Overview of research

In 2004 and 2005, Koppert carried out Amblyseius swirskii trials in strawberry crops within four enterprises in the Netherlands. On most of the trial enterprises, A. swirskii was released as a preventative measure, and the trial monitored whether the predatory mite was able to establish itself in a strawberry crop in flower. In these trials, the predatory mites could be seen in large numbers in the leaves and in the flowers. It is well known that Amblyseius cucumeris is also very difficult to spot in strawberry crops. For this reason, the decision was made to carry out a trial in which both species of predatory mite were released in two sections of the same enterprise. The trial then looked at which predatory mite was detected in the largest numbers. The clear result of this trial was that A. swirskii was found in greater numbers than A. cucumeris (see graph 1). The number of predatory mites detected in this trial (a summer crop with light thrips infestation) was considerably higher than in other trials in which the infestation level was zero.

Alongside thrips, whitefly and spider mite, strawberry mite (Tarsonemus pallidus fragariae) is a further strawberry crop infestation that can be tackled using A. swirskii. In a trial carried out in the laboratory, one female A. swirskii per 15 strawberry mites was released on 10 affected leaves. At the beginning of the trial, the number of strawberry mites per leaf was between 29 and 63. Consequently, two to four A. swirskii were released per leaf. The result was that the numbers of strawberry mites declined rapidly, whereas the numbers of predatory mites rose. (see graph 2)

Results

A. swirskii can establish itself in strawberry crops.

Greater numbers of A. swirskii than A. cucumeris are detected in strawberry crops when both species of predatory mite are released in equal numbers.

A. swirskii predates strawberry mite

See graph 1 > Number of A. swirskii and A. cucumeris when both species are released in equal numbers.

See graph 2 > Average number of strawberry mites and A. swirskii per leaf.