Cultural Practices
The most common rose diseases are caused by fungus. Selecting the right rose for your location and careful attention to cultural practices can easily control the spread of fungal diseases. Also, because insects prefer weak plants, preventing these fungal diseases will indirectly help to control insect problems.
Choose disease resistant varieties.
Not all varieties of roses are considered to be disease resistant, but you may want to grow them anyway. Reduce their vulnerability by buffering a susceptible rose with a disease resistant variety on either side. Avoid group plantings of susceptible varieties.
Continually remove and destroy fallen leaves and debris from around the rose.
Avoid splashing water onto the rose.
Water always at the base of the rose, in fact, work the nozzle of your hose right into the mulch to prevent splashing. Some fungi are spread in tiny droplets of water.
Avoid gardening in wet periods.
It is good horticultural practice to avoid the garden altogether during and immediately following rain.
Ensure good air circulation.
Proper spacing and keeping the centre of the bush open will ensure good air circulation. There is nothing better than air movement for drying plant surfaces. Open the centre of the bush by removing crossing branches and always prune to an outward facing bud. This ensures the growth is directed away from the centre.
Fall Clean Up!
When all leaves have dropped from the shrub, gather them all and destroy them immediately - don't compost. Fungus on infected leaves can easily over-winter and return the following season.
Watch for infected leaves.
Check the underside of leaves every couple of days. Usually the lower leaves will show infection first. You can prevent so much spread by simply removing these infected leaves and destroying them immediately. Pay particular attention when humidity is high and temperatures are between 18°C and 24°C (65°F and 75°F).
