Effects of soil temperature and snow cover on the mortality of overwintering pupae of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Predicting the Distribution of Neoceratitis asiatica (Diptera: Tephritidae), a Primary Pest of Goji Berry in China, under Climate Change

Climate warming affects the growth and development of pests, resulting in changes in their geographical distribution, which increases the difficulty in terms of prevention and control. The fruit fly, Neoceratitis asiatica (Becker), is a predominant frugivorous pest that causes serious yield loss in the goji berry, Lycium barbarum L. In recent years, with the expansion of cultivation area, the damage induced by the pest has become increasingly severe, significantly impeding the production of the goji berry. In this study, the potential suitable habitats of N. asiatica under current and future climate scenarios were simulated and predicted using the optimal MaxEnt model, based on the screening distribution records and environmental factors. The changes in the pest distribution under climate change were determined using ArcGIS. The results showed that the best combination of parameters for MaxEnt were feature combination (FC) = LQPT and regularization multiplier (RM) = 1. The dominant environmental factors influencing pest distribution were mean temperature of driest quarter, mean temperature of coldest quarter and precipitation of coldest quarter. Under different climate conditions, the suitable habitats of the pest primarily ranged between 27°-47° N and 73°-115° E. Under current climate conditions, the area of moderately and highly suitable habitats was 42.18 × 104 km2, and mainly distributed in Inner Mongolia (13.68 × 104 km2), Gansu (9.40 × 104 km2), Ningxia (5.07 × 104 km2), Qinghai (4.10 × 104 km2), and Xinjiang (3.97 × 104 km2) Provinces. Under future climate scenarios, the suitable area was projected to be lower than the current ones, except SSP245-2050s and SSP370-2070s, and the centroids of suitable habitats were mainly shifted to the northeast, except SSP370-2050s and SSP585-2070s. Our results provide valuable guidance for the monitoring and management of N. asiatica, as well as the selection of pest-free goji berry cultivation sites.

Temperature and water availability drive insect seasonality across a temperate and a tropical region

The more insects there are, the more food there is for insectivores and the higher the likelihood for insect-associated ecosystem services. Yet, we lack insights into the drivers of insect biomass over space and seasons, for both tropical and temperate zones. We used 245 Malaise traps, managed by 191 volunteers and park guards, to characterize year-round flying insect biomass in a temperate (Sweden) and a tropical (Madagascar) country. Surprisingly, we found that local insect biomass was similar across zones. In Sweden, local insect biomass increased with accumulated heat and varied across habitats, while biomass in Madagascar was unrelated to the environmental predictors measured. Drivers behind seasonality partly converged: In both countries, the seasonality of insect biomass differed between warmer and colder sites, and wetter and drier sites. In Sweden, short-term deviations from expected season-specific biomass were explained by week-to-week fluctuations in accumulated heat, rainfall and soil moisture, whereas in Madagascar, weeks with higher soil moisture had higher insect biomass. Overall, our study identifies key drivers of the seasonal distribution of flying insect biomass in a temperate and a tropical climate. This knowledge is key to understanding the spatial and seasonal availability of insects-as well as predicting future scenarios of insect biomass change.

Effects of climate change on different geographical populations of the cotton bollworm Helicoverpa armigera (Lepidoptera, Noctuidae)

The effects of climate change on pest phenology and population size are highly variable. Understanding the impacts of localized climate change on pest distribution and phenology is helpful for improving integrated pest management strategies. Here, the population dynamics of cotton bollworms (Helicoverpa armigera) from Maigaiti County, south Xinjiang, and Shawan County, north Xinjiang, China, were analyzed using a 29-year dataset at lower latitudes and a 23-year dataset at higher latitudes to determine the effects of climate change on the population dynamics of H. armigera. The results showed that all generations of H. armigera at both sites showed increasing trends in population size with climate warming. Abrupt changes in phenology and population number occurred after abrupt temperature changes. Climate change had a greater effect on the phenology of H. armigera at higher latitudes than at lower latitudes and led to a greater increase in population size at lower latitudes than at higher latitudes; the temperature increase at higher latitudes will cause a greater increase in the adult moth population size in the future compared to that at lower latitudes; and abrupt changes in the phenology, temperature increase, and population size at lower latitudes occurred earlier than those at higher latitudes. Thus, it is necessary to develop sustainable management strategies for Helicoverpa armigera at an early stage.

Low winter precipitation, but not warm autumns and springs, threatens mountain butterflies in middle-high mountains

Low-elevation mountains represent unique model systems to study species endangered by climate warming, such as subalpine and alpine species of butterflies. We aimed to test the effect of climate variables experienced by Erebia butterflies during their development on adult abundances and phenology, targeting the key climate factors determining the population dynamics of mountain insects. We analysed data from a long-term monitoring of adults of two subalpine and alpine butterfly species, Erebia epiphron and E. sudetica (Nymphalidae: Satyrinae) in the Jeseník Mts and Krkonoše Mts (Czech Republic). Our data revealed consistent patterns in their responses to climatic conditions. Lower precipitation (i.e., less snow cover) experienced by overwintering larvae decreases subsequent adult abundances. Conversely, warmer autumns and warmer and drier springs during the active larval phase increase adult abundances and lead to earlier onset and extended duration of the flight season. The population trends of these mountain butterflies are stable or even increasing. On the background of generally increasing temperatures within the mountain ranges, population stability indicates dynamic equilibrium of positive and detrimental consequences of climate warming among different life history stages. These contradictory effects warn against simplistic predictions of climate change consequences on mountain species based only on predicted increases in average temperature. Microclimate variability may facilitate the survival of mountain insect populations, however the availability of suitable habitats will strongly depend on the management of mountain grasslands.

Detecting mismatches in the phenology of cotton bollworm larvae and cotton flowering in response to climate change

Current evidence suggests that climate change has directly affected the phenology of many invertebrate species associated with agriculture. Such changes in phenology have the potential to cause temporal mismatches between predators and prey and may lead to a disruption in natural pest control ecosystem. Understanding the synchrony between pest insects and host plant responses to climate change is a key step to improve integrated pest management strategies. Cotton bollworm larvae damage cotton, and thus, data from Magaiti County, China, collected during the period of 1990-2015 were analyzed to assess the effects of climate change on cotton bollworm larvae and cotton flowering. The results showed that a warming climate advanced the phenology of cotton bollworm larvae and cotton flowering. However, the phenological rate of change was faster in cotton bollworm larvae than that in cotton flowering, and the larval period was prolonged, resulting in a great increase of the larval population. The abrupt phenological changes in cotton bollworm larvae occurred earlier than that in cotton, and the abrupt phenological changes in cotton flowering occurred earlier than that in larval abundance. However, the timing of abrupt changes in larval abundance all occurred later than that in temperature. Thus, the abrupt changes that occurred in larvae, cotton flowering and climate were asynchronous. The interval days between the cotton flowering date (CFD) and the half-amount larvae date (HLD) expanded by 3.41 and 4.41 days with a 1 °C increase of T_mean in May and June, respectively. The asynchrony between cotton bollworm larvae and cotton flowering will likely broaden as the climate changes. The effective temperature in March and April and the end date of larvae (ED) were the primary factors affecting asynchrony.

Presence of snow coverage and its thickness affected the mortality of overwintering pupae of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Helicoverpa armigera causes serious damage to most crops around the world. However, the impacts of snow thickness on the H. armigera overwintering pupae are little known. A field experiment was employed in 2012-2015 at Urumqi, China. At soil depths of 5, 10, and 15 cm, overwintering pupae were embedded with four treatments: no snow cover (NSC), snow cover (SC), increasing snow thickness to 1.5 times the thickness of SC (ISSC-1), and to two times the thickness of SC (ISSC-2). Results suggested that snow cover and increasing snow thickness both significantly increased soil temperatures, which helped to decrease the mortality of overwintering pupae (MOP) of H. armigera. However, the MOP did not always decrease with increases in snow thickness. The MOPs in NSC and ISSC-1 were the highest and the lowest, respectively, though ISSC-2 had much thicker snow thickness than ISSC-1. A maximum snow thickness of 60 cm might lead to the lowest MOP. The longer the snow cover duration (SCD) at a soil depth of 10 cm in March and April was, the higher the MOP was. A thicker snow cover layer led to a higher soil moisture content (SMC) and a lower diurnal soil temperature range (DSTR). The highest and the lowest MOP were at a depth of 15 and 10 cm, respectively. The SMC at the depths of 10 and 15 cm had significant effects on MOP. A lower accumulated temperature (≤0 °C) led to a higher MOP. The DSTR in March of approximately 4.5 °C might cause the lowest MOP. The largest influence factor for the MOPs at depths of 5 and 10 cm and the combined data were the SCDs during the whole experimental period, and for the MOPs at a depth of 15 cm was the soil temperature in November.