Hosts or Prey
Nymphs of scale insects, thrips, and whiteflies and especially plant-feeding spider mites
Identification
Larvae are 6-legged, transparent, and relatively inactive. Adults and nymphs have 8 legs. Adults are pear shaped, shiny, and about 1/50 inch (0.5 mm) long. Nymphs resemble small adults. Adults and nymphs take on the color of their diet; for example, they are red after feeding on citrus red mite, yellow after feeding on citrus thrips, and white when feeding on pollen.
The eggs are oblong, and translucent to transparent. Euseius eggs are larger than the round eggs of spider mites.
Except when feeding or molting, adults and nymphs move quickly and avoid direct sunlight. They primarily occur on the underside of leaves with their prey. When held on a leaf in the sun, the tiny, shiny body of Euseius species can be observed running rapidly along the main vein or across the leaf.
Lookalikes
Euseius can be discriminated to species only by expert examination of microscopic characters. In California, Euseius tularensis is common on citrus in hot interior valleys. Euseius hibisci is prevalent in coastal areas; for example it occurs on avocado along with Euseius obispensis, E. quetzali, and E. stipulatus.
Life Cycle
The appearance and biology of Euseius species are virtually the same. Euseius hatch from an egg and develop through a six-legged larval stage and two eight-legged nymphal stages before maturing into adults. Adults and nymphs are predaceous and active searchers. Larvae generally do not feed.
Euseius tularensis development time from egg to adult is 6 to 10 days at 78° to 80°F. Females live about 30 days and lay about 17 to 27 eggs, varying by the type of diet. There are 8 to 12 generations per year in California.
Habitat
Euseius species are generalist feeders. The diet of E. tularensis in citrus is mainly citrus red mites, citrus thrips, leaf sap, and pollen. It is an important biological control of spider mites, but only assists with control of citrus thrips and does not always reduce thrips populations below an economic threshold. Densities of one-half to one Euseius tularensis per leaf generally will control citrus red mites and aid in the control of citrus thrips in the San Joaquin Valley.
Euseius tularensis on citrus is most abundant from late winter through spring and in the fall. It overwinters on succulent shoots inside the tree canopy. Its abundance increases when new leaf flush develops in spring and fall.
In citrus Euseius occur primarily along the midvein on the underside of shaded leaves infested with spider mites and under the calyx of the developing fruit where pest thrips feed. During the heat of the day, they tend to move to shaded leaves.
Euseius hibisci can build to high densities in the absence of mite prey and can successfully survive and reproduce on a diet of insect honeydew, leaf exudates, pollen, and scale crawlers. In the presence of pollen, E. hibisci consumption of spider mites is reduced, but this is offset by the pollen-feeding benefit of increased longevity and more egg laying in comparison with feeding on mites alone.
Euseius are also good indicator species of the abundance of other natural enemies. When Euseius are common the orchard will also have more of the other natural enemies. To increase the abundance of these predatory mites, avoid or reduce the application of broad-spectrum and persistent insecticides and miticides, control dust, and prune citrus trees in fall to stimulate good flush in spring. Note that pruning avocado and citrus extensively in the fall can increase foliage susceptibility to frost damage.
Species
Over 100 species of predatory mites in the Phytoseiidae family occur in California, including at least 6 Euseius species. About 230 Euseius species are known worldwide.
More Information
- Biological Control of Citrus Thrips, Scirtothrips citri, by Predaceous Phytoseiid Mites, U.S. Forest Service
- The Biology and Management of the Persea Mite, Oligonychus persea, UC Riverside
- Euseius tularensis (Acarina: Phytoseiidae), Cornell University
- Integrated Pest Management for Citrus, Third Edition, UC Integrated Pest Management Program
- Natural Enemies Handbook, UC Integrated Pest Management Program
- Phytoseiidae Database: A Website for Taxonomic and Distributional Information on Phytoseiid Mites (Acari) (PDF), Fundaçao de Amparo a Pesquisa do Estado de Sao Paulo
- Protecting Natural Enemies and Pollinators, UC Integrated Pest Management Program
Scientific classification:
- Phylum: Arthropoda
- Class: Arachnida
- Order: Acari
- Family: Phytoseiidae
