In Honour of Amblyseius

At this point in time, the Phytoseiidae are one of the most intensely studied families of mites. They are the only group of mesostigmatan mites to have significantly diversified among the foliar environment (on and around plant leaves) where they are mostly predators on other small invertebrates. The taxonomic history of phytoseiids is storied and complex but one taxon that has been consistently recognised as a major part of the family is the genus Amblyseius.

Swirski mite Amblyseius swirskii, from here.

When reviewed by Chant & McMurtry in 2004, Amblyseius was a sizeable assemblage of close to 350 known species (I quite expect that number to have expanded by now). Species of Amblyseius are lightly sclerotised, mostly pale in colour, and usually have a smooth shield covering most of the dorsum. The genus is characterised by the presence of eighteen or nineteen pairs of setae on the dorsum of the idiosoma (the central body) with three sublateral pairs being particularly long: one about the level of the third pair of legs (referred to as the s4 pair) and the other two towards the rear of the body. Except for a few pairs forward of the s4 setae, the remaining dorsal setae are all minute.

The primary focus of human interest in phytoseiids has been their role as predators of crop pests. I described some of the ways in which phytoseiids have been commercially utilised in an earlier post. Species used in this way include several Amblyseius though matters are complicated slightly by changes in taxonomy (for instance, one species which has been widely traded as Amblyseius cucumeris is now placed in the genus Neoseiulus). One of the most widely used of the commercial phytoseiids in recent years has been Amblyseius swirskii, commonly known as the Swirski mite (E. Swirski being an acarologist after whom the species was named). This species was first described in 1962 from almond trees in Israel and subsequently identified from a wide range of plant and crop species. Its history in pest control has been described in detail by Calvo et al. (2015).

The Swirski mite feeds on a range of prey, including mite, thrips and whitefly species, as well as on pollen and micro-fungi. It was first promoted as a commercial control for silverleaf whitefly Bemisia tabaci in the early 2000s. However, it did not get taken up in a big way until media publicity about pesticide residues on capsicum crops in Spain led to a crash in demand. Farmers in that country were forced to look for alternative means of pest control and found great success with A. swirskii (previous attempts to use the cooler-clime preferring Neoseiulus cucumeris in Spain had not been promising). Since then, the Swirski mite has been adopted in numerous countries for use on a range of crops to control various pests such as western flower thrips Frankliniella occidentalis. Because of its ability to grow and thrive on non-insect foods, including artificial diets, this mite is easily cultured commercially. It may also be released on crops before pest infestations develop, building up numbers on a diet of pollen until suitable prey presents itself. For the same reason, Swirski mite populations do not crash before pest control is complete. Overall, a remarkable success and a prime example of the value of Amblyseius species to mankind.

REFERENCES

Calvo, F. J., M. Knapp, Y. M. van Houten, H. Hoogerbrugge & J. E. Belda. 2015. Amblyseius swirskii: what made this predatory mite such a successful biocontrol agent? Experimental and Applied Acarology 65: 419–433.

Chant, D. A., & J. A. McMurtry. 2004. A review of the subfamily Amblyseiinae Muma (Acari: Phytoseiidae): part III. The tribe Amblyseiini Wainstein, subtribe Amblyseiina n. subtribe. International Journal of Acarology 30 (3): 171–228.