Spider Mite Management Isabelle Esber-tolentino & Hannah StEagall

Spider Mite Identification
  • Adult females are 1/20 in.
  • They live in colonies on the undersides of leaves
  • They are often spinning webs
  • feed with piercing and sucking, piercing leaf tissue and sucking up the plant fluids
  • Feeding marks show up as light dots on the leaves
  • As feeding continues, the leaves turn yellow and may dry up and drop off
Spider Mite Life Cycle and Biology
  • They spend overwinter as eggs on the bark and leaves of host plants
  • In some parts of California, spider mites may feed and reproduce all year on plants that retain their green leaves throughout the winter.
  • They become more active again as the weather warms and become more of a nuisance when the weather is hot and dusty
Biological Control
  • Spider mites have many natural enemies that limit the number of spider mites
  • Predatory mites are the most common type of spider mites predator
  • Galendromus Occidentalis, and the Phytoseiulus species are common spider mite predators
  • Predatory mites could have established habitats in crops, or they can be bought and placed in large plantings or orchards
Cultural Control
  • When conditions are dusty: apply water to pathways and other dusty areas at regular intervals. Water-stressed trees and plants are less tolerant of spider mite damage. Be sure to provide adequate irrigation. Mid­season washing of trees and vines with water to remove dust may help prevent serious late-season mite infestations.
  • In gardens and on small fruit trees, regular, forceful spraying of plants with water often will reduce spider mite numbers adequately. Good coverage on underside of ring. If more control is required, use an insecticidal soap or oil in your spray, but test the product on one or two plants to be sure it isn’t damaging to them
Chemical Control
  • use selective materials, preferably insecticidal soap or insecticidal oil. Both petroleum-based horticultural oils and plant-based oils such as neem, canola, or cottonseed oils are acceptable
  • also a number of plant extracts formulated as acaricides that exert an effect on spider mites
  • includes: garlic extract, clove oil, mint oils, rosemary oil, cinnamon oil and others. Don’t use soaps or oils on water-stressed plants or when temperatures exceed 90°F.
Chemical Control Warning
  • Spider mites frequently become a problem after applying insecticides. Such outbreaks are commonly a result of the insecticide killing off the mites’ natural enemies but also occur when certain insecticides stimulate mite reproduction
  • For example, spider mites exposed to carbaryl (Sevin) in the laboratory have been shown to reproduce faster than untreated populations. Carbaryl, some organophosphates, and some pyrethroids apparently also favor spider mites by increasing the level of nitrogen in leaves. Insecticides applied during hot weather usually appear to have the greatest effect, causing dramatic spider mite outbreaks within a few days.

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