Target Pests

Fungus gnats (Bradysia spp.)

Western flower thrips (Frankliniella occidentalis)

Description

‘Stratiolaelaps’ is a native species of soil-dwelling mite, which feeds on small insects and mites (e.g., springtails, root mealybug crawlers, root aphids, spider mites).

·        Adults are tan in colour, less than 1 mm long (1/20th inch). They move rapidly over the soil surface.

Use as a Biological Control

·        Stratiolaelaps are used primarily to control young larvae of fungus gnats in the soil (for information on fungus gnats, see Sheet 330). They also help control soil stages of thrips and may account for up to 30% of thrips control (see Sheet 320). Stratiolaelaps do not control shore flies or moth flies, but will feed on other soil organisms, such as springtails, root aphids 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.

Monitoring Tips

Use a headband magnifier or 10-15 X hand lens to look for the mites in the top 1-2 centimeters (1 inch) of soil or growth media and at the base of plants.

Life Cycle

The complete life cycle takes about 18 days at 20oC (68oF).

·        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.

Product Information

Stratiolaelaps is supplied in a pasteurized peat/bran mixture in 1 L (1 qt) containers with a shaker lid for distributing the mixture over the soil.

There are 50,000 predators per liter, or about 50 predators per cc. The mixture also contains another species of mite as a food source for the predators.

To check the product for live mites, inspect under 10-15 X 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, out of direct sunlight, at 16-21oC (60-70oF) 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.  One application of Stratiolaelaps per crop cycle is usually sufficient, if used early in the season.

·        Soil Culture – Apply 1 L/100 m2 (1000 ft2) to the soil at the time of planting. Be sure to treat wet, exposed areas of soil, where fungus gnats are likely to breed.

·        Sawdust bag or Rockwool culture – Apply 8-16 L/ hectare (3-6 L/acre) to at least one plant in every bag or rockwool slab. Vegetable transplants may be treated 1 week before planting out.

·        Pot Culture – Apply 1 L/ 100 m2 (1000 ft2) of bench area.  Treat the floor of the greenhouse if it provides 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, at 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 Hypoaspis shortly after planting and before fungus gnat levels reach more than 20 adults/trap/week.

·        To control high numbers of fungus gnats, use of Stratiolaelaps can be integrated with insect parasitic nematodes (e.g., Steinernema spp.) and Bacillus thurinigiensis israelensis (BTI) (Gnatrol, Vectobac®), both of which control the larval stage of fungus gnats.

Using Pesticide

See Sheet 180 for expected effects of pesticides on Hypoaspis. In general, do not apply Hypoaspis to soil that has been treated with lime or pesticides (particularly soil treated with 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 Hypoaspis.

Microbial pesticides, such as Vectobac® (BTI) will not harm Hypoaspis.