Plant and Insect Diagnostic Clinic Update - August 13, 2008

The following are a few of the problems among the dozens of samples received the past two weeks.

Diseases and Disorders

  • Summer patch fungus disease of turfgrass is often related to stressful growing conditions. See HHPN June 30, 2005.
  • Rose rosette disease reported earlier is still being seen around the state.
  • Apple scab is a spring-time, fungal infection of apple and crabapple tree foliage, but now is the time the symptoms are most obvious as discolored leaves fall from susceptible trees. See HHPN June 4, 2008.


  • Bagworm and Japanese beetle calls continue to roll in. It is too late, or very close to too late, for effective control. Check trees carefully for actively feeding insects before deciding to treat. Spraying after bagworm cases are closed and tied to the twigs is a waste of time.
  • Aphids in the landscape. Aphids are doing very well this summer as evidenced by soybean aphid controls being applied around the state. Aphids in the landscape are also abundant now. Here are a few examples. Greenbug aphid on turfgrass causes tannish-orange discoloration under trees. Maple aphids cause slow and gradual discoloration of the foliage followed by premature leaf drop. Woolly aphids that line the underside of hawthorn stems may be one of the most interesting to look at but they too stress infested trees and cause leaf discoloration. Most aphid populations are kept in check by natural controls including natural enemies such as lady beetles and lacewings. Treat aphids only when there is a clear indication that treatment is justified; e.g., when aphid populations are high, when significant damage is likely to occur, and when the timing is appropriate for the pest. Otherwise, avoid use of insecticides in order to preserve predators and other natural enemies.

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