US ENT 17-A1
The identity and ecology of economically important mites (Acari) in vineyards
Pringle, K L
Objectives and Rationale
Plant-parasitic mites are extremely damaging pests with a rapid generation time, high fecundity and a tendency to over-exploit their hosts. The diversity of mites in vineyards in South Africa is virtually unknown. Surveys have been done with predatory mites and phytophagous mites being recorded, but no recent studies focussing on their ecology, pest status and seasonal cycles have been collected. The aim of this study was to survey phytophagous and predatory mite diversity and to
investigate pest status of the plant feeding mites of South African grapevine, including the recently introduced, invasive Brevipalpus lewisi.
Sampling was done over a two-year period and included four conventional farms found in the Winelands region of the south Western Cape, South Africa. Each conventional farm contained a motherblock, nursery and commercial vineyard. At each site vine branches were collected on a regular basis from November 2016 to April 2018. During the winter months weed and cover crop samples were also collected at the conventional farms. Mites were collected from vine leaves with a mite brushing machine. Weeds and cover crops were inspected with a microscope and mites were collected from them with a fine brush. Mites were slide mounted and identified.
The predatory mite diversity from plant samples was much higher than expected. Eueseius addoensis and Typhlodromus praeacutus were the most abundant predatory mites found in the commercial vineyards and nursery material with T. praeacutus and Neoseiulus barkeri the most common in motherblocks. Brevipalpus species were the abundant plant feeding mites, with Brevipalpus lewisi being the most dominant species.In commercial vineyards E. addoensis and T. praeacutus were the only predatory mites that were present throughout the entire season. The other predators were present for one or two months. Motherblocks and nurseries had sporadic occurrences of predators. In all three vineyard types B. lewisi was dominant throughout the year. Mites that were found on both ground cover and vines were Tydeus grabouwi (predator) and Tetranychus ludeni (plant feeding mite).
Key Conclusion of Discussion
The findings of this study forms baseline data to develop management strategies to be used in the wine industry. Understanding the diversity and seasonal cycles of the mites occurring on grapevine will make for better decision making in pest control. Awareness about the importance of the different groups of mites and their roles should be raised among nurseries and producers. Further research is recommended into the effect of various cover crops on mite abundances, and how this can be used to suppress plant feeding mites.
Recommendation to Industry / Key take-home message
Based on the predatory mites’ seasonal cycles it would be best not to apply treatments at the start of the growing season (November, December) as important predatory mites were most abundant during the beginning of the year (i.e. between January and March). These predatory mites are important as they tend to provide services like preying on pest mites, as well as being a food source for larger predators.The alternate host survey showed there is definite movement of mites between ground cover and grapevines. Predatory mites, for example, overwinter in broadleaf weeds, thus ground covers can provide refuges for these beneficial mites. Important to note that it was a very dry season, which may have influenced the occurrence of mites. There is a fine balance between applying chemicals for treating a pest without disrupting their natural enemies. An
integrated approach is therefore strongly recommended through management of cover crops and timing of application of pesticides, including sulphur.
Vermaak, M and Addison, P. 2017. Mite diversity survey on grapevine mother blocks and nurseries in the Wellington (Western Cape) region. Paper presented at the ESSA / ZSSA Combined Conference. 3-7 July, Pretoria, South Africa.