Eldana saccharina (African sugarcane borer).

E. saccharina is the most serious sugarcane pest in tropical and sub-tropical Africa, and in situations of high pest pressure total crop failure can result.

Genetic Variability and Heritability among Sugarcane Genotypes in Plant Crop for Some Agronomic Traits under Tropical Dry Climate of Ferké, Ivory Coast

Aims: The study aimed to determine the best performing cane genotypes among 29 clones tested under sprinkler irrigation, in comparison with a check variety (R579). Study Design: The experimental design used was a randomized complete block (RCB) with 30 cane genotypes in three replications. Every plot consisted of two dual rows of five meters with 0.5 and 1.90 m of inter-row spacing, i.e. 19 m² per plot and about 600 m² for the whole experiment. Place and Duration of Study: It was carried out on a commercial sugarcane plantation of Ferké 2 located in the northern part of the country, over 10 months as a late season crop from late May 2018 to late March 2019. Methodology: Over each micro-plot, data were collected at harvest from both dual rows consisted of millable stalk number/ha, cane yield, juice quality traits (sucrose, purity, and recoverable sucrose), fiber content, and damaged internodes by stem borer Eldana saccharina. Results: Based on sugar yields, seven cane genotypes were equivalent to the check variety R579 which gave 17.6 t/ha. Their yield performances ranged from 12.2 to 15.4 t of sugar/ha and from 134.2 to 160.8 t of cane/ha compared to 176.0 t/ha for the check. Higher heritability values ranging from 52 to 85% were observed in traits like sugar yield, juice purity, juice sucrose, recoverable sucrose, sucrose percent, fiber content and stem borer infestations. Differences between PCV and GCV for most traits were small, indicating high prospects for genetic progress through selection under conditions of this study. Conclusions: Findings obtained need to be confirmed over the 2019-20 cropping season in first ratoon crop to determine promising cane genotypes for the advanced selection stage.

Population dynamics of Eldana saccharina Walker (Lepidoptera: Pyralidae): application of a biophysical model to understand phenological variation in an agricultural pest

Understanding pest population dynamics and seasonal phenology is a critical component of modern integrated pest-management programs. Accurate forecasting allows timely, cost-effective interventions, including maximum efficacy of, for example, biological control and/or sterile insect technique. Due to the variation in life stage-related sensitivity toward climate, insect pest population abundance models are often not easily interpreted or lack direct relevance to management strategies in the field. Here we apply a process-based (biophysical) model that incorporates climate data with life stage-dependent physiology and life history to attempt to predict Eldana saccharina life stage and generation turnover in sugarcane fields. Fitness traits are modelled at two agricultural locations in South Africa that differ in average temperature (hereafter a cold and a warm site). We test whether the life stage population structures in the field entering winter and local climate during winter directly affect development rates, and therefore interact to determine the population dynamics and phenological responses of E. saccharina in subsequent spring and summer seasons. The model predicts that: (1) E. saccharina can cycle through more generations at the warm site where fewer hours of cold and heat stress are endured, and (2) at the cold site, overwintering as pupae (rather than larvae) confer higher relative fitness and fecundity in the subsequent summer adult moths. The model predictions were compared with a large dataset of field observations from scouting records. Model predictions for larval presence (or absence) generally overlapped well with positive (or negative) scout records. These results are important for integrated pest management strategies by providing a useful foundation for future population dynamics models, and are applicable to a variety of agricultural landscapes, but especially the sugarcane industry of South Africa.