Dog Heartworm Treatment

The Western Tree Hole Mosquito, Aedes sierrensis, is a common pest mosquito in Alameda County and the most important vector (carrier) of Canine (Dog) Heartworm. The mosquito is found in areas where older trees have had time to develop rot cavities or pockets between limbs which can hold rain or irrigation water. Occasionally it is also found in containers in which organic debris and leaves have accumulated.

Adult mosquitoes of this species are characteristically very small, dark insects with brilliant white bands on their legs. The adults are long-lived (up to six months) and are found from March through June and often appear as swarming white spots.

Tree hole mosquitoes are persistent biters of man and animals. They most commonly bite in the evening although they will readily bite all day in shady areas. Both the male and the female are attracted to potential hosts, giving the impression of many more biting mosquitoes. Only the female bites for a blood meal. The male feeds on plant juices and does not take a blood meal. Occasionally the males will form a swarm in shady areas. Tree hole mosquitoes are normally outdoor biters, but may enter homes on occasion.

The life cycle of this species is centered around tree holes and containers. Female mosquitoes lay eggs on the damp surfaces just above the water line. The eggs remain dormant until the container is refilled with water by rain or irrigation. The eggs hatch shortly after submersion, producing young larvae which progress rapidly through four instars. Larvae transform to pupae when temperatures have reached levels that are suitable for adult mosquito activity. The pupa is a transition stage between larva and adult. An adult mosquito emerges from a pupal case in just a few days. If an adult female mosquito is successful in obtaining a blood meal, she will return to a tree hole to lay eggs, beginning the cycle again.

Control of Tree Hole Mosquitoes

The best method to control tree hole mosquitoes is to eliminate tree holes and containers that hold water around your home. Tree holes, especially those which hold water, are causing damage to the tree. Although very effective for controlling mosquitoes, filling, drilling, or cutting may expose new wood or hold moisture causing the rot to spread. For the health and preservation of the tree, it would be ideal to keep cavities and tree holes dry by installing deflectors to prevent water entry. Old stumps can be removed, filled, or buried. It is recommended that you consult with a tree specialist or nursery advisor for information on stopping the damage caused by rot cavities. This is especially important if the affected tree is a valuable part of your landscaping.