Gardeners face quite a lot of points within the panorama that may trigger destruction to vegetation. A type of culprits is powdery mildew. Powdery mildew is a fungal illness that impacts many host vegetation, together with ornamentals, shrubs and bushes. On some decorative vegetation, reminiscent of rose, lilac, ash, crape myrtle, oak, photinia and zinnia, the illness may be very harmful.
The severity of the illness is determined by the number of the host plant, age and situation of the plant, time of an infection and climate circumstances throughout the rising season. If identified early, powdery mildew may be successfully managed to stop extreme harm to vegetation.
The primary signal of the illness is the event of a white to grey or barely brownish progress of mycelium over the floor of leaves or different plant elements. Powdery mildew fungi can also assault stems, buds and flower petals of assorted decorative vegetation. Powdery mildew could trigger the curling and twisting of broadleaf vegetation and a discount in measurement of contaminated leaves. Contaminated buds could fail to open, and infections can unfold to mature flowers, inflicting a flower blight. Additionally, nuts of the pecan may be contaminated, inflicting a discount in high quality.
Humid circumstances with extensively fluctuating temperatures, which isn’t uncommon for Oklahoma, enhance the prevalence of powdery mildew. The illness is widespread in crowded plantings the place air circulation is poor and in damp, shaded areas. That is another excuse spacing and well-drained soil are necessary when planting. Illness improvement is enhanced when cool, moist nights are adopted by heat daytime temperatures.
A number of practices will assist cut back or forestall improvement of powdery mildew. Earlier than vegetation are bought, it could be to your benefit to inquire if the decorative selection desired has any resistance to powdery mildew. If solely inclined varieties can be found, keep away from planting in low, shady places. If powdery mildew turns into an issue, elimination and destruction of contaminated plant elements must be practiced.
An alternative choice is to prune crowded plant materials to assist enhance air circulation round leaves. Late summer season utility of nitrogen fertilizer must be prevented to restrict manufacturing of succulent tissue, which can be inclined to powdery mildew an infection within the fall. Water solely within the mornings in order that the foliage might be dry by night.
If cultural controls fail to stop illness build-up or if the illness stress is simply too nice, fungicide spraying could also be essential. The perfect plan of action is to mix each approaches, utilizing cultural strategies in addition to following a very good spray schedule.
When powdery mildew has been an issue in earlier years, a really helpful fungicide spray schedule must be began within the spring as new progress develops. The fungicide additionally must be utilized throughout the flowering interval to keep away from blossom blight. Remember to observe the directions on the label to be used on particular functions.
David Hillock is a client horticulturalist with Oklahoma State College Cooperative Extension.