Mites as an Ecological Sustainability Indicator in Orchards
We are currently working on an index to determine ecological sustainability based on species diversity of phytophagous and predatory mites. Mites are ideal indicators of the ecological state of an orchard. In fact, acarologists can determine the health and management history of an orchard solely based on the presence or absence of certain species of mites. Mite functional ecology can also be used to assess the sustainability of an orchard ecosystem.
Tree stress in tree fruit orchards is caused by many factors and is expressed in many different ways. Major insect pests of cherry trees cause problems like reduced yield and quality. Although mites are not direct pests, leaf feeding mites can cause tree stress. Damage done by an uncontrolled population of mites can result in leaf bronzing and early defoliation. In severe cases, mite-induced tree stress reduces winter acclimation ultimately leading to tree death during harsh winters. Two-spotted spider mite, European red mite and rust mites are a few of several phytophagous mite species that contribute to tree stress.
Use of organophosphate (OP) and OP alternatives disrupts natural control of pest mites. Pesticides such as OPs, synthetic pyrethroids, neonicotinoids and others can kill predator mites. To exacerbate this, pest mites develop resistance to these pesticides because of their defense mechanisms against naturally occurring compounds in the plant. Both of these phenomena increase pest mite populations and consequently cherry tree stress.
About Mites
Mites are small Arachnids that belong to the class Acari. They are generally under 1 mm in length and are found in many habitats. They are ubiquitous, serving their habitat as phytophages, predators, detritus feeders, parasites, soil decomposers or a combination of several.
All mites are extremely small and have one apparent body segment and eight legs. In the orchard they are found on the trunk, leaves and bark of the tree and in the soil. Some can produce spider like webbing for protection, while others have hard, elytra-like integument as protection.
Mites have five life stages: egg, larvae, protonymph, deutonymph and adult. In general larvae are egg sized and shaped and have six legs. Protonymph and deutonymph stages are progressively bigger than the larvae, have eight legs and resemble the adults as they grow.
REFERENCES
University of California Statewide Integrated Pest Management Program
HortNET
Forestry Images
Mid-Florida Research and Education Center
Mites in Stored Foods By: Jim Kalisch
The Virginia Fruit Web Site: Virginia Apples
Plant Protection-NZ
Natural Resources Conservation Service By: Roy A. Norton
Soil Mites and Other Animals
Project on Sustainable Cotton Production
Biological Control: A Guide to Natural Enemies in North America
Midwest Institue for Biological Control
Department of Entomology, Texas A&M University By: W. Sterling
Dibleys Nurseries
University of Florida: Woodybug
Federal Biological Research Centre for Agriculture and Forestry, Institute of Integrated Plant Protection, and Institute of Technology Assessment in Plant Protection Kleinmachnow
HYPP Zoology
Pacific Agri-Food Research Center
