The Japanese beetle, Popillia japonica (Newman, 1841) (Coleoptera: Scarabaeidae), was first detected in southern Washington State in 2020. Widespread trapping efforts ensued, and over 23,000 individuals were collected in both 2021 and 2022 in this region known for specialty crop production. The invasion of Japanese beetle is of major concern as it feeds on over 300 plant species and has shown an ability to spread across landscapes. Here, we created a habitat suitability model for Japanese beetle in Washington and used dispersal models to forecast invasion scenarios. Our models predict that the area of current establishment occurs in a region with highly suitable habitat. Moreover, vast areas of habitat that are likely highly suitable for Japanese beetle occur in coastal areas of western Washington, with medium to highly suitable habitat in central and eastern Washington. Dispersal models suggested that the beetle could spread throughout Washington within 20 years without management, which justifies quarantine and eradication measures. Timely map-based predictions can be useful tools to guide management of invasive species while also increasing citizen engagement to invaders.

Viral insect‐borne plant pathogens have devastating impacts in agroecosystems. Vector‐borne pathogens are often transmitted by generalist insects that move between non‐crop and crop hosts. Insect vectors can have wide diet breadths, but it is often unknown which hosts serve as pathogen reservoirs and which non‐crop host harbours the highest density of vectors. In the Pacific Northwest USA, the pea aphid (Acyrthosiphon pisum) is a key virus vector in pulse crops. Despite pea aphid having a large number of potential non‐crop plant hosts occuring in the region, no reservoir has yet been identified for the economically‐costly pathogen Pea Enation Mosaic Virus (PEMV). We addressed these issues by linking field surveys of an aphid vector and plant virus with statistical models to develop risk assessments for common non‐crop legumes; in 2018, we completed a 65‐site survey where aphids were surveyed in weedy legumes within and outside dry pea fields. We quantified the abundance of pea aphids on 17 hosts, and plant tissue was tested for PEMV. Relatively high densities of A. pisum were found in habitats dominated by hairy vetch (Vicia villosa), which was the only legume other than cultivated dry pea where PEMV was detected. Our results indicate that V. villosa is a key alternative host for PEMV, and that pest management practices in this region should consider the distribution and abundance of this weedy host in viral disease mitigation efforts for pulses.

Vector-borne plant viruses are a diverse and dynamic threat to agriculture with hundreds of economically damaging viruses and insect vector species. Mathematical models have greatly increased our understanding of how alterations of vector life history and host–vector–pathogen interactions can affect virus transmission. However, insect vectors also interact with species such as predators and competitors in food webs, and these interactions affect vector population size and behaviors in ways that mediate virus transmission. Studies assessing how species’ interactions affect vector-borne pathogen transmission are limited in both number and scale, hampering the development of models that appropriately capture community-level effects on virus prevalence. Here, we review vector traits and community factors that affect virus transmission, explore the existing models of vector-borne virus transmission and areas where the principles of community ecology could improve the models and management, and finally evaluate virus transmission in agricultural systems. We conclude that models have expanded our understanding of disease dynamics through simulations of transmission but are limited in their ability to reflect the complexity of ecological interactions in real systems. We also document a need for experiments in agroecosystems, where the high availability of historical and remote-sensing data could serve to validate and improve vector-borne virus transmission models.

Soil rhizobia promote nitrogen fixation in legume hosts, maximizing their tolerance to different biotic stressors, plant biomass, crop growth, and yield. While the presence of soil rhizobia is considered beneficial for plants, few studies have assessed whether variation in rhizobia abundance affects the tolerance of legumes to stressors. To address this, we assessed the effects of variable soil rhizobia inoculum concentrations on interactions between a legume host (Pisum sativum), a vector insect (Acyrthosiphon pisum), and a virus (Pea enation mosaic virus, PEMV). We showed that increased rhizobia abundance reduces the inhibitory effects of PEMV on the nodule formation and root growth in 2-week-old plants. However, these trends were reversed in 4-week-old plants. Rhizobia abundance did not affect shoot growth or virus prevalence in 2- or 4-week-old plants. Our results show that rhizobia abundance may indirectly affect legume tolerance to a virus, but effects varied based on plant age. To assess the mechanisms that mediated interactions between rhizobia, plants, aphids, and PEMV, we measured the relative expression of gene transcripts related to plant defense signaling. Rhizobia concentrations did not strongly affect the expression of defense genes associated with phytohormone signaling. Our study shows that an abundance of soil rhizobia may impact a plant’s ability to tolerate stressors such as vector-borne pathogens, as well as aid in developing sustainable pest and pathogen management systems for legume crops. More broadly, understanding how variable rhizobia concentrations can optimize legume-rhizobia symbiosis may enhance the productivity of legume crops.

In agroecosystems, plants frequently confront multiple biotic stressors, including herbivores and pathogens. The nature of these interactions plays a crucial role in mediating the activation of plant defense mechanisms. However, induction of plant chemical defenses has been more well studied than the induction of physical defenses. Here, we assessed the physical and chemical defense responses of pea (Pisum sativum) plants after exposure to three stressors: a vector herbivore (pea aphid, Acrythosiphon pisum), a non-vector herbivore (pea leaf weevil, Sitona lineatus), and a virus (Pea enation mosaic virus, PEMV). We used various histochemical staining techniques show that viruliferous A. pisum (transmitting PEMV) strongly induced callose deposition (aniline blue staining) and antioxidant-mediated defenses (DAB and NBT staining) in peas, primarily through accumulating reactive oxygen species (ROS). High-throughput phenotyping showed that viruliferous aphids reduced plant photosynthetic efficiency, but plants infected with PEMV had increased cell death (trypan blue staining). However, herbivory by aphids and weevils did not strongly induce defenses in peas, even though weevil feeding significantly reduced pea leaf area. These results show that not all herbivores induce strong defensive responses, and plant responses to vector species depends on their virus infection status. More broadly, our results indicate that variable stressors differentially regulate various plant responses through intricate chemical and physical defense pathways.