Types of Garden Enemies
The first symptom is a slight curling of leaves, then a light white weft of mycelium soon covered with the powdery spore chains. The buds may not open or the flowers are misshapen. Leaves are sometimes somewhat blistered under the white mycelium and have a reddish or purple cast, becoming almost black. On canes there is a heavy felt near thorns. Perithecia are rare, the fungus wintering in buds or on canes. Mildew is prevalent on succulent growth encouraged by excess nitrogen. Certain floribunda varieties are particularly susceptible.

Control. Any copper or sulfur spray or dust started in time will control mildew. When the coating is well established, it is easier to eradicate the fungus with sprays which wet the felt than with dusts. A polysulfide spray, Orthorix, similar to lime sulfur, is used by many West Coast gardeners. Most of the carbamate sprays-Fermate, Dithane, Parzate, etc.- do not control mildew, but the new Manzate may be more effective. My personal preference is still for the ammoniacal copper in Tri-ogen because it is so very safe in hot weather as well as being very effective. Sulfur often burns when temperatures are above 85F., and strong coppers, as in bordeaux mixture, injure in cool weather. Iscothan (renamed Mildex) is a rather new chemical being used for rose mildew in greenhouses. Actidione, an antibiotic, has possibilities.

Some varieties are relatively resistant to mildew. The Fairy, a polyantha that becomes a large, spreading shrub, seldom requires spraying. Climbers like Dr. Van Fleet, with shiny foliage, are mildew tolerant. The delightful pink floribunda Else Poulsen is rather subject to mildew, but Betty Prior, a similar color, seldom gets the disease.

LIVE-OAK MILDEW (Sphaerotheca lanestris). A disease very destructive to coast live oaks and some other oaks along the Coastal Plain in California. Some shoots are stunted, covered with a white powdery growth, some are swollen, fleshy, with foliage reduced to bract-like leaves which brown and shrivel, giving a witches' broom effect. Leaves growing from normal buds are covered with mycelium turning brown with age.

Control. A fairly new chemical-Isothan Q 15-has given promising control. Do not prune heavily; this stimulates new succulent growth susceptible to mildew.

PSYLLIDS

Psyllids are jumping plant lice in the order Homoptera, family Chermidae. In western states the potato psyllid by its sucking produces a disease of potatoes and tomatoes known as psyllid yellows. BOXWOOD PSYLLID (Psylla buxi). Terminal leaves are cupped (Figure 43B), and young twig growth is checked, but this insect is not nearly so important as the boxwood leaf miner. In spring soon after new growth starts you can usually find, inside cupped and curled tips, small gray or greenish nymphs covered with white cottony wax




      (c)2005, common-garden-pests.com