Chapter 5 Flashcards
Diseases of Ornamental Plants
_____ capable of causing diseases of ornamental plants include bacteria, fungi, nematodes, and viruses. Adverse growing conditionsor environmental factors, however, produce symptoms similiar to those of plant diseases.
Pathogens
Most accurate diagnosis can of diseases can be provided by __________________ personnel
county and state extension
______ are multicelled microbes that feed on living or dead organic matter. They cause most of the diseases affecting ornamental plants. _______ spores can be spread from plant to to plant vy wind, water, insects and tools. Spores need adequate moisture and correct air temperature to begin an infection.
Fungi
_______________ can be used to prevent a disease or to slow the spread of an established disease. Cultural management includes avoiding over irrigation, removing diseased plant parts, spacing plants correctly and using disease-resistant species or cultivars
Fungicides
_________ _________ includes avoiding over-irrigation, removing diseased plant parts, spacing plants correctly and using disease-resistant species or cultivars
Cultural Management
Fungal ____ ______ usually appear as definite spots of varying sizes, shapes and colors. They have distinct margins and sometimes are surrounded by a yellow halo. Sports or dead areas may enlarge to cover an entire leaf. Leaves may yellow, die, and drop. Leaf spots usually appear first on lower leaves and progress up the plant. A pinhead-sized structure or a moldy growth of spores appears in the center of many spots.
Leaf spots
Leaf spots are more common in the early _____ and _____ when more moisture is present. Infected, fallen leaves can harbor spores, even during the winter, which may infect healthy plants. Leaf spots occur on almost all ornamental plants.
spring, fall
_______ _____ is the most serious disease of roses.
Black spot
______ ______ affects both leaves and fruit of apple, crab apple and related plants. Leaf blights affect plants similiarly, but usually produce longer, more irregularly shaped diseased areas. Dogwood anthracnose can begin as a leaf spot that may develop to a leaf blight, then progress to twigs and branches causing dieback and even death. Anthracnose disease is also common and potentially severe on sycamore
Apple scab
_____ produce spots called postules, which are similiar in appearance to leaf spots. Pustules may be on the upper and/or lower leaf surfaces and can be brown, reddish brown, orange or yellow. They are usually raised above the leaf surface and rubbing the affected area will leave a dusty ____ color, caused by spores on the fingers. Twigs, branches and fruit may also be attacked. Wind can transport spores from diseased to healthy plants
rust
Rust diseases have very complicated life cycles often involving _______ seperate hosts to complete the life cycle. Removal of either one of the hosts can break the cycle. Cedar apple rust causes galls on red cedar and related plants and leaf spots on apples
2
________ _______ appears as a white or gray growth on leaves, stems, buds, or flowers. Young shoots and leaves may be twisted and distorted and damge to flower buds may result in misshapened flowers. Airborne spores infect plants at moderate termperatures (60-90 degrees F) Temperatures greater than 90 degrees often inhibit fungal growth. Cool nighttime temperatures, high relative humidity and succulent, abundant growth resulting from high nitrogen fertilization favor ______ ______ development
powdery mildew
Many herbaceous and woody ornamentals are affected by powdery mildew. such as crepe myrtle, common lilac, rose, crab apple, begonia and zinnias. __________ should be applied as soon as mildew is detected. Cultural control methods include using disease resistant cultivars, preventing leaf wetness, avoiding extreme nitrogen fertilization and spacing plants to encourage air movement
Fungicides
_______ ______ are found on many woody ornamentals, especially azalea and camelia. They become apparent on new growth in the spring when part of the leaf becomes distorted with a pale green, pink or white thickening. Later, in humid weather, they become covered with a white powdery growth (spores). Then they shrivel, turn brown and hard and fall to the ground. Plant vigor can be affected and dropped vegetation can contain viable spores. To reduce incidence, remove ______ as soon as they appear, remove dead infected plant material, even from the ground, and encourage air circulation around plants. Apply fungicides at bud break.
Leaf Galls
______ _______ usually occurs in areas of excess soil moisture. Symptoms first appear as a gradual loss of vigor and leaf yellowing or wilting. Plants with extensive damage decline and die during dry periods. Diseased roots appear decayed, brown to black in color and may be mushy or spongy. Buy healthy stock and plant in well-drained areas. Fungicide drenches are NOT recommended.
Root Rot