Evaluation of the use of wound-protectant fungicides and biological control agents against stem canker (Neofusicoccum parvum) of blueberry

Abstract

Economically, blueberry (Vaccinium corymbosum) has become a very important fruit crop in Chile, and stem canker (Neofusicoccum parvum) has frequently been observed as a major disease. The symptoms are characterized by partial or total death of the foliage associated with extensive reddish-brown canker lesions at the base of the stems. Pruning wounds appear to be the main infection route. In this study, fungicide pastes and biological control agents were evaluated for their effectiveness as pruning wound-protectants against N. parvum. The mycelium of N. parvum was highly sensitive to benomyl, tebuconazole, and iprodione in Vitro, with median effective concentrations (EC50) of 0.15-0.25, 0.26-0.33, and 0.52-0.68 mu g.mL(-1), respectively. The pastes formulated with 0.1% benomyl, 0.5% tebuconazole, and 0.06% iprodione also provided considerable protection of pruning wounds against N. parvum on the stems of Duke blueberries under field conditions. However, pyraclostrobin, with relatively high EC50 values (>2 mu g.mL(-1)) in vitro, was largely ineffective in vivo at a 0.1% concentration, and 75% citrus extract (Citrus SL), Bacillus subtilis QST713 (Serenade Max), and Trichoderma spp. (Trichonativa) were also ineffective. Additionally, pastes formulated with 5% boric acid, although effective, were phytotoxic. FU - Comision Nacional de Investigacion Cientifica y Tecnologica (Conicyt) de Chile through Fondecyt projectComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1100246] FX - The authors are very grateful for the financial support received from Comision Nacional de Investigacion Cientifica y Tecnologica (Conicyt) de Chile through Fondecyt project 1100246. NR - 16 PU - PONTIFICIA UNIV CATOLICA CHILE, FAC AGRONOMIA INGENIERIA FORESTAL PI - SANTIAGO PA - AV VICUNA MACKENNA 4860, SANTIAGO, 00000, CHILE