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Sap dripping from tree branches

Sap dripping from treeHave you found drops of honeydew on your car after you've parked it under a tree?  You're probably dealing with aphids or scales, common insects that occur on many trees and shrubs.

They are most commonly found on rose, ash, oak, elm, maple, willow, and fruit trees. Aphids and scales are small, sap-sucking arthropods. Aphid and scale populations can vary greatly in size through time. A large population one year does not necessarily mean there will be an equally large or larger population the following season. 

While aphids and scales often go unnoticed, their waste, called honeydew, which is not sap, is more conspicuous. Honeydew is often described as a "clear, sticky liquid raining from trees." It coats bark, leaves, and objects beneath the plant.

What you can do:

There are several options for aphid and scale management. The first option is tolerance, since populations are naturally regulated in many ways, including natural enemies and weather, such as heavy rainfalls. Remember that leaving aphids alone generally causes little damage to the unstressed plant, and has the added benefit of giving natural enemies the chance to exert natural control. 

Don't over-fertilize. Too much fertilizer promotes succulent new growth that attracts aphids. Organic fertilizers release nutrients slowly ensuring plants receive appropriate amounts of fertilizer. Adequate water and light will help produce unstressed plants that can fend off aphids and scales.  For trees that are completely infested with scales, dormant oil can be used as a means of control. 

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