Effects of intercropping marigold, cowpea and an insecticidal soap on whiteflies and aphids in organic squash

Abstract

AbstractThe silverleaf whitefly MEAM1 (Bemisia tabaci) Gennadius (Hemiptera: Aleyrodidae), the cowpea aphid (Aphis craccivora Koch), the green peach aphid (Myzus persicae Sulzer) and the melon aphid (Aphis gossypii Glover) Hemiptera: Aphididae are major insect pests of squash (Cucurbita pepo L.), causing significant yield losses of up to 80% in Florida. We hypothesized that intercropping African marigold (Tagetes erecta L.) and cowpea (Vigna unguiculata L. Walp.) with zucchini squash will encourage an abundance of beneficial arthropods and increase cultural and biological control against these key insect pests by significantly reducing their populations and consequently improve yields. In a 2‐year field experiment, five treatments were evaluated in a randomized complete block design consisting of four replicates. Three diversified cropping treatments were implemented: (1) intercropping squash with marigold, (2) intercropping squash with cowpea, (3) intercropping squash with marigold and cowpea (mixed). These treatments were compared with an organic grower standard insecticide, (4) M‐Pede (potassium salts of naturally derived fatty acids) sprayed on monocropped squash and (5) monocropped squash with no pest management (control). Results indicated that squash intercropped with marigolds accounted for the highest marketable yields. Squash intercropped with cowpea had marginally high yields but attracted the highest densities of aphids. M‐Pede did not increase squash yields, but reduced aphids, whiteflies and associated squash silverleaf (SSL) disorder ratings and showed no deleterious effect on populations of natural enemies. We conclude that a mixture of marigold and cowpea could be used to suppress pests by increasing beneficial arthropod diversity while enhancing marketable yields of organic squash. M‐Pede could be used as a last resort when experiencing high hemipteran pressure.