Aphids Problems

by Stephanie Suesan Smith on November 21, 2010

Aphids are the bane of both vegetable and ornamental growers. A few winged aphids show up, drop off the kids (larvae), then move on, leaving your plant to babysit. The larvae and adults feed by sucking plant juices from the leaves. They reproduce until the plant is overcrowded, then a few aphids develop wings and the process is repeated. One plant with aphids can end up infecting an entire house or greenhouse.

In most cases, aphids are just nasty looking and the plant does not thrive. However, aphids secrete what scientists call “honeydew”, which is a sticky substance that ants love. Sometimes ants will “farm” aphids for the stuff. The ants protect the aphids and the aphids feed the ants.

There are two cases where an aphid infestation is more than cosmetic. The honeydew will allow sooty mold to grow on the plant, further stressing it. The other thing is that aphids do not brush their teeth between plants. So, they may carry viruses that infect and kill the plant with one bite.

Control requires vigilance. Check your plants weekly for problems. You need to especially check the underside of the leaves, an aphid’s favorite place to be. If you find aphids on more than 5% of a plant, you need to treat the plant with a contact pesticide. This means the pesticide has to touch the aphid to kill it. As an aside, Sevin® Dust does not kill aphids.  Since pesticide licensing laws vary, you will have to check with your local Extension Agent for exact recommendations on what will kill them.  Lady beetles and lace wings also eat aphids.  Make sure whatever you treat the aphids with doesn’t kill the good bugs.

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{ 3 comments… read them below or add one }

Phil Nauta - Smiling Gardener November 22, 2010 at 12:39 pm

Hi Stephanie,

I have a bit of a different viewpoint on aphids and all “bad” insects. Both from my own experience and doing a lot of research, I believe insects only attack unhealthy plants. In fact, they don’t have the enzymes to digest healthy plants. They need nutritionally imbalanced plants, generally with excess soluble nitrogen and sugars. Spraying pesticides will not make the plant healthy, which is what we really need to do. In fact, insecticides hurt plants. If we instead focus on creating health in the plants, the aphids will leave them alone. At least that’s what I’ve found. Thanks for letting me share. Check it out here: Non-Toxic Pest Control
Phil Nauta – Smiling Gardener recently posted..Drip Water Irrigation – Slowly Killing Gardens Around The WorldMy Profile


Stephanie Suesan Smith November 22, 2010 at 2:45 pm

I agree that insects prefer to feed on unhealthy plants and that the best way to combat problems is keep plants healthy. Once they are infested, however, you can’t get them healthy without getting rid of the insects.


Miriam Matthews November 27, 2010 at 1:12 am

Summary Aphids sometimes called greenfly are small insects that suck plant juices and can severely stunt or even kill their host plants. Early detection and control with insecticidal soap are the keys to managing aphids in house plants gardens and landscapes. Because aphids are somewhat host plant specific these pests rarely spread from one plant to a completely unrelated species.


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