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Monday, April 21, 2014

Shiny Leaf Sheen on Roses May Be Aphids Feeding

Q. There's a glossy sheen on my rose leaves that's not suppose to be there. I have the problem every year and I usually just give them a good spray with the hose and that helps but doesn't seem to be the cure. Any suggestions that don't involve chemicals?

A. I think what you are seeing may be some residue from some feeding insects on roses. These insects excrete (release) a sugary substance from their feeding that falls on plant parts like leaves.

Aphids on unopened rose buds/flowers. They feed on plant sap. They use the sugars in plants sap as a food source for energy. The remaining sugars are excreted from the aphids where they cause a shiny sheen on leaves that is sticky. This attracts ants and bees.
If this is what you are seeing it should be slightly sticky and may attract ants and bees that will collect this residue for feeding. These insects pull out plant sap that contains sugars for their own feeding and there is so much of it in the plant sap that their excretion contains a lot of sugars. Insects that release this kind of “honeydew” as it is sometimes called include aphids, scale insects, leafhoppers and whiteflies. Roses aren’t the only plants these insects feed on. We will seed them on most trees, shrubs and even pines.
Aphids on undersides of pepper leaves
Repeat applications of soap and water sprays will usually control them until hot weather comes. High temperatures are not a good thing for insects like aphids and help to keep them under control until the cool fall weather sets in when we may see them again.

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