Grape Dead Arm Info: Tips For Grape Dead Arm Treatment

Grape Dead Arm Info: Tips For Grape Dead Arm Treatment

Dead arm is the name of a grapevine disease that has all but been phased out, since it was discovered that what was thought to be one disease was, in fact, two. It is now commonly accepted that these two diseases should be diagnosed and treated separately, but since the name “dead arm” still comes up in literature, we will examine it here. Keep reading to learn more about recognizing and treating dead arm in grapes.

Grape Dead Arm Info

What is grape dead arm? For about 60 years, grape dead arm was a widely recognized and classified disease known to affect grapevines. Then, in 1976, scientists discovered that what had always been thought to be a single disease with two distinct sets of symptoms was, in fact, two different diseases that almost always appeared at the same time.

One of these diseases, Phomopsis cane and leaf spot, is caused by the fungus Phomopsis viticola. The other, called Eutypa dieback, is caused by the fungus Eutypa lata. Each has its own distinct set of symptoms.

Grape Dead Arm Symptoms

Phomopsis cane and leaf spot is usually one of the first diseases to appear in the vineyard’s growing season. It manifests as small, reddish spots on new shoots, which grow and run together, forming large black lesions that can crack and cause the stems to break off. Leaves develop yellow and brown spots. Eventually, fruit will rot and drop off.

Eutypa dieback usually shows itself as lesions in the wood, often at pruning sites. The lesions develop under the bark and may be hard to notice, but they tend to cause a flat area in the bark. If the bark is peeled back, sharply defined, darkly colored lesions in the wood can be seen.

Eventually (sometimes not until three years after infection), the growth beyond the canker will begin to show symptoms. This includes stunted shoot growth, and small, yellowed, cupped leaves. These symptoms may disappear in midsummer, but the fungus remains and the growth beyond the canker will die.

Grape Dead Arm Treatment

Both diseases that cause dead arm in grapes can be treated by application of fungicide and careful pruning.

When pruning vines, remove and burn all dead and diseased wood. Leave only obviously healthy branches. Apply fungicide in the spring.

When planting new vines, choose sites that receive full sunlight and lots of wind. Good airflow and direct sunlight go a long way in preventing the spread of fungus.


How to Manage Pests

Grape

Phomopsis Cane and Leafspot

Pathogen: Phomopsis viticola (sexual stage: Diaporthe ampelina)

(Reviewed 12/14 , corrected 12/16 )

SYMPTOMS

Phomopsis cane and leafspot appears as tiny dark spots with yellowish margins on leaf blades and veins. Spots first show 3 to 4 weeks following rain. Leaf death may occur if large numbers of spots build up. Basal leaves with heavy infection become distorted and usually never develop to full size. On shoots, small spots with black centers similar to those found on leaves occur usually on a basal portion of the shoot. After spots lengthen a few millimeters, the epidermal layers of the shoots usually crack at the point of infection. Heavy infection usually results in a scabby appearance of the basal portions of the shoot. On clusters, spots similar to those that occur on shoots occur on the flower cluster stems.

Lesions on leaves, shoots, and clusters become inactive during the summer heat but rain just before harvest can cause light brown spots on clean berries and spots quickly enlarge and become dark brown. Berries may shrivel and become mummified. Infected canes appear bleached during the dormant season. Severely affected canes or spurs exhibit an irregular dark brown to black discoloration intermixed with whitish bleached areas. The black specks visible in the bleached areas are pycnidia that develop during the dormant season.

Diaporthe ampelina can also be a trunk disease pathogen causing perennial wood cankers, lack of spring growth, and dead spurs and cordons. For more information on management practices for this disease see the EUTYPA DIEBACK section.

COMMENTS ON THE DISEASE

Because moisture is required for infection, this disease is most severe in northern grape-growing regions (North Coast and northern San Joaquin Valley) where spring rains are common after budbreak. Infections generally occur when shoots begin to grow. Spores are released in large quantities from the overwintering pycnidia on diseased canes and spurs. These are splashed by rain onto early developing shoots and infection occurs when free moisture remains on the unprotected green tissue for many hours.

MANAGEMENT

Spur and cane lesions provide the inoculum for new infections. Reducing the source of the disease is important. Look for presence of lesions on spurs and canes in areas in the vineyard exhibiting poor budbreak. A treatment of liquid lime sulfur at 10 gallons per acre in 100 gallons of water before rainfall in winter will reduce the viability of pycnidia as well as reduce overwintering Botrytis sclerotia and powdery mildew spores.

In all areas where the disease is prevalent, spring foliar treatments are advisable if rainfall is predicted after budbreak. Apply materials before the first rain after budbreakand before 0.5 inch shoot length (and again when shoots are 5 to 6 inches in length). Contact materials such as ziram, and mancozeb must be reapplied after significant rainfall in order to protect shoots up to 18 inches in length. If several rains are predicted, use systemic fungicides such as kresoxim-methyl.

PUBLICATION

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448

Diseases

R. J. Smith, UC Cooperative Extension, Sonoma County
L. J. Bettiga, UC Cooperative Extension, Monterey County
W. D. Gubler, Plant Pathology, UC Davis

Acknowledgment for contributions to Diseases:

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2017 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California


Main diseases

Grapevine fanleaf virus:

The plants have under-developed sprouts, with short inter-knots, placed in a zig-zag form. The plant also has a dense aspect due to the chaotic sprout growth. The leaves are under-developed, deformed and have a fan aspect. Sometimes, on the affected organs, greasy spots appear, which give the plant a mosaic aspect. If the attack is severe, the grapes remain small and don’t reach maturity. The virus is transmitted through grafting, through root contact and nematodes.

Prevention and control measures:

  • Using healthy planting material
  • Preventing soil nematodes. Products to be used: Basamid, Nemasol

Grapevine vein mosaic virus:

This disease’s characteristic symptoms are main veins turning yellow. Therefore, the leaf will have a mosaic aspect. The plant’s growth is not affected. This disease spreads only through grafting and layering.

Prevention and control measures:

  • Using healthy planting material

Grapevein leaf roll virus:

The plants which have been attacked by this disease have their growing pace severely slowed down. The red grape species have red leaves and the white grape species have yellow leaves as a result of the disease. As the disease evolves, the leaves twist alongside the veins. As autumn approaches, the affected leaves intensify their specific colors (red or yellow). After the attack, the production decreases both in quantity and quality and the plants are sensitive to frost. The virus is transmitted through the European fruit lecanium and through the infected vegetal material.

Prevention and control measures:

  • Using healthy planting material
  • Removing the affected plants from the crop

Mycoplasma infections:

Mycoplasma like organism:

The symptoms can be seen on a few sprouts. The leaves of the affected sprouts turn yellow, either partially or totally and have a specific metallic color. The attack is followed by a twist and fall off of the leaves. After the attack, the sprouts are sensitive to frost, the grapes no longer grow as they should and they have a low sugar quantity. This disease is transmitted through cicadas (Scaphoideus littoralis).

Prevention and control measures:

  • Burning the affected plants
  • Applying pesticides to keep the cicadas population under control

Crown Gall Disease, caused by Agrobacterium radiobacter pv. tumefaciens:

When attacking the grape vine, this disease affects the trunk and cordons of the plant and rarely, the roots. Big and specific tumors grow on the trunk, small and coral shaped little tumors grow on the cordons.

Prevention and control measures:

  • Using healthy planting material
  • Avoid causing any wounds when performing maintenance works
  • Bathing the cuttings’ roots in a mixture of Captan 0.2 % or Zeama bordeleza 1 % for 15-20 minutes
  • Cutting off the affected parts and applying a cicatrizing mastic
  • During early spring, applying a treatment using Zeama Bordeleza 2-3 % or copper based products. Products to be used: Champ, Copernico Hi-Bio, Funguran

Downy Mildew of Grape, caused by Plasmopara viticola:

This disease affects all the plant’s organs. During spring, greasy spots with vague margins and varied sizes appear. As times passes, the spots turn brown and the leaves look burned. On the inferior side of the leaves, next to the spots, a white fluff appears. During autumn, the plants are more resilient to the attack of this disease. Therefore, small and pointy spots can be seen on the leaves, next to which, the tissues turn brown. During this period, the white fluff no longer appears on the inferior side of the leaves. On the sprouts, the fungus produces brown, elongated spots, next to which the bark dies. The grape bunches remain small, the fruit no longer mature as they should, they become wrinkled and easily fall off. The fungus spends the winter as resistance spores, which will germinate during spring and will cause infection spots. This gets into the plants through stomates and cause new infections.

Prevention and control measures:

  • Gathering and burning the leaves from the crop
  • Destroying the crops
  • Performing the needed maintenance works on time
  • 3-4 treatments, using Folpan, Equation Pro, Curzate Manox, Polyram, Aliette

Powdery Mildew of Grape, caused by Uncinula necator:

This fungus affects the leaves, young springs, bunches and fruit. On the leaves, the attack is visible as white to gray, felt looking like spots, which are either isolated or united, where a white and smooth powder appears. The sprouts are covered by a white to gray mycelium, which turns gray as it evolves. The fruit attack is frequent and damaging, similar to the attack on the leaves and sprouts. During a dry season, the fruit break open and the bunches are destroyed. During moist days, the affected fruit become covered by a gray mold. As autumn approaches, on the infected organs, black, small appear, which represent the fungus’ resistance fruition. This disease normally attacks during hot and dry period of times.

Prevention and control measures:

  • Planting resilient species
  • Balanced fertilizing
  • Performing the needed maintenance work (cutting, putting together, etc.)
  • Cutting off or burning the affected sprouts
  • Chemical treatments, using Folicur Solo, Topas, Karathane, Shavit, Thiovit Jet

Anthracnose on grape, caused by Elsione ampelina:

This disease affects the plants during spring, before the downy mildew and it affects all the green orangs of the plant. Small, pointy spots appear on the leaves, next to which the tissues turn brown. As the disease evolves and the affected areas become torn apart, the leaves will look pierced. Big, brown spots, margined by a dark cherry red halo appear. After the attack, the sprouts no longer grow and they are fragile. The fungus spends the winter on the bark of sprouts. The attack of the fruit is really damaging. The fruits become dry and wrinkled during a dry period and during a wet period, they rot.

Prevention and control measures:

  • Only healthy cuttings need to be used
  • During the vegetative break or during spring, treatments with Zeama Bordeleza 3 % need to be applied
  • Chemical treatments to be applied during the vegetative period, using: Captan, Thiovit Jet, Funguran, Champ

White Root Rot, caused by Rosellinia necatrix:

The affected plants no longer develop as they should, their leaves turn yellow, the sprouts don’t grow and are affected by the blizzards. In 2-3 years from the first symptoms, the plant dies. If you look at the root, a white mycelium can be seen. This makes its way into the marrow and destroys the bark of the roots. This disease is frequent on the clay and moist soils and it spends the winter as sclerotium inside the soil or on the affected roots.

Prevention and control measures:

  • Taking out the affected plants from the crop
  • The roots of the cuttings need to be bathed before planting in a Zeama Bordeleza 2% mixture

Dead Arm of Grape Vine, caused by Eutypa lata:

This disease affects all the organs from the plant’s shoot system. The affected plants grow slowly, have short sprouts or inter-knots, small and twisted leaves. The inflorescences no longer grow normally, the flowers abort. If the attack is severe, the stem will have deep cracks. The disease is transmitted through spores which get into the plant through different wounds resulted from maintenance works. This is not a dangerous disease. This disease is specific only to untidy crops, where no phytosanitary treatments were applied.

Rotbrenner (Red Fire), caused by Pseudopeziza tracheiphila:

The symptoms of this disease are visible on the leaves. The attack occurs during spring or at the beginning of the summer and it can be recognized as big, yellow or yellow-purple spots, located on the edges on the limb. The tissues burn brown, starting with the center of the spots, the leaves look burned. After the attack, the plant prematurely loses its leaves. The photosynthesis capacity is reduced, the bunches have small fruits which will never grow. The fungus spends the winter on the affected leaves from the surface of the soil.

Prevention and control measures:

  • Burning the leaves from the surface of the soil
  • Balanced fertilizing and using complex composts
  • Performing the needed maintenance works (binding, cutting, etc.)
  • Treatments used against the downy mildew can also be used to prevent and treat this disease

Grey Mold Rot, caused by Botryotinia fuckeliana:

This fungus aggressively grows during rainy autumn seasons. The representative attack can be seen during autumn on the leaves, after the leaves have stored enough sugar. After the attack the skin turns brown and the berries break open. As the disease evolves, the fruits will get covered by a grey mold. If the weather is rainy, the fruit become dried and wrinkled.

Prevention and control measures:

  • The grapes need to be harvested later than usual if the plant is attacked by this fungus
  • Cutting the leaves around the grape branches to increase the air circulation
  • Chemical treatments, using Bravo 500 SC, Ortiva 250 SC, Rovral 500 SC, Teldor 500 SC, Switch 62.5 WG

False Turkey Tail, caused by Stereum hirsutum:

The first symptoms can be seen once the first inflorescences appear. The base leaves turn yellow (for the white grape species) or red (for the red species). As the disease evolves, the affected tissues turn brown, become united and the plant foliage is destroyed. This disease is favored by high temperatures and drought. The affected trunks will be completely dried out within few hours. When the weather is moist, the fungus’ fruitions appear on the affected trunks, with a hat shaped fan. The fungus spends the winter as a mycelium in the bark of the old cordons and it makes its way into the plant using the wounds resulted from cuts.

Prevention and control measures:

  • Taking out the affected plants from the crop
  • Applying a cooper based treatment during the vegetation period. Products to be used: Champ, Funguran, Melody Compact
  • During the vegetation, treatments using Verita or Mikal Flash

Honey Fungus, caused by Armillaria mellea:

The leaves of the affected plants are small, bleached and they fall off prematurely. The cordons become dried from the superior part towards the base and, if the roots are checked, you can see that it is brown and rotted. The roots have thick cordons which represent gatherings of the fungus’ filaments, of a white color and with a powerful inflorescence. As autumn approaches the fungus grows its fruitions in the form of a yellow hat with a thick stem. The affected trunks will become dry after 4 years of infection.

Prevention and control measures:

  • The crops need to be planted on well drained soils
  • Taking out and burning the affected plants
  • Bathing the cutting in a Zeama Bordeleza 3 % mixture
  • Burning the leaves of the affected plants

Phomopsis Cane and Leaf Spot, caused by Phomopsis viticola:

During the first days of spring, elliptical wounds can be seen on the young sprouts, wounds which are brown, united and solitary. The sprouts have their growth slowed down, they don’t grow flowers and fruits, and, if the attack is severe, they are destroyed. As the disease evolves, during summer the spots grow, turn brown-black and the affected tissues will have longitudinal cracks. During autumns, the affected cordons are white. The leaves can also be affected and they can have the same symptoms as the sprouts.

Prevention and control measures:

  • Performing the needed maintenance works correctly and on time
  • Burning the affected organs
  • Chemical treatments, using Rovral, Cabrio Top, Universalis, Ortiva, Thiovit Jet

Nectria Canker, caused by Nectria destructor:

The plants which are the most affected are the ones aged from 2 to 8. The affected plants no longer start their vegetation period and become dry during summertime. If the root system is examined, you can see that it is visibly deformed. Also, after peeling the bark away, it can be clearly seen that the tissues are brown. This disease is specific to the crops which are not taken care of, where no phytosanitary protection measures have been taken.


Management

In a new vineyard, early prevention is the best approach to managing GTDs. As with any grapevine disease, sustained management depends on proper diagnosis. A cursory diagnosis based on symptoms is usually sufficient, but there are circumstances where knowing the pathogen name is useful. If necessary, have affected tissues inspected by an experienced plant diagnostician or state viticulturist. In Texas, submit samples to the Texas A&M AgriLife Extension Service, Texas Plant Disease Diagnostic Lab (see http://plantclinic.tamu.edu) for a clinical diagnosis.

Complete control or eradication of GTDs in a vineyard is virtually impossible. The pathogens are everywhere, the Texas climate is usually conducive to infection, commercial grape varieties are susceptible to one or more of the pathogens, and every wound made on the vines is a potential location for canker development. There are, however, many economically favorable measures that, when applied in a broad and integrated approach, can delay the impact of GTDs and prolong winegrape production. Successful management of GTDs must be a goal from the planting of new vines throughout the duration of the vineyard.

Cultural practices

The pathogens that cause GTDs are more severe on stressed, poorly maintained vines. Practices intended to keep vines in good health, particularly in young vines, delay the detrimental effects of the GTDs. Using clean, healthy propagation materials, including scion and rootstock, proper planting, avoiding over-cropping when vines are young, and maintaining suitable fertility are cultural practices that contribute to good vine health and will discourage canker development.

In addition to the following recommendations, never prune vines during rainy, wet weather. Regularly scout the vineyard, particularly when growth is new and has not yet obscured the presence of dead spurs and shoots. When you identify infected wood, excise (cut out) it at least 4 inches into healthy, green wood and properly dispose of it by burning or burying it to eliminate spore production.

Modified routine pruning practices

There are two pruning methods recommended for suppressing GTDs: double pruning and delayed pruning. Double pruning consists of a “prepruning” cut of canes to about 10 to 12 inches above the intended spurs, sometimes made with a mechanical pruner. Make this first pruning during the dormant season, in December or January. During the second pruning (in February, just before or at bud break), remove any wounds that have become infected. At this time, the vines are better suited to respond to and resist infections than during the winter.

Wound protection

Paints for use on grapevines protect pruning cuts and other types of wounds from diseases. The ideal pruning paint must be durable and effective in reducing various GTD pathogens for at least 2 to 12 weeks to reduce infection. Manually apply the paint to all wounds. There are several formulations available that contain protectants such as resins, essential oils, or some other carrier. Some formulations contain boric acid or a fungicide to provide added protection from infection beyond simply creating a physical barrier.

Tractor-applied fungicide sprays can also help protect grapevines. In Texas, fungicides are labeled for dormant season sprays to control GTDs caused by Botryosphaeria, Eutypa, Phaeoacremonium, and Phaeomoniella (refer to the Grape Pest Management Guide listed in Other Resources, below).

The effectiveness of sprays depends on the timing of the pruning and when rains occur, which can wash the fungicide from the cut surface as well as trigger spore production

Always refer to product labels for specific instructions on the use of dormant sprays to control GTDs.

Surgery and retraining vines

The following practices help prolong production:

  • Rehabilitate diseased vines by renewing trunks and retraining new cordons.
  • Enhance these efforts in advance by training for multiple trunks. Then periodically replace older, diseased trunks with new ones derived from shoots that grow from basal buds. During the dormant season, excise diseased wood a minimum of 4 inches below the discol ored wood.
  • Identify and train new shoots the year before removing a diseased cordon (Fig. 10).
  • Protect all pruning wounds from infection.

When properly done, vine surgery can prolong the life of the vine, but there are drawbacks. Excision is not effective in the case of Petri disease, where the pathogens are systemic infections in the xylem rather than localized cankers. Pruning practices that produce large wounds create new, susceptible infection courts. If unprotected, these new wounds will likely succumb to infection and the incidence and severity of GTDs in the vineyard will persist. Vine surgery to control GTDs is a delaying tactic anticipate the eventual need to rogue (cull) diseased vines.


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Common name Amount per acre** R.E.I.‡ P.H.I.‡
(Example trade name) (hours) (days)
UPDATED: 12/14
When choosing a pesticide, consider efficacy and the general properties of the fungicide as well as information relating to environmental impact.
DORMANT SEASON
A. LIQUID LIME SULFUR# Label rates See label See label
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Multi-site contact (M2)
COMMENTS: Reduces overwintering structures of Phomopsis as well as Botrytis and powdery mildew spores.
Spring foliar treatment
A. KRESOXIM-METHYL
(Sovran) 3.2–4.8 oz 12 14
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Quinone outside inhibitor (11)
COMMENTS: Begin application at budbreak.
B. AZOXYSTROBIN
(Abound) 11–15.4 fl oz 4 14
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Quinone outside inhibitor (11)
COMMENTS: Do not apply more than 3 sequential sprays rotate with a fungicide that has a different mode of action. Apply before disease development begins. Follow label directions, especially as they pertain to number of applications allowed per year.
C. CAPTAN 50WP 3–4 lb 4 days 0
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Multi-site contact (M4)
COMMENTS: Captan-treated grapes are prohibited in Canada. Do not apply more than 24 lb/acre per year. Do not apply in combination with, immediately before, or closely following oil sprays.
D. MANCOZEB
(Dithane M-45) Label rates 24 See comments
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Multi-site contact (M3)
COMMENTS: Do not apply after fruit set or more than 7.5 lb/acre per season. Do not apply after bloom.
E. PYRACLOSTROBIN + BOSCALID
(Pristine) 8–10.5 oz 24 14
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Quinone outside inhibitor (11) and Carboxamide (7)
COMMENTS: Do not apply on Concord, Worden, Fredonia, Niagara, and related varieties. Do not make more than 2 sequential applications rotate to a fungicide with a different mode of action. The R.E.I. is 5 days when conducting cane tying, turning, or girdling.
F. ZIRAM
(Ziram 76DF) 3–4 lb 48 10
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Multi-site contact (M3)
COMMENTS: Apply before buds swell and repeat after blossoming but before fruit forms. Do not apply after bloom.
G. SULFUR#
(Micro Sulf) 10 lb See comments See label
MODE-OF-ACTION GROUP NAME (NUMBER 1 ): Multi-site contact (M2)
COMMENTS: In some counties there is a 3-day restricted entry period when using sulfur consult your county agricultural commissioner. Apply just before or immediately after post-budbreak rains. Do not apply within 3 weeks of an oil application.
** Apply with enough water to provide complete coverage.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for use on organically grown produce.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different Group number are suitable to alternate in a resistance management program. For more information, see http://www.frac.info/.