Identify and deal with rose fungal diseases, such as black spot disease and rust, and rose pests such as aphids and thrips to ensure healthy rose gardening.
Roses will enhance any garden and any gardener can grow them with great success. However, growing them successfully will be made all the more easy if a few simple facts are understood from the outset and followed through as the year progresses. Roses, like most plants, can have problems and setbacks and in the case of roses the main culprits will be either fungal problems or problems with pests. Both of these sets of problems can be kept safely at bay by a little understanding and by keeping a wary eye for any signs of attack.
Rose Fungal Diseases
The most common of all rose fungal problems is Black Spot followed by rust, both powdery and downy mildew, leaf spot, botrytis blight and some viral diseases. Luckily viral infections are rare because these can be lethal and will destroy the plants.
Black Spot is so simple to diagnose, it appears as a black spot on the leaf and sometimes the spots can be numerous enough so as to join together taking over the complete leaf. From certain light directions a yellow circle may be obvious around the individual black spots. Diseased leaves should be removed and burned to prevent any spreading. Black spot can be difficult to control; regular spraying during the growing season will be necessary.
Rust is easy to spot and there can be no mistaking it. It is a fungal disease which appears as little rust colored mounds on the underside of leaves. Also difficult to control and affected leaves should be burned. If a certain rose is maligned continuously with rust it is best to remove it completely and burn it. Otherwise the rust fungus will spread to nearby plants.
Powdery mildew occurs in late summer and it looks like sprinkled powder on the top side of leaves. It usually appears when the rose bushes are left dry around the roots and when the air is humid. Apply a good quantity of mulch during the spring and keep the soil moist around the roots.
Downy mildew is mildew, plain and simple and it can be seen at a glance. It is a widespread problem and it covers new leaves and buds. It usually occurs in cloudy damp conditions.
Leaf spot is as simple to see as black spot only the spots are yellow. Any affected leaves must be removed and destroyed.
Botrytis blight sounds nasty and rightly so. It appears as a gray mold and can attack rose buds which will perish and drop off.
Most, if not all fungal diseases respond well to fungicide treatment and modern fungicide preparations have a broad spectrum effect. It is a good idea to read the list of ingredients looking for a sulfur compound. Captan and Triforine are tried and trusted systemic fungicides.
Rose Pest Problems
The majority of rose pests are most active at night so it is very difficult to actually see the insect at work and therefore difficult to eradicate it but the main culprits for rose damage are:
Aphids. Aphids or more commonly called greenfly and blackfly are the greatest pest of roses. Greenfly is particularly difficult to get rid of but very easy to see so constant spraying will be necessary. Ordinary household soapy water will wash away the greenfly but will not kill it and it will quickly dry itself off and return to continue with its banquet.
Red Spider Mite. Tiny reddish insects and their presence will turn the leaves yellow.
Thrips. Brownish flying insects and they leave blotches on the leaves and buds which will develop in a deformed manner.
Slugs. The common garden slug is a real pest and will make so many holes in the leaves they will look like skeletons.
A systemic insecticide will eradicate most of these common pests. Systemic pesticides are water soluble and are easily absorbed by the complete plant – stems, leaves and buds. So any pests which may be missed by spraying will be nabbed by gorging on the pesticide rich plant.
Roses in all their shapes and sizes – bush, patio or climbing – may all be subjected to pest problems from time to time and the wary rosarian will deal with these problems swiftly to prevent an epidemic by spraying regularly with reputable pesticides and fungicides. Always read the instruction carefully, both for amount to be used and for the repeat application timescale. All garden chemicals must be kept away from children, pets and direct sunlight.