Assessment of management methods against pome fruit mites

Mites are an increasing problem in certain pome fruit growing regions in the Western Cape Province, South Africa due to a combination of factors such as drought/climatic conditions, acaricide resistance, incorrect application of monitoring protocols and management practices, or a breakdown in biological control. The aim of this project is to investigate potential contributing factors in the Ceres, Villiersdorp and Elgin areas to determine the reasons for these mite outbreaks over two seasons. The project will allow for the current integrated management recommendations to be objectively reviewed and amended where needed.

A questionnaire will be distributed to farmers to assess awareness of, and adherence to, correct mite monitoring and control protocols in orchards.

• Monitoring and spray application data will be obtained, where available, to assess relevant drivers of spatio-temporal mite distributions.
• Mite populations will be monitored both on trees and in surrounding cover crops, to determine correlation between percentage cover and type of cover crops to mite infestations.
• Bioassays will be performed to determine the susceptibility of both phytophagous and predatory mites to registered acaricides.

§ Data will be analyzed via machine learning to determine interactions between the different patterns and draw overall conclusions.

A questionnaire was compiled and widely circulated, but there were only four respondents, so no analysis could be done. Cultivar appeared to have the biggest influence on our data, but only one farm in one region could be analysed. 77 Cover crop species were sampled, but no strong correlation could be found with either predatory or phytophagous mites.

Limited number of mites could be found during monitoring activities, making analyses and bioassays difficult. Long term monitoring data revealed cultivar to have a strong influence on mite numbers, but other factors could not be measured due to data being obtained from only one region.

Phytophagous mites appear to be generally well managed by most growers, based on the fact that mite numbers were very low when scouting.