Aphid activity in the landscape is on the increase at this time. The following is more information.
Aphids are abundant on many plants (from climbing roses to copper beeches). However, our earlier rain and cool temperatures have also produced many beneficial insects (i.e. lady beetles) so scout for beneficials before you spray.
Woolly apple aphids on apples, pear, hawthorn, mountain ash and elm has also been found. These aphids produce a waxy substance and are often found clustered in pruning scars and wounds of branches. As populations increase, woolly apple aphids will move down the tree and feed on the roots. Root feeding by these aphids can cause significant damage on young trees.
Monitoring: Look for honeydew and sooty mold on foliage from aphids and the wax of woolly aphids.
Control: If present in the landscape, syrphid fly larvae, lady bird beetles and lacewing larvae are good predators of aphids. A parasitic wasp, Aphelinus mali, is a common predator of the woolly apple aphid. Insecticidal oil and horticultural soap can be used and have minimal impact on beneficial insects.
Photo of aphids on hellebore by Bill Miller in the current Maryland TPM/IPM report.
Information from the University of Delaware Ornamentals Hotline and the University of Maryland TPM/IPM Report.