How to Control Aphids

Every new season brings a parade of irate customers into the garden centre clutching little baggies, jars and plastic containers full of infested and diseased plant bits.  By far the most common insect we see is aphids.  Green aphids, black aphids, red, bronze and purple aphids – they come in many colours!  I thought I’d share my favourite method to control aphids with you now, before these common insects (sometimes called plant lice) really get going in your garden.

Aphids - photo courtesy photobucket

Aphids

When temperatures are warm enough, the first generation of aphids hatch out – all female and ready to reproduce at a truly terrifying rate.  The result of this fecundity is a population explosion that puts bunnies to shame…

Most years this occurs during June around here, but a mild spring will invoke earlier invasions, and of course the aphids have been in your trees, feeding and reproducing for a few weeks before the damage is evident.

Eventually you notice that the tips of the branches look odd, the leaves all curled up and distorted, and when you unfurl one of these leaves there are about a million little critters on the underside – disgusting!  You may find a sticky substance coating the leaves (and your car, if you park underneath an infested tree) and a parade of ants marching up and down the limbs of your tree.

The sticky stuff is called honeydew, it’s actually excretions from the aphids and it’s sweet and delicious if you’re an ant – so that’s what they’re doing.  Sometimes ants will “farm” aphids, carrying them up into a plant to provide a source of honeydew, clever little buggers they are!

Ants 'farming' aphids - photo courtesy photobucket

Ants 'farming' aphids

Aphids are very soft-bodied, and if you’re not squeamish you can control the ones within reach by squashing them between your fingers (gloves makes this practice slightly less revolting).

If you have an aphid infestation on a plant that’s too large for this method you can spray the tree with any number of insecticides – aphids are relatively easy to kill, but I don’t like to use any pesticides if I can possibly avoid them, and I’ve discovered a method that works well for me.

I drag my hose out to the infested tree or shrub, with my old brass nozzle attached, crank up the pressure and slay the dastardly aphids with plain water!  Some are crushed, some simply blown off the plant, and I like to think that a few are drowned!  I have ample water pressure to reach even the topmost branches of my trees (of course in my new garden none are too tall yet).  Three or four days later I repeat the process, and I keep on doing this until I no longer need to.

Aphid control tool

My trusty aphid control tool

How do I know when I can stop?  Well, that’s the best part of spraying with water!  When you use a pesticide, even an organic pesticide, you leave a residue on your plant.  That residue deters insects, even the good ones, so any remaining aphids (the extra-tough ones that survive your pesticide or the ones that hatch out after you spray) will flourish unimpeded and produce a second wave of infestation unless you spray more pesticides.  This is why most pesticides recommend that you re-apply every ten days or so.

I am NOT doing that all summer!  It’s way too much work, not to mention costly, and you might eventually damage the plant you’re trying to protect, depending on which pesticide you’re using.

Ladybugs and aphids - photo courtesy photobucket

Ladybugs are voracious predators of aphids

Spraying with plain old water, on the other hand, doesn’t leave any smelly residue, so beneficial insects (aphid eaters) will eventually discover the little colony on your tree, a buffet for them!  Usually after I spray three or four times I notice that while I’m spraying the aphids off I can see a lot of other insect action.  The aphid eaters don’t much like the high pressure water either so they play dodgeball with my watery cannon, and I can clearly see them!  Ladybugs, lacewings, wasps and various other insects are feasting on my plant pests.

Ladybug larva - photo courtesy photobucket

Ladybug larva devour aphids as well, so if you see these guys don't panic! They're on your side...

When I see lots of these good bugs I know that I can stop spraying.  Please note that this post is named How to Control Aphids, not How to Eradicate Aphids!  I certainly won’t get rid of all the aphids, but a balance is reached where the plant can cope without showing noticeable signs of damage, and that’s all good.  Hmmm, I should probably write another insect-related post; It’s Impossible (and counterproductive) to Rid your Garden of Insects so STOP TRYING!

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About hortophile

I am a very opinionated, slightly obsessed gardener with decades of experience in the retail nursery industry. A lucky resident of the "Wet Coast" of British Columbia I tread a muddy path between practicality and beauty, with my veggie patch, herb garden and fruits vying for position with the beautiful trees, shrubs and flowers that I can't resist. DON'T ask me to choose between them! I believe in environmental responsibility and common sense.
This entry was posted in Garden Advice, Pest Control and tagged , , , , . Bookmark the permalink.

16 Responses to How to Control Aphids

  1. Interesting method to disuade aphids. We’ve had an unusually warm winter this year andthe bugs are arriving in my garden to party – it’s incredible! I’ve even devoted a poem to them :) I could use the water cannon method on trees not in bud, but was considering using some soapy water on my lemon and lime tree. Now I’m wondering what to do.
    I can’t remember seeing any ladybirds in my garden. Our biggest problem is mealy bug.

    • hortophile says:

      You could try the soapy water method on a small part of your citrus tree at first to see how it goes – damage will likely show within a few days. Use a well diluted pure soap product (not full of perfumes and dyes) and don’t spray when the sun is out. Good luck!

  2. barb19 says:

    Very interesting information, thank you. Will try my hose on the little buggers next time!

  3. This is very good information, I hope you don’t mind me reblogging to spread the word. (Full credit to you of course!)

  4. Reblogged this on Three Pea Homestead and commented:
    Valuable information from Hortophile. I’ve already been battling the aphids here, so you may want to go out and check your plants before they become a plague.

  5. PJ Girl says:

    Thanks for showing a picture of the Ladybug lava as I probably would have squashed him too! Phew! You saved me from killing a good guy :-)

  6. door251 says:

    Hey,

    Love the blog, you def have a new follower.

    I was wondering if you knew what kind of plants are good for heavily shaded gardens? we have a tiny tiny city garden, but it is surrounded by big oak trees which i suspect are sucking the life out of everything, couple that with it not getting an ounce of sun and me being a complete novice, i’ve no idea what to plant in there, everything from last year died.

    thanks for your help!!

    door251.com

    • hortophile says:

      Argh, dry shade under big trees, one of the most difficult areas to plant! If it’s tiny I would consider container gardening – that will bypass the root competition issues and then all you need are shade plants appropriate for your climate, and an unobtrusive micro-irrigation kit will help with the watering! Maybe I should do a post about gardening in dry shade – but I can’t illustrate any of that in my own yard – my shade is decidedly damp, verging on sloppy!

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  8. Bill says:

    How do I rid my weeping cherry of Aphids? They’ve attacked and eaten most of the leaves. It’s July in NE Ohio. Can I be sucessful in the heat of summer and while the tree is not dormant?

    • hortophile says:

      Hi Bill,

      If your cherry tree leaves have been eaten, then you have some other pest – aphids are a sucking insect and don’t chew up and eat the leaves. If you do have aphids, the advice I give in the post for aphids is applicable whenever you find them on your plants. Just be careful about spraying any liquid on a plant when the sun is shining on it as the magnifying effect of sunlight can cause the leaves to burn. You might have to get up really early and spray before the sun is up and shining strongly or on a cloudy day. If your leaves are chewed you will need to find and identify the pest to determine the best way to deal with it. Local nurseries are likely to be your best resource for advice. Take a sample of the leaf and an insect if you can find one, in a jar or ziplock baggie to your local independent nursery or garden centre and ask for help.

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    • hortophile says:

      Well of course… you are sorely mistaken if you think you can eradicate aphids. And from another angle, they are a valuable food source for lacewings, ladybeetles, wasps and others.

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