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Understanding the circumstances under which insect herbivores will adopt a novel host plant is a longstanding question in basic and applied ecology. While geographic variation in host use can arise through differences in both herbivore preference and plant characteristics, there is a tendency to attribute geographic variation in host use to regional differences in herbivore preference alone. This is especially true for herbivores specialized to one or a few plant species. We compared how geographic variation in herbivore preference and host plant origin shape regional differences in host plant use by the specialized herbivore,Euphydryas phaeton. In parts of its range,E. phaetonuses only a native host,Chelone glabra, while in others, it also uses an introduced host,Plantago lanceolata. We offered female butterflies from each region the non-native host plant sourced from both regions and compared their oviposition behavior. The non-native host was almost universally rejected by butterflies in the region where only the native plant is used. In the region where butterflies use both hosts, females accepted non-native plants from their natal region twice as often as non-native plants from the other region where they are not used. Acceptance differed substantially among individual butterflies within regions but not among plants within regions. Thus, both individual preference and regional differences in both the insect and non-native host contributed to the geographic variation in different ways. These results highlight that, in addition to herbivore preference, regional differences in perceived plant suitability may be an important driver of diet breadth.

Wild pollinators are critical to maintaining ecosystem services and facilitating crop production, but habitat degradation and resource loss are leading to worldwide pollinator declines. Nutrient enrichment and changes in rainfall due to global warming are drivers of global environmental change, and likely to impact pollinator foraging behavior and reproductive success through changes to the growth and phenology of flowering plants. Here, we provide a short review of pollinator conservation in the context of nutritional ecology and plant-pollinator interactions. Then, we present novel research into the effects of nutrient and rainfall variation on plant phenology. In this study, we experimentally manipulated the amount of water and supplemental nutrients available to wild sunflower (Helianthus annuus) and goldenrod (Solidagospp.) throughout their growing season. We evaluated how changes in growth and bloom time could impact resource availability for bumble bee (Bombus impatiens) queens preparing to overwinter. We found that fertilizer and rainfall alter plant bloom time by 2–18 days, though flowering response was species-specific. Fertilizer did not significantly affect plant growth or number of flowers produced when plants were grown under drought conditions. When water was not limiting, fertilized sunflowers bloomed in floral pulses. These findings carry important implications for growers and land managers, providing insight into potential drivers of wild pollinator decline and possible conservation strategies.

1. Multivariate climate change is expected to impact insect densities and plant growth in complex, and potentially different, ways. Tea (Camellia sinensis) is a unique crop system where the increase in quality from chemical defences induced byEmpoasca onukii(Homoptera: Cicadellidae) feeding can outweigh reductions in yield and make attack by this leafhopper desirable to tea farmers. Differential impacts of weather attributes on tea and herbivores could impact feasibility of this unique farming strategy in a rapidly changing climate.

2. We monitored leafhopper densities and tea shoot growth at a tea farm in Fujian Province, China for 2 months (June and July). We used distributed lag non‐linear models to capture potentially delayed and non‐linear effects of weather attributes on tea growth and leafhopper densities.

3. Weather attributes had contrasting effects on leafhopper density and tea shoot growth. Leafhopper densities were highest with low daily mean and maximum temperatures, while warm temperatures favoured tea growth. Effects of temperature on leafhoppers were delayed, while effects on tea growth were immediate. Precipitation reduced tea growth, and had a delayed positive effect on leafhopper density.

4. The delayed effects of weather attributes on leafhoppers indicate that earlier, less conspicuous life stages (i.e. eggs and early instar nymphs) may be susceptible to desiccation. Although increasing annual mean temperature is commonly predicted to benefit multivoltine insect pests, our results show that cool, wet conditions benefitE. onukiiduring summer months when they are most abundant. These results have implications for tea green leafhopper management strategies.

Trees attacked by multiple herbivores need to defend themselves against dynamic biotic challenges; appropriate responses to one stressor can elicit hormonal responses that are antagonistic to another. Hemlock (Tsuga canadensis) infestation by hemlock woolly adelgid (HWA;Adelges tsugae) results in the accumulation of the defensive hormone salicylic acid.