Predatory insects are an important component of Integrated Pest Management and organic cannabis production. Predators kill and feed on several to many individual prey during their lifetimes. Predatory beetles, flies, lacewings, true bugs (Order Hemiptera), and wasps feed on various pest insects or mites. Most spiders feed entirely on insects. (UC IPM) Predatory mites are commonly used in cannabis horticulture and are one of the most diverse classes of predatory insects.
Many of the species of predator mites can also survive on pollen. Multiple species of predatory mites are commercially available and growers use biological control as a complementary tool to chemical control.
Predatory mites belong to four categories – Type I, Type II, Type III, and Type IV.
Type I: These predatory mites are specialists feeding exclusively on spider mites (family Tetranychidae) that produce considerable webbing. They require feeding on spider mites for their survival and reproduction. Type I predators are aggressive and voraciously feed on pest mites. Because of their dependence on spider mites, Type I specialists rapidly decline and cannibalize when pest mite populations decline.
Type II: These are also specialist predators, but they feed on spider mites and other species of mites. They also feed on pollen and in some cases on thrips and other species of predatory mites. Having more food choices for survival and reproduction, Type II specialists continue to be present in the absence of spider mites and are less likely to cannibalize.
Type III: These are generalist predators that feed on multiple species of mites that include spider mites, eriophyid mites, and tarsonemid mites and insects such as thrips and whiteflies. They also feed on pollen, honeydew, and plant juices. Type III generalists are also known to cannibalize and feed on other species of predatory mites in the absence of pest mites or other food sources.
Type IV: These mites primarily feed on pollen and can also feed on pest mites.
Phytoseiulus persimilis is a Type I specialist that exclusively feeds on spider mites. It is bright orange, teardrop-shaped and moves rapidly. It prefers cooler temperatures and is sensitive to hot and dry conditions. So, it is more effective during earlier parts of the production season before temperatures increase.
Amblyseius andersoni is a Type III generalist predator. It can tolerate high temperatures when relative humidity is high.
Neoseiulus californicus (McGregor) is a Type II specialist that primarily feeds on spider mites, but also has Type III generalist characters. It appears similar to N. fallacis. It can withstand warmer conditions better than P. persimilis and N. fallacis. It can withstand cold temperatures for short periods and tolerates relative humidity range from 40-80%.
Neoseiulus fallacis (Garman) is a Type II specialist that primarily feeds on spider mites. It is translucent to peach or orange and appears to have a flatter body compared to spider mites or P. persimilis. It is also sensitive to hot and dry conditions.
Galendromus occidentalis (Nesbitt) also known as western predatory mite is a Type II specialist that primarily feeds on spider mites. It prefers warm temperatures and tolerates dry conditions as low as below 30% relative humidity. It is sensitive to cooler temperatures.