Swirskii for Whitefly Control

Description

<em>Amblyseius swirskii</em> adult

Amblyseius swirskii is a predatory mite useful in the control of whitefly predominantly, and with some impact to spider mites as a noted side benefit. Over the past few years these predatory mites have also demonstrated the ability to suppress whiteflies and may also feed on spider mites, possibly including broad mites and other tarsonemid mites.

A. swirskii are normally shipped as adults and are very similar to A. cucumeris in terms of color, unless they take on coloration of their diet — but they appear smaller and have a non-segmented pear-shaped body. They cannot be readily distinguished from A. cucumeris with the naked eye. Like A. cucumeris this species can consume pollen in the absence of pests making them useful preventively (they are also alternatively supplied in slow-release packets like A. cucumeris). These mites can also be used in hotter conditions than A. cucumeris provided a fairly high relative humidity is maintained on the leaf surface.

Life-style

After progressing through their 5-6 day immature phase, the female mites can lay up to 2 eggs per day throughout adulthood and can multiply their numbers readily in a greenhouse. Please note, however, any life-cycle numbers may vary greatly dependent upon the availability of food and environmental conditions. The conditions for optimum performance will be between 77-82°F with a relative microclimate humidity of around 70%. But these are optimum conditions and not necessarily a prerequisite of successful implementation. Please note, however, significantly cooler or warmer temperatures and, especially humidity fluctuations, may hamper reproduction and development a certain degree.

If sufficient food is available and conditions are favorable, A. swirskii are known to establish well and may stay where they are put (where they are needed) cleaning up before spreading their range. A lot, however, does depend on the humidity on the leaf’s under surface. If too dry the eggs will not hatch so one will be forced to make do with the adults being released.

Benefits

Benefits include rapid development and a wide-ranging appetite — from whitefly eggs and first instar larvae. Moreover, as mentioned, they can also consume spider mites. This means if one pest is controlled, another can sustain these predators. This makes them more useful and allows them to stick around longer making them quite economical. Also as mentioned, these predatory mites can do well in conditions warmer than some other predators which allows them to be performing at their peak when the pests will be. They won’t do as well on the other end of the scale, though (see Drawbacks, next).

In addition to the attributes noted above, A. swirskii do not undergo diapause due to short day-lengths or low temperatures meaning they can be used late into the fall and into the winter indoors. Bear in mind, though, that at around 59° A. swirskii will become inactive — becoming active again when temperatures rise.

A. swirskii have a good appetite: They can eat up to to 19 whitefly eggs/15 larvae per day.

Drawbacks

A. swirskii may survive cooler conditions and become active again quickly, but this predator cannot survive frosts and cold conditions. It’s native to the eastern Mediterranean so these facts are understandable. A. swirskii may need to be supplemented with other predators or parasites, especially during the off-peak parts of the growing season or if they’re newly introduced or not yet established or, of course, if pest populations demand a heavier handed approach.

We advise the use of caution if using A. swirskii in a greenhouse where Phytoseiulus persimilis or Aphidoletes aphidimyza are in use. There could possibly be a compatibility issue.

Other challenges may exist. For example, A. swirskii may avoid honeydew from whiteflies and the webbing of certain spider mites. How much these factors will contribute to the overall success of this predator remains to be seen (see Advisories).

Scouting

With magnification the scout can find the eggs underneath leaves near the veins and between hairs. And the adults can be seen if the lighting is conducive, but distinguishing these mites from others will be difficult. Scouts need to be aware of this if any other clear/white mites of similar size, such as N. cucumeris, are being used in the same crop.

Advisories

If used with P. persimilis or A. aphidimyza, please use caution. If used in a greenhouse with mites and whiteflies, try to clean up honeydew deposits and excessive webbing prior to release. Try to maintain microclimate humidity at 70%, though this isn’t that difficult in most greenhouses. Supplement via misting or other methods if things get too dry.

Usages

Greenhouses and interiorscapes will be the most likely places this predator can be used, but we certainly encourage trials in other crops settings such as gardens.

Release Rates for Amblyseius swirskii

ClassificationRelease Information
Shaker tube2-5/sq.ft., bi-wkly, as needed
Bulk bag2-5/sq.ft., bi-wkly, as needed. Use provided scoop.
Slow release sachetsEvery 6 feet of crop row, monthly as needed

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