In the Garden with Pat Rubin

Bee garden writer Pat Rubin writes about everything that grows, from flowers and trees to vegetables and lawns. Pat volunteered for several years as a Placer County Master Gardener and has written about gardening for many national and regional publications. In addition to gardening, she spends time raising and showing miniature horses and miniature donkeys.

In the Garden will include news, events, advice and other gardening tidbits. Pat will also answer reader questions.

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May 15, 2007

Aphids and ants

There’s a sticky residue on some of the cherry leaves. Others are all curled up. The tender new stems of my Artemesia Powis Castle look black, and if I rub my hands cross some of the rose buds, they feel wet and sticky.

Yikes! I have aphids.

A strong shot of water from the hose will wash away the pesky little creatures. There are also insecticidal soaps that are safe to use that kill the aphids by smothering them. The trick with the soaps is to actually spray the aphids; you can’t spray the leaves to prevent aphids. Some gardeners use aluminum foil mulches around plants. The idea behind that is the sun’s reflection on the aluminum foil will confuse the aphids and they will fly away from the plants.

Tiny though they may be, aphids can cause more trouble than you think. If aphid populations are high, they can weaken a plant. They can spread viruses from plant to plant, especially on squashes, cucumbers, melons, chard, beans, beets, potatoes and lettuces. And if there’s one aphid, there are probably 100. Aphids can reproduce asexually most of the year. According to a UC Cooperative Extension handout on aphids, adult females give birth to as many as 12 offspring per day without mating. When the weather is warm, it says, “many species of aphids can develop from newborn nymph to reproducing adult in 7 to 8 days. Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.”

Often, ants are often the real culprits because some species of ants tend aphids the way farmers do cows. The aphids suck plant juices out of stems and leaves, and produce a sticky substance called honeydew. The ants eat the honeydew. I’ve read that the ants will protect the aphids from other ants or insects by stinging or biting them. And when the aphids have sucked the plant juices dry, the ants will move the aphids to another location.

I’ve found washing away and spraying the aphids with insecticidal soap not only kills the aphids, but also discourages the ants enough that the problem goes away.

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