Concept 6: Ecological concepts

There are two types of pest, based on their ecological features that have major implications for the way in which they are managed:

Endogenous pests – these are pests that remain mainly in the field, such as weeds, nematodes and soil-borne diseases. They reproduce within or close to the rice field and can build up from one rice crop to the next if not controlled. For instance, annual grass weeds, such as Echinochloa species, by shedding their seeds within the rice field, contribute to a seed bank in the soil that is a source of weed plants for many years into the future. Management of these pests requires a strategic approach to keep them at acceptable levels from year to year.

Exogenous pests – these are pests that move into the crop, such as migratory insects, like the brown planthopper, vertebrate pests like rats, and air-borne diseases. These pests may only be a problem in particular years, either dying or migrating from the crop at the end of the crop season. Management action for these pests tends to depend on the size of the population for that particular season.