Aphids come in many sizes and colors, with some variation in shape, and many target a particular species or family of plants. Aphids have soft bodies and long slender mouthparts that they use to pierce plants and suck out the fluids. A female can produce 12 live offspring each day and up to 80 offspring a week. Newly born females can start reproducing in as short a time as a week, which can result in aphid populations growing quite quickly.
The person who brought in the aphid had concerns as to whether these insects could damage her tree. While this person didn’t want to resort to a harsh control method to eliminate the aphids, the sad fact is that the first response many people have to a pest is to get out the strongest control they can find regardless of whether the insect is causing any real damage.
As an Extension agent I know there are times when there truly is a need to resort to a strong pest control, but it’s less often than people think. Of course, on the other side of this control issue are those people who feel doing nothing about any pest is the answer – and it’s quite often a poor decision also. Generally, the thought is that if the pest is harmful to people or could damage a plant to the point where it might not recover then yes, control should be undertaken, taking into account environmental concerns, of course. Even when control is warranted, start with a really basic control rather than a harsh control and see if it does the job.
A cottonwood isn’t likely to be negatively affected enough to need control, and even with plants aphids attack fairly often such as fruit trees, the damage is most often cosmetic, such as curling, yellowing or distortion of foliage, although high numbers of the pests could cause some damage to the fruit. However, aphids that are infected with viruses, should they attack vegetables, could transmit those viruses, resulting in mottling, yellowing, curling and stunting of foliage and growth. That can leave you with poor fruit or vegetable production.
Since aphid populations can grow quite fast it’s best to start early and take a proactive role to actively search them out. Luckily, if caught early, aphids are easy to control. When aphid numbers are low a strong stream of water sprayed on the top and bottom of leaves, such as with fruit trees, or basically all over the plant on a daily basis for a few days to a week can be enough to disrupt the cycle. Other easy control methods for most plants would include soaps, such as Safer soap. For fruit trees or other hardier plants a summer horticultural oil also works well. On a vegetable plant with high numbers of aphids the control measure could involve pulling up and disposing of the plant before the aphids can spread to other plants in the garden. Aphids also have many natural enemies and with plants that don’t generally need our control efforts, such as cottonwoods, just wait and let nature take its course.
Thought for the day: “If you think you are too small to be effective, you have never been in bed with a mosquito.” —Betty Reese
For more information about these topics call the Utah State University Extension Grand County office at 435-259-7558 or email Mike Johnson at firstname.lastname@example.org.