Garden Checklist

From the Fresno Bee, May 21, 2009:

"Heat Works Against Powdery Mildew"
by Elinor Teague

Here in the valley, we have less fungal diseases, because our late spring and summer seasons are dryer than other areas (our main rainfall is in February and March). Although, these last few weeks we seem to be having more problems with powdery mildew, which attacks many different plants. [This picture shows powdery mildew on one of my crape myrtles].

The spores of powdery mildew are carried by the wind from plant to plant. "The first signs of powdery mildew generally appear as a white, powdery substance covering new leaves and shoots. The new leaves and shoots become stunted and distorted."

Powdery mildew can become a serious problem "to the health of woody plants and trees such as sycamores and crape myrtles." The trees' food supply is reduced when the infected leaves fall off, and the branches may be more exposed to sunburn. Smaller plants may be killed when badly infected with powdery mildew.

On the positive side, powdery mildew can't survive temperatures of 95' or more. Treatment can be as easy as spraying a strong spray of water from the hose on the infected areas. "Infected new growth on susceptible varieties of tender-stemmed plants such as begonias and roses can be trimmed back."

Another solution could be the use of horticultural oils, jojoba oil and neem oil, which are less toxic. These oils both prevent and eradicate powdery mildew. There are fungicides that prevent powdery mildew, but they are more toxic. They must be applied before signs of the fungus or at the very earliest stages, are not to be applied when temperatures are above 90', and several applications are needed.

The only sure solution is our summer heat, which will eliminate most of the powdery mildew.

. . . . .

Tasks: use a 3" layer of mulch around trees and shrubs to retain moisture, supress weeds and cool soil temperature.

Pruning: remove suckers on roses and fruit trees.

Fertilizing: a little used more often is better than a lot at one time.

Planting: Russian sage (Perovskai), gloriosa daisy (Rudbeckia); fortnight lily (Dietes); potatoes, tomatoes; abutilon; plant from seed---petunia, marigold, black-eyed Susan vine (Thunbergia alata).

Miscellaneous: scale insects are easy to control with horticultural oil (insecticides work also, but I'd go the natural route with the horticultural oil), repeat in June