Aphids 101

Aphids 101

By: Rob Sproule

Aphid Lifecycle
Recognizing Aphids
Aphid Damage
Killing Them

Here in Alberta we’re pretty lucky when it comes to insects.   We don’t have termites that eat houses or army ants that eat everything, but we do have aphids.   Also known as plant lice, the lowly aphid ranks up there with mosquitoes as most loathed local insect.

Aphid Lifecycle:

Before I tell you how to kill them (don’t worry I’ll get to that), I want to tell you about their fascinating life cycle. They are the most remarkably adapted little buggers I’ve ever seen!

Aphids reproduce like crazy, both sexually and asexually. In the spring, overwintered eggs hatch into females that are already pregnant with thousands of young. Until the fall aphids are all female, and a single female can hatch dozens of generations in 1 season. The nymphs mature in a week and start their own “families”. It’s an exponential curve that quickly adds up to millions of critters. Some species even give birth to females who are already pregnant!

In the fall the females start hatching both females and males. Some of them then sprout wings and fly into the familiar black swarms that we all hate in late August and September. They overwinter by attaching their eggs to plants. In late fall spray your plants down with a strong spray of water to knock the eggs off.

Recognizing Aphids:

In most ways, aphids are very easy to spot. They are pear shaped and always appear in clusters, grouping in dense masses on the tips of new plant growth or on the undersides of leaves. They love heavily fertilized plants because there are lots of yummy new leaves.

In other ways, they’re tricksters. Numerous species are native to Alberta and they can be black, green, grey, spotted, and even furry. If you want a reminder of what they look like, check your nearest petunia in September!

Learn more about aphids, with Alberta’s Best Gardening Blog

Aphid Damage:

Aphids are sap suckers and, because they are exceedingly good at it, are very destructive. Depending on the afflicted plant, you may notice yellow discolorations or wilted/ curled leaves.

They secrete a sticky, tell-tale honeydew that often attracts ants which “farm” the aphids by stroking their bodies with their antennae to collect the honeydew. The secretion can make it easier for fungus and mold to set in. Oh and did I mention aphids can pass along disease?

Killing Them:

Luckily, aphids are the twinkies of the insect world. They have almost no physical defences and almost everything likes to eat them. The best way to control them is to encourage predators.

If you start early you shouldn’t need to resort to chemicals. Spraying the undersides of the leaves with a strong jet of water will usually knock the bugs off. Releasing ladybugs is a great way to control the populations. As long as there is a juicy buffet in the garden the lady bugs should hang around. If ladybugs don’t work, try applying some neem oil.

If the numbers are getting of control, start by spraying insecticidal soap. You’ll need to repeat spraying a few times to stop their life cycles. If the problem is getting out of control, you may have to resort to pyrethrum, which is the active ingredient in many pesticides, to control them. Be warned, however, that pyrethrum will wipe out the good guys as well is the bad guys, and the much simpler aphids will bounce back a lot faster. In other words, using harsh chemicals is like resorting to a drug; it only makes the situation worse in the long run.


Read through our Growing Guides for tips to enrich your garden! 

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