Troubleshooting Your Roses

by Jenna Marshall

Roses are notorious for being difficult to grow and plagued with problems. Here are a few examples of the troublemakers you may encounter, and some practical ways to deal with them.

There are several types of fungal diseases and they can occur in almost any garden. Catch them early and you will prevent major problems later.

Some of the most common are:

Black Spot - This is the most widely seen type. Anyone who has ever grown roses has seen this one. It starts out as a black or brown spot, usually on the lower leaves, which quickly causes the area around it to turn yellow. The fungi kills the leaves as it progresses. The more serious the infestation becomes, the weaker the plant gets. It will eventually cause the stems to die off and the plant becomes less productive. These already weakened plants will experience more damage during harsh winters.

Powdery Mildew - This type is particularly damaging, and can attack any type of roses. In the early stages, it looks like little blisters on the top of the leaves. It is not very noticable at first, but this is why it is important to check your plants regularly. You will begin to spot minor differences if you have kept a close eye on them. When the disease progresses, it can be identified by a white or gray film or "flocking" on most all areas of the plant. This type can grow anywhere, but prefers warm days and cool, muggy nights.

Downy Mildew - This type looks a lot like Blackspot. The way to tell the difference is to notice where it first appears. It will show up at the top if the new growth parts. Black Spot starts on the lower leaves. The leaves affected byt the disease will develop splotches, irregular in shape, that are a reddish-purple color. As the disease progresses, you will find a whitish-gray fuzz on the bottom side of leaflets. This type thrives in cool, moist areas.

Rust - This is another type that can be found anywhere, but it spreads best in coastal areas. Rust is an orange and powdery, usually forming pustules on the underside of leaves. These will eventually get bigger as the fungi spread. The leaves will turn brown and you will be able to see it on both sides of the leaves.

Once a fungal disease has found its way into your rose garden (and it will), the best thing you can do is to act quickly. These diseases are spread by tiny spores, and should be removed before further damage occurs.

Prevention is the best medicine. - Be sure your roses have plenty of ventilation. - Prune them yearly, and be sure they are planted in a spot that has good air flow. - Avoid overwatering and do not water the foliage. Water the ground only. - Tend to your plants regularly - this way it will be easier to spot problems before they become severe. - Keep debris cleaned up to discourage pests and disease.

Start by removing the infected areas. Fungal infections spread quickly. Once the problem has been identified, act fast. Remove all debris and dispose. Do not put these infected leaves and canes in your compost - it will only spread more later. Be sure you thoroughly clean any tools used so you don't spread the disease further.

Next, treat your plants. Below are some good, organic choices.

Baking Soda and Horticultural Oil - Mix 1 Tbsp. baking soda, 1 Tbsp. horticultural oil, and 1 gallon of water. Spray this mixture on the plant once a week. Be sure to keep the spray on the plant only since baking soda can change the pH of the soil.

Neem Oil - This is inexpensive and can be found in a number of mixtures. Follow the directions on the package.

LEAF DROP

Leaf drop can be caused by many different things. Not enough or too much water, disease or insects are all common causes. It is a good idea to eliminate each possible cause systematically.

- Inspect your plant for insects. If you find an infestation, treat the plant with insecticidal soap at least once a week. Treat again after each rain.

- If your watering practices are the cause, find out why. Is your plant drying out too quickly? Is drainage too poor to accommodate regular waterings? Try working more organic material into your soil.

YELLOWING LEAVES

Yellow leaves can also come from many causes. It is a common problem, and as always, should be addressed early. Some possible causes include:

- Lack of fertilizer. Generally, roses should be fertilized regularly since they are heavy feeders. It may be that you are not giving them enough. Try this first to see if the problem is corrected.

- Insects are also another common cause of yellow leaves. Scale insects (usually on the bark of the plant) and spider mites (tiny insects, about the size of a speck of dust) can cause big problems for your plants. Good solutions for these are insecticidal soap or a mixture of organic pyrethrin and canola oil. Spray your plants regularly to keep them pest free. Insecticidal soap is a good preventative measure, too. At the beginning of the growing season, begin spraying it weekly to prevent infestations.

- If none of the above treatments have helped, you may be facing a viral problem with your plant. These are serious problems that are difficult to treat, and they can spread. You may choose to contact your agricultural extension office to confirm this. Plants infected with viral diseases should be removed completely - roots and all - to prevent further infections. The virus is in the entire plant, not just the visibly sick part of the plant. Pruning will not help.

Be persistant. Bringing your roses back to health will take a little time and patience.