Amblyseius fallacis on bean leaves

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)

Description: “Fallacis” is a native predatory mite that feeds on several different mites, including spider mites and rust mites, as well as other small insects. Fallacis may also feed on pollen, and can survive for periods on pollen alone, which makes them an excellent preventative insect. It is one of the most important biological control agents in North American berry and orchard crops. Adults are bout 0.5mm long, with pear-shaped bodies. They are tan to light orange in color, shiny, with long legs. Immature Fallacis are cream colored and semi-transparent. Eggs are oval and about 0.3mm long.

Use as Biological Control: 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, Integrated Pest Management (IPM) programs for field berry crops are based on using Fallacis as the primary control for spider mites. Fallacis is more resistant to pesticides than most biological controls, and a strain highly resistant to pesticides is available commercially. Unlike other predatory mites, such as the Persimilis, Fallacis can remain in areas with low levels of spider mites by feeding on other small arthropods and pollen. 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 and displaces them in cooler growing areas in the Northern United States.

Life Cycle: Development from egg to adult takes from 7-9 days at 70°F, to 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 per 100 leaves, to 200-500 predators per 100 leaves in just 2 weeks.

Adult females lay 1-5 eggs per day, for a total of 26-60 eggs over their lifetime (which could be between 14-62 days). The eggs hatch in 2-3 days, which are oval in shape and twice the size of the two-spotted mite eggs. Newly hatched predators do not eat, but later stages and adults feed on all stages of prey. Female Fallacis can eat 2-16 spider mites per day.

Adult females enter diapause in response to the short days in the fall (less than 14 hours of daylight). 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 (18°C) or above.

For Best Results: In field crops, placing higher numbers of predators on the prevailing upwind side of the crop will increase their dispersal throughout the crop via wind. In greenhouses, Persimilis should always be applied along with Fallacis. If spider mite numbers are high (there is visible webbing and clusters of mites stringing down from leaves), use an integrated pesticide such as fenbutatin oxide or insecticidal soap to reduce pest numbers before releasing predators. Fallacis needs a 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 spider mites in greenhouses where temperature and humidity are consistently high (over 72°F and 70% respectively), release Persimilis as well as Fallacis. Persimilis works better in high density spider mite populations under these conditions. The mite eating lady beetle Stethorus punctillum 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.


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Fallacis on Bean Leaves

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