Watch out for Durian Stem Borer Beetles
The current hot and dry weather during the day, combined with cooler temperatures at night, may trigger an infestation of durian stem borer beetles, which are commonly found during the period when durian trees produce new leaves.
Damage Symptoms
Both the larval and adult stages of the stem borer beetle tunnel into and feed on the trunk and branches of durian trees, particularly near the base of the trunk and on large branches. Damaged durian trees can be identified by small holes near the base of the trunk, and fine worm droppings are often found around the entrance holes. The beetles burrow 2-3 centimeters deep into the trunk or branches. If the tree is small, this may cause the tree to die. However, if the tree is larger, the damage may not immediately kill the tree, but the entry holes can allow root rot and stem rot pathogens to enter, potentially leading to the tree's death. Typically, stem borer beetle infestations occur alongside root and stem rot outbreaks. Sometimes, the damage from the beetles can be used as an indicator for identifying areas with rotting wounds under the bark.
Prevention and Control Methods
- Regularly inspect the durian trunks. If dry branches are found with signs of borer damage, they should be pruned and burned immediately to prevent the beetles from spreading to other trees.
- For large trunks or branches that cannot be pruned, insecticides may be necessary. For example, use fipronil at a rate of 30 milliliters per 20 liters of water, spraying on the trunk or branches with borer holes. Alternatively, mix fipronil at 30 milliliters per 5 liters of water with a fungicide and apply it to the wounds caused by rot.