An evaluation of biological and abiotic controls for grapevine powdery mildew. 2. Vineyard trials

Abstract

Grapevine powdery mildew (Erysiphe necator) affects grape yield and fruit quality worldwide. Managers of conventional vineyards rely mainly on synthetic fungicides and sulfur to control powdery mildew, while in organic vineyards sulfur is the main control agent, often in rotation with canola‐based oils, bicarbonates and biological control agents. The efficacy of those materials has not been evaluated critically under field conditions in Australia. Accordingly, a range of materials showing most promise in previous greenhouse trials (Crisp et al. 2006 Australian Journal of Grape and Wine Research12, pp. 192–202) were assessed via field trials in commercial vineyards. Applications of either milk or whey (alone, or mixed with a canola oil‐based product), as well as applications of potassium bicarbonate (commercial formulation), all reduced the severity of powdery mildew compared with untreated vines. Eight applications of a 1:10 dilution of milk, 45 g/L whey powder or programs comprising rotations of potassium bicarbonate plus oil and whey, applied at 10–14 day intervals, reduced the severity of powdery mildew to levels not significantly different from that on vines sprayed with sulfur (wettable powder, 3–6 g/L). However, the relative control of powdery mildew by the test materials in field trials was dependent on the susceptibility of the grapevine cultivar and the extent of spray coverage achieved. In vineyards where highly susceptible cultivars were planted, and spray coverage was compromised, the resultant control of powdery mildew was reduced; and sometimes to commercially unacceptable levels.

Evaluation of ‘alternative’ materials to sulfur and synthetic fungicides for control of grapevine powdery mildew in a warm climate region of Australia

“…Furthermore, the variable spray distribution and the large canopy type may have contributed to the poor control of disease. Crisp et al (2006b) reported similar results in South Australia where similar test materials failed to control powdery mildew adequately due to a large, dense canopy. As these 'alternative' materials probably act as contact fungicides, it is important that spray coverage is maximised (Crisp et al 2006c) and that vine vigour is controlled.…”

“…Results of trials during three grape growing seasons suggest that 'alternatives' to sulfur would be suited to controlling powdery mildew on less susceptible cultivars such as Cabernet Sauvignon (Doster and Schnathorst 1985) and Shiraz rather than Chardonnay (Crisp et al 2006b). Control of powdery mildew early in the season using an effective fungicide is crucial in warm, dry regions, after which time 'alternative' materials such as milk and whey may be used.…”

“…'Alternative' fungicides were tested in glasshouse and preliminary field trials in South Australia for efficacy in controlling grapevine powdery mildew (Crisp et al 2006a, b). Bovine milk and whey applied alone or in combination with a botanical oilbased product (Synertrol Horti Oil) and a commercial formulation of potassium bicarbonate (Ecocarb) provided control similar to that achieved with sulfur, without compromising berry quality (Crisp et al 2006b). However, cultivar susceptibility and spray coverage were limiting factors in achieving commercially acceptable control of powdery mildew.…”

Physicochemical composition, minerals, and pesticide residues in organic grape juices

“…The international bibliography concerning the production of organic grapes covers different aspects of this field, such as those related to a) minimize the use and effect of copper application (Dagostin et al, 2011); b) search alternative products for different diseases (Crisp et al, 2006); c) control nematodes (Coll et al, 2012); d) fertilization and mineral nutrition (Coll et al, 2011); e) the impact and evaluation of the organic viticulture (Reeve et al, 2005;Fragoulis et al, 2009). Serra Gaúcha, the most important Brazilian viticultural region was also influenced by this scientific and technological development with the use of different agricultural inputs − such as fungicides, insecticides, herbicides, growth regulators, fertilizers −, and enological -such as yeasts, enzymes, stabilizers, antioxidants.…”

A critical review of plant protection tools for reducing pesticide use on grapevine and new perspectives for the implementation of IPM in viticulture

“…For example, potassium bicarbonate represents a practicable alternative to synthetic chemical fungicides or sulphur (Crisp et al, 2006), although it is commonly less effective than these ones. Other examples are plant extracts and seaweed (laminarin), COS-OGA, chitin or chitosan mainly act by inducing systemic resistance in the plant (Iriti et al, 2011;van Aubel et al, 2014;Vera et al, 2011).…”