Insect Highlights

Insect Highlights for the Week of July 8, 2005

Spider mite feeding
Spider mite feeding

Spider mite on rasberry
Spider mite on rasberry

Spider mite webbing
Spider mite webbing

Dry Weather Problems

We are starting to see spider mite problems on ornamental plants because of the lack of rain. Spider mites can attack almost any plant and often the damage is not noticed until the plants change color or start to dry up. A close up shows small yellowish spots called “stippling” – but in effect the damage is much like a sandblasting of the surface. Watering the whole plant will help and insecticidal soap sprays are as effective as any treatment. Most insecticides are not very effective and in some cases repeated insecticide use can make spider mite problems worse.

Spider mite on oak
Spider mite on oak

Root weevil
Root weevil

Weevils in the Home

There are a number of weevil species that migrate indoors during mid summer. They are harmless inside and most are associated with various trees and shrubs outdoors. The grubs are root feeders and cause little damage. Indoors, the slow-moving beetles seem to just get in the way. A vacuum may be the best indoor treatment and caulking and insecticides can be used along the outside foundation. See http://www.uwex.edu/ces/wihort/pests/ControlWeevils.htm for more information.

Strawberry root weevil

Strawberry root weevil

Giant grub
Giant grub

Giant Grubs

The large scarab grubs found in stumps and rotten wood will grow up to be either a stag beetle (see http://www.entomology.wisc.edu/diaglab/02hilite/7_8.html) or an Osmoderma leather beetle (see http://www.entomology.wisc.edu/diaglab/hilites/hilt717.html). The beetles do not cause the damage but live and feed on the soft rooting wood.

Giant grub
Giant grub

Magnolia scale
Magnolia scale

Scale
Scale

Magnolia Scale

The white growths and sticky leaves are caused by the magnolia scale. I have seen quite a bit of activity in the last two years. Best treatment time in late August or early September with a foliar spray. Trees can be treated with a systemic like imidacloprid now (Bayer’s tree and shrub insecticide or Merit), but a late summer application should still be used for best control. For background see http://ohioline.osu.edu/hyg-fact/2000/2003.html.

Symptoms of scale
Symptoms of scale

dragonfly iconReturn to Entomology Home Page.
URL is http://www.entomologyl.wisc.edu/diaglab/05hilite/07_08.html. Updated 07/08/05.

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1630 Linden Drive
Madison, WI 53706
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For more information contact: 
Phil Pellitteri, 608/262-6510
or e-mail Phil Pellitteri.