The Effect of Intercropped Radishes on Butternut Squash Yield, Fungal Disease, and the Insect Community

Abstract

Intercropping is an agricultural planting method that mixes two or more crops in the same spatial and temporal region, often increasing yields without the use of chemical fertilizers or pesticides. In this study, I investigated whether intercropping radishes (Raphanus raphanistrum subsp. sativus) in a butternut squash field (Cucurbita moschata) would increase fruit yield, alter the insect community and disrupt disease transmission. On a farm in New Jersey, I tested the widespread idea that radishes produce odors that repel major squash pests, and examined whether radishes could disrupt disease transmission by altering the canopy structure. I found that intercropped squash plants grew bigger and produced four times more squash than monocropped squash. However, there was no evidence that radishes repelled pests. In the intercrop there were more chewing insects, higher rates of herbivory, and similar abundances of sap sucking insects. Radishes rows did seem to attract beneficial insects, and there were more parasitoid wasps in the intercrop. For disease, there was no difference in powdery mildew severity or fusarium wilt leaf loss. These results suggest that radishes repelling pests or disrupting disease transmission did not cause the increased yields in intercropped rows. This indicates that reduced competition for above and belowground resources most likely caused the increased yield in the intercrop, however more research is needed to determine the exact mechanism.