What happens in Dead Arm (Eutypa Dieback)?

What happens in Dead Arm (Eutypa Dieback)?

• A. It causes rapid, healthy shoot growth.
• B. It leads to permanent green growth on canes.
• C. Infected vines experience stunted shoot growth as the fungus releases toxins, and an infected cane may die—the dead arm.
• D. It improves fruit set.

Answer: (C)

Dead Arm is a grapevine disease caused by Eutypa lata that lodges in the wood and enters through pruning wounds. Once inside, the fungus colonizes the xylem and releases toxins that disrupt water and nutrient transport, causing shoots on infected canes to grow poorly or be stunted. In some cases, the affected cane eventually dies, which is why the symptom is called the dead arm. This pattern—stunted shoot growth and possible death of a cane—fits what the disease does, rather than producing rapid growth, retaining green growth, or boosting fruit set. Preventive steps focus on reducing wound infection (pruning in dry weather, sanitation of tools) and removing infected wood to lower the source of the pathogen.

Dead Arm is a grapevine disease caused by Eutypa lata that lodges in the wood and enters through pruning wounds. Once inside, the fungus colonizes the xylem and releases toxins that disrupt water and nutrient transport, causing shoots on infected canes to grow poorly or be stunted. In some cases, the affected cane eventually dies, which is why the symptom is called the dead arm. This pattern—stunted shoot growth and possible death of a cane—fits what the disease does, rather than producing rapid growth, retaining green growth, or boosting fruit set. Preventive steps focus on reducing wound infection (pruning in dry weather, sanitation of tools) and removing infected wood to lower the source of the pathogen.