Combating aphids requires attentiveness
Last year, I didn’t notice that the aphids had invaded until it was too late for me to win the war. Our poor cherry tree ended up with these unsightly balls of crumpled leaves hanging from the canopy, oozing syrupy aphid honeydew.
To add insult to injury, black mold took over after the aphids finished their business and the disfigured, sooty leaves hung on the tree like shrunken heads, announcing that the fight was over.
Although they are tiny, aphids can cause major damage in a relatively short period of time. They multiply exponentially. That means if I noticed them three days ago and didn’t take action, there are probably thousands more of them today (maybe millions, depending on how bad an infestation I have).
They can be a variety of colors, ranging from a light green to an almost metallic black (like the black cherry aphid). They’re extremely prevalent and feed on everything from rose bushes to fruit trees.
Aphids are called “piercing-sucking” insects. They literally suck the life out of your plants, damaging young tissue and causing the leaves to curl up around them. They also can serve as vectors for diseases, meaning that they transport disease to plants and trees, so it’s best to discourage them from sticking around.
To combat the aphids, you have to force your way into the curled, disfigured leaves. This makes it difficult to spray effectively.
Last spring around this time, I noticed a large number of ants marching up and down the trunk of the infested cherry tree. After watching the ants and the aphids for a little bit, I realized that the ants were attracted to the aphids. Sure enough, ants like to eat the honeydew excreted by the aphids. In return for the aphid colony’s waste products, the ants protect them (sounds like a science fiction story to me). One Colorado State University Cooperative Extension Service fact sheet even said ants can keep the aphid eggs over the winter and introduce them to host plants. I had tiny devil farmers on my hands.
My fight against aphids began early this spring, with a thorough spraying of dormant oil to suffocate the aphid eggs that overwintered on my cherry trees. Obviously, I must have missed a few spots, or the devil ants outsmarted me by keeping the aphid eggs in their underground lair.
Although I monitored my trees fairly closely, I didn’t notice the aphids until I spotted the severely curled leaves (too late to try knocking them off the leaves with a jet of water). This literally must have happened in a matter of a few days.
Clearly, taking time to peruse your plants and turn over some leaves for inspection every few days is an important step in managing pests.
I needed a plan. Yes, lady beetles, lacewings, and some other natural predators eat aphids, and they were trying to help. But I had a true infestation on my hands, I knew I didn’t want to re-do last year’s debacle, and it was time for action.
I started with insecticidal soap. It worked fairly well in some areas. But the aphids were back within a week.
Then I tried a Neem oil spray, which comes from an Indian evergreen tree. The Neem oil didn’t make a dent in the colony and the population exploded. Finally I gave in and opted for a chemical pesticide, which I don’t like to do, but I have sort of a three-strike rule and it was time for the big guns.
I’ll continue monitoring the tree just in case, but in the meantime those aphid-farming ants are next on the list.
For information on controlling aphids, contact Colorado State University Cooperative Extension at 244-1836, or visit them at http://www.extension.colostate.edu.