FAIRBANKS — It’s a buggy, buggy summer. Leaves on birch and willow trees have turned brown with leafminers. Lawns are loaded with leafhoppers. But it’s the aphid that gets my vote as the most troublesome garden pest of this season.
That sticky substance that rains down on your car is likely aphid honeydew. Aphids have piercing, sucking mouthparts and feed on phloem sap. They do not chew holes in leaves. The sap goes in one end of the aphid and passes out the other. You might notice this shiny honeydew before even seeing aphids on your plants.
Where aphids have taken up residence, you’ll also see their cast skins. As the insect grows bigger, it sheds its exoskeleton. These little white flecks are often easier to see than the live aphids, especially if they’re green. Aphid species have their own characteristic colors, but even a single species can include multiple colors. A colony of green peach aphids might include green, yellow, and pink and gray individuals.
The aphids you see this summer are all females. They give birth to live young that already have baby aphids developing inside them. No wonder populations quickly grow given a new mom is already a grandmother. When it gets too crowded, wingless aphids can produce young capable of flying away from home when they grow up.
Last fall, I set up an aphid breeding room in my house. I brought my lemon verbena into the laundry room and shut the door. As the aphids got thicker and thicker, winged aphids began appearing. Most headed for the window. I also started seeing the golden, hollow mummies of parasitized aphids, and on the ceiling were hundreds of tiny wasps. You can see parasitized aphids in the garden. If you have good eyes, you’ll notice a circular hole through which the parasitic wasp emerged after killing its host.
A lot of insects — including immature lacewings, ladybugs and syrphid flies — eat aphids. If you see a jelly-like blob nestled among your aphids, it’s a syrphid fly larva having lunch. The adult syrphid fly is a bee mimic that you’ll find hovering over flowers. Ladybug larvae also look nothing like their parents. They are voracious aphid feeders, so learn to identify them. The air has been humming with yellow jackets this summer; if you’re not allergic to their sting, you’ll be happy to know that yellow jackets also eat aphids.
If you have an aphid problem and don’t want to wait for the drama of nature to unfold, there are ways to control them that aren’t too toxic. Because of the way they reproduce and their preference for succulent new growth, aphids can often be found clustered on the tips of stems, where they’re easy to squash if not too numerous. If you’re squeamish about aphid goo, prune off the aphid-harboring part of the shoot. This will bide you some time before populations build up again.
In the greenhouse, tougher control is warranted. Insecticidal soap is one option. Commercial products are available, but you won’t find the word “soap” on the label listed under active ingredients. It will read potassium salts of fatty acids. It’s the soap that acts as the insecticide. In order for the product to work, it must contact the aphid when sprayed. There is no residual effect after it dries.
Products containing neem oil or azadirachtin, one of its derivatives, provide longer-lasting aphid control. Neem oil comes from a tree indigenous to India. Many of the pesticides that include neem as the active ingredient bear a seal of approval from OMRI, the Organic Materials Review Institute.
Even though insecticidal soap and neem products are organic, as with any pesticide you choose to use, the site to which it is applied must be listed on the label. Examples include flowers, vegetables, ornamentals, trees, fruit, greenhouses, indoors, residential areas and landscapes.
Good luck with your aphids. I hope you appreciate how amazing they are now that you’ve learned more about them. There will be aphids in the garden next year, but let’s hope they won’t be so numerous.
Julie Riley is horticulture agent for the Cooperative Extension Service. If you find dandelion aphids massing on the side of your house this fall, please bring live specimens to the Tanana District Office at 1000 University Avenue, UAF University Park.