Insect pests in a changing climate: Implications for pest management in apple orchards

Outbreaks of insect pests impacting agricultural crops are increasingly attributed to global climate change. Temperature, moisture regimes, relative humidity, and other climatic variables can all directly influence the development, distribution, and abundance of agricultural pests. Eye-spotted bud moth, Spilonota ocellana (Lepidoptera: Tortricidae), has recently reached economically damaging levels in organic apple orchards of semi-arid interior of British Columbia. To investigate how climate variables impact S. ocellana survival, we focused on spring frost events during emergence of overwintered larvae, and the characteristically hot, dry mid-summer weather during oviposition. While spring events such as emergence and budbreak are occurring earlier in response to warming, this earlier start to the season can also mean greater exposure to frost for insect herbivores. Meanwhile, mid-season dry heat events can lead to desiccation and mortality of immobile egg life stages. Under controlled conditions, we determined the threshold sub-zero recovery temperature and exposure limit of recently emerged spring larvae, along with the optimum temperature and moisture conditions for egg development and survival.