Three-step broad mite detection protocol as an IPM-tool in pot azalea

The broad mite Polyphagotarsonemus latus Banks (Acari: Tarsonemidae) is an important pest in ornamental plants like pot azalea Rhododendron simsii hybrid Planch. As the biology, physical properties and behaviour of P. latus hinder detection, the pest is often identified when malformation of flower buds and terminal leaves have already caused severe economic losses. Consequently, growers call for a reliable scouting method, allowing early broad mite detection. In addition, efficiency of (chemical) control of P. latus recently became more important, as the number of available acaricides is decreasing while acaricide resistance is increasing. To optimize the efficacy of broad mite control within an integrated pest management (IPM) strategy, a better understanding of the pest biology and dispersion within the crop is needed. Indeed, the development of an adequate sampling and isolation protocol is essential to obtain consistent and reproducible data necessary to determine treatment thresholds, optimal timing of treatments and preventive measures. Although a variety of methods for extracting broad mites from plants are described, a standardized quantitative protocol for sampling and isolation was lacking. Recently, a novel protocol for broad mite detection was developed (Mechant et al., 2014). This three-step detection protocol for P. latus on R. simsii consists of (1) sampling of shoot tips, (2) isolation with ethanol 70%, and (3) broad mite counting facilitated by vacuum filtration. In this paper, we discuss the validation of this protocol under different climatic conditions and its potential for early broad mite detection in practical conditions. Results indicate that the three-step detection protocol is suitable for replicated sampling of P. latus on R. simsii in an experimental environment as well as for reliable scouting in a grower environment, regardless of climatic conditions. Hence, the three-step detection protocol can serve as an IPM-tool for broad mite control in pot azalea.