance. In total, 4,332 specimens were collected from 1,245 different sampling records. The dominant species collected was Limonius agonus (Say) (Coleoptera: Elateridae) comprising 71.5% of the specimens. The remaining wireworm specimens were identified as Hypnoidus abbreviatus (Say), Melanotus similis (Kirby), M. cribulosus (LeConte), M. depressus (Melsheimer), M. communis (Gyllenhal), Agriotes mancus (Say), Aeolus mellillus (Say), and Hemicrepidius spp (Germar). Multiple wireworm species were found to commonly occur within the same field and the same sample. Path analysis was conducted to investigate whether site, soil, and agronomic characteristics influenced wireworm distribution and abundance. Several significant relationships were found between wireworm species and geographic factors, soil texture, and agronomic practices. The results of this survey provide critical information that can be used to improve integrated pest management of the major wireworm genera found in corn and soybean agroecosystems in Ontario.

Identifying dormancy traits is important for predicting insect population success, particularly in a changing climate that could disrupt evolved traits. The mountain pine beetle (Dendroctonus ponderosae Hopkins) is native to North America, is responsible for millions of acres of tree mortality, and is expanding northward in Canada. Research has identified thermal traits important to epidemic-phase ecology that vary among populations. Genomic research identified 3 mountain pine beetle haplogroups representing Pleistocene glacial refugia. Significant variation in generation timing aligning with the haplogroups has been observed. The adult stage was previously identified as the likely cause of differences among populations, although the mechanism(s) remain unclear. We tested for an adult summer diapause that varies among populations from 2 haplogroups, southern Colorado (CO) (central haplogroup) and southern Idaho (ID) (eastern haplogroup) using respirometry and reproduction experiments. Warm temperatures (25 °C) resulted in reduced respiration rates of central haplogroup mountain pine beetle compared to a cool temperature treatment (15 °C), whereas respiration of the eastern haplogroup did not differ between the treatments. Mated pairs of central haplogroup mountain pine beetle reared/held at 15 °C were more likely to be classified with a higher reproductive success rating compared to pairs reared/held at 25 °C. These results support a facultative summer adult diapause in southern CO central haplogroup mountain pine beetle. Manifestation of this diapause was low/absent among adults from the northerly ID location. This diapause likely serves to maintain univoltinism shown to be important for mountain pine beetle epidemic-phase ecology. The variation occurring among haplogroups highlights the long-term, evolved processes driving local adaptations in mountain pine beetle.

Avocado lace bug, Pseudocysta perseae (Heidemann) (Hemiptera: Tingidae), is a sap-feeding insect that feeds on the underside of avocado leaves. First observed in 2019, P. perseae has spread throughout the Hawaiian islands, causing premature leaf drop and decrease in avocado yield. Due to Hawai'i's approximately 200 cultivars comprised of all 3 avocado races with extensive racial hybrids, we were able to investigate whether certain cultivars were more prone to experiencing higher P. perseae abundances and infestations compared to others. We conducted longitudinal abundance surveys on Hawai'i Island across several common avocado varieties monitoring changes in P. perseae abundance. These surveys were supplemented with longitudinal infestation severity surveys across 4 avocado lineages (Mexican, Guatemalan, West Indian, and Guatemalan × West Indian hybrid). Additionally, we collected leaves of 'Sharwil', 'Hass', 'Kahalu'u', and 'Nishikawa' cultivars looking at associations between P. perseae abundance and cultivar, herbivory-related biomechanical traits, and soluble sugar content. We found that some cultivars, such as 'Malama', typically experience lower P. perseae abundances compared to cultivars such as 'Kahalu'u', 'Beshore', and 'Sharwil'. Guatemalan × West Indian hybrid trees were also shown to have a higher probability of experiencing more severe P. perseae infestations compared to other lineages. Lastly, soluble sugar content, specifically fructose content, had a positive effect on juvenile P. perseae abundance. These findings suggest that cultivar differences in P. perseae infestations may exist, but tree-to-tree leaf compositional differences, such as soluble sugar content, may be a large driver of variation in P. perseae abundance.

Oxyclozanide (OXY) is an anthelmintic widely used in the treatment of flatworm infection and fasciolosis. It also has antiadenovirus, antibiofilm, antifungal, and antibacterial activities. Various chemicals have been suggested as alternative chemicals in insect pest management. Here, the oxidative and genotoxic effects of OXY on 7th instars, pupae and adults of the model organism Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) were examined. First-instar larvae were reared on 0.003, 0.03, 0.3, and 1.5 g OXY per 100 g artificial diets. Compared with all tested OXY concentrations and controls without OXY, dietary OXY led to increased antioxidant capacity and genotoxic effects. Concentrations of malondialdehyde, an oxidative stress marker, were significantly increased in adults of larvae reared on OXY-charged diets at 0.3 and 1.5 g/100 g compared to the adult control group. We also recorded a significant increase in the genotoxic test data (Tail length, Tail DNA %, Tail moment) at the same stages and concentrations. We recorded significant increases in glutathione-S-transferase, superoxide dismutase (SOD) and glutathione peroxidase activities in larvae fed high OXY concentrations. SOD and catalase activities were also significantly increased at the concentration of 0.03 g/100 g of OXY in the pupal and adult stages. Cytochrome P450 monooxygenase activity was significantly increased at the highest concentration of OXY in the larval and pupal stages. Also, our regression analysis indicates a correlation between the markers of oxidative stress, antioxidant enzymes and comet parameters. These data indicate that OXY induces oxidative stress and antioxidative enzyme response.

Certain species of true fruit flies (Diptera: Tephritidae) cause tremendous damage to commercially important fruits and vegetables, and many countries operate continuous trapping programs which rely on male-specific lures such as trimedlure (TML), methyl eugenol (ME), and cue-lure (CL). Traditionally, these attractants have been applied as liquids to cotton wicks inside traps, although this results in high evaporative loss of the lure. Slow-release, polymeric plugs have been widely adopted for TML, but such devices are not widely used for ME or CL. Recent data, however, suggest that ME and CL plugs may be attractive for as long as 12 wk in the field. The present study investigates whether ME and CL plugs weathered for 18 or 24 wk are effective in capturing males of Bactrocera dorsalis (Hendel) and Zeugodacus cucurbitae (Coquillett), respectively. For B. dorsalis, 6 g ME plugs were as effective as the control treatment (fresh liquid on a wick) after 12 wk of weathering but not after 18 or 24 wk. For Z. cucurbitae, 3 g CL plugs were as effective as the control treatment (fresh CL plugs) after 12 and 18 wk of weathering but not after 24 wk. The residual content and release rate of the 2 lures were also measured over time, but, with the exception of the residual content of ME, we did not find a direct correlation between these parameters and numbers of flies captured.

The wetsalts tiger beetle, Cicindelidia haemorrhagica (LeConte) (Coleoptera: Cicindelidae), is found in several active thermal hot spring areas in Yellowstone National Park (YNP) where substrate surface temperatures can exceed 50 °C. However, relationships between surface temperatures and the time adults spend on them remain poorly understood. Therefore, we characterized thermal profiles of Dragon Spring and Rabbit Creek, 2 thermally active research sites containing C. haemorrhagica in YNP, to quantify the time adults spend at different surface temperatures. We took 58 thermal video recordings of adults over 6 total days of observation ranging from 10 to 15 min for each adult. Thermal video analysis results indicated a positive relationship between the total time adult beetles spent on surface temperatures from Dragon Spring and Rabbit Creek as temperatures increased from 20 °C. Once surface temperatures exceeded 40 °C, the total time spent at those surface temperatures declined. Adults were recorded on substrates exceeding 50 °C at one of the 2 research locations. Rabbit Creek had substantially more instances of adults present with surface temperatures exceeding 40 °C, including one individual on a surface temperature of 61.5 °C. There were 3 instances of beetles spending more than 4 min at a particular surface temperature, all within the preferred range of 30-40 °C. Our thermal profile results and previous behavioral observations suggest that adults may be resistant to the heat produced from the thermal waters that influence the substrate temperatures but may not be subject to high surface temperatures as previously reported.

The stink bugs Acrosternum arabicum Wagner and Brachynema germari Kolenati (Hemiptera: Pentatomidae) damage developing pistachio nuts in Iran. Ooencyrtus egeria Huang and Noyes (Hymenoptera: Encyrtidae) parasitizes eggs of both species, alternating between them seasonally. We compared the biological and life history attributes of O. egeria reared for 3 generations on each host species with those that had been transferred to the alternate host for 2 generations. We also tested female responses to host egg density. Eggs of B. germari were parasitized at higher rates and yielded faster wasp development, heavier female progeny with greater fecundity, and a more female-biased sex ratio, than eggs of A. arabicum. Rearing on A. arabicum did not diminish wasp fitness on B. germari, and the F1 progeny of wasps switched to A. arabicum inherited some beneficial parental effects from rearing on B. germari. Regardless of host species, females parasitized fewer eggs in 8 h as density increased from 10 to 30 eggs, but progeny sex ratio (% female) increased. The anomalous response to host density appears to arise from a combination of behavioral and egg load constraints. Females mature only 10-12 eggs per day. Carefully inspect egg clusters before selecting the most suitable eggs for oviposition, a more time-consuming process for large clusters. Our results indicate that rearing O. egeria on eggs of A. arabicum, which are more convenient and cost-effective to produce than those of B. germari, will not diminish its performance on B. germari following augmentative release, beyond a slight reduction in female fecundity.

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is a key pest in Southeastern peach production by infesting fruit and decreasing yield. In Northeastern apples, plum curculio was found to have an "edge effect," where more plum curculio are present next to a forested border than in the center of an orchard, and their propensity to fly or walk depended on air temperature. We conducted field studies over 3 seasons (2019-2021) to investigate whether plum curculio in small Southeastern peach plots exhibits the edge effect and to determine its primary mode of movement (flying or walking). Our results revealed that plum curculio did not exhibit the edge effect in Southeastern peaches. Thus, unlike Northeastern apples where plum curculio exhibits the edge effect, the reduced-input application program where insecticide sprays mainly target a few perimeter-row trees instead of the whole orchard for plum curculio management is not recommended for Southeastern peaches. Additionally, we observed that plum curculio in Southeastern peaches did not exhibit a primary mode of movement, and in most of the sampling weeks, the numbers of flying and walking plum curculio were not significantly correlated in the field. These results emphasize that using plum curculio sampling tools that only capture flying or walking plum curculio is not ideal for monitoring plum curculio activity in the Southeast. Overall, our findings indicate that plum curculio in Southeastern small peach plots and Northeastern apples does not exhibit the same behavior (i.e., edge effect and propensity to fly or walk).

Phytoplasmas can negatively or positively alter vector host fitness. "Candidatus Phytoplasma pyri," is the causal agent of pear decline in commercial pear (Pyrus communis L.; Rosales: Rosaceae) and peach yellow leafroll in peach [Prunus persica (L.); Rosaceae]. This plant pathogen is transmitted by several species of pear psyllids (Cacopsylla spp. Hemiptera: Psyllidae). We sought to explore the relationship between the pear decline phytoplasma and its US vector, Cacopsylla pyricola (Förster), at the molecular genetic level through transcriptomic analysis using RNA-sequencing methodology. We also focused on phytoplasma and insect effectors, which are secreted proteins that can modulate interactions within a pathosystem. In this study, we identified 30 differentially expressed genes, 14 candidate insect effector genes, and 8 Ca. Phytoplasma pyri candidate effectors. Two strains of Ca. Phytoplasma pyri were identified based on immunodominant membrane protein sequence analysis from C. pyricola collected in the Pacific Northwest agricultural region. Here, we present a first genetic look at the pear decline pathosystem and report gene candidates for further exploration of infection mechanisms and potential tools for integrated pest management.