The synthesis of secondary metabolites is a hallmark of plant defence against herbivores. These compounds may be detrimental to consumers, but can also protect herbivores against parasites. Floral nectar commonly contains secondary metabolites, but little is known about the impacts of nectar chemistry on pollinators, including bees. We hypothesized that nectar secondary metabolites could reduce bee parasite infection. We inoculated individual bumblebees with Crithidia bombi , an intestinal parasite, and tested effects of eight naturally occurring nectar chemicals on parasite population growth. Secondary metabolites strongly reduced parasite load, with significant effects of alkaloids, terpenoids and iridoid glycosides ranging from 61 to 81%. Using microcolonies, we also investigated costs and benefits of consuming anabasine, the compound with the strongest effect on parasites, in infected and uninfected bees. Anabasine increased time to egg laying, and Crithidia reduced bee survival. However, anabasine consumption did not mitigate the negative effects of Crithidia , and Crithidia infection did not alter anabasine consumption. Our novel results highlight that although secondary metabolites may not rescue survival in infected bees, they may play a vital role in mediating Crithidia transmission within and between colonies by reducing Crithidia infection intensities.

Neonicotinoids are widely used systemic insecticides that have been associated with spider mite outbreaks on diverse plants. These insecticides have complex effects on plant physiology, which have been speculated to drive enhanced performance of spider mites. We used RNA-Seq to explore how neonicotinoids modify gene expression in soybean thereby lowering plant resistance. We exposed soybean (Glycine max L.) to two neonicotinoid insecticides, thiamethoxam applied to seeds and imidacloprid applied as a soil drench, and we exposed a subset of these plants to spider mites (Tetranychus cinnabarinus). Applications of both insecticides downregulated genes involved in plant—pathogen interactions, phytohormone pathways, phenylpropanoid pathway, and cell wall biosynthesis. These effects were especially pronounced in plants exposed to thiamethoxam. Introduction of spider mites restored induction of genes in these pathways in plants treated with imidacloprid, while expression of genes involved in phenylpropanoid synthesis, in particular, remained downregulated in thiamethoxam-treated plants. Our outcomes indicate that both insecticides suppress genes in pathways relevant to plant–arthropod interactions, and suppression of genes involved in cell wall synthesis may explain lower plant resistance to spider mites, cell-content feeders. These effects appear to be particularly significant when plants are exposed to neonicotinoids applied to soybean seeds.

In organic agronomic cropping systems, the use of synthetic insecticides and transgenic varieties are prohibited and producers rely mainly on biological control, tillage, crop rotation, and other cultural practices to manage pests. We measured damage to organic corn (Zea mays L.) from multiple invertebrate pests, including slugs (Gastropoda: Mollusca), European corn borer (Ostrinia nubilalis Hübner), corn earworm (Helicoverpa zea Boddie), and fall armyworm (Spodoptera frugiperda Smith), early and late in the growing season in four cropping systems that varied in tillage frequency and intensity and in winter cover crop species. Specific management tactics included two cover crop mixtures preceding corn, the use of a roller-crimper or tillage to terminate cover crops preceding corn, and the establishment of interseeded cover crops after corn emergence. Prevalence of early-season damage was high, but severity of damage was very low and unrelated to corn yield. The proportion of corn plants affected by chewing pests early in the season was lower in plots in which tillage compared to a roller-crimper was used to terminate cover crops. Cropping system did not affect the numbers of late-season caterpillar pests or corn yield. Predation by natural enemies appeared to effectively maintain damage from chewing pests below yield-damaging levels. These results support the inclusion of winter and interseeded cover crops in organic agronomic crop rotations to gain environmental benefits without increasing risks of damage by insect pests.

The widespread establishment of Drosophila suzukii (Matsumura) has instigated a classical biological program in the United States and Europe for this invasive pest of soft-skinned fruits. This study reports the first release of an introduced key Asian larval parasitoid, Ganaspis kimorum Buffington (Hymenoptera: Figitidae), in 3 Mid-Atlantic states (Delaware, Maryland, and Pennsylvania), where a total of 26,950 wasps were released in 6 counties during the 2022 and 2023 fruit seasons. Pre-release monitoring in 2023 and 2024 recovered G. kimorum individuals, indicating successful overwintering of parasitoids released in 2022 and 2023. A total of 617 pre- and post-release fruit collections were conducted in a temporal sequence of ripening fruits of 30 different fruit species throughout the 2022 and 2023 fruit seasons at all release locations. G. kimorum were recovered in 40 post-release samples from 9 different host plants at all release locations. However, the overall levels of mean parasitism by G. kimorum were <2% at this early stage of release. At the same time, adventive populations of an unreleased key Asian larval parasitoid, Leptopilina japonica Novković & Kimura (Hymenoptera: Figitidae) were found from 16 sampled host plants throughout the fruit season. Mean parasitism of D. suzukii (primarily by L. japonica) ranged from 0% to 20.0%, which varied by season and host plant but peaked with fruiting of the most D. suzukii-infested wild hosts. We discuss potential ecological mechanisms that may affect the establishment and impacts of these key parasitoids on D. suzukii in this region and future release strategies for G. kimorum.