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Two-Spotted Spider Mite

 
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Two-Spotted Spider Mites

Pest ID of Two-Spotted Spider Mites

  • Nymphs resemble full-size adults, but may have 6 or 8 legs, depending on stage, but do not have the ability to reproduce.
  • Adults are very small at only 1/60 (female) to 1/80 (male) inch in size - approximately the size of salt grains - when fully developed. Adults are greenish yellow to orange to brown with 2 darker spots - similar to saddle bags - on their body.

Symptoms

Two-spotted spider mite damage on leaf
Leaf shows spider mite stippling.
  • Two-spotted spider mites damage crops by piercing leaves and feeding on the plant juices. Mites suck on the bottom sides of soybean leaves, removing plant moisture and nutrients, resulting in a yellow or whitish spotting on the top side of the leaf surface. In heavy infestations, it's common to see leaf burning and stippling.
  • Hot spots will typically be noticed first on field margins, as infested plants take on a wilted appearance. Drought-prone fields or field areas that contain lighter soils or sands are often affected first by spider mites. As populations increase, two-spotted spider mites will move across the entire field if left unchecked.
Spider mite feeding in a soybean field.
Spider mite feeding in a soybean field.

 

Life Cycle

  • Two-spotted spider mites have 4 stages of development: egg, larva, nymph and adult.
  • This pest overwinters as adults in field edges and roadsides bordering fields, feeding on weeds until spring.
  • After early spring mating, female spider mites lay eggs on weeds that usually hatch in 3 to 5 days.
  • Two-spotted spider mites do little feeding during the first larval stage of development.
  • Females live 20 to 30 days and typically produce 50 to 100 eggs during their lifetime.
  • The entire life cycle of this pest can be completed in 5 to 14 days. This pest has the potential for up to 10 generations per year during the growing season.
  • Populations of spider mites increase significantly during extended hot, dry conditions.

Management of Spider Mites

Paper test for Two-spotted spider mites
  • Two-spotted spider mites are difficult to see with the naked eye so conduct a simple "paper test" by shaking the plant over a white paper plate. This will allow a grower to see the tiny orange- to yellow-colored mites slowly moving on the paper.
  • Some universities suggest treating for this pest if 20-50% of the leaves are discolored before pod set. After pod set has begun, the suggested treatment threshold is 10-15% of the leaves discolored.
  • Natural predators, including fungi and thrips, can help keep populations in check.
  • If a spray treatment is made, the most consistent performance has been with a full rate of an organophosphate.
  • Natural predator populations can be affected by spray applications of synthetic pyrethroids.
  • Residual control of most treatments is short-lived and applications only control adults and nymphs. Scout fields 5 to10 days after spray applications to check for re-infestation.
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