Black dead arm
| Dead arm of grapevine | |
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| Common names | grape canker Eutypa dieback Phomopsis leaf Cane spot Fruit rot disease Eutypiosis |
| Causal agents | Eutypa lata and Phomopsis viticola |
| Hosts | Vine, Prunus, apples, pears, walnuts, pistachios |
| EPPO code | PHOPVI |
| Distribution | Australia, North America |
Dead arm, sometimes grape canker, is a disease of grapes caused by a deep-seated wood rot of the arms or trunk of the grapevine. As the disease progresses over several years, one or more arms may die, hence the name "dead arm". Eventually the whole vine will die. In the 1970s, dead-arm was identified as really being two diseases, caused by two different fungi, Eutypa lata and Phomopsis viticola (syn. Cryptosporella viticola).
Dead arm is a disease that causes symptoms in grapevines in many regions of the world. This disease is mainly caused by the fungal pathogen, Phomopsis viticola, and is known to affect many varieties of grape. Early in the growing season, the disease can cause leaves to turn yellow and curl, along with stunted growth. Small, brown spots on the shoots and leaf veins are very common first symptoms of this disease. As the name of this disease suggests, it also causes one or more arms of the grapevine to die, often leading to death of the entire vine.
Dead arm of grapevine is caused by an ascomycete fungal plant pathogen. This pathogen produces sexual spores (ascospores) in the teleomorph stage and asexual spores (conidia) during the anamorph stage. When the pathogen is in the teleomorph stage it is referred to as Cryptosporella viticola and during the anamorph stage is it called Phomopsis viticola.
The teleomorph stage of the pathogen involves sexual combination of the antheridium with the ascogonium to produce ascospores inside an ascus. This stage provides a survival structure encasing the ascus called the perithecium and allows genetic variation. The anamorph stage is known to occur in nature and produces the main inoculum associated with this plant pathogen. During favorable conditions, conidia are released from ascospores in infected lesions of a leaf and dispersed onto another plant. Once the new leaves are infected, conidia are released throughout the season as the secondary cycle of this polycyclic disease. Phomopsis viticola overwinters as pycnidia until favorable conditions arise again.
The severity of dead-arm in grapevine varies greatly between growing seasons. Since this disease is caused by a fungal pathogen, moisture increases the intensity of disease outbreaks. As the amount of rainfall changes between the seasons, so does the amount of pathogen present in the field. Prolonged rainfall early in the season has been correlated with greater disease outbreaks. Temperature has also been shown to influence the infection rate. It has been found that the pathogen experiences the fastest rate of reproduction between 23°C and 25°C. Although temperature is important, it has been shown that the amount of rainfall has a greater impact on this pathogen than the temperature.
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Wikipedia