Population monitoring of Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) using pheromone traps

Abstract

The flight phenology of the stem borer, Chilo partellus (Swinhoe) at the ICIPE’s Mbita Point Field Station (MPFS) and on a nearby farmer’s field was monitored using pheromone traps. The relation between pheromone trap catches of males and sorghum plant age, infestation, larval/pupal population density and sorghum cultivars used was examined. At MPFS C. partellus males were caught throughout the year in pheromone traps. Fluctuations of trap catches indicated that the pest completes two main generations on each of the long and short rain sorghum crops. On farmers’ fields, males continued to be caught in large numbers after harvest, implying that the pest continues to breed on the sorghum stalks and tillers. Significantly lower observed catches of males occurred only on one (MB-3) of the eight different sorghum cultivars, during the period of 2–6 weeks after plant emergence. In general, positive correlations were observed between the number of males caught in pheromone traps and larval pupal population density, males and percentage plants infested, and males and plant age. However, the pheromone trap appeared to be less effective under high population density, particularly during the flight of the second generation moths, due to competition between pheromone trap and wild females. But the flight phenology as monitored by pheromone traps appeared to reflect major events in population development of C. partellus. Pheromone traps would be useful in detecting C. partellus and for monitoring its flight phenology.