the predominant species is the
rose aphid (Macrosiphumrosae). Rose aphids are small (about ? inch
long). They are soft-bodied, pear-shaped, pink or green insects that are found
in clusters on new growth of buds, leaves and stems.Aphids feed on plant sap
with their piercing-sucking mouthparts. A low population of aphids does little
damage to a rose bush; however, aphids reproduce very rapidly and can quickly
reach numbers that cause damage. Their feeding results in distorted growth.
Heavy infestations can reduce the number and quality of blooms. As they feed,
aphids excrete honeydew, a sugary substance that attracts ants and wasps. The
honeydew supports the growth of unsightly, dark-colored sooty mold fungi on the
Aphids have several natural
enemies, including parasitic wasps, ladybird beetles (ladybugs) and larvae, and
green lacewing adults and larvae. Their natural enemies tend to keep aphid
populations under control except in cool weather. Ants are sometimes associated
with aphid infestations and will protect them from their natural enemies. If
ants are present, they should be controlled.
Aphids can be hosed off with a
strong stream of water directed above and below the leaves. Spraying with water
should be repeated frequently as needed, focusing in particular on new growth.
Roses can also be sprayed with insecticidal soap to control aphids.
Insecticidal soap must be sprayed onto the aphids to be effective. Repeat spray
three times at 5-7 day intervals. Higher toxicity insecticides are available.
However, it is important to note that aphids are very difficult to control
because they multiply so rapidly. Leaving even one aphid alive can result in a
large population very quickly. In addition, these insecticides kill the natural
enemies of rose aphids.
If insecticides are deemed
necessary, the following are available in homeowner size packaging. Sprays
containing bifenthrin, cyfluthrin, horticultural oil, lambda cyhalothrin,
malathion, neem oil, permethrin, or pyrethrin will control aphids. Soil
drenches or granular applications of imidacloprid or dinotefuran will control
aphids and last longer within the plant to prevent future infestations.