Effect of Diversified Cropping System On Beneficial Insects and Key Pests In Zucchini Squash

Several species of aphids including melon aphid, Aphis gossypi Glover, cowpea aphid, Aphis craccivora Koch and green peach aphid, Myzus persicae Sulzer are key pests of organic squash in north-central Florida. The silverleaf whitefly-B biotype, Bemesia tabaci (Gennadius) is also a major pest of organic squash. Feeding by immature whitefly produces squash silverleaf (SSL) disorder.  The density of immature whiteflies feeding on plants determines the severity of SSL symptoms as well as the amount of yield reduction. Both aphid and whiteflies vector viruses, and excrete honey dew that facilitates the development of sooty mold on squash plants. This interferes with photosynthesis resulting in reduce yield and a decrease in plant vigor. In field tests using a randomized complete block design with four replicates, we evaluated diversified cropping treatments that included buckwheat, Fagopyrum esculentum Moench intercropped with organic squash and white clover, Trifolium repens L intercropped with organic squash. These treatments were compared to a grower standard, white mulch, an IPM recommendation, aluminized (reflective) mulch, and a bare ground (control).  Aphid and whitefly populations decreased in diversified cropping systems as well as aluminized mulch. Silverleaf disorders were also lower in diversified cropping systems. However, only the white and reflective mulch and buckwheat lower incidence of viruses compared with the control. Populations of natural enemies increased in diversified cropping system but overall marketable yields were lower in this system.  Manipulating habitat design may increase the potential for increasing marketable yields while still achieving the benefits of pest reduction, disease suppression and increasing natural enemy populations.