Roses In My Garden - Fungal Diseases

The reality of growing roses in your garden is that they can be vulnerable to rose diseases and rose pests, and are not always trouble free. In this article I will look at fungal problems and what precautions you can take to reduce the risk of your roses being affected by them, and if they are affected what you can do to cure them.

Despite the seemingly huge problems which seem to be awaiting the rose grower, it is well worth taking the time, care and perseverance involved in growing them because they add such unsurpassed beauty to our gardens.

Steps To Prevent Fungal Problems.

The key here is to prevent trouble from the beginning. There are certain things you can do, right from the start, to prevent or minimize troubles. The first and most obvious thing to do is always make sure your new roses are disease free when you buy them, but we will assume you already know this!

Unless you have specific requirements, always try to buy low-maintenance roses like shrub and landscape roses. Always try to choose tough roses that are suited to your particular region. Look for disease resistant varieties. If your summers are quite hot and humid, buy only varieties that do well and thrive under those conditions. 'Knock Out' roses appear to have exceptional resistance to diseases and their foilage appears to be impervious to black spot.

Seek advice from a good local nursery with a knowledgeable staff. They will guide you to the correct plant selections.  Local Rose Societies are also excellent resources for information on roses for your climate situation, as they are well aware of rose varieties that would do well in your area, and which ones to stay clear of.

Plant your roses properly in areas that have as much sun as possible, good air circulation and good well composted soil. Pay attention to the surrounding environment. Whilst everybody loves to see a bed full of roses, by restricting an area to one species you will be increasing the chances of problems later, and if one does occur it is more likely to spread rapidly if surrounded by potential 'victims'. Keeping different types of flowers and plants in with your roses will help to provide your roses with a better and more balanced ecosystem to live in.

A two inch layer of mulch at the base of roses is a good way to prevent soil born diseases, and will keep moisture below ground rather than above.

As a general rule, any fungal problem is aggravated by moisture, and roses are no exception to this rule. Probably the most important prevention technique, when it comes to fungal diseases, is watering.
Watering roses from the top, soaking foliage, flowers and buds is inviting problems. Always water at the base of the plant, directly on to the roots and try not to splash water all over the lower branches.

A good watering technique is to use a 'soaker' hose system. This is simply a hose which has many tiny holes in it. Lay the soaker hose on the soil and cover with mulch. Then you simply connect to a tap and turn it on! Water will then seep from the hose, soaking the soil beneath the mulch. The mulch will prevent water spraying up onto the plants.

To get through an entire rose growingseason without a problem would be unusual, but by paying attention to the above points you will dramatically increase the chances of a trouble-free season.

Symptoms And Control Of Common Fungal Infections.

Unfortunately, even following all the above preventative measures will not necessarily keep your roses free of fungal problems. Below are suggestions of how to deal with the most common forms.

Black Spot

Black Spot is probably the most common rose fungus disease. To infect rose foilage, black spot fungal spores must stay wet for about 7 hours. A rainy day or wet foilage overnight can be all it takes for infections to start. Hence the need for care when watering. However, I haven’t yet found a way of stopping the rain!

By late summer, it is not unusual to find most roses have at least a little black spot. As the name suggests, the infection shows in the form of black or dark brown spots on leaves. Severe infections may cause leaves to turn yellow and fall off reducing the vigour of the plant.

Remove and burn diseased plant parts and fallen leaves to further prevent the spread of fungus. Spray with fungicides at the first sign of infection. With most fungicides, repeat applications every 7 to 10 days are recommended, so gardeners should try to start spraying three to four weeks before temperatures are expected to hit 80 degrees F, or 26 degrees C, in their part of the country, and also try to work in two or three fungicide spraying sessions.

If you prefer not to use fungicides, an excellent, non-toxic, proven preventative treatment is to spray with baking soda mixture. Mix together 2 tablespoons fine horticultural oil with 1 tablespoon mild dish soap and a large tablespoon of baking soda. Mix with one gallon of water and stir thouroughly.

Powdery Mildew On Roses

This fungal disease is common when humidity is high with warm days and cool nights. The damage to roses are white or gray patches with a powdery appearance on leaves, shoots, buds and flowers. The leaves then become crinkled and distorted, followed by premature leaf drop.

To control rose bush diseases such as powdery mildew on roses, pick off and destroy damaged and infected foilage, and clean up dropped leaves. Spray with a baking soda mixture to prevent further infection.

Spray only when the roses are shaded, early morning or evening. Spray all foilage and the canes comletely.

To prevent powdery mildew from attacking your roses, spray weekly with the baking soda solution when leaves first appear in the spring, then every two weeks thereafter.

This is the proper way to apply the Baking Soda Solution:

To prevent spreading the disease, remove all affected leaves and destroy them. Water the soil before spraying the rose bush and spraying the soil beneath it, making sure you spray the leaves undersides as well on top of the leaves. Spray all canes, in fact, thoroughly soak the bush with the solution, leaving nothing unsprayed. The reason the soil should be sprayed as well, is because there are 'fungus spores' in the soil as well. So you want to get rid of those also, to prevent the fungus from coming back."

Rust On Roses

Rust appears in the form of rust-coloured patches on the undersides of foliage which look like velvet and reddish-orange lumps on the upper leaf surface. The undersides will eventually turn to black pustules.

Preventative measures include good sanitation and proper and timely pruning. Prune before bud breaking in early spring to reduce the number of fungus spores. Dust with sulfur powder every one to two weeks, starting from early spring and continuing throughout the growing season.

If infection develops, pick off and destroy all infected and dropped leaves. Follow with a spraying of the baking soda mixture or lime sulfor, to stop the spread of this disease.

To give good rose health care and prevent any common rose diseases from infecting your plants, inspect your roses frequently, so if any problems crop up, you'll spot it quickly and can take appropriate measures before it gets out of hand. Spraying with a dormant non-toxic oil during the winter months can also be a great help.