Implications of Intercropping (Sweet Pepper - Tomato) for the Biological Control of Pests in Glasshouses

Abstract

The effects of intercropping on the distribution of pests were analysed in a cropping system composed of rows of sweet peppers alternating with rows of tomatoes in a 80 m2 glasshouse. The levels of populations of Myzus persicae, Tetranychus urticae and Frankliniella occidentalis and their predators or parasitoids were compared among the rows. Significant differences in pest, predator and parasitoid density were observed. This was partially attributed to differences in plant suitability influencing the predator-prey balance. Moreover, highly significant differences in pest density were recorded among the rows of the vegetable species which favoured high pest outbreaks. This effect was probably due to negative effects caused by the other plant species on the dispersion of the pest. In fact, glandular trichomes heavily entrapped aphids on tomatoes, which probably greatly affected the pest dispersal in the crop. On the other hand, the fact that spider mites were maintained on the sweet pepper plants at very low levels by predatory mites was certainly a factor which contributed to the low spread of the pest in the crop. These results lead to the conclusion that such intercropping seems to locally limit pest outbreaks, and thus may reduce the amount of biological auxiliaries or pesticides needed to control them in comparison with monoculture.