Mélanie Bomo Boua’s scientific contributions

The African stalk borer Eldana saccharina is an endemic pest of high economic importance in sub-Saharan Africa which often causes heavy infestations in rainfed plant cane subjected to a cycle of 15-17 months. The present study aimed to reduce overall damage due to this borer by early harvesting of sugarcane at three different periods. It involved two experiments carried out in Ferké 1 and Ferké 2 sugar estates over 17 months in rainfed plant cane, following a randomized complete block design (RCBD) with four different treatments. Treatments were composed of three harvesting periods (T1: November 15, T2: December 15, and T3: January 15), and a control (T0, no harvest), all in 4 replicates. The Ferké 1 experiment was planted with the variety N21 on 25/07/2017 and harvested on 23/06/2019. That of Ferké 2 was planted on 15/06/2017 with the variety M2592/93 and harvested on 05/12/2018. The study showed that variety N21 with high fiber content was more tolerant to stem borer than variety M2593/92 credited with a moderate fiber content. Stem borer infestations were significantly reduced across crop cycle following early harvesting on M2593/92, as opposed to N21. Without early harvesting, M2593/92 was much more infested than N21, with respectively 24 and 10% of internodes bored. Borer infestations recorded were strongly dependent on crop cycle duration and the intensity of crop water stress. Data showed that early harvesting in rainfed plant cane could be beneficial in the prevention of heavy infestations by E saccharina.

Heavy stalk borer infestations broke out over the last three cropping seasons in sugarcane plantations of both Ferké sugar mills of Northern Ivory Coast. The study objective was to determine the cause of heavy infestation observed on cane and sugar yields in order to implement a proper pest management strategy. The study which covers from 2006-06 to 2017-18 cropping seasons was based on sampling of all sugarcane plantations at harvest for cane juice analyses and assessment of stalk borer damages in terms of percentage of internodes bored. This allowed to cluster harvested lands depending on the intensity of infested canes and assess the amount of sugar production losses due to E. saccharina. It came out that infestations of this borer observed at harvest broke out only three years ago in Ferké 1 and two years ago in Ferké 2. Heavy infestations occurred over 45-55% of the sugarcane area in Ferké 1 as opposed to 25-35% in Ferké 2. Except for variety SP71-8210, all main sugarcane varieties grown were only heavily infested in Ferké 1. Although infestations were of concern on plantations no matter their water status, they seemed to be much more severe on rainfed and semi-irrigated crops compared to irrigated ones. Sugar production loss due to E. saccharina occurred over the last three years in Ferké 1 as opposed to the last two years in Ferké 2 but more importantly in 2016-17 for both sites with, respectively, a loss of 2600 and 2300 tons of sugar. Significant reduction in sugar production as a result of the limitation in nitrogen fertilizer rates was achieved in 2017-18 compared to 20116-17 by 62 and 50%, respectively, in Ferké 1 and Ferké 2. This was one aspect of an integrated stalk borer management strategy to be implemented involving the application of silicone fertilizer, the growing of resistant or tolerant cane varieties and cropping practices preserving natural enemies such as mechanized green harvesting and growing service plants.