Entomologists in Washington state are alerting the public to the spread of the European pine sawfly, an invasive insect that resembles a wasp. These insects are causing aesthetic damage to pine trees in Pierce County, a popular tourist area that is home to Mount Rainier National Park. While not a direct threat to forest health, the infestation raises ecological and economic concerns.
The Current Situation
Experts have observed the European sawfly laying eggs in pine needles and feeding on pine foliage throughout Pierce County. According to Todd Murray, an entomologist at Washington State University, the primary impact of these insects is aesthetic. Their feeding habits create large, bare patches on trees, which can detract from the natural beauty of the landscape.
Native to Europe, the sawfly was first identified in Washington in 2008. Its spread has been relatively slow because the adult insects are not strong fliers. The species primarily moves to new areas through the transportation of infested nursery plants, soil, and other materials.
Ecological and Economic Concerns
The spread of the sawfly is concerning for several reasons:
- Economic Impact: In a popular tourist region, the visual damage to trees could negatively affect visitors' experiences and impact income from recreation. The insects also pose a threat to commercial businesses like ornamental nurseries and Christmas tree farms.
- Ecosystem Disruption: Although sawflies typically do not kill their host trees, the repeated loss of needles can slow tree growth and leave them more vulnerable to other insects and diseases.
- Invasive Species Threat: Like all invasive species, the sawfly disrupts the local ecosystem's balance by consuming resources that native plants and animals rely on for survival.
Management and Control Methods
Officials recommend several approaches to manage the sawfly population:
- Physical Removal: For small-scale infestations, the most environmentally friendly solution is to simply knock the insects off the plants.
- Natural Predators: Birds are natural predators of the pine sawfly. In many cases, allowing nature to take its course is the best solution for controlling their numbers, unless an infestation is particularly large.
- Promoting Biodiversity: Homeowners can contribute to a long-term solution by planting native species in their lawns. Native plants attract local wildlife, including the sawfly's natural predators, which helps to create a balanced ecosystem that can manage pest populations naturally. Insecticides are also an option but should be used as a last resort.
