Climate change effects on walnut pests in California

Abstract

Increasing temperatures are likely to impact ectothermic pests of fruits and nuts. This paper aims to assess changes to pest pressure in California's US$0.7 billion walnut industry due to recent historic and projected future temperature changes. For two past (1950 and 2000) and 18 future climate scenarios (2041-2060 and 2080-2099; each for three General Circulation Models and three greenhouse gas emissions scenarios), 100 years of hourly temperature were generated for 205 locations. Degree-day models were used to project mean generation numbers for codling moth (Cydia pomonella L.), navel orangeworm (Amyelois transitella Walker), two-spotted spider mite (Tetranychus urticae Koch), and European red mite (Panonychus ulmi Koch). In the Central Valley, the number of codling moth generations predicted for degree days accumulated between April 1 and October 1 rose from 2-4 in 1950 to 3-5 among all future scenarios. Generation numbers increased from 10-18 to 14-24 for two-spotted spider mite, from 9-14 to 14-20 for European red mite, and from 2-4 to up to 5 for navel orangeworm. Overall pest pressure can thus be expected to increase substantially. Our study did not include the possibility of higher winter survival rates, leading to higher initial pest counts in spring, or of extended pest development times in the summer, factors that are likely to exacerbate future pest pressure. On the other hand, initiation of diapause may prevent an extension of the season length for arthropods, and higher incidence of heat death in summer may constrain pest population sizes. More information on the impact of climate change on complex agroecological food webs and on the response of pests to high temperatures is needed for improving the reliability of projections.

Simulated climate-warming increases Coleoptera activity-densities and reduces community diversity in a cereal crop

“…Insect pests and pathogens are currently responsible for the loss of up to 25-30% of crops in Europe and the United States of America, and this is predicted to rise as a result of global warming (Maxmen, 2013). Thus, modelling the impacts of climate change scenarios on agricultural insect pests, predators and their ecological interactions is a research priority (Luedeling et al, 2011;Ziter et al, 2012;Tylianakis et al, 2008;Schweiger et al, 2012). However, for future modelling projections to be accurate they need to be parameterised and validated by experimental evidence, which is mostly lacking.…”

Walnut (Juglans spp.) ecophysiology in response to environmental stresses and potential acclimation to climate change

“…Certain walnut growing regions could be impacted according to current predictions of future climates, such as the western USA (Allen et al 2010) and portions of Europe under Mediterranean and temperate continental climates (Lindner et al 2010). There is already some modeling evidence suggesting climate change may lower chilling requirements in California, making walnut more vulnerable to frost-induced embolism in early spring (Baldocchi and Wong 2008) and pest attacks (Luedeling et al 2011). Similarly, phenological models indicate that increasing spring temperatures may advance bud break by up to 4 weeks in central Europe, thus increasing spring frost hazard (Crepinsek et al 2009).…”

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…These findings could have significant implications for mite outbreaks under future climate change scenarios, when longer periods of drought and less water availability are expected for irrigated crops like tomato in semiarid environments (IPCC, 2013). Moreover, T. urticae is expected to have more generations per year as a direct effect of rising temperature on mite developmental rates, increasing mite pressure (Luedeling et al, 2011), which might contribute to exacerbate mite damage.…”

“…However, frequent acaricide applications have often led to development of resistance, as this species is the arthropod with the most pesticide numbered resistance reports . Besides more generations per year are expected for T. urticae induced by global warming according to climatic and distribution models (Luedeling et al, 2011), whereas a negative effect of dry and hot conditions is expected on some of its predators (Ferrero et al, 2010), which might increase the risk of outbreaks in the future. Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae), the tomato red spider mite, is an emerging pest of solanaceous plants worldwide.…”

“…The intimate relationship between plants and herbivores, which in some cases results in devastating crop losses, will be altered by global climate change. In the case of arthropods, the increase in temperature will shorten their life cycle, having as consequences more generations per year and an earlier appearance of the pest (Luedeling et al, 2011;Delucia et al, 2012;Bebber, 2015). In addition, phytophagous pests will expand their distribution area as a consequence of increases in northern temperatures, a process that will be helped by trade, a factor responsible for introduction of invasive species (Parmesan, 2006;Meynard et al, 2013;Bebber, 2015).…”