- The larvae bore in to the tender terminal shoots feeding on internal tissues resulting in blackening and decaying of affected shoots.
- The attacked portion of the shoots dries up and dies.
- Caterpillar pupates within the larval tunnel.
- The younger plants suffer the most.
- Due to the continuous killing of terminal shoots the growth of the plant is arrested.
Select 20 standards at random from the plot and count the number of plants showing damaging symptoms. Less than 5 plants mild; 5-10 plants moderate and >10 plants severe.