The United States has been under assault for decades by a wide variety of alien plants and animals, and it is not often that one of these aliens faces a counterpunch. But in a collaborative project between scientists from several universities in the Northeast, researchers have scored a knockout blow.
The Birch leafminers are no longer a pest in the Northeast,” said Richard Casagrande, Delaware Beneficial Insects Rearing Lab introduced several European parasitoids to fight the pest, and one of them, Lathrolestes nigricollis, became established in the Mid- Atlantic States. Later, groups from URI, the New Jersey Biological Control Laboratory released more of the parasitoids in their respective regions.
The birch leafminer is not a fatal pest to birches. It disfigures the trees by mining within the leaves, and since birches are often used for landscaping, the effect became an aesthetic issue. Birches do have a fatal pest – the bronze birch borer – which can kill white-bark birches very quickly, but no biocontrol has been found for this native pest.
Casagrande said it is satisfying to be able to state publicly that a biocontrol program has succeeded.
“The birch leafminer program is a good example of the results of a coordinated, long-term approach to classical biological control,” Casagrande said. “We’re seeing similar success with programs for purple loosestrife, cypress spurge, mile-a-minute weed, and, perhaps, lily leaf beetle, but as you can see, it takes time – 34 years in this case for complete control.”