DIRECTIONAL MOVEMENT OF PREDATORS BETWEEN THE IRRIGATED RICE FIELD AND ITS SURROUNDINGS

摘要

The paper presents the preliminary results of catches of predators in pitfall traps around an irrigated lice field at IRRI, Los Banos, the Philippines, during the first half of the rainy season of 1998. The most common predators caught were spiders, carabids and ants. Results indicate that directional movement between the field and its surroundings, as well as total catches of predators, depend on farm operations and crop age. The bund may be an important source of predators for the young rice field.Unsprayed, irrigated rice fields have proven to be almost pest free, largely due to the predator fauna in the rice field. Early establishment of a predator complex may be one of the reasons for the pest control observed. An early establishment requiresthat predators either remain in the field during fallow or that they move into the field from the outside. In the present study we assessed the possible impact of nearby surroundings supplying predators to a newly established irrigated rice field or viceversa. A clear trend of movement into or out of the field would then serve as an indicator of a possible impact of the rice field surroundings. In the present paper we report the intermediate results covering late fallow until mid cropping season of anexperiment assessing directional movement between the rice field and its surroundings.