Purple Loosestrife Reprise
A loosestrife monoculture -- Wikipedia image
It is, of course, a bit late in the season to write about purple loosestrife, but several readers have written to ask (and complain) about its return.
Through the summer this is a quite beautiful plant, its reddish-purple two to five-foot spikes enhancing the beauty of meadows and wetlands. Now those bright colors have been replaced by the goldenrod's yellow and the aster's purple, but a few of the loosestrifes' elongated leaves are still the bright red they take on for a few weeks each fall.
Unfortunately this beautiful alien invader poses serious dangers to our native plants and, when it takes over a marsh or forest edge, it severely reduces bird and mammal activity as well.
Loosestrife is native to much of the Eastern Hemisphere: Europe, northwestern Africa, Asia and even (making quite a jump) southeastern Australia. It is not, however, native to North and South America. Although it has relatives like wing-angled and hyssop-leaved loosestrifes that are native to this country, purple loosestrife is an alien here. A common garden perennial in Europe that occasionally grows wild there as well, it was brought to North America by early colonists. It was imported most often as an attractive garden plant. It soon escaped from the colonials' gardens and has been, since before 1850, a widespread wildflower in the eastern United States and Canada. Interestingly it is less common in Europe today. A Cornell graduate student who spent a summer studying loosestrife there had difficulty finding wild specimens.
This plant poses no problems in its home countries. Why then is it a bother to us? The answer is the same as it is for so many aliens: zebra mussels, giant hogweed, house sparrows and starlings, round gobies and phragmites here; pythons in Florida; rabbits in Australia; and even our gray squirrel in England. These travelers do not bring along the natural enemies that keep their population in control. As a result and if they find a comfortable setting, they flourish far beyond their normal populations and cause problems.
The problem created by purple loosestrife is crowding. Each plant produces hundreds of seeds so that it spreads quickly. It clones as well, establishing new plants through its root systems. By these means it forms very dense clusters, leaving no room for neighbors. The clusters are so tight, in fact, that most birds are excluded and other animals have trouble penetrating the dense undergrowth and root systems.
Enter entomologists. In the early 1990s Stephen Hight of the United States Department of Agriculture brought to this country three insect species from northern Germany that feed solely on purple loosestrife and former Senior Wildlife Biologist Dan Carroll established the Tonawanda Wildlife Management Area as the North American center for raising and distributing these predators. Nurtured there, they provided the natural insect predator vs. plant balance that is found in Europe.
The introduction process was complicated. Collected in Germany, on arrival at the Beneficial Insects Laboratory in Maryland, they had to be quarantined long enough to insure that they did not carry a dangerous fungus. Only then were they allowed to feed in an Oak Orchard outdoor screened plot. The project was successful and the beetles were then widely distributed, causing a sharp decline in the loosestrife population over the next decade.
This year, however, loosestrife returned with a vengeance and many of us wondered why. Could the beetles have been so successful that they ran out of food and died? Did spraying insecticides to control mosquitoes wipe out the loosestrife beetles?
I contacted Paul Fuhrmann, who heads our regional alien control activities, to pose those questions. Paul responded that the beetles overwinter in ground detritus and thus are subject to problems with high water levels and he reminded me of last spring's rains and associated virtual inundation.
Cornell entomologist Bernd Blossey added more information. He pointed out that last fall brought a bad late frost that killed many of the insects, but he added that this year's loosestrife flowering was months late indicating poor pollination. His projection is very positive: "In many control programs we see a bit of up and down, but it is nothing to worry about."
I hope Blossey is correct. Next summer will provide answers.-- Gerry Rising