'Salivary Secretions' of Eriophyoids (Acari: Eriophyoidea): First Results of an Experimental Model

This paper concerns an approach to direct collection of eriophyoid 'salivary secretions', and reports preliminary results on biological assays providing evidence for the presence of plant growth promoting substances in these secretions. Eleven species belonging to the Phytoptidae, Eriophyidae and Diptilomiopidae, characterized by different host-plant interactions, were studied by immersing mites into the following oils: condensate of cedar oil, oil for immersion lenses, two kinds of olive oil, alpha-terpineol, hystolemon, vaseline oil, and soybean oil. Some species secreted small droplets of lipophobic substances at the tip of their mouthparts when they were immersed in objective lens oil. Mite mortality and percentage of secreting specimens depended on the species and the medium used. Aceria caulobia (Nalepa) was selected as the candidate for subsequent study, because this species displayed a higher percentage of secreting mites than the other species and numerous specimens were easily collected by means of an airflow and filtering device. The induced secretions were studied from January to June of 2000, 2001 and 2002. Rapid salivary bioassays were performed during the period of maximum induced secretion in 2001. They were evaluated using a wheat-coleoptile and an excised-radish-cotyledon growth test, respectively, for indole-3-acetic acid-like and cytokinin-like activity. The bioassays suggested the presence of chemicals with plant growth regulatory effects. A brief account of eriophyoid mortality in the oils was also given.