Rose blossoms are beginning, although somewhat late this year, to open. Along with the beautiful blossoms are sure to be aphids.Roses can be the host for a number of different aphids such as the potato aphid and the cotton aphid.The most common aphid that feeds on roses is, quite appropriately, the rose aphid.This aphid is a soft-bodied, pear-shaped insects approximately 1/4 inches long and may vary in color from green to pink to red.
Rose aphids spend the winter in the egg stage on rose canes.They typically emerge and start feeding on roses in early spring as the new flush of growth emerges, clustering on leaves, stems, and developing buds. Rose aphids have piercing-sucking mouthparts and feed on plant sap, often in large groups as they feed on new growth. Leaves show characteristic curling symptoms from aphid feeding - look closely, they may be on the underside of the leaves.Flower buds with significant aphid feeding may abort and fall prematurely before opening.
Do you have lots of ants on your roses?This is generally a sign that there are aphids and the ants are feeding on the honeydew that they produce. Honeydew is a clear, sticky liquid produced as a byproduct of their feeding. Honeydew may also attract bees and wasps as well as serve as a growing medium for sooty mold, a black fungus
There are a number of natural enemies that prey on the rose aphid. These include parasitic wasps, ladybird beetles and green lacewings. These natural enemies may provide sufficient control if the population of aphids has not had the chance to expand exponentially. Another good natural control is to spray the plants with a strong spray of water a couple times a week. This dislodges the aphids and they are not strong enough to climb back up on the plants. Be sure to do this early in the morning so that the sun has a chance to dry the foliage early in the day. Otherwise you might be promoting diseases such as black spot.
There are also chemical controls that are very effective. I prefer systemic pesticides that are taken up by the plant and therefore can’t be washed off by rain the way contact insecticides can. You do not have to be as rigorous in getting overall coverage with a systemic as you do with a contact insecticide either. Consult your local garden center or nurseryman for the latest and most effective chemical controls.
Photos from Rose Magazine and University of Washington.