Meta-Analysis Reveals a Critical Period for Management of Powdery Mildew on Hop Cones

Abstract

Nelson, M. E., Gent, D. H" and Grove, G. G. 2015. Meta-analysis reveals a critical period for management of powdery mildew on hop cones Plant Dis 99:632-640.Results of 28 field trials conducted over a 12-year period investigating management of hop powdery mildew caused by Podosphaera macularis were quantitatively summarized by meta-analysis to compare product ef ficacy and use patterns by mode of action as defined by Fungicide Resistance Action Committee (FRAC) groups. Availability of original observations en abled individual participant data meta-analysis. Differences in control of powdery mildew on leaves and cones were apparent among fungicide FRAC groups when individual products were evaluated over the course of a growing season. FRAC groups 13, 3, and U13 provided the most efficacious control of powdery mildew on leaves. Percent disease control on cones was influ enced by midseason foliar disease and fungicide mode-of-action. FRAC 13 provided significantly better disease control on cones than all other groups except U 13,3, and premixes of 7 with 11. Disease control on leaves was sim ilar when a rotational program of fungicides was used, independent of the modes of action, but improved on cones if FRAC groups 13 and 3 were both included compared with programs consisting of FRAC groups 11 and 3, 11 and 5, or 3 and 5. Disease control on cones was improved from 32 to 52%, on average, when the fungicide quinoxyfen (FRAC 13) was applied at least once during the early stages of cone development, defined in this analysis as 20 July to 10 August, as compared with all other treatments. Efficacy of disease control on cones by quinoxyfen was moderated by and interacted with the incidence of leaves with powdery mildew. Disease control on cones was fur ther improved if two applications of quinoxyfen were made during this period. Collectively, these findings suggest that disease control during juve nile stages of cone development largely influences the success of fungicide programs and point to the critical importance of focusing management efforts during this stage of development, independent of what actual management strategy is employed.

Distribution and Characterization of Podosphaera macularis Virulent on Hop Cultivars Possessing R6-Based Resistance to Powdery Mildew

“…In the short term, management of powdery mildew on all of these cultivars will require adopting practices commonly deployed on other susceptible cultivars such as thorough spring pruning (Gent et al 2012), canopy management such as removal of basal foliage (Gent et al 2008), careful consideration of harvesting timing (Gent et al 2014;Mahaffee et al 2009), and appropriate deployment of fungicides (Nelson et al 2015). The cost of implementing these practices will be substantial in individual hop yards and in aggregate to the industry.…”

Meta-analysis Reveals That the Genus Pseudomonas Can Be a Better Choice of Biological Control Agent against Bacterial Wilt Disease Caused by Ralstonia solanacearum

“…As described in detail previously ( Nelson et al, 2015 ; Rosenberg et al, 2004 ), meta-analysis is quantitative review of data collected from different studies, which is typically performed in order to estimate the influence of various experimental factors on effect sizes and assessing the publication bias. Now-a-days, meta-analysis has been widely used in plant growth and health management studies to draw a holistic conclusion from many of the primary experimental studies ( Kiær et al, 2009 ; Nelson et al, 2015 ). In 2005, Stiling and Cornelissen, performed a meta-analysis to evaluate the effect of different types of biocontrol agents (parasitoids, predators, and pathogens) attributes of several weed and pest populations.…”

Individual Participant Data Meta-Analysis of Foliar Fungicides Applied for Potato Early Blight Management

“…A mixed-effect analysis of variance model assuming a common intercept p for all trials, a random trial effect across studies, intrastudy variance of each trial, and intertrial heterogeneity was designed for this study. The model used in the present study is similar to another mixed-effect model fungicide efficacy study (Nelson et al 2015):…”

“…It incorporates the treatment responses across studies and differences in the treatment effects for each study (Riley et al 2010). MA is a statistically reliable tool for combining results from multiple studies having similar research objectives (Madden and Paul 2011;Nelson et al 2015;Ngugi et al 2011). Application of MA in plant pathology has increased in the past 5 years, especially in fungicide efficacy studies (Madden and Paul 2011; Ngugi et al 2011).…”

“…When using the one-stage approach, data from all individual studies are simultaneously modeled while accounting for clustering of participants within studies (Riley et al 2010). Both approaches have merits and, when heterogeneity among trials is large and the number of trials included in the study is small, the one-stage IPD-MA approach is more appropriate (Ahmed et al 2012;Nelson et al 2015;Stewart et al 2012).…”