Preventing Fungal Disease on Roses
Many of us in Santa Barbara have problems with fungus. We see diseases such as Rust, Blackspot and especially Powdery Mildew.
Powdery Mildew loves warm days and cool damp nights, pretty typical south coast weather, spring to fall.
The best control is preventative: plant in full sun with good air circulation. Modern roses with glossy foliage seem to be more resistant.
We recommend a preventative spraying program to prevent disease especially if you have had problems in the past. The use of a hose end or other sprayer that allows you to direct under and over the leaves is best. Do not spray in the heat of the day.
Three products we like are Organicide, Neem Oil (Rose Defense) and Paraffinic Oil (Year Round and All Seasons). These products smother fungal spores as well as as sucking insects such as aphids.
Organicide is derived from sesame oil. Neem oil is formulated from the Azadirachtin Tree. The “ultrafine” type Paraffinic oils form a barrier, coating the leaves so fungal spores don’t settle.
Of course this advice is not just for roses. If you had trouble last year with other plants ornamentals or edibles, preventative spraying may be a good idea for you.
Have a great week!