苹果的病虫害管理

Apple scab
Disease Development:
Caused by the fungus Venturia inaequalis. The fungus overwinters in the previous year's diseased leaves that have fallen under the tree. In the April, May and June, the fungus produces millions of spores in the old leaves on the ground. These spores are shot into the air and carried by the wind or splashing rain to young leaves, flower parts and fruits. A free film of water on leaves and fruit is required for the spores to germinate and infection to occur.
Plant Health Management for Backyard Apple Plantings
Prepared by
Mike Ellis
Professor and Extension Specialist
Graduate Research Assistant
Department of Plant Pathology The Ohio State University OARDC/OSUE Wooster, OH, 44691
Cedar-apple rust
Symptoms:
On upper side of the leaves:
Pale yellow or orange spots appear during May or June. Small black fungal fruiting bodies (pycnia) form within the spots and may exude an orange fluid.
Omer Erincik
and
Early Season Diseases of Apple
Apple scab Cedar apple rust Powdery mildew
These diseases develop in the orchard between bud break and early to mid summer. Control measures for these diseases need to be conducted during this period.
Cedar-apple rust
Symptoms:
On Fruit: Similar yellow-orange spots appear, usually at or near the calyx end. These spots are much larger than the spots on leaves. The tube-like aecia may form on the slightly raised fruit lesions. Infected fruits are often stunted and misshapen, and may drop early.
Cedar apple rust
Disease devBaidu Nhomakorabealopment:
Sporidia are carried by wind to nearby apple leaves, fruits, and twigs where they penetrate the cuticle and lesions develop on the upper leaf surface and on fruit. After 10 to 14 days, the orange to black pycnia develop in the spots on the upper leaf surface. Several weeks later, the aecia form on the under leaf surface. The aecia produce another type of spore (aeciospores) that are carried by wind to junipers or cedars, where they cause infections resulting in galls; thus, completing the disease cycle.
On lower side of the leaves:
During late spring and early summer,yellow spots develop on the underside of the leaf. Within these spots a number of small, orange-yellow tubular projections (aecia) appear. Infected leaves may turn yellow and drop. Defoliation of rusted leaves is most common in dry summers.
Canopy management
Control timing and amount of nitrogen fertilizer to prevent excessive growth. Prune out and destroy all dead or diseased shoots and limbs while trees are dormant (mid-March is usually a good time). Prune healthy growth to improve air movement and sunlight penetration, to minimize shading and decrease drying time of leaves and fruit during the growing season.
Site selection
Select a site with good air movement all-day sun light, and good soil drainage. Do not plant trees in shaded areas.
Management of Early Season Apple Diseases
Cedar-apple rust
Disease development:
Caused by the fungus Gymnosporangium juniperi-virginianae. The fungus overwinters as mycelium in galls on juniper or cedar. Large yellow to orange gelatinous sporehorns are formed on the galls in the spring and spores (teliospores) are produced. Each teliospore germinates and produces four to eight sporidia or basidiospores.
Powdery mildew
Disease development:
Caused by the fungus, Podosphaera leucotricha. The fungus overwinters as mycelium in terminal buds and twig tips infected during the previous year. As buds break dormancy, the powdery mildew fungus resumes growth and colonizes developing shoots causing primary infections. The powdery white appearance on infected shoots consists of many thousands of spores which are responsible for spreading the fungus later in the growing season. Powdery mildew infections occur when the relative humidity is greater than 90% and the temperature is between 50-77 degrees F. Free water is not required for infection.
Management of Early Season Apple Diseases
Free water (wet conditions) is required for most fungal pathogens to infect plants. Any practice that promotes faster drying of fruit and foliage is beneficial for disease control.
Powdery mildew
Symptoms:
Small, whitish patches of fungal growth appear and quickly cover the entire leaf. Diseased leaves become narrow, crinkled, stunted and brittle. Infected blossoms shrivel and produce no fruit. By mid-summer, tiny, black round specks (fungal fruiting bodies) show up on the surfaces of the infected areas. Fruit symptoms are not usually seen unless the disease has built up to high levels on susceptible cultivars. Diseased fruit have a fine network type surface blemish called russetting.
Apple scab
Symptoms:
On leaves:
Velvety olive-green spots with unclear margin appear on the leaves. Later, the lesions enlarge, and become darker with more distinct margins. Heavily infected leaves become distorted and drops early in the summer.
On fruit:
Spots are similar to those found on leaves. Spots darken with age and become black and “corky” or “scabby”. Scabs are only skin deep. Cracks often develop on these scabby areas.