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Oak Spider Mites

| By | Pests

Oak Spider Mites (Oligonychus bicolor)

GDD Window (base 50): 802-1265 (1st generation)

Overview:​​​

  • Classified as a warm season mite
  • Overwinter as eggs on bark​​
  • Thrives in dry conditions  ​
  • Feeding occurs through the summer months on the upper side of the leaves (unique with this species) ​
  • Infestations are highest on the foliage of lower branches ​
  • Use piercing-sucking mouthparts to feed in leaf plant cells and remove fluids  ​
    • Causes chlorotic stippling that is initially dull and yellow  ​
    • Bronzing appears on upper leaf surfaces as dead tissues dry  ​
  • Eggs are deposited on upper leaf surfaces, along the mid-vein  ​
  • Multiple generations, peak populations in mid to late summer  ​
  • Trees growing along streets or in parking lots can have higher infestations due to higher temperatures in these areas​
  • Bronze discoloration on upper leaf surfaces of red oak group trees​
  • Symptoms often concentrated along major leaf veins ​
  • White eggshells and cast skins can be observed in the vein crevices  ​
  • Eggs laid on upper leaf surfaces become reddish and barrel shaped before hatching  ​
  • Final generation lays eggs on the woody bark to overwinter​
  • Host plants: red oak group, birch, chestnut, beech, elm, hickory​

Management:

Cultural Practices:
  • Natural predators:  lady beetles, minute pirate bugs, big-eyed bugs, predacious thrips, or predatory mites​
  • Syringing for small trees​
    • Mites on upper leaf surfaces​
  • Do not apply excessive levels of nitrogen​
  • Do not spray carbaryl ​
    • (aphrodisiac)​​
Materials:
  • Contact insecticides: ​
    • Pyrethroids [3]                                    ​
  • Systemic / Translaminar insecticides:​
    •  Bifenazate [20D] (reduced risk)​
    • Acequinocyl [20B] (reduced risk)​
    • Abamectin [6]​
    • Acephate [1B] (translaminar)​
  • Considerations:​
    • Will harm non-target species
Biorationals:
  • Horticultural oil / Insecticidal soaps​
    • For overwintering eggs​
    • Target sprays in webbed areas​
  • Mite growth inhibitors: (MGRs)​
    • Hexythiazox [10A] & spiromesifen [23]​
    • (Will not control adults)​
  • Beauvaria bassiana​
  • Note: Miticides are not recommended
    unless stippling damage is evident
    on over 10% of the foliage and
    beating tray counts average more
    than 10 mites with branches
    tapped (double when predators
    are numerous)​

Resources:

Cool Season Mites Fade, As Warm Season Mites Surge – PPA

Summer Pests on Oaks: Oak Sawflies, Oak Spider Mites & Oak Lace Bugs

 

Various signs from oak spider mites are observed on the upper leaf surface of the sawtooth oak leaf. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Turn the sawtooth oak leaf over to view the undersides & it appears clean. No spider mite signs observable. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Feeding symptoms by oak spider mites can be seen on these oak leaves. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Closer view allows the white cast skins & white egg shells to be seen congregating along the crevices of the leaf veins. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
An even closer view shows a greater accumulation of spider mite cast skins & egg shells as the color contrast makes these signs obvious. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Active oak spider mites & eggs can be washed off leaves with a strong jet-spray of water. (Photo Credit: David Shetlar, Ohio State Coop. Ext.)
Disclaimer – Materials do not cover all possible control scenarios and are intended for licensed professionals. Tradenames do not imply endorsement and are used as examples. You must strictly follow the label for each compound prior to use. Rutgers is not responsible form is used materials or damages thereof. The label is the law. Labels will provide detailed information on use and restrictions. Additionally, application intervals, compatibility, surfactant use, PHI, PPE, important and other key information is described in detail. Always discuss treatments with your local agents. Note: Neonicotinoids can only be legally applied in commercial agriculture settings by licensed applicators. Guidelines and recommendations made in this presentation are specific to the state of New Jersey.