Arvind Kumar

Blackline is a viral disease related to English walnut (Juglans regia). It is caused by a strain of cherry leafroll virus (CLRV-W), and is transmitted through graft wood or infected pollen. Symptoms include poor shoot growth, yellowing and drooping leaves, premature leaf drop, and eventual dieback and death of the trees.

Blackline disease is prevalent in the coastal regions of California and San Francisco bay area counties.

Thanks!

I think that the Black Line Disease is associated with avocado trees.

Symptoms:

• The appearance of a dark black line on the bark at the graft union between the rootstock and the scion.
• Gradual separation of the scion from the rootstock.
• Leaf wilting and drop.
• Poor overall growth of the tree.
• In advanced cases, the tree may die completely.

The disease is usually linked to a viral infection or incompatibility between the rootstock and scion.

Black line disease is a serious viral disease that affects coconut trees. It is characterized by the appearance of a distinct black line or crack at the junction where the stem meets the nut, eventually leading to the death of the affected nut and sometimes the entire inflorescence. The disease weakens the tree’s productivity by reducing nut yield and quality. Black line disease is mainly spread through infected planting material or by certain insect vectors. Managing the disease involves removing and destroying infected trees, using disease-free seedlings and practicing good field sanitation to prevent its spread.

lack line disease primarily affects walnut (Juglans spp.) trees, notably English walnut (Juglans regia) cultivars grafted onto rootstocks such as Northern California black walnut (Juglans hindsii) or Paradox hybrids. The disease is caused by the Cherry leafroll virus (CLRV), which induces a hypersensitive reaction at the graft union, leading to the formation of a distinctive black line that girdles the tree and disrupts nutrient flow.