Stratiolaelaps scimitus (formerly Hypoaspis miles) is a soil-dwelling mite capable of the prevention, control, and management of sciarid flies, shore flies, various thrips and soil pests. Not only are these mites predators of thrips’ prepupal and pupal stages, they are very effective fungus gnat predators as well. STRATIOforce™ are shipped as adults, immatures and eggs in liter-size shaker bottles or 5 liter bulk bags filled with a loose vermiculite carrier and a percentage of clean peat. In this form, STRATIOforce™ are very easy to distribute in the crop. STRATIOforce™ can help prevent thrips from becoming intolerable. They can also be instrumental in assisting another predator with the timely and efficient control of an outbreak. Some of the species they can devour are listed under the thrips predator, A. cucumeris. Moreover, by themselves, they can control all the fungus gnat species mentioned in the page on parasitic nematodes. And if that’s not enough, these little carnivores (meat eaters)/detrivores (recyclers) also eat springtails (species in the insect order Collembola). Currently under investigation is the potential for these mites to impact root mealybugs (Rhizoecus arabicus and other Pseudococcidae family members), sow bugs and pill bugs, also known as rolly-pollies (Portcellio spp. and Armadillidium vulgare, respectively).
These robust 0.8 mm. richly-colored tan to brown mites live, eat and reproduce in the soil or soilless medium in containers and planters and, on the walkways and floors of greenhouses. The STRATIOforce™ females’ eggs — of which there are many — hatch into super small larvae which develop into tiny dark brown, almost black, nymphal forms before reaching adulthood. These, too, are fierce predators, consuming many pests, mostly the eggs and smaller larvae (first and second instar) of fungus gnats and the pupal stages of thrips. The life-span of these predators is about 13 days from egg to ever-after. But they reproduce profusely in what little time they have. The conditions for optimum performance will be between 60-72°F, and we’re talking about soil temperatures, with a relative humidity equal to that found in a friable, slightly moist medium, compost or soil. But these are optimum conditions, and not necessarily a prerequisite of successful implementation. Please note, however, considerably cooler temperatures will hamper reproduction and development a certain degree.
STRATIOforce™ are very cost-effective. A little bit goes a long way and they can last such a long time. These predators, like Amblyseius cucumeris, are supplied with some prey mites (Tyrophagus putrescentiae). These prey mites are merely a non-sustainable food source (but only after the contents are distributed, left in the bottle the prey mites will reproduce) for the predatory mites while they’re in transit. These predators are compatible with many insecticides; a real plus in an Integrated Pest Management (IPM) program. Part of the reason for this is simple: these mites are protected in the soil during spraying. They do wander at night, though, so caution is still advisable. This wandering, however, has its advantages: the mites can usually establish themselves in the entire area.
You get a lot, but you have to use a lot. Good thing they’re inexpensive. These mites like humid conditions. Therefore, growers of some herbs, most cacti and some succulents may not have suitable soil conditions for these predators. They probably won’t have fungus gnats either. And as far as thrips…? Perhaps. STRATIOforce™ can reduce thrips populations by only about 30%, but this isn’t necessarily the fault of the mites (see Advisories).
Using the paper method (discussed in greater detail under A. cucumeris’ Scouting) and yellow and blue sticky traps to detect thrips is a sure way to progressively determine your predators’ efficacy. Using yellow sticky traps (lying sticky-side-up at surface level) and potato disks to monitor fungus gnat levels will do the same. Unless your scouting is really top-notch, you’ll probably miss most of the predators present in the soil or medium. But this doesn’t have to be the case. First look at the mites in the container. (They’re sometimes under the lid, if they’re not readily visible, try blowing gently into the bottle. More often than not this will bring them up from the vermiculite depths.) This way you may be better able to identify the mites later. Now, in the release site (this works best in other than small containerized plantings) place stones, small pieces of bark, etc. around the site. Then, during your weekly scouting rounds, you can flip over the “little shelters” to look for your beneficial mites. But it’s not unheard-of to find these tough survivors up to a year after a release. This isn’t always the case. It happens mostly in large planters and greenhouse floors.
For fungus gnat control, 6" pots and up are probably the best bet for containerized plant applications. If they’re smaller than that, we normally recommend parasitic nematodes (see Parasitic Nematodes). For thrips control, however, it is best to use the mites in nearly every application — but not alone. The thrips’ in-ground stages make up only a small percentage of their overall life-span. This is why the STRATIOforce™ can only handle about 30% of the overall population. An above-ground predator, like one of the other organisms in this section, really should be used. However, let it be known that the impact of STRATIOforce™ on this extremely pernicious pest is noticeable at worst. 30% is 30%! Do not rely entirely on the long-term establishment of STRATIOforce™. This happens, almost always to a certain extent, but not necessarily to such a degree that pest control can be maintained. Multiple and regular releases are, like it is for our other biocontrols, recommended. One rule-of-thumb to consider: the bigger the container or release site the longer the interval between releases can potentially be (and thus fewer releases); and the opposite is true for smaller containers or growing areas.
Greenhouses/interiors are where these mites are most often used. However, We’ve heard excellent reports from outdoor nurserymen who’ve had outstanding results.
Release Rates for Stratiolaelaps scimitus
|Preventative||10 per square feet|
|With existing pest populations||30 per square feet|
|Comments||Friable floor, potting mix, and other locations should be treated as well, not just the planting media.|