Entomopathogenic fungi to control bark beetles: a review of ecological recommendations.

There is considerable interest in applying entomopathogenic fungi as a biological control to limit insect populations due to their low environmental and human applicator impacts. However, despite many promising laboratory tests, there are few examples where these fungi were successfully applied to manage bark beetles. Here, we explore how environmental conditions unique to bark beetle habitats may have limited previous entomopathogenic fungus applications, including variable temperatures, ultraviolet light, bark beetle symbiotic microorganisms, tree phytochemicals, and cryptic bark beetle behaviors. Based on the existing literature, we provide a framework for interpreting the pathogenicity of entomopathogenic fungi to bark beetles, with emphasis on both standardizing and improving laboratory approaches to enhance field applications. Our synthesis indicates that most previous laboratory evaluations are conducted under conditions that are not representative of actual bark beetle systems; this may render fungal isolates functionally non-pathogenic in field settings. We recommend that future studies place particular effort into understanding entomopathogen response to the presence of bark beetle symbiotic microorganisms, plant phytochemicals, and potential as a tree endophyte. Additionally, field application methods should aid entomopathogens in overcoming stressful conditions and allow the fungus to infect multiple bark beetle life stages. © 2021 Society of Chemical Industry.

Bark beetle outbreak enhances biodiversity and foraging habitat of native bees in alpine landscapes of the southern Rocky Mountains.

Landscape-scale bark beetle outbreaks alter forest structure with direct and indirect effects on plants and animals in forest ecosystems. Using alpine spruce forest and a native bee community as a study system, we tested how tree mortality from bark beetles impacts bee foraging habitats and populations. Bees were collected across the growing season (early-, middle-, and late-season) for two years using passive trapping methods, and collections were used to analyze patterns in species abundances and diversity. Three important findings emerged: (1) forest stands that were post-outbreak had 62% higher floral density and 68% more floral species during peak bloom, respectively, than non-affected stands; (2) bee captures were highest early-season (June) and were not strongly affected by bark beetle outbreak; however, mean number of bee species and Shannon-Weiner diversity were significantly higher in post-outbreak stands and this effect was pronounced early in the growing season. Corresponding analysis of ß-diversity indicated higher accumulation of bee biodiversity in post-outbreak stands and a turnover in the ratio of Bombus: Osmia; (3) bee captures were linked to variation in foraging habitat, but number of bee species and diversity were more strongly predicted by forest structure. Our results provide evidence of increased alpine bee biodiversity in post-outbreak stands and increased availability of floral resources. We conclude that large-scale disturbance from bark beetle outbreaks may drive shifts in pollinator community composition through cascading effects on floral resources, mediated via mortality of overstory trees.

Hazardous Agricultural Tasks Completed by Youth as Part of their Supervised Agricultural Experience (SAE): A Descriptive Study.

This study describes tasks that middle school and high school youth, ages 13 to 18 years, completed during the 2015-2016 academic year as part of their supervised agricultural experience (SAE). The overarching goal was to collect information useful in directing classroom instruction to better prepare youth prior to engaging in agricultural tasks identified as hazardous by the U.S. Department of Labor. Using a list of eleven tasks currently identified as hazardous and 17 tasks proposed as hazardous, teachers were asked how many of their students engaged in each of the 28 tasks as part of their SAE. The 320 teachers from four U.S. geographic regions reported that students most frequently completed SAEs in the areas of livestock production (f = 6746, 26.6%), agricultural mechanics (f = 2695, 10.6%), home and/or community development (f = 2296, 9.0%), and crop production (f = 2250, 8.9%). Students often engaged in tasks associated with ATV/UTV operation (f = 7618, 10.3%), tractor operation (f = 5554, 7.5%), and assisting tractor operation (f = 5,081, 6.9%) as part of their SAE. All of these tasks are well documented in the literature as contributing to injuries and fatalities of both youth and adults.

Laboratory and Field Evaluation of the Entomopathogenic Fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) for Population Management of Spruce Beetle, Dendroctonus rufipennis (Coleoptera: Scolytinae), in Felled Trees and Factors Limiting Pathogen Success.

An isolate of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) was tested for its ability to reduce survival and reproduction of spruce beetle, Dendroctonus rufipennis (Kirby) (Coleoptera: Scolytinae), under laboratory and field conditions. Conidial suspension applied directly to adults or to filter papers that adults contacted had a median survival time of 3-4 d in laboratory assays and beetles died more rapidly when exposed to conidial suspension than when treated with surfactant solution only. In the field, conidial suspension was applied to the surface of felled and pheromone-baited Engelmann spruce (Picea engelmannii) trees using a backpack sprayer. Mortality of colonizing parent beetles (F0), reproduction (abundance of F1 offspring in logs), and emergence of F1 beetles from logs was compared between treated and nontreated logs. Application of spore suspension increased mortality of F0 adults by 36% on average. Total F1 reproduction was reduced by 17% and emergence from logs was reduced by 13% in treated logs, but considerable variability in reproduction and emergence was observed. Viable spores were re-isolated from treated logs up to 90 d after application, indicating that spores are capable of long-term persistence on the tree bole microhabitat. Subsequent in vitro tests revealed that temperatures below 15°C and exposure to spruce monoterpenes likely limit performance of B. bassiana under field conditions, but exposure to low-intensity light or interactions with spruce beetle symbiotic fungi were not strongly inhibitory. It is concluded that matching environmental tolerances of biocontrol fungi to field conditions can likely improve their usefulness for control of spruce beetle in windthrown trees.