Description
Amblyseius fallacis is a native predatory mite that feeds on spider mites, rust mites and small insects. It is one of the most important biological control agents in North American berry and orchard crops. Adults have pear-shaped bodies (.5mm) long. They are tan to light orange in color, shiny and have long legs. Immature predators are cream colored and semi-transparent. Eggs are oval and .3mm long.
Target Pests
Two-spotted Spider Mite (Tetranychus urticae) European Red Mite (Panonychus ulmi), Spruce Spider Mite (Oligonychus ununguis), Southern Red Mite (Oligonychus ilicis), Bamboo Mite (Schizotetranychus celarius).
Life Cycle
Development from egg to adult takes 7-9 days at 70°F and 3 days at 85°F. At 78°F a fourfold increase in numbers can occur within 4 days. In the field, under optimum conditions, populations can increase from 10 predators/100 leaves to 200-500 predators/100 leaves, in just 2 weeks.
Adult females lay 1-5 eggs per day, for a total of 26-60 eggs over their 14-62 day lifespan. The eggs hatch in 2-3 days. Eggs are oval and twice the size of two-spotted mite eggs. Newly hatched predators do not eat, but later stages and adults feed on all stages of prey. Female A. fallacis eat 2-16 spider mites per day.
In the fall adult females enter diapause in response to short days (daylight less than 14 hours). They stop reproducing and move into sheltered areas, such as under bark or ground cover. They do not enter diapause in greenhouses or interior plantscapes if the temperature is 64°F or above.
Monitoring Tips
Use a headband magnifier or 10-15x hand lens. The predators are usually easy to tell from their prey, which are slow moving. Adult mites often hide under leaf hairs and along the edge of leaf veins. They are most easily seen on parts of the leaf where spider mite numbers are low or around the edges of the main spider mite infestation. Eggs are usually found singly or in pairs in crevices along the leaf midrib or where prey is abundant.
Use in Biological Control
Amblyseius fallacis is used to control two-spotted spider mites and other mites on greenhouse peppers, field strawberries, raspberries, currants and mint. In British Columbia, Washington and Oregon, IPM programs for field berry crops are based on using Amblyseius fallacis as the primary control for spider mites.
Amblyseius fallacis is also used on container and field grown nursery stock. Research in Oregon found that fallacis can control spider mites and bamboo mites on woody ornamentals. Fallacis also feeds on apple rust mites, cyclamen mites and tomato russet mites, however whether or not it controls these species is not known.
Amblyseius fallacis is more resistant to pesticides than most biological controls and a strain highly resistant to pesticides is commercially available.
Unlike other predatory mites such as persimilis, fallacis can remain in areas with low levels of spider mites; they survive in the absence of mite prey by feeding on other small arthropods and pollen. Amblyseius fallacis feeds and reproduces over a wide range of temperatures, 48-85°F. They do best where there is a dense plant canopy and when relative humidity is over 50%. Fallacis can reproduce at lower temperatures than other predatory mites (persimilis, californicus) and displaces them in the cooler growing areas in Canada and the Northern USA.
Application Instructions and Rates
Lay the container on its side at room temperature, out of direct sunlight, for 1/2 hour. Check the product by looking through the bottle or by sprinkling some of the vermiculite onto a sheet of black paper and using a 10-15x lens or magnifier. Active mites should be visible. Gently rotate the bottle to mix the mites within the carrier and distribute the contents over the infested plants.
Amblyseius fallacis is most effective when applied at the first sign of a mite infestation. Fallacis will usually become established in the crop after one introduction, where they remain if mites or pollen are available for food. When prey becomes scarce, fallacis moves to the top of the plant and usually disperses throughout the corp on air currents. When predators are found on each infested leaf it usually means that the biological control program will be successful. It may take another 2-6 weeks for new plant growth to show improvement, depending on growth rates.
General Introduction Rates 0.1 - 0.5 fallacis/square foot. For greenhouse crops, apply predators to all infested plants. Use the lower rate for preventative introductions onto mite susceptible plants and the higher rates if there are established pest mite populations.
Greenhouse Peppers. As soon as flowers have pollen, or spider mites are present, apply 1 predator/ 5 plants. Also, apply P. persimilis to all outbreak areas when using A. fallacis because spider mites can reach high densities on this crop during hot weather. Research in British Columbia has shown that better control of spider mite can be achieved when both A. fallacis and P. persimilis are used together on greenhouse pepper.
Woody Ornamentals and Container Plants. Apply 0.1 - 0.5 predators per square foot to all spider mite susceptible plants early in the season, or as soon as spider mites are detected. Use higher rates for established spider mite populations. Use compatible miticides to treat 'hot spots' until the A. fallacis populations build up.
Field Crops. Before introducing Amblyseius fallacis, monitoring counts should be done to determine numbers of spider mites and existing predators. Spread fallacis evenly throughout the field using 150-200 release point/ha or 60-80/acre. Concentrate extra predators where there are higher mite counts.
Strawberries and Mint. For new plantings release 10,000 predators/acre as soon as possible after planting or 10 days after applying insecticides to control aphids. On producing fields, release 7,000/acre if needed in spring or early summer so predator numbers have enough time to build up and provide control before September. Before planning a strawberry biocontrol program, refer to the Oregon State University web site which includes a fallacis release rate calculator.
Raspberries and Currants. Release 7,000-10,000 predators / acre. Inoculate only those fields with spider mite populations of 0.3 mites/leaf and higher. Release predators early in the spring to achieve control the same season. Release them during the summer for control the next season.
For Best Results
In field crops, place higher numbers of fallacis on the prevailing upwind side of the crop to increase their dispersal by wind. In greenhouses, P. persimilis should always be applied along with A. fallacis. If spider mites numbers are high (there is visible webbing and clusters of mites stringing down from leaves), use a pesticide or insecticidal soap to reduce pest numbers before releasing predators and in hot spots after release.
Amblyseius fallacis needs relative humidity of over 50% to survive, particularly in the egg stage. In hot, dry conditions, raise the humidity by watering or misting plants. For two-spotted mites in greenhouses, where temperatures and humidity are consistently high, release persimilis as well as fallacis. P. Persimilis works better in high density spider mite populations under these conditions.
Where over 60% relative humidity can be maintained, both persimilis and the predatory midge Feltiella acarisuga can be used with fallacis. The mite eating lady beetle, Stethorus is less affected by low humidity and may be used along with fallacis on greenhouse cucumber, pepper and nursery crops. Stethorus is able to fly and can detect and control small colonies of mites before they become well established.
Content Courtesy of Applied Bio-nomics Ltd.
