Sticky drippy time is here. Have you ever parked under a tree and later found your car covered with sap? Or, all your patio furniture so gooey you couldn’t sit on it? Almost every plant has one or more aphid species that can feed on it and then exude a gummy residue called honeydew.
Aphids suck so many juices out of a plant that it overflows out two “pipes” on their abdomen called cornicles. Some plants such as ash trees, flowering plums, dogwoods, lettuce, apples and roses are extremely susceptible to aphids. Low to moderate infestations usually do not damage plants, so insecticides are rarely needed. Usually natural predators and enemies can keep aphid populations in check.
Aphids are common in the garden because they like lush spring growth. To manage aphids, avoid high nitrogen fast-release fertilizers, and use organic or slow-release fertilizers. Also, avoid overwatering. Ants protect aphids from natural enemies, so if you notice ants on plants, hose them off repeatedly. Prune out the areas where the aphids congregate or blast them off with a stream of water from the hose. I squish the aphids on my roses, a little messy on my fingers, but a quick solution. Protect crops such as lettuce with row covers. There are products you can buy or you can use old sheer curtains.
Preserve aphids’ natural enemies, which include birds, lady beetles, both adults and larvae, lacewings, parasitic wasps and others. These predators come into your yard when aphid populations rise. Using chemical insecticides will kill aphid enemies. However, if insecticides seem necessary, use those that are the least damaging to the beneficial insects such as insecticidal soaps or summer horticulture oils. Soaps and oils smother the aphids, so application must be thorough. While they also kill beneficial insects they contact, they will not kill insects that come after you spray. Soaps and oils don’t work on the aphids hidden inside rolled up leaves. Pruning those out works best. New leaves will follow, so the pruning won’t harm the plants. If you are patient, you can often outwait the aphids. Most aphids are heat-intolerant and will be gone by mid-June. (This information taken from University of California Cooperative Extension.)
For more detailed information see the publication “Aphids and Their Management in Home Gardens” on the University of Nevada Cooperative Extension website http://www.unce.unr.edu/publications/files/ho/2002/fs0210.pdf. Or you can call me at 887-2252 or email me at firstname.lastname@example.org for a copy.