Research results in aubergines
The big difference between aubergine and cucumber or sweet pepper, for example, is that the leaves are densely covered in hairs. Moreover, every leaf hair is umbrella-shaped with diagonal protrusions covering the leaf (see photograph). This dense covering of hairs ensures that predatory mites are not able to run across the leaves as quickly.
WUR Greenhouse Horticulture researched the performance of six types of predatory mite in combating thrips on the densely hair-covered leaves of aubergine plants (graph 1).
In the assessment of the number of predatory mites, A. swirskii emerged as the species that had increased its numbers the most. Nine weeks after release, there were on average 12 predatory mites per leaf (compared to 10 predatory mites per plant initially). Treatment with A. swirskii also resulted in the fewest thrips by far being found. It was striking that the population growth in aubergine crops was slower than in cucumber crops, for example.
Koppert began a practical trial in France in April 2005. Whitefly was treated in three tunnel greenhouses using three different strategies.
1. A. swirskii + parasites
2. Macrolophus caliginosus + parasites
3. only parasites
The results of the trial showed that A. swirskii quickly established a population with an average of 10 predatory mites per leaf and that this number declined to two to three per leaf after a while. The control of whitefly in the tunnels with A. swirskii and M. caliginosus was respectively comparable with and better than the tunnel with only parasites. After a few weeks, A. swirskii and M. caliginosus were also found in tunnels in which they had not been released, and the differences between the tunnels regarding whitefly damage became less (graph 2).
See graph 1 Research into the best predatory mite in aubergine crops
See graph 2 Development of glasshouse whitefly per tunnel in the practical trial in France.