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Ministry of Agriculture, Food and Rural Affairs

phomopsis

Early phomopsis lesions Early phomopsis lesions on cane Phomopsis lesions on cane Phomopsis lesions on cane Phomopsis lesions on wood Early phomopsis on leaves Phomopsis symptoms Phomopsis lesions on cane Early phomopsis micro-lesions Phomopsis on red cultivar Phomopsis on white cultivar Click to enlarge.

Beginner

Scientific Name
Phomopsis viticola

Identification
Shoots

  • small elongated black lesions
  • resembling a nick or lengthwise cut
  • most frequently in the basal 5-6 internodes
  • the lesions may coalesce, causing the shoot to appear cracked or blotchy
Rachis
  • sections of rachis in the cluster may be girdled, dry up and fall away
  • may remain as dark, discrete, elongated lesions
  • may coalesce into dark brown areas, where the cluster may break as fruit matures
Leaves
  • characteristically small light green or chlorotic spots with dark centres
  • leaf veins may have dark brown or black necrotic spots
  • found primarily on basal 5-6 leaves
  • leaves with heavy infections are usually puckered or distorted, and often torn with a “shothole” appearance where the necrotic spots have fallen out
Berries
  • close to harvest infected berries develop a light-brown colour
  • black pycnidia are then produced and the berry shrivels
  • berry infections are not often observed in Ontario

Often Confused With
Mechanical injury on leaves- no yellow halo surrounding dark centre

Black rotsymptoms on berries usually develop before veraison; symptoms on leaves much larger than phomopsis and with pycnidia; cane lesions not as elongated as phomopsis

Botrytis bunch rot – infected berries covered with greyish-tan sporulation; no pycnidia; slip skin

Herbicide injurynecrotic lesions not restricted to basal areas of shoots, associated with weed death under vine row: on fruit, black spots that do not develop pycnidia

Period of Activity
The most extensive development of this disease occurs from bud break until shoots are 15-20 cm in length.  The majority of conidia are released by shortly (2 weeks) after bloom.  Newly emerging leaves are very susceptible to phomopsis infection but once they are fully expanded they become resistant.  The risk of infection is low for all tissues once inoculum is exhausted. Fruit infections are not often seen in Ontario. When they occur symptoms are not obvious until after veraison.

Scouting Notes
Focus on varieties and areas of the vineyard where Phomopsis has historically been a problem.  Inspect new shoots, leaves and rachises as they emerge for symptoms.  These will frequently be found on tissues close to or below an infected cane which acts as a source of conidia. To identify phomopsis on the leaf, hold leaf up to light to see the characteristically small, light green or chlorotic, spots with dark centres.

Threshold
Since Phomopsis does not have a secondary infection cycle, some disease can be tolerated in the vineyard.  Where Phomopsis has historically been a problem, there is no threshold for applying fungicides so this should be done before the appearance of symptoms.

Advanced

Scientific Name
Phomopsis viticola

Identification
Shoots

  • small elongated black lesions
  • resembling a nick or lengthwise cut
  • most frequently in the basal 5-6 internodes
  • the lesions may coalesce, causing the shoot to appear cracked or blotchy
Rachis
  • sections of rachis in the cluster may be girdled, dry up and fall away
  • may remain as dark, discrete, elongated lesions
  • may coalesce into dark brown areas, where the cluster may break as fruit matures
Leaves
  • characteristically small light green or chlorotic spots with dark centres
  • leaf veins may have dark brown or black necrotic spots
  • found primarily on basal 5-6 leaves
  • leaves with heavy infections are usually puckered or distorted, and often torn with a “shothole” appearance where the necrotic spots have fallen out
Berries
  • close to harvest infected berries develop a light-brown colour
  • black pycnidia are then produced and the berry shrivels
  • berry infections are not often observed in Ontario

Often Confused With
Mechanical injury on leaves- no yellow halo surrounding dark centre

Black rotsymptoms on berries usually develop before veraison; symptoms on leaves much larger than phomopsis and with pycnidia; cane lesions not as elongated as phomopsis

Botrytis bunch rot – infected berries covered with greyish-tan sporulation; no pycnidia; slip skin

Herbicide injurynecrotic lesions not restricted to basal areas of shoots, associated with weed death under vine row: on fruit, black spots that do not develop pycnidia

Biology
Phomopsis overwinters as pycnidia in lesions on one- to three-year-old wood. When it rains in the spring, conidia ooze from from pycnidia on overwintering lesions. and are splashed onto nearby developing leaves and shoots. Phomopsis infections are most severe with cool wet springs and slow leaf maturation and resistance to infection. Symptoms will appear on leaves within 7-10 days after infection.  Lesions on canes require 3-4 weeks to develop.

Most fruit infections occur pre-bloom to two weeks post-bloom.  Once inside the berry, the fungus becomes latent and the disease does not continue to develop until after veraison.

Because no new pycnidia are produced in lesions formed in the current growing season until very late in the growing season (on berries only), there is very little risk of secondary infections of this disease.

Period of Activity
The most extensive development of this disease occurs from bud break until shoots are 15-20 cm in length.  The majority of conidia are released by shortly (2 weeks) after bloom.  Newly emerging leaves are very susceptible to phomopsis infection but once they are fully expanded they become resistant.  The risk of infection is low for all tissues once inoculum is exhausted. Fruit infections are not often seen in Ontario. When they occur symptoms are not obvious until after veraison.

Scouting Notes
Focus on varieties and areas of the vineyard where Phomopsis has historically been a problem.  Inspect new shoots, leaves and rachises as they emerge for symptoms.  These will frequently be found on tissues close to or below an infected cane which acts as a source of conidia. To identify phomopsis on the leaf, hold leaf up to light to see the characteristically small, light green or chlorotic, spots with dark centres.

Threshold
Since Phomopsis does not have a secondary infection cycle, some disease can be tolerated in the vineyard.  Where Phomopsis has historically been a problem, there is no threshold for applying fungicides so this should be done before the appearance of symptoms.

Management Notes
Pruning debris should be removed from the vineyard and burned, or shredded and disked into the vineyard floor.

Training and pruning systems that maintain a lot of old canes and stubs increase the potential for providing a source of Phomopsis inoculum, particularly if dead wood is retained. Only healthy, symptom-free material should be retained.

Infected clusters and shoots should be removed from the canopy and either dropped to the ground and buried or removed and burned outside the vineyard.  Do not keep them in a pile beside the vineyard without burning as rain-splashed spores can blow into the vineyard in the spring.  Retain only healthy, lesion-free canes.

Management with fungicides – Fungicides are used to control Phomopsis in most commercial vineyards as a side benefit to controlling other diseases. See OMAFRA Publication 360, Guide to Fruit Production - Chapter 5 Grapes (PDF): Recommendations for Phomopsis at Shoot length 10-15 cm and 20-25 cm.  If Phomopsis was a problem in the previous year, start sprays at first leaf, 1,25-5 cm shoot length. 

Different cultivars all have different susceptibilities to diseases.  See Table 5-5 Relative Susceptibility of Grape Cultivars to Diseases.

Fungicides have different modes of action, and differ in their activity on grape diseases. See Table 5-6 Activity of fungicides on grape diseases.