Biorational products in the management of leaf spot and grape ripe rot in Vitis labrusca

Abstract

Leaf spot (LS) (Pseudocercospora vitis) and ripe rot (Colletotrichum spp.) cause significant losses to rustic grapevine cultivar ‘Bordo’ (Vitis labrusca), which is cultivated for juice production. The demand for juice from organic agriculture has been growing, resulting in the need for biorational products to manage disease with more environmentally friendly products. In this study, the potential of two products were evaluated in the field for managing LS and RR in the cultivar ‘Bordô’ over two seasons. The bacterial suspensions of Bacillus alcalophilus and eugenol acetate + potassium bicarbonate (750 mg L^− 1) applied with conventional spraying (first season) and conventional and electrostatic spraying (second season) were assessed for disease control. Standard winter treatments, along with pest and weed control was performed. Severity of LS was evaluated over time, and the area under the disease progress curve (AUDPC) was used to compare treatments. RR incidence was assessed at harvest and post-harvest during storage, simulating the commercialization period. With post-harvest disease data, the relative risk of ripe rot symptom expression was calculated. B. alcalophilus in both seasons and, eugenol acetate with electrostatic application in second season reduced LS severity. Electrostatic and conventional spraying did not differ in disease control potential in the evaluated season. The ripe rot symptoms achieved 67% of incidence in the control treatment and the treatments tested were not effective in reducing the incidence of the disease. Cluster weight and total soluble solids did not differ between treatments. The biorational products tested are not effective for ripe rot control, however, they may be recommended for LS control in an organic system.