Pests and Diseases: Aphids

 

Happy Tuesday to everyone! I received a note from a reader that is just beginning her gardening journey and she wanted to know more about aphids. She was wondering if I could go over what exactly they were and why she needs to be concerned about them. That made me realize that sometimes I talk about things that beginning gardeners may not be familiar with. I need your help with recognizing when that happens! Send me an e-mail or comment below if you’re unsure about something I’ve mentioned. I’d be happy to re-visit the items that I may have unknowingly just skimmed over. With all of that out of the way, here we go!

AphidsAphids are insects which means they have six legs. That may seem elementary but lots of people think spider mites are insects too…they aren’t and that totally changes the way you control them chemically. Anyway, aphids are ravenous little suckers, literally. They suck the plant’s juices, primarily the phloem, and weaken the plant. The phloem is responsible for transporting the food that is made through photosynthesis by the leaves down to the rest of the plant. (As a side note, if you have trouble remembering which is which, remember that the xylem transports up [x and u are close together in the alphabet] and phloem transports down). OK, back on topic. So the aphids remove valuable resources from the plants by sucking on plant juices and thereby weakening the plant. It’s as if someone allowed you all the water you wanted (provided by the xylem) but never let you have any food (provided by the phloem). At some point, you would kick off too.

The main problem with aphids is that they pro-create so darn rapidly. Eggs that survive the winter generally produce females and these females in turn produce more and more offspring. Even though a typical adult will only live for around 30 days, she can pump out lots o’ live babies which in turn produce more live babies and so on. I’m sure you’ve seen the cat statistics in the vet’s office about how many cats can be produced by a pair of unspayed and un-neutered cats…it’s kind of like that but multiplied by a higher number as the mama aphid can produce hundreds of live babies at a time.

Aphids come in all kinds of colors, ranging from green to black to white to peach. There are over Aphid4000 species of aphids so you can imagine that they have adapted to fit in with their local surroundings. Once you learn what an aphid looks like, you’re unlikely to ever forget. One very distinguishing characteristic of aphids are the cornicles…these are two little projections that protrude from their lower back. If you see these, rest assured that you have aphids.

SO WHAT DO YOU DO IF YOU HAVE APHIDS?

It really depends on how bad the infestation is. If you only have a few here and there, just squish them between your fingers…they are only 1/10 of an inch long. More than likely, by the time you see them though, you’ll have quite the infestation on your hands. Here are some ways to control them:

  1. Give them a harsh spray with your garden hose. Sure you won’t kill them all but if you can knock out some of the females, you’ll be cutting your future population down.
  2. Avoid spraying pesticides. I know that sounds counterintuitive but nature has a predator
    Aphid controller - ladybug larvae

    Ladybug larvae - aren't they beautiful?

    for every pest and there are many that enjoy aphids. Lady bugs, lacewings and parasitic wasps will all work diligently to curb the population. Of course they can’t kill all the aphids because then they wouldn’t have anything to eat. Keep that in mind when you feel like the predators aren’t doing their jobs swiftly enough. To the right is a picture of an immature ladybug…I’m surprised by how many people don’t know what they look like. If you see these little guys crawling around, leave them be so that they can grow up and do your work for you.

  3. Cut back on your fertilizer. Aphids love, love, love fresh new succulent plant growth and will flock to your overfertilized plants like moths to a flame. Again, nature knows how fast a plant is supposed to grow and when we go and pour on the nitrogen to get them to grow at a quicker pace, we have upset a natural balance.
  4. If you have tried all of the above methods, you can spray a tomato leaf spray. That may sound peculiar but it has worked for many generations of folks and it doesn’t kill the predators. You can find the recipe here.

 

I hope that I’ve been able to shed some light on aphids and the problems they pose for plants and gardeners alike. I know that I rambled a bit today and I apologize for that even though it is my nature. Many of you have commented that you don’t mind my rambles so I won’t refrain from them quite yet. If you have any experience with controlling aphids in your garden, please leave a comment below or e-mail me at stacey@midatlanticgardening.com. Happy gardening!

January 17, 2012Permalink 3 Comments