Mission Statement of the Nebraska Crop Surveillance Network:
Mitigate the impact of crop diseases and insect pests and safeguard Nebraska's agriculture against threats of bioterrorism.

Insects: Two-Spotted Spider

Taxonomy:

Common Name: Two-Spotted Spider Mite
Scientific Name: Tetranychus urticae

Distribution:

  • Widespread.

Identification:

  • Mature two-spotted spider mites are less than 1/32" long, with two well-defined spots near the front of the body.

  • Adults have 8 legs while nymphs have 6.

  • Eggs look like small clear or pale marbles when viewed through a hand lens.

Two-spotted spider mite

Life Cycle:

  • Over winter primarily in alfalfa and other broadleaf plants bordering the fields.

  • In the spring or summer, mites crawl or are carried by wind to soybean fields.

  • Mites lay small, round, pearly-white eggs on the underside of the leaves.

  • Eggs usually hatch in about three or four days.

  • Young mites resemble the adults.

  • It takes about five to 10 days after hatching (depending on the temperature) before mites are mature and begin to produce eggs.

  • All stages of mites may be present at the same time.

  • There may be seven to 10 generations during the growing season.

  • Early mite reproduction and damage often appears first on the south and west edges of fields due to the prevailing wind direction.

  • Infestations also may arise in "hot" spots scattered throughout the field.

Host Range:

    Feed on many species of grasses, as well as on soybeans, fruit trees and a variety of vegetables and ornamental plants.

Injury & Damage:

  • Feed on undersides of leaves, causing yellow spots visible from the top of leaves.

  • Damage caused by heavy infestation includes leaf drop, accelerated senescence and pod shattering.

  • Left untreated, early and severe mite injury can completely eliminate yields.

  • Injury occurring during the late vegetative and early reproductive growth stages will reduce soybean yields between 40 and 60 percent.

  • Spider mites can cause yield reductions as long as green pods are present.

  • May be present throughout the growing season, particularly in drought-stressed field areas.

  • Most common in July, August, and September (statewide).

Monitoring:

  • The cause of yellow spots should be determined first by turning leaves over and examining the underside.

  • Spider mite feeding can be easily identified by presence of mites, eggs and webbing.

  • A magnifying glass or 10X hand lens is helpful in examining plants for the presence of mites.

  • Mite outbreaks in Nebraska fields are infrequent, but can occur in periods of drought or when weather is particularly hot and dry.

Management:

  • Miticides are available for high and rapidly increasing populations.

Notes: