Improved predatory mite release system

Abstract: Slow release sachets with predatory mites have been used for many years to ensure a continuous release of phytoseiid mites into the crop for several weeks, especially when prey levels are low and no alternative food sources are present. Slow release sachets are the best option to ensure establishment of the predatory mites and are recognized by growers for their ease of use. The currently used sachets perform well under moderate temperature and humidity conditions. However, when ambient humidity levels are low, the content of the sachets becomes drier due to evaporation through the outer wall of the sachet. As a consequence the mite populations inside the sachets collapse. Therefore Koppert has developed a new sachet that can be considered drought resistant.The new sachets containing Amblyseius swirskii were compared to the current Swirski-Mite Plus sachets under extremely dry condition in a semi-field test. At an average relative humidity of 48% and average temperature of 21 °C, the Swirskii Mite Plus sachets produced only 180 mites compared to 500 plus from the new foil sachets. The new sachets were also tested with Amblydromalus limonicus, a predatory mite for which no slow release sachets are available so far. These sachets produced more than 500 predatory mites with a starting population of 100 under standard laboratory conditions. With this new development we expect that the use of sachets will not only make predatory mite release more reliable in protected crops, it will be also suited to release predatory mites in outdoor crops.