High Elevation Gardening Web Log "Blog"

Adelgids, similar to aphids, can produce comparable harm to hemlocks, spruce, and other evergreens, causing them to form galls and drip sticky goo onto sidewalks, cars, and decks, ruining the car's finish. Aphids use sucking mouthparts or stylets to dine on the sap of leaves, roots, and tree limbs. They also carry viruses from one plant to another, often more destructive than the aphids themselves. They're related to leafhoppers, spittlebugs, and cicadas. Like other members of the insect family, aphids are found in fossils, longtime visitors at the garden parties.

The aphid lifecycle reveals the key to success for this diminutive yet formidable foe. The website www.backyardnature.net, says that aphid eggs hatch in the spring, producing wingless females which parthenogenetically, that is, asexually, bear up to 80 newborn replicas after only a week. A week later, each offspring delivers up to 80 more. Generations of these wingless females survive until hot weather comes or their host plant dies. Some females grow wings to fly to another host, a plant of another species, and continue reproducing tiny duplicates. Late in the summer, some develop into winged males, fly back to their original host, a plant of the original species, and mate with female aphids. Their eggs overwinter in garden soil in temperate climates. The following spring, with no male aphids in sight, the cycle starts anew.

Given the aphids' explosive birth rate and their gluttonous taste for many plants, it's tempting to use drastic measures to annihilate them. The University of California's Pest Notes 7404, recommends four steps for aphid pest management. First, inspect garden vegetation twice weekly to catch infestations early. In Northern Arizona, two wildflowers indicate aphid activity, the giant dandelion-like goatsbeard or salsify in the late spring, and the milkweed in the summer. Also, any sign of ants may indicate the presence of aphids, because ants savor the honeydew produced by the aphids. What's worse is that ants often protect aphids from predators by carrying them to safety at night and transporting them to juicier plants to keep the honeydew flowing.

Second, savvy gardeners should encourage natural predators like ladybugs, green lacewings, parasitic wasps, hover flies, and birds because they can be as effective as chemical controls, though not as quick or as satisfying. Third, tidy up the garden by removing aphid favorites like salsify and mustards. Examine all plants bought at nurseries, plant sales, ordered through the Internet or mail for these tiny hitchhikers since they may survive temperature extremes in transit. Prune and dispose of infested foliage. Use row covers to prevent winged aphids from targeting young plants. For colonies on trees and shrubs, knock them off with water from a garden hose.

Fourth, carefully use chemicals like insecticidal soap or neem oil. Aphid predators and parasites become abundant only after their prey do, so using insecticides that lose their effectiveness over time may provide more long-term control at the risk of killing a few. Check labels for use above 90 degrees F, and around children and pets. The Nursery Manual by L.H. Bailey, originally published in 1891, recommends the use of tobacco extract to dip or spray on infested branches in the fall to kill aphid eggs. Experimenting with diluted hot sauce, chili powder, or lemon juice may produce the same result.

Seeing aphids encrusting our apple blossoms or insolently doing the wave on our irises can be distressing. Keeping a watchful eye, pruning or removing infested plants, encouraging natural predators, and using environmentally friendly insecticides will keep these prolific creatures at bay, allowing us to grudgingly admire these miniscule residents of our gardens.

Freddi Steele is a Master Gardener volunteer and a former naturalist with the National Park Service. Dana Prom Smith is a Master Gardener volunteer and the coordinating editor for the Master Gardener Column. He can be contacted at stpauls@npgcable.com. For more information about the Master Gardener Program, call Hattie Braun at 774-1868 ext.17 or visit our Web Site: highelevationgardening.arizona.edu.