Proper air circulation is a must for control. Where poor circulation exists, infestations can be severe. If fungicides are selected, they should be applied on a regular basis with particular attention paid to periods of rapid growth. For other means of control, see Rose Diseases and Their Control . This disease is most commonly confused with Blackspot.
Infected leaves develop purple-red, irregular splotches.
Downy Mildew is happiest under cool, moist conditions where air currents and splashing water can transmit the spores. Collection and destruction of diseased leaves is paramount. For other controls, see Blackspot above. This disease is the nemesis of rosarians primarily along coastal regions. There are nine species of this disease, however, and they can show up most anywhere given the right growing conditions.