Evaluation of a Disease Warning System for Downy Mildew of Grapes

Abstract

An electronic warning system for grape downy mildew— based on models for the infection of leaves of Vitis lambrusca, production of sporangia by Plasmopara viticola in lesions, and sporangial survival—was tested over 7 years in Ohio. Grapevines were sprayed with metalaxyl plus mancozeb (Ridomil MZ58) when the warning system indicated that environmental conditions were favorable for sporulation and subsequent infection. Over the 7 years, plots were sprayed from one to four times according to the warning system, and from four to 10 times according to the standard calendar-based schedule (depending on the date of the initiation of the experiment). The warning system resulted in yearly reductions of one to six sprays (with median of three sprays). Disease incidence (i.e., proportion of leaves with symptoms) in unsprayed plots at the end of the season ranged from 0 to 86%, with a median of 68%. Incidence generally was very similar for the warning-system and standard-schedule treatments (median of 7% of the leaves with symptoms), and both of these incidence values were significantly lower (P < 0.05) than that found for the unsprayed control, based on a generalized-linear-model analysis. Simplifications of the disease warning system, where sprays were applied based only on the infection or sporulation components of the system, were also effective in controlling the disease, although more fungicide applications sometimes were applied. Effective control of downy mildew, therefore, can be achieved with the use of the warning system with fewer sprays than a with a standard schedule.

Effect of Y-trellis and vertical shoot positioning training systems on downy mildew and botrytis bunch rot of grape in highlands of southern Brazil

“…A combination of frequent rain and sustained humidity, particularly in spring and summer, provided conditions for leaves and berries remain wet, enabling infections by P. viticola and B. cinerea. Previous studies have shown that for P. viticola, optimal growth is at temperatures of 20-25°C (Madden et al, 2000;Kennelly et al, 2005) and B. cinerea growth is optimal at 15-23°C (Wilcox, 2005;Hed et al, 2009).…”

“…The latent period (time from infection to spore production) is expected to take several hours for B. cinerea (Pearson and Goheen, 1988;Wilcox, 2005) and 5-18 days for P. viticola (Madden et al, 2000;Kennelly et al, 2005). Thus, it is estimated that infection by P. viticola may have occurred as early as mid to late October, whereas B. cinerea infection likely did not occur until early November.…”

Produtos alternativos na proteção da videira contra o míldio

“…& de Toni] é o responsável pelos maiores danos (Garrido et al, 2004). As perdas com o míldio, quando ocorre elevada precipitação durante o desenvolvimento vegetativo da planta, podem atingir 100%, o que torna essa enfermidade, que também tem efeito sobre a qualidade de frutos, uma das maiores restrições à produção de uvas no Brasil e no mundo (Madden et al, 2000).…”

“…O método de controle adotado com maior frequência pelos produtores é a pulverização com fungicidas de contato e sistêmicos (Sônego & Garrido, 2005), que requerem diversas aplicações durante o ciclo de crescimento e produção da videira (Madden et al, 2000).…”

Características físico-químicas e produtivas da videira 'BRS Clara' sob cultivo protegido

“…A porcentagem de ocorrência de míldio nos cachos foi avaliada a partir do início do enchimento das bagas, sendo a última avaliação realizada uma semana antes da colheita, através de amostragem em quatro ramos por parcela, dois de cada lado da planta, com um cacho por ramo, perfazendo quatro cachos (MADDEN et al, 2000). Os dados foram submetidos à análise de variância, e a separação das médias foi realizada pelo teste Scott-Knott, a 1% de probabilidade, utilizando o aplicativo SISVAR, versão 4.3 (FERREIRA, 2000).…”