SASEX / CIRAD report : visit to Marromeu and Mafambisse sugar estates (Mozambique) 5th to 14th June 2002

The spotted borer, Chilo sacchariphagus Bojer (Lepidoptera: Crambidae), is a major pest of sugarcane in southern Asia and islands of the south-west Indian ocean (Goebel FR, 1999). Since 1999 when this pest species was positively identified in Mozambique (Way & Turner, 1999) CIRAD and SASEX have collaborated with two sugarcane estates in Mozambique on a biological control programme against this major pest, namely Marromeu and Mafambisse. The development of a pheromone trap in Mauritius for this pest has facilitated some field monitoring (Anon, 1975). The task of monitoring moth populations in the field forms an integral part of the biological control programme because the pupal parasitoid (Xanthopimpla stemmator) is being released as a first step (Conlong & Goebel, 2002). The purpose of this visit was mainly to confirm the efficiency of a simple pheromonebaited trap that is routinely used in Reunion to monitor Chilo populations in the field. The other purpose was to determine the current status of this pest in the sugar estates, particularly in Marromeu, where the sugarcane crop has been re-established recently. Infestation level and natural egg parasitism were evaluated. The efficacy of these types of traps was confirmed which is very encouraging for further work using this monitoring method. The advantage of these traps is that they are easily constructed, and they are relatively simple to operate. These particular features would make these traps particularly suitable for use under the conditions experienced in Mozambique. These traps are also presently being used to monitor for the presence of this sugarcane pest species in South Africa. It was particularly encouraging to see that these traps are effective at low moth populations which makes them ideally suited for use as an early warning system of low populations. An added advantage from this work is from the experience and skills obtained in the field on pheromone trapping techniques. This will be incorporated into the current collaborative SASEX/CIRAD research project on the development of a pheromone trap for the stemborer species Eldana saccharina Walker (Lepidoptera: Pyralidae) (Anon, 2002). Of the three trap models evaluated in Mozambique the inverted funnel trap was the model that was effective. Field trials showed that these traps when placed at canopy height (23m) and baited with 2mg of the synthetic pheromone yielded the highest catches. No clear information was obtained about the required density of the traps, due to low catches. The opportunity to visit Mozambique to study these pheromone-baited traps has provided valuable information that can be used for the work on this topic by CIRAD and SASEX on this important topic. (Résumé d'auteur)