Friday, August 21, 2009

Bubbles with a bug inside

Nancy wondered about a problem on her very old Poplar tree - it was probably "an original" in the city she thought and it had "Bubbles with a bug inside".

Dr. Ken Fry, Entomology Instructor at Olds College had already helped me out with this problem last summer so I called up his notes:
"The moth species mining poplar and willow have one generation per year. The larvae feed within the leaf during the summer and then spin a silken cocoon in the mine to pupate. The adult emerges in late July or early August. The adult overwinters in leaf litter or debris on the ground. Eggs are laid on either the upper or lower leaf surface in the spring. The larvae then chew their way into the leaf.
       My neighbour has this moth infesting his willow. I also saw this leaf miner on old poplar at the Confederation golf course. A systemic insecticide (one that is injected into the tree and the tree delivers the insecticide to all tissues) would be effective. The reason "Cygon", the commonest systemic insecticide used by homeowners has been removed from sale is it is very toxic to humans and the majority of pests it was used against are not very serious and did not justify the use of such a toxic product (as judged by today's standards).
       Commercial applicators do have systemic products registered for such purposes. However, Donna is correct in mentioning that your trees are in the twilight years of their life and beginning to decline. Insects and diseases exploit this decline in vigour and attack the tree. It is merely another step in the cycle. The tree will eventually die and be recycled by wood-boring insects, wood peckers, leaf-cutter bees nesting in the rotting wood, etc.
       Leaf miners will not cause the death of the tree, merely stress it. As Donna has said, providing nutrients and ample water will allow the trees to weather the assault from the moths. Plan for the future by planting replacement trees now and be sure to have an arborist evaluate the trees as they age for risk of blow-down in a storm."

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