Keep plants vigorous with proper culture and disease control. Although they look like caterpillars, products with a BT are not effective because they are not larvae of moths or butterflies. Maintain vigor with fertilization and watering. Common rose slugs are green with a light tan head and often have may hairlike bristles. Mildew is spread by wind and develops rapidly during periods of warm, dry days followed by cool, humid nights. Control consists of pruning out buds and applying insecticide if the problem persists. Make the cut well below the affected tissue. In fact, there are a number of cultivars that are very prone to severe disease injury. A 25 percent concentration reduces the time needed to about 10 seconds. The fungus overwinters in fallen leaves and stem cankers. Infected leaves turn yellow and fall off prematurely. They feed on very young succulent shoots, causing distortion. It is very difficult to apply sprays in a timely and satisfactory way. Eventually they turn black. Insecticidal soaps are also effective in controlling mites. Severely infected plants become stunted and fail to grow properly. Good garden sanitation and removing spent flowers often result in good control of this disease. Controlling the mite has been labeled as an option but attempts at controlling it have proven inconclusive. Some roses are less susceptible than others, so cultivar selection is important. Infection occurs after leaves are wet for several hours, making it more serious during rainy periods. Rose mosaic is caused by a virus. Beware of Japanese beetle traps. The fringed margin and black color distinguish this leaf spot from others. It is unusual to see the insects at work, but they make their presence known by the perfectly round holes cut near the edges of the leaves. They prefer flowers and flower buds but will also attack foliage. Galltrol-A, a non-pathogenic bacteria, has been used to prevent crown gall. Phenotypic resistance is when a cultivar is resistant to a disease in one location or part of the country but not in another. The rose midge is a tiny fly that lays eggs in the buds and shoots of roses. Mature leaves are less likely to be affected. The rasping mouth parts of thrips causes this injury when they scratch the petal surface to feed. Avoid buying plants with suspicious swellings or gall on lower stems or crowns. It is frequently found on older flowers and other plant parts. It causes irregularly shaped, rough, dark-colored masses (galls) to appear on stems near the soil line. Under certain conditions it may also attack healthy tissue. This pathogen (not yet positively identified) is spread by an eriophid mite. Protect the plant from cold or freeze injury by providing adequate cover over the winter. Infection can be reduced through sanitation and fungicide spray programs. A deformed flower with flecked or scratched petals is usually a sign of a thrips problem. Canker is a disease of stress. Control can include hand picking and the use of horticultural oils or insecticidal soaps. There are no effective chemical controls for canker disease. Crown gall is a bacterial disease that can survive 15-20 years in the soil. The larvae that develop start feeding and causes bent, mishapen or blasted flower buds and withering of the stem tips.

Aphids are soft-bodied insects that can be red, green, yellow, or black. When roses are mulched before the soil freezes, moisture can be trapped around the canes and this can increase the damage caused by canker disease. Dipping the blades in a 10 percent solution of chlorine bleach and water for 60 seconds can do this. Avoid wetting the leaves when watering and locate plants where there is good air circulation. This means that reapplication needs to be done on a regular basis to protect the foliage and flowers. The damage they cause is strictly cosmetic and warrants no control. Hand picking is also a suggested control for small numbers of beetles. For more videos from the University of Illinois Extension, please check out our YouTube Channel. You want to select by cultivar, not by class. For this reason, roses should not be planted where plants susceptible to crown gall have been removed because of the disease. All infected plants should be removed and destroyed to reduce the spread of the virus to other plants. Do not cover roses too early in the fall. Symptoms include rapid growth of shoots, development of "witches' broom," development of tufts of small, deformed reddish leaves and excessive thorniness. There are no effective controls for crown gall. Another interesting fact about diseases is that plants can have two types of resistance: phenotypic or genotypic. Whereas blackspot is usually most severe on the lower part of the plant, mildew affects the top part of the plant. Prune out all dead and diseased canes to reduce initial fungus infection. The cane dies, and leaves wilt from that point outward. There are several fungi that cause cankers on roses. A pest control program starts with proper site selection, good soil preparation, good drainage, proper spacing, cultivar selection, and plant maintenance. Botrytis favors moist, wet conditions, often causing the disease to attack entire flowers and produce a gray fuzzy mold. If they are used, they should be placed in areas away from the rose garden. The larvae look like caterpillars but are actually more closely related to bees and wasps. Infections of mildew are actually discouraged by the presence of water on the leaves. A high-pressure washing with water from a garden hose directed to the underside of the leaves every 2-3 days can manage mites. Cankers should be pruned out each year. Splashing water spreads blackspot. They can be red, black, or brown in color. University of Illinois at Urbana-Champaign, Daconil 2787 or fungicides containing Daconil. All too often, many gardeners assume that shrub roses (the class) are very tolerant or resistant to disease and make their selection based solely on class. Roses may survive without a basic pest control program, but they may not be very attractive.

This disease is often called gray mold. Blackspot is identified as circular black spots that appear on the upper surface of the leaves, starting at the bottom of the plant and moving upward. Roses are susceptible to a number of disease and insect pests. Rose rosette is becoming more common and can result in significant damage. This will interrupt their life cycle. Miticides such as dicofol help in heavy infestations. A fine web is a sign of a heavy infestation. Thrips are extremely small, brown insects usually living and feeding inside of the blooms. Plants decline over time. Infections on canes are identified as reddish-purple spots. Home gardeners still find that Sevin provides the best control, but it is only topical. However, keeping plants wet all night to avoid mildew provides an environment that allows other diseases to develop. It is often used as a dip on cane root roses prior to planting. Sometimes small black specks can be seen on the cane surface within the borders of the canker. When selecting roses, note the resistance to disease of a particular cultivar or named variety within a class. These are fungal spore-forming structures. Bright yellow patterns made up of wavy lines may appear on the leaves of some varieties. Severely infected plants should be dug up and discarded and roses should not be planted in that area for at least 5 years. Aphids are often kept in check by natural predators. The common rose slug causes skeletonizing or window pane like damage to rose leaves in spring and early summer. Mites flourish in crowded, stagnant gardens. Alternative control measures include the use of insecticidal soaps, strong streams of water to knock them off the plant, or insecticides. Because the larvae fall to the soil to pupate, an effective control is to place weed barrier fabric under the plants to catch the larvae and prevent them from entering the soil to pupate. Protect plants from injury on stems during cultivation. That is why, when the term "resistance" is used as a blanket term and assigned to a variety or class, it may or may not apply depending on where you garden. Plant virus-resistant roses if possible. Mites are very tiny relatives of spiders. Some control can be achieved using materials such as orthene, malathion, or insecticidal soap, but even these often give poor results.

These galls can appear as small swellings or be several inches in diameter. Crown gall is not specific to roses and can affect apples, raspberries, honeysuckle, euonymus, and many vegetables. As the disease progresses, leaves become covered with white powdery fuzz. Mites pierce the underside of rose leaves and suck sap, causing the leaf to turn gray or bronze. When this is insufficient in providing adequate control, a preventative spray program may be necessary. Because new growth is especially susceptible, thorough coverage of new growth with fungicide is important. Botrytis blight is a fungal disease that generally attacks dying tissue. These hard-shelled, metallic-green, black, and gold insects can cause extensive damage to roses just by their sheer numbers and voracious appetite. Virus-infected plants cannot be cured. Fungicide spray programs need to be started as soon as new leaves appear in the spring. However, do not confuse crown gall with normal swellings that you see as a result of the budding process. Midge damage usually shows up in July. Mites reproduce rapidly, resulting in high populations in a short time. These leaf pieces are used to make egg partitions inside their burrows. Raking and removing these leaves as well as pruning out affected canes by spring before the buds swell may help provide some control. If plants are kept actively growing, they stand a better chance of avoiding cankers. If you are pruning virus-infected plants, don't prune healthy plants unless you first disinfest your pruners. Thrips are especially attracted to yellow or light-colored roses. Japanese beetles are difficult to control because they are strong fliers and constantly reinvade the area. Genotypic resistance is due to the presence of genes that are not affected by climate, location, or horticultural practice. This fungal disease can cause almost complete defoliatiation of bushes by early fall, resulting in a weakened bush on which cane die-back and cankers become severe. Traps are almost too effective and will draw a great number of beetles into an area, making the problem worse. Fungicides generally recommended for blackspot control include: Frequently used fungicides for control of powdery mildew include: As with all spray materials, follow label directions carefully for mixing and applying. The different fungi can cause different-looking cankers, but they usually produce brown, oval-shaped, sunken, or shriveled areas anywhere on the cane. Try to control insects, especially aphids, since they help spread the virus. Plant roses in areas where they receive good air circulation and where the foliage can dry off rapidly in the early morning to prevent many types of diseases. Because affected plants can't be cured, it is best to dig out the affected plant and destroy it. These all foster healthy roses that are better able to withstand the pressure of disease and insects. Aphids are very common pests. They tend to be worse during late June, July and August when temperatures are warm. Other varieties may show no yellow lines, but may be stunted and weak due to virus infection. Powdery mildew is a fungus disease that affects young leaves, causing them to curl and twist and develop a purple coloration.