Evaluation of spring-planted Brassica cover crops for use in muskmelon (Cucumis melo L.) and eggplant (Solanum melongena L.) production systems

Members of the Brassica family produce glucosinolates which upon hydrolysis are reported to impact soilborne pathogen populations. Oilseed radish ( Raphanus sativus (L.) var. oleiferus Metzg (Stokes)), Oriental mustard (Brassica juncea (L.) Czern.), and yellow mustard ( Sinapis alba L.) are Brassicas that are often used as cover crops. This research evaluated suitability of these species for use as spring- planted cover crops. In one field experiment, cover crops were spring-planted preceding muskmelon (Cucumis melo L. Group Reticulatus) and eggplant (Solanum melongena L.). In another field experiment, oilseed radish and Oriental mustard were spring-planted, then muskmelon, honeydew (Cucumis melo L. Group Inodorous), and cucumber ( Cucumis sativus L.) were planted at five day intervals after cover crop incorporation to study cover crop phytotoxicity. In the laboratory, lyophilized and non-lyophilized oilseed radish root and shoot extracts were tested on muskmelon, honeydew, and cucumber germination and radicle growth. Results indicate that while these cover crops do aid in nutrient cycling, they do not confer significant protection against soilborne disease caused by Verticillium dahliae Kleb. under our field conditions. They should be used with caution due to their ability to inhibit cucurbit seed germination and cash crop growth. Laboratory results further suggest phytotoxic compounds are likely primarily volatile in nature.