Abstract
Downy mildew is a severe disease of grapevines treated by repeated fungicide applications during the growing season. The impact of these treatments on human health is currently under scrutiny. Fungicide application long before disease onset is not thought to be greatly beneficial for grape production, but the first fungicide treatment is applied at least six weeks before disease onset in more than 50% of the vineyards in the Bordeaux region, a major French vine-growing area. We estimate that applying one fungicide every two weeks at disease onset would reduce fungicide applications against downy mildew by 56% (95%IC = [51.0%, 61.3%]), on average, relative to current levels. This decrease is slightly greater than the level of exposure reduction resulting from the random suppression of one out of every two fungicide treatments (i.e. 50%). The reduction is lower when treatments are sprayed weekly but still reaches at least 12.4% (95%IC = [4.3%, 20.8%]) in this case. We show that this and other strategies reducing the number of treatments would decrease operator exposure to pesticides as effectively as the use of various types of personal protective equipments in the Bordeaux region. The implementation of this strategy would significantly decrease fungicide use, health risks, and adverse environmental impacts of vineyards.
Highlights
Downy mildew is a severe disease of grapevines treated by repeated fungicide applications during the growing season
We found that postponing the first fungicide application to disease onset would decrease operator exposure to pesticides by the same order of magnitude as the use of protective equipment (PPE)
According to this source of information, about 95% of the questioned vine growers in the Bordeaux region applied their first grape downy mildew (GDM) treatment between cw 12 and cw 21 (Fig. 1). These results were confirmed by a three-year survey conducted by the French Ministry of Agriculture’s Statistics and Prospective Service (SSP), which found that about 95% of the Bordeaux vine growers questioned applied their first GDM treatment between cw 15 and cw 20 (Fig. 1). Both farm surveys showed that 90% of vineyards received their first treatment against GDM before cw 19, our statistical survival analysis of the on-field GDM disease observations revealed that almost none of the 266 untreated site-years, i.e. the combination of monitored vineyard site and year, displayed any symptoms of GDM before cw 19
Summary
Downy mildew is a severe disease of grapevines treated by repeated fungicide applications during the growing season. Grape downy mildew (GDM) attacks can cause yield losses[1,2] and reduce grape quality[3] This disease is currently controlled mostly by intensive pesticide use, in Bordeaux, a major vine-growing area in France[4]. Many vine growers start applying fungicides early in spring, and spraying is repeated regularly throughout the growing season, about two or three times per month, depending on their action period This strategy keeps damages levels low but entails a large number of fungicidal treatments (7.9 treatments per vineyard and year in average in France5), with potential environmental implications, high production costs[6] and risks to human health, for vine growers[7,8,9,10,11]. The degree to which fungicide use and operator exposure can be reduced by this approach has never been quantified
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