Chapter 5

Question 1

_____ 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.

Answer 1

Pathogens

Question 2

Most accurate diagnosis can of diseases can be provided by __________________ personnel

Answer 2

county and state extension

Question 3

______ 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.

Answer 3

Fungi

Question 4

_______________ 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

Answer 4

Fungicides

Question 5

_________ _________ includes avoiding over-irrigation, removing diseased plant parts, spacing plants correctly and using disease-resistant species or cultivars

Answer 5

Cultural Management

Question 6

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.

Answer 6

Leaf spots

Question 7

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.

Answer 7

spring, fall

Question 8

_______ _____ is the most serious disease of roses.

Answer 8

Black spot

Question 9

______ ______ 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

Answer 9

Apple scab

Question 10

_____ 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

Answer 10

rust

Question 11

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

Answer 11

2

Question 12

________ _______ 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

Answer 12

powdery mildew

Question 13

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

Answer 13

Fungicides

Question 14

_______ ______ 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.

Answer 14

Leaf Galls

Question 15

______ _______ 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.

Answer 15

Root Rot

Question 16

______ ______ caused by soil-inhabiting fungi, affect primarily herbaceous ornamentals such as chrysanthemum, geranium and petunias. Plants wilt initially, then become more wilted and die. Stems may be brown or black and shrunken at the soil line. Ornamental seedlings die of damping-off when stems and roots decay. The fungi causing ____ ____ can be spread in infected debris, on cuttings or when infected soil is moved. Apply fungicides in early spring

Answer 16

Stem Rot

Question 17

_________ are localized, diseased areas on trunks, stems and limbs of woody plants. Bark tissue shrinks and dies, then cracks open, exposing the wood underneath. _____ begin as small, discolored spots that sometimes appear water soaked. The spots enlarge and the centers become tan or gray. ______ can enlarge and girdle the stem, causing death to plant parts above the girldle. Infection usually begins in a wound or injury to the bark or wood. _____ should be pruned out. Fungicides can be applied after pruning. ____ also occur on branches of junipers and other evergreens affected with Phomopsis blight, which also causes death of foliage initially and then kills stems and branches

Answer 17

Cankers

Question 18

A common disease of ornamental fruit trees, _____ ______ begins as a swellings on small twigs. As the disease spreads, elgongated swollen areas appear on other limbs. Initially the _____ are greenish and soft, but later become black and very hard. All _____ should be removed and destroyed. Fungicides will help control.

Answer 18

Black Knot

Question 19

________ ______ are caused by fungi invading the water-conducting vessels of woody plants and restricting water flow. Infection can begin in roots as with Verticillium and mimosa wilt or in the upper branches as with Dutch elm disease. Often one side of the plant is first affected, causing individual limbs or branches to wilt and die back. Discolored streaks usually occur in the wood of infected branches. Fungicides provide little benefit. Severely infected trees, including roots should be removed. Use of resistant varieties is the best way to avoid problems

Answer 19

Vascular wilt

Question 20

___________ affect pines, causing spots or bands on needles. Other symptoms include girdling of needles, needle tip dieback and needle drop. Mature trees are rarely killed. Fungicide applications are usually not economical except for young trees.

Answer 20

Needlecasts

Question 21

_______ are single celled microorganisms that can be spread by wind, water, insects and tools. Infection often occurs when bacteria enter plant woundds or natural openings. Few __________ diseases can be controlled with chemical bacteriacides.

Answer 21

Bacteria

Question 22

Soft swelling of the roots or stems is the first symptom of ____ _____. The swelling will enlarge, becoming firmer and darker and the outer surface of the ____ becomes rough. After ____ have fully developed they decompose and release more bacteria that can reinfect the plan or infect new ones. Crown gall bacteria can survive in the soil for years in old, infected ____. Young trees and shrubs may be stunted or killed.

Answer 22

Crown Gall

Question 23

This disease can begine as a light green, water-soaked area that may later turn to brown and then to black. They are usually more irregularly-shaped than fungal leaf spots. The ____ ____ will appear soft and mushy in moist conditions, brittle in dry conditions. Tissue may fall from spots, forming a shothole-type symptom. Infected leaves may fall prematurely and become sources of bacteria the following year. Bacteria are usually spread in water. Encourage air movement among plants and keep foliage as dry as possible. Remove infected plant debris and reduce overhead irrigation. Use bacteriacides at bud break.

Answer 23

Bacterial leaf spot

Question 24

The most common bacterial blight is ____ ______, which is particularly destructive on apple, pear, flowering crab apple and pyracantha. Infection usually occurs in the spring when susceptible plants are in bloom; most damage occurs during long periods of cool, wet weather. It can be spread by insects that visit flowers, such as honeybees. Leaves and twigs have a dark discoloration; then sunken, discolored cankers may appear on limbs and branches. Blighted twigs have a scorched appearance. Because the bacterium overwinters in cankers, diseased branches should be pruned out. Bacteriacides are applied at blossom.

Answer 24

Fire Blight

Question 25

A disease of shade trees, leaf scorch causes premature leaf browning and drop in late summer. Leaf margins may become brown. Infected trees gradually decline. Leafhoppers are believed to transport the bacteria.

Answer 25

Bacterial leaf scorch

Question 26

_______ are extremely small particles that multipy only inside living cells. Symtoms produced are chlorosis, leaf scorch, mottling, ring spots and deformed growth. Infection occurs in wounds made by insects or by mechanical means. ______ of woody ornamentals are often spread by propagating diseased stock. Insects, tools, hands, and clothing can also spread viruses. Pesticides usually don’t control these diseases. Prevention may be obtained by controlling insect vectors and by practicing sanitation.

Answer 26

Viruses

Question 27

__________ are microscopic round worms with spear like mouth parts that live in the soil and feed on plant roots. _____ suck juices from plants. The injury to roots interferes with movement of minerals, nutrients, and water into plant tissues. Some feeding causes swelling of roots; some kill root tips. Above ground symptoms include wilting, yellowing, of foliage or stunting and a general decline of the plant. Symptoms may be confused with those produced by fungi. An assay of the roots or soil near the roots can determine if ______ are a problem

Answer 27

Nematodes