Improvement of sachet systems to increase release numbers of the predatory mite Amblyseius swirskii (Acari: Phytoseiidae)

Abstract

Long-life sheltered sachets (LSSs) are used to control small arthropod pests in Japanese crop production. This setup consists of a long-life breeding sachet (LBS), known as a high-performance sachet of predatory mites, and two distinctive materials (water-retaining polymer and a felt patch) that encourage their multiplication inside the shelter made of water-resistant paper. Although LSSs can release large numbers of predatory mites [Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae)] over several weeks, their performance may be further enhanced by the inclusion of supplemental sugar as prey mite food. We first verified this possibility in a laboratory using felt patches treated with 10% or 50% honey solutions. We found that the inclusion of a 50% honey solution resulted in a higher and longer predator release (median: 2147.5 individuals, 2nd–9th weeks) from LSSs than an identical setup but with 10% honey solution (1423.5 individuals, 2nd–7th weeks) or no supplementary food (972.5 individuals, 2nd–7th weeks). We then assessed the effects of cheaper foods on performance using felt patches treated with 25% and 50% soft-yellow sugar solutions. The results showed that 25% soft-yellow sugar solution (2047.0 individuals), 50% soft-yellow sugar solution (2296.0 individuals), or 50% honey solution (1953.5 individuals) resulted in greater numbers of predators released from LSSs than with no supplementary sugar supplied (1204.5 individuals). We concluded, from the viewpoint of predator release and production costs, that soft-yellow sugar solutions (25–50%) are suitable supplementary food sources for this novel sachet system.