Leaf Spot Management on Spinach Using Bio and Conventional Chemistries

摘要

Spinach (Spinacia oleracea) popularity and consumption has increased with the rise of the spring mix salad industry. The crop however is susceptible to a number of leaf spot diseases including anthracnose, Stemphylium leaf spot, and Cladosporium leafspot, all of which can be seed-borne. The incidence of the latter is caused by the fungal pathogen Cladosporium variabile Link and has noticeably increased in frequency and severity in recent years. Cladosporium leaf spot lesions are typically round andtan rarely exceeding 1 cm in diameter. The disease is favored by long periods of leaf wetness but is usually only a minor problem in the baby spinach grown for spring mix. Cladosporium leaf spot can however be a significant problem in Florida leaf spinach grown for the fresh market. Consequently, an experiment was conducted to investigate the effectiveness of fungicides for controlling this important foliar disease. A field experiment was conducted at the Everglades Research and Education Center in Belle Glade, FL whereby leaf spinach (variety Bloomsdale) was direct-seeded in double rows atop of six-inch raised beds formed on three-foot centers using the resident organic soil. The experiment consisted of a randomized complete block design with four replications of twelve treatments. The disease was established in the trial by distributing leaf material infected with Cladosporium leaf spot between unsprayed spinach rows which also served as buffers between experimental units .The fungicide applicationswere made using a CO, backpack sprayer and a 36-inch hand-held boom equipped with three Tee-Jet 11003 flat fan nozzles angled inward for maximize coverage. Foliar sprays at a volume of 62 GPA commenced at the two-to-four leaf stage and were subsequently followed by weekly applications (Table 1).