Figure : Typical gummosis symptoms on a branch of Nagpur mandarin tree
Symptoms
The first and most obvious symptom is defoliation, caused by coalescing cankers that girdle the stem or branches. Stem cankers are not always readily visible on the outer bark. If the bark is peeled away from the collar region, the wood appears watery grey, often with red streaks that intensify in colour upon exposure to air.
In the advanced stages of the disease reddish fluid exudes from cankers that dries into a rusty deposit. The pink or light brown cortical tissue darkens to brown and blackish streaks can often be seen.
Root rot, fruit rot, canker and gummosis of the trunk and branches can occur at once, causing a rapid death in 10-20 days, but a tree can survive for up to a year following infection before the leaves drop and the tree dies.
