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

Abstract

The 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.

Evaluation of Biopesticides for Management of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) in Florida

“…Overall, those samples resulted in egg/nymph counts that were not different from the UTC. Previous greenhouse [ 40 ] and field [ 42 ] studies had contrasting results, with M-Pede being effective in reducing both adult and immature whitefly populations. Although M-Pede was applied carefully in our study, field conditions inherently introduce more variability and challenges in ensuring thorough coverage, especially on plants with complex architectures like tomatoes.…”

“…Biopesticides, including biochemical and microbial insecticides, offer a more environmentally friendly approach, potentially reducing the reliance on synthetic chemicals and mitigating resistance development. Biochemical insecticides, such as insecticidal soaps and mineral oils, have shown potential in managing B. tabaci populations by mechanisms of action that likely do not select for resistance, including suffocation and anti-feedant properties [ 37 , 38 , 39 , 40 , 41 , 42 ]. Similarly, microbial insecticides containing Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) and Cordyceps javanica (Kobayasi & Shimizu) (Hypocreales: Cordycipitaceae) as active ingredients have demonstrated efficacy against B. tabaci through the pathogenic activity of the fungi [ 41 , 43 , 44 , 45 ].…”