"Greasy" spots on leaves #412281 - Ask Extension

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"Greasy" spots on leaves #412281

Asked July 06, 2017, 6:17 PM EDT

Hello. In the last week shiny, sticky spots have appeared on the leaves of all the plants in one section of my yard. The plants include Linden trees, hostas, currants, Virginia creeper, maple, and various weeds. It looks like the leaves were sprayed with a squirt bottle full of grease. What could be causing it? Are the spots dangerous for the plants and us there anything I should do about it? Thank you in advance. Ani

Hennepin County Minnesota

Expert Response

My guess would be this is honeydew, the secretion from an insect (aphids, scale), possibly in a tree above or possibly on the plants themselves. The honeydew is harmless, although messy, but the cause of the honeydew (aphids or scale) might be a problem. Read here:
http://extension.missouri.edu/p/g7274 
https://www.extension.umn.edu/garden/insects/find/aphids-on-deciduous-trees-and-shrubs/
Dennis White Replied July 07, 2017, 2:32 PM EDT

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