Autumn kaolin treatments and early spring oil treatments against Myzus cerasi in Sweet cherries

The black cherry aphid Myzus cerasi FABRICIUS (Hemiptera: Aphididae) is a major pest in low‐stem cherry orchards with rain protective covering and hail nets. In autumn, winged aphids migrate from their secondary hosts back to the cherry orchards. We applied kaolin (Surround ® WP) in the autumn of 2019 (three applications) and 2020 (two applications) to young cherry trees to prevent the immigration and establishment of aphids, with the aim to reduce the number of fundatrices in the following spring. We compared the kaolin treatment with paraffin oil sprayed in spring, a combination of both treatments and an untreated control. In autumn 2019 with a denser kaolin residue and a higher assessment frequency than in autumn 2020, there were significantly less unwinged and winged aphids on trees treated with kaolin than control trees, whereas there was no significant difference in 2020. However, kaolin significantly reduced the number of aphid colonies in the following spring in both 2020 (95 %) and 2021 (77 %). Five days after the application, paraffin oil showed no significant effect in both years, but further assessments in 2021 revealed increasing efficacy up to 83% 25 days after application. The combination of kaolin applications in autumn with a paraffin oil application in spring had an efficacy of 86-99 % and prolonged the effect of kaolin. As the white residue on leaves in autumn does not harm photosynthesis, assimilation or transpiration and since kaolin is not toxic to beneficial arthropods, kaolin applied in autumn is a promising tool to control M. cerasi in organic cherry production