Distribution and survival of the predatory mite Blattisocius mali on cucumber leaves with the addition of bran, yeast and pollen

Abstract

Biological control has a special position in sustainable agriculture that requires continuous exploration and diversification in bio-agents to cope with emerging crop pests. Blattisocius mali is a promising biological control agent against some acarid mites, nematodes and moth pests. This study aimed to examine factors that could increase survival and diminish dispersal of B. mali deprived of its prey, the mold mite Tyrophagus putrescentiae, from cucumber plants. The impact of the presence of males on starving females’ lifespans and the influence of different substrates, i.e., wheat bran, dry yeast pellets, and cattail pollen, on the distribution and survival of starving females in groups with males were examined. Experiments were performed on cucumber leaf platforms in Petri dishes filled with water. The results showed that females lived longer and a lower percentage drowned in water when accompanied by males. On the platforms with the addition of a substrate, the mites mainly stayed within the substrate, and eggs were only recorded in the substrate. They clearly preferred bran over pollen or pollen + yeast pellet aggregations. However, the quality of the substrate deteriorated within the first days, and some mites died of entrapment in the substrates. On the 3rd day, the lowest mean percentage of live individuals was observed on platforms with yeast + pollen (54.4%) followed by pollen (68.9%) alone. At that time, females also stopped laying eggs, and cannibalism towards hatched larvae and adults was observed. By the end of the experiment, 54.67% of the mites had been found dead on the leaf surface, and none of the substrates had significantly influenced their lifespan. The females lived on average 8.19 days and the males 5.06 days. The obtained results are discussed in the context of potential application of B. mali in biological control strategies.