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Rose Diseases and Pests

As beautiful as they are, Roses are susceptible to disease and pests. These include black spot, powdery mildew, spider mites, aphids, and others. Many rose varieties are breed for disease resistance; many are not and require spraying to stay healthy.

There is a big debate in the rose world, to spray or not to spray? In some areas of the country, you have to spray or you will just not keep healthy roses, especially in hot humid areas. Growing roses in semi-arid areas is great because it's harder for fungal diseases such as black spot and powdery mildew to develop. Roses diseases left alone without spraying can weaken and kill whole rose beds or individual bushes. Prevention is the key to keeping roses healthy. If you buy disease resistant roses to start, giving them proper care and planting will help prevent rose diseases. This includes getting good sunlight, proper air circulation, using soaker hoses to water, watering in the morning, and keeping your gloves and gardening tools sanitized so you won't spread disease. Even taking all these precautions is still sometimes not enough. Every summer for the last 25 years I have been growing roses has been different . During the summers that are dry, diseases do not develop; in especially hot, humid summers, black spot appears by the end of that summer.

Spraying will prevent disease and pests. Organic methods can work, but the research and debate is still out on organic methods. There are fungicidal soap sprays, natural Pyrethrum sprays and others. Nurseries and big box stores sell a variety of both kinds. It is your choice. I have used both methods, and even though I would prefer not to use any chemical sprays, they have worked the best for me in my rose garden.

Pests can also be quite another problem. In the northern midwest, the Japanese beetle has not invaded yet, but they have been quite destructive in other parts of the country. Insects can be a problem at any time in a rose garden, so it is best to be prepared if they arrive. There are insects that are good for your garden like Lady Bugs that will eat other insects. Sometimes just picking off insect or shaking the bush also work. But if you get a full-fledged outbreak of pests, you can try organic sprays or chemicals to rid the infestation.

Here is a list of the most common rose pests to watch for:

  • Aphids
    The most common of pests, they suck the juices out of the leaves on a shrub and cause them to curl up and die. Aphids are prolific and can survive the winter. You can control them organically with ladybugs that will eat the aphids or spray to prevent them from the start. Spaying with a dormant oil spray at the end of the season also helps aphids.

  • Leafhoppers
    Leafhoppers suck the juices on the undersides of the leaves and can winter over, if you have a healthy plant to start and you keep it well watered, Leafhoppers can be prevented. Pick then off when you see them and hose down the plant.

  • Mites
    Mites or spider mites are a nuisance. They can be signal your roses are not receiving enough water. Water and spray all the leaves with water. A good rose spray will prevent mites. Early in spring before growth or in the fall, you can spray with dormant oil spray to prevent mites.

  • Leaf Cutter Bees
    Leaf Cutter Bees are small fly-like creatures that cut holes in rose leaves when they hover over the plant. I tried to spray with water; they seem to disappear when the weather gets hot in early summer. They are a beneficial insect and do not usually do much damage.

  • Japanese Beetles
    The Japanese beetle is small bug and is iridescant, copper-colored, and has a green thorax and head. They cannot fly very well but goes in cycles in gardens. They can be quite destructive on roses and completely defoliate the shrub. Hand-picking of the beetles and droping them in soapy water works. However, you really have to keep after them or you will have to find a spray that will control them.

Here is a list of the most common Rose fugal rose diseases to watch for:

  • Black spot
    Black or brown spots appear on leaves, turning them yellow and causing them fall off. This is the most-common rose disease. If left untreated, it will infect the whole plant and can winter over if diseased leaves are not raked away. Spraying can prevent and cure this disease.

  • Powdery Mildew
    A white powder develops over the leaves; this can be prevented by spraying and healthy plants to start with proper fertilizing. Spraying will get rid of powdery mildew and prevent it.

  • Rust
    spotted rusty patchy spots appear on the underside of the leaves, spray and remove infected foliage as it can be wintered over like black spot.

  • Viruses
    Organisms that develop in the plant world, where it stunts the plant, you get little new growth and yellow leaves. Sadly the best thing to do is shovel-prune that plant and start over in a new hole with a new rose. These roses cannot recover and can infect other plants, do not compost roses with Viruses, burn them.

  • Canker
    Spreads by poor sanitation and pruning on wood, it can be prevented by proper pruning, burn when found do not compost.

  • Crown Gall
    It is found at the roots of roses and is caused by bacteria can be caused by injury to the plant, it does effect vigor and longevity of the plant, it's best to shovel-prune the shrub, do not put in compost or burn it can spread that way.

You're local garden center will carry different rose sprays you can choose from to get rid of pests and diseases; it's a matter of choice organic or chemical. Get one that covers diseases & pests, (fungicide and insecticide) check the label and carefully follow directions! Prevention is best when you start planning for roses, starting with healthy plants, a good growing location and proper fertilizers will keep your roses healthy.