Impact of intensive trapping of Sitophilus oryzae with probe or PC traps baited by pheromone or food attractant on insect population dynamics

Abstract: In large flat-storage facilities, primary insect pest populations that were quiescent at the end of winter season start again their multiplication when located in zones where temperature exceeds again the lower limit for development. This situation generally takes place close to the surface of the bulk. Early detection of insect presence in this zone is crucial in IPM programs. A pilot scale trial was carried out to evaluate the potential of high density trapping in this upper zone of a grain bulk. This trial had three objectives: i/ to evaluate the percentage of Sitophilus oryzae adults that can be caught through high-density network of traps displayed from the surface of the wheat bulk, baited with lure or attractant, vs. non-baited; ii/ to compare the yield of the different traps when baited or not with sitophilure and/or attractive oil; iii/ to evaluate the impact of trap catches on the rice weevil population dynamics. A randomized experimental design was built with 400 kg wheat batches stored in containers. After initial infestation of each wheat batch by a low density of hidden stages of S. oryzae and setting traps, the grain condition was continuously monitored and insect catches were checked every 3 weeks during 4 months of storage at 22 to 25 °C. The percentage of weevils trapped by this high-density trapping (10 traps per 400 kg batch) reached more than 30% in the better case with a peak during the second month of storage. At the same period, it was observed a significantly reduction of weevil numbers in traps baited with sitophilure. Conversely, traps with attractive oil catch significantly more weevils. Nevertheless, in spite of the high number of weevils trapped, the population dynamics trends were not significantly affected by continuously trapping a part of the population in the conditions of this pilot trial.