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ROSE CARE FOR JULY AND AUGUST
by Barbara Picarelli, Consulting Rosarian
by Barbara Picarelli, Consulting Rosarian
Whoa, what are those bugs that are eating my roses? All of us at one time or another has gone out to see thousands of aphids munching and sucking away on our lovely rose buds.
APHIDS are a rose grower’s nightmare. Those little white/green insects seem to materialize out of nowhere. Commonly most active in spring and fall, these little 1/8 inch long nuisances suck the juices from the tender parts of buds, foliage and peduncles. They are found on other plants too. They excrete a honey dew substance that attract ants and favors the growth of sooty mold. The honeydew attracts the ants that then carry the aphids to other plants. Aphids multiply VERY rapidly especially in warm weather.
Damage is usually minor, mostly unsightly and a strong stream of water will knock them off. Since most cannot fly they will not be able to get back onto the plant easily (here come the ants!), and some natural predators will also destroy them, i.e. Lady Bugs, lacewing larvae and parasitic wasps. There are also insecticides that will control aphids.
LEAF CUTTING BEES are also a summer threat to roses. You have a lovely rose and suddenly there are sections of the leaves missing leaving an unsightly leaf on your exhibition prize rose! While rarely seen doing the damage these bees are about the size of a honeybee and actually do serve a purpose of pollinating plants especially crop plants. This “insect” is especially difficult to control and the use of insecticides is questionable.
THRIPS are the ones I hate. They are tiny slender brownish winged insects that are barely visible, but very active. They hide inside the bud or blooms and using their rasping mouthparts suck away to their nasty hearts content! They prefer lighter colored blooms, but will attack any color, and are hard to control since they hide inside an unopened bloom. If your favorite rose is suddenly full of little holes or doesn’t open properly, blame the thrips.
In this case, other than living with the damage done, Orthene (or its replacement product) can be sprayed on without damaging the flower. Pay particular attention to spraying the buds and top foliage to get the best control.
SPIDER MITES are a part of the arachnid family and are really not an insect but a true spider. The Consulting Rosarian Manual says that the two spotted mite is most common and especially in hot weather. Frankly, the things are so tiny, who can see their spots, but under a magnifying glass it’s possible. It’s suggested to hold a piece of white paper under a leaf when shaking it to see the tiny mites fall off. The most symptomatic sign is webbing and eggs on the underside of a leaf, with some curling of the leaf. This tiny sucking insect will cause leaves to turn yellow usually starting at the bottom foliage and work their way up.
Turn on the hose! A strong spray of water to the underside of the leaf helps, but must be done three or four times a week to have effect. Barring that, the use of a miticide will kill the spider mite but not their eggs, so it must be repeated to have control. Mites can become resistant to chemical sprays, so it is advisable to spray BEFORE applying winter protection. For those who do not wish to use chemical controls, safer soap or insecticidal oils are useful, but again must be used to the underside of the leaves. Removing all infected material BEFORE spraying is most beneficial. Either way, we’ve got our work cut out for us to outsmart the bugs!
Consulting Rosarian Manual used for reference.
A YEAR OF ROSE CARE:
January
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Last Modified: 7/15/06