While aphids don’t spread rose diseases and damage from minor infestations of healthy plants is typically slight, the little critters just look so awful. Left to their own devices, the horrible little beasts can colonize a rose bush from spring through fall and spread from plant to plant. Some species even have the audacity to over-winter on garden rose bushes. However, for all their fortitude, aphids are somewhat delicate and you can send them packing with some organic and cultural control tactics.
Inspect your rose plants carefully every day throughout the growing season. Check the undersides of leaves thoroughly. Squash any aphids that you find with your fingers. Pick off any infested leaves and drop them in a bucket of soapy water.
Shake healthy rose bushes briskly once daily throughout the growing season. This will easily dislodge aphids from the plants. These insect pests don’t climb very well and are commonly sought by predators, so they typically die once removed from the plant host.
Fertilize rose plants with slow-release nitrogen products throughout the growing season. Use composted manure, packaged urea- or ammonium-based rose food, or fish meal. This will reduce the incidence of excessive foliar nitrogen flushes. depriving aphids of nutrition and starving them out. Follow packaging instructions carefully.
Treat your roses with insecticidal soap from early spring through late summer to control aphids and powdery mildew. Coat all surfaces of the plant generously. Pay particular attention to new growth and the undersides of leaves. Follow the manufacturer’s recommendations for repeat applications.
Trim out any damaged, diseased or dead rose limbs from early spring through late summer with clean, sharp shears. Pay particular attention to stems in the center of the canopy to encourage air movement and help dry stems and foliage quickly, reducing humidity.
Remove and destroy rose trimmings immediately to prevent the possibility of spreading diseases and pests. Do not add the clippings to your compost heap.
Shoot a strong spray from the garden hose directly onto all surfaces of the rose plants to knock aphids off during the heat of summer. Once environmental conditions are no longer favorable for black spot growth, hosing goes a long way toward controlling aphids and powdery mildew. Do this is from early to mid-afternoon on bright, sunny days. Repeat every 3 to 5 days throughout the growing season.
Deadhead rose plants as soon as blooms are spent. Flowers are common attractants and hiding place for aphids, and this will help with removing colonies from the plant. It also heads off early powdery mildew infections. Destroy the trimmed plant material; do not add it to your compost heap.
Spray your rose plants with horticultural or neem oil in early spring. Coat all surfaces generously to suffocate the eggs of aphids as well as mites. Repeat the application during the dormant season to suffocate the pest eggs while they’re over-wintering. Follow the package recommendations carefully.
Prune out weak, dead, diseased or damaged stems during the winter to open the canopy and increase air flow to the plant, reducing the incidence of over-wintering pests and diseases.
Things You Will Need
- Soapy water
- Composted manure, packaged urea- or ammonium- based rose food or fish meal
- Insecticidal soap
- Clean, sharp shears
- Horticultural or Neem oil
- Avoid using chemical pesticides if at all possible. They’re deadly to aphid predators such as green lacewings, ladybugs and parasitic wasps.
- Do not hose rose plants down for aphids if black spot is present.
- Do not use horticultural or neem oil within 30 days of sulfur product applications, to avoid burning rose plant leaves.
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