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Flowers, Fruits, and Frass

Local and statewide information on a variety of current topics for home gardeners and market growers.
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When Magnolia blooms scout for Spruce Spider Mite, Zimmerman Pine Moth and Eastern Tent Caterpillar

  • Spruce Spider mite

– Problem

  • Feed on needled evergreens and most active during the spring. Damage appears as stippling as mites feed on chlorophyll. Heavily attacked foliage will turn brown.

– Detection

  • Hosts are Juniper, pine, douglas fir, fraiser fir, and larch.
  • Spend the summer as eggs, hatch again in the fall.
  • Vigorously shake the tree to scout on top of white paper. Smash dots. Those making greenish streaks are usually spider mites that are feeding on the foliage; those making yellow-orange streaks are usually predaceous mites that are feeding on the spider mites.

– Control

  • Insecticidal soap, miticides, and spray again in another week.
  • Hard water spray foliage.
  • Look for predators
  • Zimmerman Pine Moth

– Problem

  • Pitch flows from wounds of trees.
  • Kills branches.

– Detection

  • Host all pines but primarily Scots and Austrian pine.
  • Adults active in mid-July to mid-August laying eggs.
  • Eggs hatch in August.
  • Larvae feed on bark and buds.
  • Overwinter in hibernaculum (silken web).
  • Emerge in April and bore into stems.

– Control

  • Prune out damaged branches.
  • Drench bark with permethrin in spring and then again in mid-August for younger larvae.
  • Plant resistant varieties.
  • Eastern Tent Caterpillar

– Problem

  • Heavily infested trees defoliate but soon leaf out again.
  • Stresses tree.

– Detection

  • Larvae hatch at bud break of their hosts.
  • When newly hatched the larvae are black but develop yellowish whitish stripes.
  • Larvae migrate to crotch angle of a tree where they form a communal tent.
  • They leave the tent throughout the day and feed on leaves as they grow bigger so does the tent.
  • When they are fully grown caterpillars they find a protected source and pupate.
  • Adult moths emerge two weeks later brown with white bands.
  • After mating, female moths lay their eggs in reddish brown clusters that wrap around pencil-size-diameter branches. Each egg mass is about 1/2 inch long and contains 100 to 300 eggs. These eggs do not hatch until the following spring when bud break occurs.

– Control

  • Removal tents at night.
  • Spray Bacillus thuringiensis kurstaki, Spinosad, Neem Oil or Permethrin.
  • Apply as young larvae have hatched when saucer magnolia is in pink bud.
  • Resources

– Phil Nixon. University of Illinois Extension Specialist in Entomology.

– Pest Management for the Home Landscape. University of Illinois Extension

– Coincide: The Orton System of Pest Management. Donald A. Orton and Thomas L. Green Ph.D.

– Insects that Feed on Trees and Shrubs. Warren T. Johnson and Howard H. Lyon

– Morton Arboretum Plant Health Care Reports

– Home, Yard and Garden Pest Newsletter. University of Illinois Extension


Photos by Phil Nixon and Rhonda Feree

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