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Black spot.There are hundreds of different kinds of roses, but you may not see roses in many home gardens because all but a few are high maintenance. Part of the high maintenance upkeep of roses is because this plant easily develops disease and attracts pest and both of them kill the roses. -
Powdery mildew.There are three diseases to watch out for with roses. Two of them are fungi. The fungi are powdery mildew and black spot. Powdery mildew is caused by not giving the plant enough air circulation or adequate light. Roses are particularly susceptible to powdery mildew in zones that have cool nights and warm, humid days.
Powdery mildew is a fungus that grows on the top of the leaves and flowers. It causes the leaves to turn yellow and brown and fall off. It can also affect new foliage, which will emerge distorted. To help control powdery mildew, water the plants from below, do not use a fertilizer high in nitrogen and apply fungicides. Be sure to prune every spring and throughout the year for dead and decaying wood and foliage.
The other fungus to watch out for is black spot. It shows up on young leaves in the form of irregular black circles. Sometimes the black circles will have a yellow halo. A circle is a spore colony, and each spore colony can grow up to a ½ inch in diameter. Black spot causes the leaves to turn yellow and fall off. The plant will produce more leaves, but they will also be affected. It affects the size and quality of the flowers and may completely kill the plant, as it does not have enough reserve to make it through the winter.
Control black spot by watering from the bottom and pruning properly for dead and decayed wood throughout the season, but particularly in the spring. Always deadhead (cutting the flowers off before they expire) the plants. When pruning or deadheading use pruning shears dipped in a bleach and water solution after every cut. Black spot can also be controlled with a fungicide. -
Blight.Blights are diseases caused by a fungus or bacteria that kills the plant tissue. Blights cause spotting and will also cause wilting. There are many different types of blights, and blights are species-specific. Different types of blight need different types of control, but always water from the bottom, mulch plants to help keep water from splashing onto the foliage during watering and prune accordingly to provide proper airflow. -
Thrips.There are pests that can also kill roses, including thrips, spider mites, whiteflies, aphids, caterpillars and scale insects. Most can be treated by introducing natural enemies to the flower beds. Natural enemies include parasitic wasps, ladybugs and ladybug larvae. You can also use insecticides. -
Rose in the garden of Fortress Koenigstein, Saxonia, Germany.The biggest help with controlling both pests and disease is keeping the weeds away from the plants, mulching and proper pruning. Always prune during the spring for dead and decaying wood and plant matter, then prune throughout the season as needed. Deadhead the plants just before the flowers are spent. Taking these precautions will go a long way in making a healthy rose garden.
