Editors note: Get Growing, written by the La Plata County Extension Offices Master Gardener Program, appears every other week during the growing season. It features timely tips and suggestions for your garden and landscape.
By Carolyn Brown
A walk through my garden quickly reveals that all is not well with my young cherry trees.
Leaves are curled and dying, shiny sap oozes over everything below, and a parade of ants travels up and down the trunks. On closer inspection, I find that many of the leaves have armies of black cherry aphids attached to them, draining their lifeblood.
Aphids dont usually kill the trees, but they can create stress and drain the plants of their food supply; they can also produce a winged form that will seek new food supplies if the current host becomes disabled.
Researching my gardening books and the Internet and visiting with the Extension office and nurseries, I have learned that there is a heavy infestation of fat, little, round, shiny, black aphids on cherries this year and that the battle against them has to be waged daily. The first line of defense is spraying the leaves with a powerful stream of water, dislodging the little critters. That approach, recommended by all resources, should be repeated daily. After a few days, gradual improvement will be seen.
Insecticide soaps are helpful but have to come in contact with aphids, which are usually firmly attached to the underside of leaves. Contact with insecticide soaps can also kill natures intended controls: ladybugs, lacewings and parasitic wasps. Poisons used to kill aphids also kill beneficial insects and in almost all cases are not recommended.
Because I am spraying aphids often with water, using insecticide soap occasionally and trying to stop ants from farming the aphids, I am seeing less damage. Because I have no cherries on my trees (spring frost), I am arming for next years onslaught. I intend to keep the plants stress-free this year and then spray with a dormant oil during the late winter. The aphid battle will begin at the first signs.
Carolyn Brown has been a Colorado Master Gardener since 2009.