Insects in the Garden: Aphids

Goldenrod Aphid on Goldenrod.  Photo by Marianne Balkwill

There are many aphid species in North America. These insects suck the sap out of the plant which can distort the leaves, buds and shoots.  They also secret a sugary waste called honeydew, and with enough aphids, the plant will get sticky and some leaves and flowers will drop off.  As of now we haven't had problems with aphids in our vegetable gardens, but we did have some Goldenrod Aphids on our goldenrod "weeds" that grew in our long grass.  At a closer look however, not only did the  goldenrod attract aphids, they also attracted some beneficial insects including the Green Lacewing and Ladybugs.  Though the thought of having this weed in your yard may make you cringe, bear in mind that goldenrod is an important nector source for pollinators such as bees, something else you will benefit from in your yard.  It also attracts other beneficial insects such as Hoverflies and Minute Pirate Bugs (Orius sp.). If you have hay fever, goldenrod actually doesn't contribute to your symptoms because it isn't pollinated via wind such as other true harbingers of hay fever, mainly ragweed.  Of course if you want some goldenrod in your yard you will have to spend some time pulling out goldenrod when it starts to get out of control because IT WILL!

Ladybugs are cute insects that feed on aphids.  It's one of their primary food sources.  We all reconginze the adult ladybug as an orange to red coloured insect with spots (though they do come in other colours), however many people do not reconginze the larva that also feeds on aphids which is similar in colour, though looks nothing like the adult structurally.

Ladybug adults and a larva (at top left) on a goldenrod with Goldenrod Aphids. Photo by Marianne Balkwill

Lacewings adults are beautiful insects.  The adult is about an inch long and has delicate wings.  It almost looks like a miniature dragon up close.  The larva on the other hand looks nothing like the adult and looks somewhat frightening with those pinchers that is uses to grasp its prey.  The lifecycle of the Lacewing reminds me of the story "The Ugly Duckling" as the larva grows up into a beautiful creature.  Lacewing larva not only feed on aphids but other insects as well.

Green Lacewing adult (the swan).  Photo by Marianne Balkwill.

Lacewing larva (the ugly duckling). Photo by Marianne Balkwill

Using only the natural cycle of predator vs. prey would be ideal for managing all pests, but this of course is not always possible. When you have a lot of aphids and hardly any help of their natural predators, due to the lack of plants that attract them, you may have to take other measures . If you don't want to use chemicals, try a soapy water spray (not too soapy it will burn the plants), or a strong stream of water to knock them off (and possibly damage their mouth parts). If you can afford to loose a few plants, remove and bag up the plants that have the heaviest amount of aphids, and treat the other plants that only have a few with water or soapy water.