Description
Stratiolaelaps scimitus (also known as Hypoaspis miles) is a native species of soil dwelling mite, which feeds on small insects and mites. Adults are tan in color, less than 1 mm long. They move rapidly over the soil surface and feed just below the soil surface. Adults can consume up to 4.5 thrips pupae per day.
Target Pest
Fungus gnats (Bradysia spp.) Western Flower Thrips (Frankliniella occidentalis).
Life Cycle
The complete life cycle takes about 18 days at 68°F. The sex ratio is equal, 1:1 females to males. Eggs hatch in 2-3 days into young nymphs. each Stratiolaelaps consumes 1-5 prey per day. It can also survive as a scavenger, feeding on algae and plant debris. Populations will naturally fluctuate throughout the growing season.
Monitoring Tips
Use a headband magnifier or a 10-15x hand lens to look for the mites in the top 1 inch of soil or growth media and at the base of the plants.
Use in Biological Control
Stratiolaelaps are used primarily to control young larvae of fungus gnats in the soil or planting media. They also help control soil stages of Western Flower Thrips and may account for up to 30% of thrips control. Stratiolaelaps do not control shore flies or moth flies, but will feed on other soil organisms such as springtails and root mealybugs.
They have been used successfully in bedding and potted plant production, seedling and cutting propagation and poinsettia stock. They adapt well to the various growth media and capillary mats used in plant production, but do not survive freezing or flooding conditions.
Product Information
Stratiolaelaps is supplied in a pasteurized peat/bran mixture for distributing the over the soil. There are approximately 25,000 predators per quart (1 Liter) or about 15-20 predators per cc. The mixture may also contain another species of mite as a food source for the predators. To check the product for live mites, inspect under a 10-15x magnification. The predators are tan and move quickly compared to the food source mites, which are white or translucent and move slowly. The predators should be applied as soon as received. Do not refrigerate. If necessary, containers can be held, stored on their side out of direct sunlight at 60-70°F for up to 7 days.
Introduction Rates
Stratiolaelaps is most effective when applied before fungus gnat populations become established or while numbers are still low (below 10/trap/week). Two applications of Stratiolaelaps per crop cycle is usually sufficient used early in the season. The second application should be made 2-3 weeks after the first.
Soil Culture - Apply 5 Stratiolaelaps/sq. ft. to the soil at the time of planting, repeated in 2-3 weeks. Be sure to treat wet, exposed areas of soil, where fungus gnats are likely to breed.
Sawdust Bag or Rockwool Culture - Apply 5/sq. ft. or 500,000/hectare. Apply 4cc (1 tsp.) per every 2nd bag or rock wool slab, repeat in 2-3 weeks.
Pot Culture - Apply 1 Qt./2,000 sq. ft. of bench area. Treat the floor of the greenhouse weekly if it provides wet conditions for fungus gnats to breed and occasionally treat the perimeter of the greenhouse. It is not necessary to apply mites to every flat of bedding plants if applications are done early and at the full rate, to allow them time to spread to all flats. Mites can also be applied to propagation media before striking cuttings.
For Best Results
Do not mix predators into the growth media before potting because they do not survive. Apply Stratiolaelaps shortly within the first few weeks of planting and before fungus gnat levels reach more than 20 adults/trap/week. To control high numbers of fungus Gnats, combine Stratiolaelaps with beneficial nematodes (Steinernema feltiae) or Bacillus thuringiensis israelensis (Bti), both of which control the larval stage of fungus gnats.
Using Chemicals
Contact Sound Horticulture to determine expected effects of pesticides on Stratiolaelaps. In general, do not apply Stratiolaelaps to soil that has been treated with lime or pesticides (particularly Diazinon). It is likely that foliar sprays are less harmful than soil drenches, depending upon how much pesticide reaches the soil surface.
Fungicide drenches containing benzimidazoles are known to reduce reproduction of Stratiolaelaps. Microbial pesticides should not harm Stratiolaelaps, however, check with us for current recommendations.
Content Courtesy of Applied Bio-nomics Ltd.
