Grapes:Diagnostics

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GRAPE PESTS AND NUTRITIONAL DISORDERS



Contents

ANGULAR LEAF SPOT (MYCOSPHAERELLA ANGULATA)

‘‘‘Angular Leaf Spot (Mycosphaerella angulata) ‘‘‘ Lesions first appear on the adaxial leaf surface as small yellow flecks. As the lesions develop, a small, dark brown to black area appears in the center and is surrounded by a distinct halo. Halos are indistinct or absent on the abaxial leaf surface. Lesions become angular to irregular in shape and vary from one to several centimeters in diameter two months after infection. The dry areas appear papillate under magnification because of numerous tufts of conidiophores. Angular leaf spot can be controlled with applications of protective fungicides starting after bloom and repeated at 14-day intervals until late August. Muscadine cultivars vary in susceptibility to angular leaf spot. (Disease Caused by Fungi -- Leaf and Fruit)


ANTHRACNOSE (ELSINOE AMPELINA)

‘‘‘Anthracnose (Elsinoe ampelina) ‘‘‘ Anthracnose produces circular leaf lesions, with brown to black margins and round or angular edges. The lesions are often quite numerous and may either group together or remain isolated. The center of the lesions becomes grayish white and dries out. Young, green, succulent parts of the shoot are most susceptible to anthracnose. Lesions on shoots are small and isolated, with round or angular edges and have a violet-brown margin, which gradually becomes violet-black. The center of the lesions may extend to the pith of the shoot. The best form of control is to use resistant cultivars. During the growing season, foliar applications of fungicide are recommended at two-week intervals beginning when shoots are 5-10 cm long. (Disease Caused by Fungi -- Leaf and Fruit)


ARMILLARIA ROOT ROT (ARMILLARIA MELLEA)

‘‘‘Armillaria Root Rot (Armillaria mellea) ‘‘‘ Infected grapevines may die quickly and in the process show severe wilting. Infection may also result in a slow decline accompanied by lack of vigor, stunting, small, dark green leaves, and eventual death of the plant. Stunted plants may live through a season but frequently die during the dormant period. Leaves may lose their green color or wilt, and if so, they may show typical symptoms of sunburn. Positive identification of the fungus is made by scraping away the bark on the trunk, at or below the soil line, or on the larger roots. The fungus produces white mats between the bark and hardwood. Two fumigants, carbon bisulfide and methyl bromide, are used as controls with methyl bromide being the most effective. (Disease Caused by Fungi -- Wood and Root)


ASTEROID MOSAIC (AMV)

‘‘‘Asteroid Mosaic (AMV) ‘‘‘ Asteroid mosaic disease produces small, star-shaped spots in leaves of affected vines. The spots seem to result when tissues around a veinlet degenerate and the tissue in the center of the spot may be dry. Affected leaves are asymmetrical. (Minor Viruslike Disease)


BACTERIAL BLIGHT (XANTHOMONAS AMPELINA)

‘‘‘Bacterial Blight (Xanthomonas ampelina) ‘‘‘ The first symptoms on the young, tender shoots appear two or three weeks after the buds begin to grow. Longitudinal cracks develop, starting from the lower internodes and slowly extend upward and are surrounded by dark brown to black necrotic tissue, deepen, extend to the pith, and develop into cankers. In already contaminated vineyards, all infected branches and canes should be removed by pruning and burned, and all dead or severely infected plants should be uprooted and burned. (Disease Caused by Bacteria or Bacterial-like Organism)


BITTER ROT (GREENERIA UVICOLA)

‘‘‘Bitter Rot (Greeneria uvicola) ‘‘‘ The fungus usually invades a berry from the pedicel. Light-colored berries become brownish and often show concentric rings of acervuli and blue berries take on a roughened, sparkly appearance on the surface as the acervuli begin to develop. Within a couple of days, the berry softens and is easily detached and the bitter taste of the berry is most pronounced. Berries that do not shell continue to dry, become firmly attached, and are not as bitter in taste. When shriveled, the rotted berries look much like berries affected by black rot, ripe rot, or the fruit-infection stage of Phomopsis cane and leaf spot. Bitter rot is generally controlled by the fungicide sprays applied to control more serious diseases, and resistant cultivars. (Disease Caused by Fungi -- Leaf and Fruit)


BLACK DEAD ARM (BOTRYOSPHAERIA STEVENSII)

‘‘‘Black Dead Arm (Botryosphaeria stevensii) ‘‘‘ A mild yellowing may appear on leaves and if water transport becomes insufficient during the growing season, leaves wilt. Narrow black streaks develop in the xylem of infected spurs, arms, and trunks, but rarely in one year old canes. The streaks, initially 3-5 mm wide, expand toward the pith as well as longitudinally and laterally. Removal and destruction of diseased vine parts are recommended as a control. (Disease Caused by Fungi -- Wood and Root)


BLACK ROT (GUIGNARDIA BIDWELLII)

‘‘‘Black Rot (Guignardia bidwellii) ‘‘‘ Young leaf laminae, petioles, shoots, tendrils, and peduncles can be infected. The main symptom on leaves is the appearance of small, tan, circular spots on the lamina in spring and early summer beginning with a small, whitish dot. Lesions on peduncles and pedicels are small, darkened depressions, which soon turn black. Black rot of muscadine grapes can be effectively controlled by applying protective fungicides. (Disease Caused by Fungi -- Leaf and Fruit)


BORON

‘‘‘Boron: ‘‘‘ The first symptoms appear on tendrils near the shoot tip before bloom and dark, knotty bulges form and become dry. The distal portions of the plant dry up, and flower clusters die. During the period of rapid shoot growth, younger internodes swell slightly and the pith dries out. Leaves have short, thick petioles that sometime show longitudinal lesions or dry caverns and the blades have odd shapes and show interveinal yellowing or drying. (Nutritional Disorder)


BOTRYTIS BUNCH ROT AND BLIGHT (BOTRYOTINIA FUCKELIANA)

‘‘‘Botrytis Bunch Rot and Blight (Botryotinia fuckeliana) ‘‘‘ In early spring, buds and young shoots may be infected, turn brown, and dry out. At the end of the spring and before bloom, large, irregular, reddish brown, dry patches appear on a few leaves of a vine and are often localized on the edge of the lamina. Before bloom, the fungus may invade inflorescences, which rot or dry out and fall off. From ripening onward, the grapes are infected directly through the epidermis or through wounds and the mold progressively invades the entire cluster. The best form of control is resistant cultivars. Susceptible cultivars usually need to be protected against bunch rot by a combination of cultural practices and chemical control. Chemical control is usually necessary but can be conducted only with preventive treatments. (Disease Caused by Fungi -- Leaf and Fruit)


BUD MITE STRAIN

‘‘‘Bud Mite Strain: ‘‘‘ Common symptoms include short basal internodes, scarred epidermis of new shoots, flattened shoots, dead terminal buds on new shoots, witches-broom growth of new shoots, zigzagged shoots, and dread overwintering buds. Leaves are usually stunted and wrinkled, and the veins are prominent and drawn together.


CALCUIM

‘‘‘Calcium: ‘‘‘ Calcium deficiency appears occasionally on quartz gravel soils that are strongly acid. A narrow dry border appears at the margin of leaves and gradually moves toward the point of attachment of the petiole. Dark brown pimples may develop on the primary bark of the internodes. (Nutritional Disorder)


CERCOSPORA LEAF SPOT (PHAEORAMULARIA DISSILIENS)

‘‘‘Cercospora Leaf Spot (Phaeoramularia dissiliens) </b></S></CF> Cercospora leaf spot produces variable yellowish to dark spots. It has been reported from Pakistan through Asia Minor, Europe, and North Africa.


CHIMERAS

‘‘‘Chimeras: ‘‘‘ Variegation is a common chimera forming a mosaic pattern that spreads into new tissues and organs that develop from the point of mutation and the pattern may be separated from normal tissue by a distinct line or break in the color pattern within a single leaf. Fasciation is another common chimera characterized by shoots, petioles, or cluster pedicels that develop with a flattened shape rather than the normal roundish shape. Witches-broom is less common. All buds developing from the original mutation seem to grow a short time after they are initiated and develop into a bushy growth covering part of the vine. Other buds on the same vine produce normal growth. Individual shoots that do develop in the broomed tissues do not mature, and no fruit clusters develop on these shoots. Leaves are smaller and remain green longer in the fall than normal leaves. The fourth chimera has not been given a formal name. It is manifested chiefly as distorted growth of the leaves. Apparently only one of the two outer layers in a bud meristem mutates, which results in a mix of normal and affected tissue within the shoot that subsequently develops. The shoot appears to grow normally, but leaves are grossly misshapen and are smaller than normal leaves. Chimeras observed on young vines should be removed by pruning back to normal tissue. This does not affect fasciations, however. (Chimeras)


CITRUS NEMATODE (TYLENCHULUS SEMIPENETRANS)

‘‘‘Citrus Nematode (Tylenchulus semipenetrans) ‘‘‘ The main effect on roots is the death of feeder roots and the nematodes produce a profuse gelatinous substance to which soil particles cling. There are no control measures available at this time. (Nematode Parasites)


CLADOSPORIUM LEAF SPOT (CLADOSPORIUM VITICOLA)

‘‘‘Cladosporium Leaf Spot (Cladosporium viticola) </b></S></CF> Cladosporium leaf spot causes a leaf spot disease on older leaves of both wild and cultivated vines. The disease has been reported in Europe and in the eastern United States.

CORKY BARK

‘‘‘Corky Bark: ‘‘‘ In autumn, affected leaves become rolled and turn uniformly red or yellow, including tissues along the major veins. As buds on this cultivar break in the spring, shoots elongate rapidly but leaves on the shoots remain small, giving the vine a spindly appearance. Leaves that develop on the same shoots a few weeks later are normal in size, and as growth continues, the spindle shoot symptom disappears. In mid or late summer, leaves on affected vines of dark-fruited cultivars may turn yellow before they turn red, the wood at the base of the canes may swell slightly, and the bark may split. An effective control is the use of propagation stocks from disease-free mother vines. (Disease Caused by Viruses or Viruslike Agents)


CROWN GALL (AGROBACTERIUM TUMEFACIENS)

‘‘‘Crown Gall (Agrobacterium tumefaciens) </b></S></CF> This disease is characterized by fleshy galls developing on the lower trunk near the soil line, slightly below the soil surface, or aerial galls up to 1 meter above the soil line. These galls may girdle the young vines or appear as small, pimply galls on the vines. First season galls are white and appear in early summer near injured areas on the vines. Later in the season, these galls turn brown and become dry and corky. Dead galls may fall off the vine. The best form of control is to apply eradicant chemicals and avoid freezing weather.


DAGGER AND NEEDLE NEMATODES (XIPHINEMA SPP)

‘‘‘Dagger and Needle Nematodes (Xiphinema spp.) ‘‘‘ Most feeding takes place near root tips, and root growth stops soon after feeding begins. Proliferation and enlargement of cells often cause a bending accompanied by slight swelling. Multiple prolonged attacks can result in darkened, dry spots that spread over the entire root tip. Replant treatments with 1,3-dichloropropene or methyl bromide as described for root-knot nematodes have given good control and resulted in vigorous, productive vineyards. (Nematode Parasites)


DEMATOPHORA ROOT ROT (ROSELLINIA NECATRIX)

‘‘‘Dematophora Root Rot (Rosellinia necatrix) ‘‘‘ Infected plants may die very rapidly, may die slowly during one season, or may linger into a second year. The vines that linger frequently bear an excessively large crop the year before they die. Leaves remain attached to plants that die rapidly. On vines that decline gradually, tendrils and leaves are weak and stunted, wilting is common, and shoots may arise from the base. Dead vines can be pulled easily from the soil because of severe deterioration of the roots. The use of resistant rootstocks is the best form of control. (Disease Caused by Fungi -- Wood and Root)


DIPLODIA CANE DIEBACK AND BUNCH ROT (DIPLODIA NATALENSIS)

‘‘‘Diplodia Cane Dieback and Bunch Rot (Diplodia natalensis) ‘‘‘ Infected canes typically die back from the tip toward the base, starting in summer. Dead parts are brown to gray and are speckled with black dots. Cankers that form on canes at the base of a diseased cluster stem and also those in girdle wounds in canes and trunks may advance in any direction. To minimize inoculum, prune all diseased wood during pruning time, prune and train to prevent cluster clumping, remove prunings from the vineyard and destroy them, and do not cultivate or create dust in the vineyard during the time of bloom to shatter or when girdle wounds are open. (Disease Caused by Fungi -- Leaf and Fruit)


DOWNY MILDEW (PLASMOPARA VITICOLA)

‘‘‘Downy Mildew (Plasmopara viticola) ‘‘‘ The fungus attacks all green parts of the vine, particularly the leaves. Lesions develop on the leaves that are yellowish to reddish brown, oily, angular, and limited by the veins. Infected shoot tips thicken, curl, and become white when infested with spores and eventually turn brown and die. Similar symptoms are seen on petioles, tendrils, and young inflorescences, which, if attacked early enough, ultimately turn brown, dry up, and drop. The young berries are highly susceptible, appearing grayish when infected and covered with a downy felt of fungus sporulation. Fungicides are the most important control measure on susceptible cultivars grown in regions with high disease pressure. (Disease Caused by Fungi -- Leaf and Fruit)


DROUGHT

‘‘‘Drought: ‘‘‘ The first response of grapevines subjected to water stress is the shoots fail to elongate. Stressed plants are small, do not fill their trellis with leaves and tend to have loose clusters with small berries. Fruit set may be reduced on vines stressed before or soon after bloom. Under prolonged and severe drought conditions, basal leaves first show marginal drying and then become old and fall off. (Environmental Stress)


E. (CARPINI E. CARPINI)

‘‘‘CARPINI E. carpini: ‘‘‘ The injury it causes is similar to that caused by the Willamette spider mite in California.


EMPOASCA LEAFHOPPERS (EMPOASCA SPP)

‘‘‘Empoasca Leafhoppers (Empoasca spp.) ‘‘‘ Grape leaves injured by the potato leafhopper are spotted, with yellowed margins that roll or curl downward similar to leafroll and grapevine yellows. Yellow areas may become dry late in the growing season.


ERINEUM STRAIN

‘‘‘Erineum Strain: ‘‘‘ Erineum strain feeds on leaves and causes patches of concave, felty galls on the lower leaf surface, followed by blisterlike swellings on the upper surface. The galls are whitish at first, then yellow, and finally reddish brown.


ERYTHRONEURA LEAFHOPPERS (ERYTHRONEURA SPP)

‘‘‘Erythroneura Leafhoppers (Erythroneura spp.) ‘‘‘ Vine injury appears first as a white speckling on the upper leaf surface resembling virus infection. The speckling is at first limited to the areas along the main veins and later spreads over the leaf blade and turns a blotchy pale yellow or whitish yellow. Leaves may dry up and drop.


ESCA AND BLACK MEASLES

‘‘‘Esca and Black Measles: ‘‘‘ Foliage deterioration is the most obvious symptom. Symptoms appear after bloom, during summer or early autumn, beginning on leaves at the base of shoots and then spreading to all leaves which have yellowish or reddish patches. Large pruning wounds should be avoided and burning of dead vines is advisable. Where permitted, chemical control using a sodium arsenite drench is very effective. (Disease Caused by Fungi -- Wood and Root)


EUROPEAN RED MITES (PANONYCHUS ULMI)

‘‘‘European Red Mites (Panonychus ulmi) ‘‘‘ Injury is characterized by a fine speckling that appears at the base of leaves. The speckling develops into a bronze coloration that soon covers the entire leaf with symptoms resembling leafroll. Continued feeding by the pest may cause leaves to turn brown and fall.


EUTYPA DIEBACK (EUTYPA LATA)

‘‘‘Eutypa Dieback (Eutypa lata) ‘‘‘ The most readily recognized symptoms are deformation and discoloration of the shoots. The young leaves are smaller than normal, cupped, and yellow. They often develop small dry spots and tattered margins, sometimes with larger areas of drying, as they age. The fungicide benomyl provides a highly effective barrier against the invasion of pruning wounds by mycelia from germinating ascospores. (Disease Caused by Fungi -- Wood and Root)


EXCESS WATER

‘‘‘Excess Water: ‘‘‘ Prolonged flooding after growth begins kills roots by depriving them of soil oxygen. Vine growth is restricted, and plants often show symptoms of drought. Shoots on the excessively vigorous vines may fail to mature and may be killed by the first low temperature in fall or early winter. (Environmental Stress)


FALSE SPIDER MITES (BREVIPALPUS SPP)

‘‘‘False Spider Mites (Brevipalpus spp.) ‘‘‘ Complete dehydration and blackening of new shoot growth is common. Later, the mites are distributed on the rachis, branches, and pedicels of clusters, where dehydration results in darkened grooves that unite to form large lesions similar to several grape diseases such as Phomopsis cane and leaf spot and stem drying. The stems and berries may completely dehydrate. The foliate loses its green color a concentration of anthocyanins on the lamina of dark cultivars appear reddish.


FANLEAF DEGENERATION (GFLV)

‘‘‘Fanleaf Degeneration (GFLV) ‘‘‘ In the first syndrome, infectious malformations develop and leaves are variously and severely distorted, asymmetrical, and puckered and show acute dents. Yellow spotting may sometimes accompany foliar deformations. In the second syndrome, yellow mosaic, develops on affected vines and bright chrome yellow discolorations appear in the spring that may affect all vegetative parts of the vine. In the third syndrome, veinbanding and chrome yellow flecking is first localized along the main veins of mature leaves and then spreads a little way into the interveinal areas. Fruit set is poor, clusters are straggly, and the yield may be virtually zero. The best forms of control are resistant cultivars and fumigation for nematode vectors. (Disease Caused by Viruses or Viruslike Agents)


FLECK

‘‘‘Fleck: ‘‘‘ Fleck disease is characterized by yellow, translucent spots that usually appear in the third and fourth order veins of young and medium aged leaves. Leaves with numerous flecks are twisted and wrinkled. (Minor Viruslike Disease)


GRAPE ROOT ROT (ROESIERIA HYPOGAEA)

‘‘‘Grape Root Rot (Roesieria hypogaea) </b></S></CF> This disease is characterized by gradual decline in vigor, eventually causing vines to die. It is most associated with weakened vines growing in cold, wet soils. There are no control measures available at this time.


GRAPE RUST MITE (CALEPITRIMERUS VITIS)

‘‘‘Grape Rust Mite (Calepitrimerus vitis) ‘‘‘ Buds are killed, internodes are shortened, foliage becomes dense, and fruit production is reduced. Clusters are damaged when flowers are injured. Feeding on the surface of leaves of white grape cultivars causes a yellowing that closely resembles the appearance of leaves slightly injured by spider mites.


GRAPEVINE YELLOWS DISEASES (FLAVESCENCE DOREE)

‘‘‘Grapevine Yellows Diseases (Flavescence doree) ‘‘‘ The characteristic symptoms appear in the summer and the vine adopts a weeping posture and the shoots bend down as though made of rubber. The leaves harden, roll slightly abaxially, and tend to overlap, giving the shoot a characteristic snakelike appearance. The brittle leaves first become golden yellow in white cultivars and red in black cultivars on all parts most exposed to the sun. The best form of control is resistant cultivars if they are available. To control by insecticidal treatments, insecticides should be applied during the egg hatching period.


HAIL

‘‘‘Hail: ‘‘‘ Early in the season, hail may break shoots, leaves, or clusters and damage portions of the internode. Hail later in the season can cause tattered leaves and split fruit. Berries injured during the early stages of their development either abscise or shrivel and turn brown. (Environmental Stress)


HEAT

‘‘‘Heat: ‘‘‘ After exposure to damaging high temperatures, nonlignified portions of shoots wilt and discolor and the pith may dry and separate. Shoots then turn brown and dry up. Succulent tissues such as shoot tips, young leaves, and tendrils are most susceptible to heat injury. Berries are also damaged by excessive temperature, most often only on the top and western side of clusters exposed to the sun. (Environmental Stress)


IRON

‘‘‘Iron: ‘‘‘ Iron deficiency is especially common in regions with high-lime soils. The loss of chlorophyll starts between the small leaf veins and leaves may dry and fall and set may be reduced. Fading begins at the leaf margins but progresses interveinally. In cold, wet soils, transient iron deficiency symptoms may develop in the spring. (Nutritional Disorder)


LEAF BLIGHT (PSEUDOCERCOSPORA VITIS)

‘‘‘Leaf Blight (Pseudocercospora vitis) ‘‘‘ Spots are irregular to angular, sometimes with a serpentine outline. They are brown and group together with clearly defined borders on the upper leaf surface and diffuse margins on the lower leaf surface. Lesions soon become black and brittle and appear first on the lower, shaded leaves. (Disease Caused by Fungi -- Leaf)


LEAF BLOTCH (BRIOSIA AMPELOPHAGA)

‘‘‘Leaf Blotch (Briosia ampelophaga) ‘‘‘ Leaf lesions generally appear after mid-season and are small and have distinct, dark margins, while larger ones show distinct, light-colored zonate rings or arcs. Synnemata are produced within three or four days of the appearance of a lesion. (Disease Caused by Fungi -- Leaf)


LEAF CURL STRAIN

‘‘‘Leaf Curl Strain: ‘‘‘ Symptoms of the leaf curl strain appear in summer and include downward curling or rolling of leaves. The rolling ranges from slight to severe curling where the leaf tends to roll into a crude ball.


LEAFROLL

‘‘‘Leafroll: ‘‘‘ Affected plants are slightly smaller than healthy ones. In the spring, leaves on diseased and healthy vines appear similar, but as the season progresses, the diseased leaves turn yellowish or reddish, depending on the specific cultivar. By late summer, the leaves roll downward starting with leaves at the base of the shoot and the disease delays fruit ripening. The best form of control is to use disease-free vines. (Disease Caused by Viruses or Viruslike Agents)


LESION NEMATODES (PRATYLENCHUS SPP)

‘‘‘Lesion Nematodes (Pratylenchus spp.) ‘‘‘ Root symptoms are usually indicted by poor root development and many dead feeder roots. Occasionally rootlets are killed, as soon as or shortly after they are produced. There are specific control measures available for this disease. (Nematode Parasites)


LIGHTNING

‘‘‘Lightning: ‘‘‘ In some cases the only response is bronzing and drying of leaves, which resembles chemical burns. In other cases the entire vine or vine row can collapse and die. Evidence of lightning on the trellis or vine stakes, such as discolored wire or shattered vine posts or vine stakes, sometimes helps to confirm the diagnosis more than observations of the vines themselves. (Environmental Stress)


MACROPHOMA ROT (BOTRYOSPHAERIA DOTHIDEA)

‘‘‘Macrophoma Rot (Botryosphaeria dothidea) ‘‘‘ One or more circular, flat or slightly sunken lesions, 1-4 mm in diameter, develop on infected berries as they reach maturity. At first the lesions are black, with small tan or buff-colored centers in which pycnidia are embedded. A brown soft rot may develop from the primary lesions and spread over the entire berry in a susceptible cultivar. Affected berries drop from the vines, shrivel, and are finally reduced to dry, hollow shells with pycnidia scattered over the entire surface. The disease can be controlled by applying protective fungicides beginning after bloom and continuing throughout the fruit-ripening period and using resistant cultivars. (Disease Caused by Fungi -- Leaf and Fruit)


MAGNESIUM

‘‘‘Magnesium: ‘‘‘ Early in the season, leaf drying dominates the disease and during the summer and fall, interveinal yellowing is the major symptom. The first changes usually appear before bloom and may be small, brown-green spots near the margins and in the interveinal tissues of young, growing leaves. In early to late summer, a brightening of the tissue appears between the main veins and, with increasing yellowing, proceeds from the leaf margin toward the attachment of the petiole in the form of a wedge between the primary and secondary veins. (Nutritional Disorder)


MANGANESE

‘‘‘Manganese: ‘‘‘ In early summer the leaves at the base of shoots start as pale, small, yellow spots that appear in the interveinal tissue. The spots show a mosaic-like arrangement and are bordered by the smallest green veins. Only a very small seam along first and second order veins remains green. The symptoms are more severe on leaves exposed to the sun than on shaded leaves. (Nutritional Disorder)


NITROGEN

‘‘‘Nitrogen: ‘‘‘ When nitrogen is deficient, vine foliage turns pale green and then yellow. Shoot growth is greatly reduced and young shoots, petioles, and cluster stems become pink or red. . Excess nitrogen increases growth, internodes become long and large, and leaf blades become deep green, thick, and sometimes cupped. Shoot growth may be excessive and prolonged. (Nutritional Disorder)


OLIGONYCHUS VITIS

‘‘‘VITIS O. vitis: ‘‘‘ This disease characteristically infests upper leaf surfaces, causing heavy bronzing in late summer and early defoliation of some cultivars.


PEACH ROSETTE MOSAIC VIRUS DECLINE (PRMV)

‘‘‘Peach Rosette Mosaic Virus Decline (PRMV) ‘‘‘ The usual symptom in older vineyards is a circular pattern of missing or dead vines. Infected vines usually exhibit an umbrella-like growth habit due to shortened and crooked shoot internodes. Leaves are commonly deformed. The most efficient control is to have the soil tested for nematodes. (Disease Caused by Viruses or Viruslike Agents)


PHOMPSIS CANE AND LEAF SPOT (PHOMOPSIS VITICOLA)

‘‘‘Phompsis Cane and Leaf Spot (Phomopsis viticola) ‘‘‘ Infected leaf blades have small, light green or yellow, irregular to circular spots with dark centers and may be puckered along veins near the perimeter, or the margin may be turned under. Dark brown to black dry spots may also occur along primary and secondary leaf veins and on petioles. Infected young shoots, cluster stems, and petioles have yellow spots with dark centers. Two applications of a protective chemical, such as captan, folpet, and maneb are generally recommended, the first when the shoots are 1-3 cm long and the second when the shoots average 6-12 cm long. (Disease Caused by Fungi -- Leaf and Fruit)


PHOSPHORUS

‘‘‘Phosphorus: ‘‘‘ Plants suffering for phosphorus deficiency have little shoot and root growth and the leaves are small and dark green. Leaf margins turn down without rolling. Under severe deficiency, leaves develop red, punctiform spots. (Nutritional Disorder)


PHYLLOXERA: FOLIAR FORM

‘‘‘Foliar Form: ‘‘‘ Foliar phylloxera causes conspicuous spherical galls that protrude on the lower surface of leaves that may even gall young shoots and tendrils.


PHYLLOXERA: ROOT FORM

‘‘‘Root Form: ‘‘‘ Shoot growth and grape production are greatly reduced as population densities become high and water stress is encountered in midsummer.


PHYMATOTRICHUM ROOT ROT (PHYMATOTRICHUM OMNIVORUM)

‘‘‘Phymatotrichum Root Rot (Phymatotrichum omnivorum) ‘‘‘ Affected vines may suddenly wilt and die during early summer or midsummer. Leaves of the vines are rapidly killed and become brown, brittle and remain rigidly attached to the dead plant. Before wilting, leaves on some infected vines may gradually turn yellow or red, with interveinal yellow spots and irregular dry areas on the leaf blade and margins. Shoot growth is reduced and leaves are dull green. The best control is to avoid planting in infested soil by mapping the areas where plants of susceptible crop like alfalfa or cotton show symptoms and use only pathogen-free material. (Disease Caused by Fungi -- Wood and Root)


PHYTOPHTHORA CROWN AND ROOT ROT (PHYTOPHTHORA SPP)

‘‘‘Phytophthora Crown and Root Rot (Phytophthora spp.) ‘‘‘ Affected vines are smaller than nearby healthy plants and appear stressed with yellow leaves. A canker develops near the soil line and usually extends downward to the roots but may also extend a short distance upward. Cutting through the canker with a knife reveals dry, brown bark that blackens as the tissue decays. (Disease Caused by Fungi -- Wood and Root)


PIERCE'S DISEASE (XYLELLA FASTIDIOSA)

‘‘‘Pierce's Disease (Xylella fastidiosa) ‘‘‘ Yellow spots develop on leaf blades near the point of initial infections and over time, the discoloration intensifies, the surrounding tissues begin to wither and dry, and the spots gradually enlarge. Starting near the margin of the leaf blade, tissues become completely desiccated and die. Symptoms develop in adjacent leaves along the shoot both above and below the point of initial infection. The use of resistant cultivars is the only effective control. (Disease Caused by Bacteria or Bacterial-like Organism)


POTASSUIM

‘‘‘Potassium: ‘‘‘ During the early part of the growing season, the leaves lighten in color and a few dry spots appear along the margin of young blades. During dry weather, drying spots varying in form, number, and size develop sporadically in the interveinal tissue. Leaf margins dry and roll up or down, and blades become distorted and ruffled. In late summer, the surface of older leaves at the base of shoots, receiving direct sunlight, becomes violet brown to dark brown, especially near the clusters. (Nutritional Disorder)


POWDERY MILDEW (UNCINULA NECATOR)

‘‘‘Powdery Mildew (Uncinula necator) ‘‘‘ The powdery mildew fungus can infect all green tissues of the grapevine. Once the plants become infected, the tissues become brittle and may break as the season progresses. When green shoots are infected, the affected tissues appear dark brown to black in feathery patches, which later appear reddish brown on the surface of the dormant canes. The best form of control is to apply fungicides. (Disease Caused by Fungi -- Leaf and Fruit)


RIPE ROT (COLLETOTRICHUM GLOEOSPORIOIDES)

‘‘‘Ripe Rot (Colletotrichum gloeosporioides) </b></S></CF> This disease is characterized by fruit rotting on the vine at harvest. Salmon colored spores develop into reddish brown spots of decay on the berries. The berries shrivel and drop off the vine as the rotting progresses. The best form of control is to apply fungicides to green berries during the fruit ripening period.

ROOT-KNOT NEMATODES (MELOIDOGYNE SPP)

‘‘‘Root-Knot Nematodes (Meloidogyne spp.) ‘‘‘ The distinctive response of grape roots to root-knot nematodes is the production of small swellings or galls on young feeder roots or secondary rootlets. When the galls are broken apart, the tiny, glistening, white bodies of mature females can often be detected with the aid of a hand lens. Growers should use certified nematode-free rootings. (Nematode Parasites)


ROTBRENNER (PSEUDOPEZICULA TRACHEIPHILA)

‘‘‘Rotbrenner (Pseudopezicula tracheiphila) ‘‘‘ Lesions on leaves are initially yellow on white-fruited cultivars and bright red to reddish brown on red and black fruited cultivars. The center of the lesion then dries and becomes reddish brown leaving only a thin margin of yellow or red tissue between the drying and green areas of the leaf. Effective fungicides are the best form of control. (Disease Caused by Fungi -- Leaf and Fruit)


RUPESTRIS STEM PITTING

‘‘‘Rupestris Stem Pitting: ‘‘‘ The disease causes a slow decline of the plants and after several years of infection affected vines are considerably smaller than healthy ones. The leaves on affected vines do not become yellow or red like those on vines affected by leafroll or corky bark. The best form of control is to use certified propagation materials. (Disease Caused by Viruses or Viruslike Agents)


RUST (PHYSOPELLA AMPELOPSIDIS)

‘‘‘Rust (Physopella ampelopsidis) ‘‘‘ Small, yellowing pustules of uredia, either scattered or densely distributed, appear on the lower leaf surface and occasionally on petioles, young shoots, and rachises. On some cultivars, brown dry spots develop on the upper leaf surface opposite the uredial pustules on mature leaves. Fungicides are the best from of control. (Disease Caused by Fungi -- Leaf and Fruit)


SALT TOXICITY

‘‘‘Salt Toxicity: ‘‘‘ Vines growing in a saline environment may show injury from chloride toxicity. The primary symptom is marginal drying of mature leaves. (Environmental Stress)


SAURESCHADEN

‘‘‘Saureschaden: ‘‘‘ Shortly after the plant blooms the margins of older leaves turn yellow or light brown and brown spots develop along the margin. These spots group together into larger, elongated, rust brown areas with irregular outlines. Red cultivars may have bright red spots. (Nutritional Disorder)


SEPTORIA LEAF SPOT (SEPTORIA AMPELINA)

‘‘‘Septoria Leaf Spot (Septoria ampelina) ‘‘‘ Few to many reddish brown to black spots with thickened margins appear on the leaves usually after the mid-season. If there are several spots on a leaf, the surrounding area may become yellow. (Disease Caused by Fungi -- Leaf)


SHARPSHOOTER LEAFHOPPERS (CICADELLIDAE SPP)

‘‘‘Sharpshooter Leafhoppers (Cicadellidae spp.) ‘‘‘ Feeding by sharpshooters on leaves and cluster stems results in wilting and eventual drying of the affected parts.


SHOOT NECROSIS

‘‘‘Shoot Necrosis: ‘‘‘ Symptoms are small, brownish spots and depressed striations, which develop early in the season at the base of very young shoots. These may expand and group together, causing extensive drying and splitting of the cortex and death of the shoots. Leaves are pale in the spring. (Minor Viruslike Disease)


SPRING FREEZE

‘‘‘Spring Freeze: ‘‘‘ The younger, more succulent tissues are most susceptible to injury from spring freezes. Soon after thawing, frozen tissue collapses and turns brown. Cold injury in the spring can cause malformation of tissues. (Environmental Stress)


STEM NECROSIS

‘‘‘Stem Necrosis: ‘‘‘ Shortly after color change, shallow, elongated, brown to black dry areas appear on the rachis and its branches on vines with stem drying. (Nutritional Disorder)


T. (MCDANIELI T. MCDANIELI)

‘‘‘MCDANIELI T. mcdanieli: ‘‘‘ Young tissues are affected and become yellow with some diffused grayness and drying and young leaves show cupping and drying of the raised margins. Summer injury resembles leafroll.


TAR SPOT (RHYTISMA VITIS)

‘‘‘Tar Spot (Rhytisma vitis) </b></S></CF> Tar spot produces a black spot 2-4 mm in diameter, with or without a circular brown halo up to 1 cm in diameter.


TOMATO RINGSPOT VIRUS DECLINE (TRSV)

‘‘‘Tomato Ringspot Virus Decline (TRSV) ‘‘‘ During the first year of infection, plants produce normal growth except for a few shoots that may have leaves that are spotted and have distinct oak leaf patterns. The disease is much more evident in the second year. New growth is generally weak and sparse because many infected buds are killed or injured by low winter temperatures. Shoots are short, with distinctly shortened internodes, distorted leaves, and a leaf area only one-third the normal size. Berries on fruit clusters are sparse and develop unevenly resulting in a reduction in yield. The disease can be controlled using resistant cultivars or rootstocks and keeping vineyards free of weeds. (Disease Caused by Viruses or Viruslike Agents)


TREEHOPPERS

‘‘‘Treehoppers: ‘‘‘ The treehoppers injure grapevines by feeding directly and depositing eggs on the shoot. Shoots fed upon by the buffalo treehopper show a brownish girdling involving the epidermis and cortex and a thick, red or yellow, downward rolling of the leaves away from the girdle.


TWOSPOTTED SPIDER MITE

‘‘‘Twospotted Spider Mite: ‘‘‘ The first symptoms of attack are yellow spots caused by feeding on lower leaf surfaces where dense colonies thrive. Later, defoliation is likely to affect berry maturation and quality. Twospotted mites also attack berries, producing dark spots on the skin.


VEIN MOSAIC

‘‘‘Vein Mosaic: ‘‘‘ The best indicator for vein mosaic is a pale green mosaic affecting mostly the leaf tissue adjacent to the major veins and in some cases the tissues tend to become dry. Although foliar symptoms are not severe, the disease adversely affects plant growth, reducing both root and shoot growth. (Minor Viruslike Disease)


VERTICILLIUM WILT (VERTICILLIUM DAHLIAE)

‘‘‘Verticillium Wilt (Verticillium dahliae) ‘‘‘ In the early part of the growing season, infected vines do not show symptoms, but as temperatures rise and soil moisture declines, a few shoots start to die and the vascular elements in the wood of these shoots become discolored. By early summer the leaves on declining shoots wilt and show marginal burning. By midsummer many shoots that had developed normally during the early season collapse completely. The leaves on these shoots dry out, and some may drop from the vine. There are no control measures available for the disease. (Disease Caused by Fungi -- Wood and Root)


WHITE ROT (CONIELLA DIPLODIELLA)

‘‘‘White Rot (Coniella diplodiella) </b></S></CF> This disease is characterized by small, brownish purple spots developing on berries that have lost their turgidity. As the lesions mature, they become grayish white. Typically the disease affects clusters of berries, rather than individuals. As the disease begins to spread, newly infected berries take on a pinkish blue color and become wrinkled. As the season progresses, infected berries fall to the ground. The best forms of control include minimizing wounds caused by insects and other diseases and keep the grapes as high above the ground as possible. Some fungicides are effective against the disease.


WILLAMETTE AND PACIFIC SPIDER MITES

‘‘‘Willamette and Pacific Spider Mites: ‘‘‘ Plants infected with Willamette and Pacific Spider Mites have yellow, cupped foliage, a bronze discoloration, and heavy webbing. Pacific spider mite injury in vineyards is spotty and tends to occur on weaker vines or in water-stressed areas. Both Pacific and Willamette spider mite populations are favored by dusty vineyard conditions.


WIND AND SAND

‘‘‘Wind and Sand: ‘‘‘ Vines subjected to high winds may have broken shoots, which results in unusual branching patterns. When strong winds blow late in the season, fruit may be injured and may become prone to bunch rot. Blowing sand can cause fewer shoots, stunted growth, partial defoliation, and/or malformed leaves. (Environmental Stress)


YELLOW SPECKLE

‘‘‘Yellow Speckle: ‘‘‘ The symptoms are ephemeral, consisting of a few to several spots on leaves and are most evident at the end of the summer. (Minor Viruslike Disease)


ZINC

‘‘‘Zinc: ‘‘‘ The first symptoms of zinc deficiency are small leaf blades with opened petiolar sinuses and sharp teeth. The leaf blades are commonly asymmetric with one half of the leaf being larger than the other. The interveinal areas turn light green to yellow in a mosaic pattern and can become reddish in black and red cultivars. The leaf veins also become clear, with narrow green borders. (Nutritional Disorder)


ZONATE LEAF SPOT (CRISTULARIELLA MORICOLA)

‘‘‘Zonate Leaf Spot (Cristulariella moricola) ‘‘‘ The generally circular lesions of zonate leaf spot may appear at any time during the growing season following several days of high humidity. The central portion of older lesions tends to disintegrate, leaving a hole in the leaf. (Disease Caused by Fungi -- Leaf)