Spatial variation in response to ‘reduced input’ spray programs for powdery mildew and botrytis identified through whole-of-block experimentation

Abstract

Background and Aims: Previous work has highlighted the utility of the whole‐of‐block approach to viticultural experimentation. Here, we use this approach as a means of evaluating alternative spray programs for managing two economically important grapevine diseases at commercial scale. Methods and Results: Two experiments were conducted in vineyards in the Coal River and Rokeby districts of Tasmania. The first, carried out in a 4.5 ha vineyard planted to Vitis vinifera L. cv. Pinot Noir, sought to evaluate fungicide programs for control of powdery mildew (Erysiphe necator), in particular with a view to reducing the amount of sulphur applied in organic production systems. The second sought to evaluate the benefit (if any) of changing the time of fungicide application from flowering to pre‐bunch closure for the control of botrytis bunch rot (Botrytis cinerea) in a 2.4 ha Chardonnay vineyard. In both cases, treatments were applied to a whole‐of‐block experimental design using commercial spray equipment. Disease severity and the response to the various spray treatments, was spatially variable and related to topographic variation. Botrytis severity was also related to vine vigour. The powdery mildew results supported the retention of sulphur in organic spray programs, while Switch® (Syngenta Group, Basel, Switzerland) applied at pre‐bunch closure in the botrytis experiment reduced disease severity relative to the application at flowering. Spatial variation in the response to the latter treatment, when examined four times pre‐harvest, suggested that secondary spread may not have been an important mechanism for increasing disease severity over time. Conclusions: Consistent with the other work described in this series of papers, we conclude that the whole‐of‐block experimental approach offers both researchers and vineyard managers a means of acquiring more useful information than would be obtained from a conventional plot‐based approach. Significance of the Study: This study highlights the value of collecting spatially distributed data as a means of better understanding the incidence, spread, progression and control of fungal grapevine diseases. As such, it provides a new application for this experimental approach, which enables spatial variability to be used as an experimental tool.

Precision agriculture in Australia: present status and recent developments

“…LAWES & BRAMLEY, 2012), spatially distributed plots (WHELAN et al, 2003) or using highly replicated designs (e.g. PANTEN et al, 2010;BRAMLEY et al, 2011a) covering the entire management unit (Figure 5b) using the tools of PA for their design and establishment. Whichever approach is used, the underlying variation in the trial site is used as an experimental tool such that when the experiment is analysed using appropriate spatial analysis, spatial variability in the treatment response and in the statistical significance of treatment effects can be determined.…”

“…Part (a), which shows a 7 ha vineyard, seeks to illustrate how the results of a small plot trial could be compromised by the underlying variation -illustrated here by a yield map. A potential solution to this is shown in (b) which shows an experiment conducted over an entire 2.4 ha vineyard (Bramley et al, 2011a). The objective was to assess the effects of the timing of spray application (either flowering or pre-bunch closure; PBC) on the incidence of botrytis.…”

Whole-of-block experimentation for evaluating a change to canopy management intended to enhance wine quality

“…This calls into question the utility of plot‐based experiments as a basis for viticultural decision making or the development of management recommendations. In this, and the other papers in this series (Panten and Bramley 2011, Bramley et al. 2011a), we seek to explore and demonstrate a solution to this problem, which is provided by the whole‐of‐block or ‘landscape scale’ (Bishop and Lark 2006, Panten et al.…”

“…2010) approach. Thus, in experiments in which entire management units were used for the experiment, rather than small plots, alternative vineyard floor covers (Panten and Bramley 2011) and reduced input spray programs (Bramley et al. 2011a) were evaluated in such a way that the inherent variability of the vineyard was used both as an experimental tool and also an aid to understanding treatment response.…”

Use of nitrate non‐utilizing (nit) mutants to determine phenological stages at which Botrytis cinerea infects wine grapes causing botrytis bunch rot

“…Bramley et al . () investigated the spatial distribution of BBR severity and found that mean severity for a given vineyard block (2·4 ha) was heavily influenced by an increase in severity in particular areas within the vineyard, while severity in the rest of the block did not increase at the same rate. These findings support the hypothesis that polycyclic secondary infection may not be a necessary mechanism for increasing BBR severity over time.…”