Microbial communities are essential for plant health, but using these relationships to enhance growth and pest protection is challenging. Leveraging the natural mechanisms plants employ to manage relationships with microbes is one promising means to selectively engineer whole microbial communities with beneficial properties. This approach, known as host-guided selection, has been successful in some model species targeting performance traits (e.g., biomass). However, few studies use crop plants or focus on defensive traits (e.g., pest resistance). Our goal was to naturally engineer tomato root-associated microbiomes that increase resistance to insect pests. First, we used an iterative soil microbial inoculation process to engineer insect-suppressive rhizosphere soil microbiomes that reduce damage from aphid feeding (Macrosiphum euphorbiae) or caterpillar defoliation (Manduca sexta, Spodoptera exigua). We then characterized the bacterial and fungal microbial communities of soils associated with differences in insect performance using metabarcoding approaches. Overall, soil microbiome selection produced transient differences in aphid performance, but caterpillar growth was unaffected. In four of nine generations, the aphid population growth rate was significantly lower on plants with rhizospheres selected for low insect performance, where abundance was reduced by up to 20%. Correspondingly minor shifts in fungal and bacterial relative abundance occurred in insect-suppressive communities. However, network analysis indicated that aphid feeding disrupted rhizosphere microbiome assembly, resulting in lower community complexity and connectivity and fewer structurally important taxa compared with uninfested controls. Overall, our results highlight critical factors for successful engineering of beneficial microbiomes, particularly insect feeding guild and microbial community stability.

Larvae of the southern corn rootworm (SCR) Diabrotica undecimpunctata howardi Barber (Coleoptera: Chrysomelidae) are primary pests of peanut in the Virginia-Carolina region of the United States, and are relatively sporadic pests in southern states such as Georgia, Alabama, and Florida. Peanuts have strict quality standards which, when they are not met, can diminish crop value by more than 65%. Management of direct pests like SCR is therefore crucial to maintaining the economic viability of the crop. The soil-dwelling nature of SCR larvae complicates management due to difficulties associated with monitoring and predicting infestations. Nonchemical management options are limited in this system; preventative insecticide applications are the most reliable management strategy for at-risk fields. Chlorpyrifos was the standard product for larval SCR management in peanut until its registration was revoked in 2022, leaving no effective chemical management option for larvae. We tested a novel insecticide, isocycloseram, for its ability to reduce pod scarring, pod penetration, and non-SCR pod damage in field studies conducted in Suffolk, Virginia in 2020-2022. Overall injury was low in 2020 and 2022, and in 2022 there was not a significant effect of treatment. In 2021, 2 simulated chemigation applications of isocycloseram in July significantly reduced pod scarring and overall pod injury relative to chlorpyrifos and the untreated control. Our results suggest that isocycloseram may become an effective option for managing SCR in peanut, although more work is needed to understand the mechanisms by which it is effective as a soil-applied insecticide.

The EFSA Panel on Plant Health performed a pest categorisation of Dendrolimus punctatus (Lepidoptera: Lasiocampidae), following a commodity risk assessment of bonsai Pinus parviflora grafted onto P. thunbergii from China, in which D. punctatus was identified as a pest of possible concern to the European Union (EU). D. punctatus, also known as the Masson pine caterpillar, is present in China, Taiwan, Vietnam, India and has recently spread to Japanese islands close to Taiwan. Larval feeding on the needles of Pinus elliottii, P. luchuensis, P. massoniana, P. merkusii and P. tabulaeformis causes important damage. D. punctatus larvae can also feed on P. armandii, P. echinata, P. latteri, P. parviflora, P. sylvestris var. mongolica, P. taeda, P. taiwanensis and P. thunbergii, but full development on these hosts is uncertain. The pest has three to five generations per year; winter is spent as larvae on branch tips, on tree trunks and in the soil. The females lay egg clusters on pine needles. Pupation occurs in cocoons attached to branches or needles. D. punctatus could enter the EU either as eggs, larvae or pupae in the foliage of plants for planting or cut branches, as larvae on wood with bark or as overwintering larvae in branches, crevices in the bark or in the litter of potted plants. However, Annex VI of 2019/2072 prohibits the introduction of D. punctatus hosts (Pinus spp.) from countries and areas where the pest occurs. There are climate zones where the pest occurs in Asia that also occur in the EU, though they are limited, which constitutes an uncertainty regarding establishment. The pest's main hosts are not grown in the EU. However, the fact that it attacks the North American Pinus echinata, P. elliottii and P. taeda in its Asian native area suggests a potential capacity to shift to pine species occurring in the EU territory. D. punctatus satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. Whether the Pinus commonly found in Europe could act as hosts is unknown but is fundamental, affecting the criteria of establishment and magnitude of impact.

The forest-tundra interface is the world's largest ecotone, and is globally important due to its biodiversity, climatic sensitivity, and natural resources. The ecological communities which characterize this ecotone, and which provide local and global ecosystem services, are affected by environmental variation at multiple scales. We explored correlations between environmental variables and macroinvertebrate and soil prokaryote communities in the forest-tundra ecotone of the Yukon, Canada. We found that each tussock tundra site possessed a distinct community of macroinvertebrates and prokaryotes, and therefore represented a unique contribution to regional biodiversity. Prokaryote diversity increased with active layer depth, which could be an effect of temperature, or could be evidence of a species-area effect. Prokaryote diversity decreased with lichen cover, which could be due to antimicrobial properties of lichen. The macroinvertebrate community composition was affected by proximity to a human disturbance, the Dempster Highway. Both macroinvertebrate and prokaryote community compositions changed along the latitudinal transect, as the biome transitioned from taiga to tundra. We also found that the abundance of carnivores relative to herbivores decreased with latitude, which adds to recent evidence that predation decreases with latitude. Our survey yielded new insights about how macro- and microorganisms vary together and independently in relation to environmental variables at multiple scales in a forest-tundra ecotone.