Study design and data collection

The survey used a quantitative questionnaire which was sent to growers in March 2013 (Froud et al. 2016, Chapter 5). The study required growers to report detailed information on the occurrence of symptoms of disease and management of vines at the level of a single ‘Hayward’ kiwifruit block. Technical experts from Zespri International Ltd (Zespri), Kiwifruit Vine Health (KVH) and two kiwifruit growers assisted with the identification of factors for inclusion in the study. The questionnaire is provided in Appendix 1 and 2 and a summary of the topics covered in the questionnaire is presented in Table 7-1.

The questions were constructed to obtain quantitative data using closed questions with growers asked to select answers from a range of options. Three question formats were used: i) select all that apply (e.g. select all forms of pollination used); ii) select one possible answer from a list (e.g. did you use artificial pollination); and iii) select a rating based on a defined scale (e.g. canopy density ratings). The questionnaire was reviewed by industry technical experts and pre-tested with 10 growers to identify questions that were confusing, ambiguous or misleading, to determine if the layout and instructions given to respondents were

appropriate and to identify additions to multiple choice answer options.

Table 7-1 Topics covered in the mail-out questionnaire used to collect information from ‘Hayward’ (Actinidia chinensis var. deliciosa) blocks located in orchards affected

by Pseudomonas syringae pv. actinidiae biovar 3 (Psa)

Question number

Factor category Information sought

1-9 Disease status Description of disease prevalence and symptoms on female and male vines

10, 11, 18–21

Orchard layout Adjacent land: Current use, whether kiwifruit had been cut out, if kiwifruit present, the variety grown and Psa status 16, 22 Orchard layout Block shape and type of shelter

17 Vine management Whether organic or conventional management

23–26 Vine management Pollination methods used in 2011/12 and 2012/13 and, if artificial pollination was used, the source of pollen

27–29 Vine management Type of frost protection used and severity of frost damage 30 Vine management Type of irrigation used

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31 Vine management Canopy density rating (1-5) based on the Zespri Kiwigreen Manual

1. Open canopy with more than 30% gaps and grass

cover

2. Open canopy with less than 30% gaps and grass cover 3. Closed canopy with little grass cover

4. Dense canopy with grass cover in patches only 5. Dense canopy with no gaps and no grass cover

32, 33 Vine management Girdling of female vines in 2011/12 and 2012/13 growing seasons

34, 35 Vine management Girdling of male vines in 2011/12 and 2012/13 growing seasons

36, 37 Vine management Management of vine pruning and Psa infected material 38, 39,

42, 43

Orchard layout Female vine age, variety and ratio to male vines 40–42 Orchard layout Male vines including variety, age and layout in orchard 45–47 Disease

management

Whether weather information was used when planning orchard activities and the source of the weather information 48, 49 Disease

management

Who sprays crops for disease and reasons why spraying might have been delayed

50, 51 Disease management

Sprayer information including ownership, number of orchards sprayer is used in, and calibration

53, 54 Disease management

Use of disease hygiene measures for equipment and when pruning and girdling

To be eligible for inclusion in the study, an orchard had to have producing ‘Hayward’ vines at harvest in 2012 and be classified as infected with Psa on 1 January 2013. Further details on inclusion criteria are given in Froud et al. (2016). Zespri provided block and production data for all registered ‘Hayward’ growers producing kiwifruit for export in 2012, and KVH provided data on Psa status and date of first detection in orchards. Orchards that were recorded in both data sets formed the sampling frame. The block that was to be reported on was randomly selected from the sampling frame using an algorithm written in the ‘R’ freeware statistical package version 3.0.1.

The questionnaire was sent by Zespri Grower Services to 1669 eligible ‘Hayward’ growers in March 2013 and 442 responded. Data were entered into a database using a purpose built form designed to minimise data entry errors created using the EpiData software (Lauritsen & Bruus 2013).

7.3.2 Data analysis

Microsoft Access was used to combine the questionnaire data with the industry data sets. MS Excel and the ‘R’ freeware statistical package version 3.0.1 were used to assess the

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For the majority of orchard description questions, answers were coded as either present or not present, or used or not used. Where the grower could choose between multiple levels these answers were coded as multi-level categorical variables. For example, frost damage was a categorical variable with levels of no damage, minor damage, moderate damage or severe damage. For variables that were very similar, such as adjacent land-use categories of gully, bush and forest, and for those for which there were few observations, and it was appropriate biologically to combine categories, the data were combined into new variables. For these, the new variable is presented in the results table, below the component variables. In addition, continuous variables were visually assessed using boxplots and histograms and those that were not normally distributed were recoded as multi-level categorical variables or binary variables, such as the percentage of blocks with frost damage.

The distribution of continuous variables was explored using histograms. Non-normally

distributed data were summarised using quartiles. Means and standard deviation were used to summarise normally distributed variables. Categorical data was summarised using counts and percentages in each level.

7.4

Results

442 responses to the grower survey were received, with 12 responses excluded from further analysis either because they did not provide information about the disease status of the block (n=9), or other key information was missing (n=3). Therefore, the final dataset for this study comprised data for 430 blocks from ‘Hayward’ kiwifruit orchards. The regional distribution of survey respondents is shown in (Table 7-2). There were 205/430 (48%) responses from

growers from the Te Puke area which is both the largest growing area for kiwifruit and also the first region in which Psa (biovar 3) was detected in New Zealand. Forty-two of the 430

respondents were organic growers with the remainder using conventional growing systems: these two growing systems are described in Carey et al. (2009).

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Table 7-2 Number and percentage of respondents by region out of 430 'Hayward' orchards from Psa infected regions at 1 January 2013.

Growing region/area

Number of respondents

% of respondents Date Psa first reported in region Franklin 2 0.005 21/11/2011 Waikato 4 1 20/8/2012 Coromandel 8 2 31/8/2012 Waihi 5 1 19/9/2011 Katikati 64 15 26/9/2011 Tauranga East 50 12 5/8/2011 Tauranga West 37 9 18/10/2011 Te Puke 205 48 5/11/2010 Whakatane 29 7 29/9/2011 Opotiki 24 6 20/10/2011 Poverty Bay 1 0.002 20/11/2012 Hawkes Bay 1 0.002 10/10/2012