A note on the die-back of blue pine (Pinus wallichiana) due to beetle attack
2001
Gul, H. | Khan, M.H. (Pakistan Forest Inst., Peshawar (Pakistan))
Blue pine (Pinus wallichiana) is an important conifer in Pakistan. During the month of May, 2001 natural die-back of this specie was reported by the forest authorities from Gallies, Murree Hills and Azad State of Jammu & Kashmir areas. To investigate the reason for this die- back of blue pine, a survey was conducted in the affected localities. The results of this survey revealed that the twigs and bark of dead and dying trees were infested by the bark borer beetles i.e. Ips longifolia and Scolytus major belonging to the family Scolytidae, order Coleoptera. The main reason for the spread of these insect pests is due. to stress caused by extremely dry conditions during winters of year 2000 and preceding springs. The beetle population developed on the weak trees under moisture stress growing on warmer aspects and ridges with stony soil. The stressed trees had very little sap which made them prone to the attack of above beetles. The grubs of these beetles constructed concealed and irregular galleries in the twigs and branches, causing damage to conducting tissue by complete strangulation. Since the insect damage was mainly due to stress caused by drought and was also below the economic limit, therefore no conventional control measure were feasible, rather than to wait for improvement in the moisture conditions in coming monsoons and winters. Moisture availability in this way will reduce the stress and reset the health and vigor of the trees, thereby naturally eliminating the insect pests.
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