Effect of temperature on the phenology ofChilo partellus(Swinhoe) (Lepidoptera, Crambidae); simulation and visualization of the potential future distribution ofC. partellusin Africa under warmer temperatures through the development of life-table parameters

Abstract

Maize (Zea mays) is a major staple food in Africa. However, maize production is severely reduced by damage caused by feeding lepidopteran pests. In East and Southern Africa, Chilo partellus is one of the most damaging cereal stem borers mainly found in the warmer lowland areas. In this study, it was hypothesized that the future distribution and abundance of C. partellus may be affected greatly by the current global warming. The temperature-dependent population growth potential of C. partellus was studied on artificial diet under laboratory conditions at six constant temperatures (15, 18, 20, 25, 28, 30, 32 and 35°C), relative humidity of 75 ± 5% and a photoperiod of L12:L12 h. Several non-linear models were fitted to the data to model development time, mortality and reproduction of the insect species. Cohort updating algorithm and rate summation approach were stochastically used for simulating age and stage structure populations and generate life-table parameters. For spatial analysis of the pest risk, three generic risk indices (index of establishment, generation number and activity index) were visualized in the geographical information system component of the advanced Insect Life Cycle modeling (ILCYM) software. To predict the future distribution of C. partellus we used the climate change scenario A1B obtained from WorldClim and CCAFS databases. The maps were compared with available data on the current distribution of C. partellus in Kenya. The results show that the development times of the different stages decreased with increasing temperatures ranging from 18 to 35°C; at the extreme temperatures, 15 and 38°C, no egg could hatch and no larvae completed development. The study concludes that C. partellus may potentially expands its range into higher altitude areas, highland tropics and moist transitional regions, with the highest maize potential where the species has not been recorded yet. This has serious implication in terms of food security since these areas produce approximately 80% of the total maize in East Africa.

Predicting the Impact of Temperature Change on the Future Distribution of Maize Stem Borers and Their Natural Enemies along East African Mountain Gradients Using Phenology Models

“…sesamiae were developed based on laboratory data at constant temperatures, and they were validated with life table statistics collected at fluctuating temperatures under field conditions [51,52,56]. Daily minimum and maximum temperatures obtained during these experiments were used in stochastic simulations [51,52]. A good agreement was observed between simulated and experimental results, e.g.…”

“…fusca , the simulated development times were 8.86, 67.39 and 19.91 days when the observed development times were 8.92, 68.74 and 19.33 days for eggs, larvae and pupae respectively; similarly for C . partellus , the simulated development times were 8.30, 46.23 and 13.81 days when the observed development times were 8.22, 48.36 and 14.86 days for eggs, larvae and pupae, respectively [51,52]. These results show that the phenology models developed by Khadioli et al [51,52], can be applied to predict the insect population abundance and demographic parameters in other agro-ecological zones, what justified their application in the current study in both transects.…”

“…partellus , the simulated development times were 8.30, 46.23 and 13.81 days when the observed development times were 8.22, 48.36 and 14.86 days for eggs, larvae and pupae, respectively [51,52]. These results show that the phenology models developed by Khadioli et al [51,52], can be applied to predict the insect population abundance and demographic parameters in other agro-ecological zones, what justified their application in the current study in both transects. The phenology models consisted of a set of functions that described temperature-dependent development of the three immature life stages (egg, larva and pupae).…”

“…partellus development in Africa [51,52]. While pest models and risk mapping tools have been shown to be useful for predictions on global and regional scales, there is a general lack of information for predictions of maize stem borers at a smaller geographical scale.…”

Climate change, public health and COP21 – a South African perspective

“…For example, predicted warming may allow Chilo partellus, a damaging cereal stem borer, to expand its range from warm lowlands into higheraltitude areas, highland tropics and moist transitional regions. [14] Climate change also threatens social structures and political factors in SA. Resource-poor communities currently face a number of stresses that curtail quality of life, livelihood options and opportunities.…”