Thursday, March 23, 2017

Some Unexpected Management Partners

Small but mighty: Galerucella beetle perched on an unsuspecting purple loosestrife leaf. Photo by A. Rusch

As much as I love a good cliffhanger, before moving on to introduce the next major thug (Phragmites) in what I’m recognizing is becoming a lineup of criminal invasive species, I think it’s worth telling the rest of the purple loosestrife story. While the battle for real estate in Lake Erie coastal marshes (and wetlands all over the state and region) was definitively being won by PL, new recruits to take on the fight were being investigated.

Traditional management methods (e.g. water level manipulation, mowing, disking, spraying) proved to have little lasting impact to curb the sea of purple. Ironically, the solution – or at least a meaningful step toward it – again came in the form of some tiny beetles from far-away lands. And unlike the borer that indiscriminately killed all the ash trees (see 3/21/17), these tiny insects were intentionally introduced as a carefully scripted form of “biocontrol.”

While studies were being conducted throughout the U.S. (and abroad), the Division of Wildlife was the group most actively engaged in introducing Galerucella beetles to Ohio. The long-time owner of a neighboring private marsh was distraught at the seismic shift in habitat he was witnessing and as such was willing to be a guinea pig. Beetles were first introduced into the broader Bay View marsh complex in the early to mid-1990s as one of the first test sites in the state. The results have been astounding. There are plenty of examples of biocontrol efforts gone bad (think Frankenstein fish), but this was a case where the beetles took hold, ate what they were supposed to eat when they were supposed to eat it, and left everything else pretty much alone. As PL numbers decline, so do beetle numbers.

This has been the case now for more than two decades. Loosestrife still exists on the marsh, but the populations are isolated and the beetles are lying in wait to rise up and consume anything that gets too out of control. (As an aside that we can talk about later, the resulting “seed bed” – viable seeds residing in underlying sediment – from all those years of rampant proliferation by PL give the beetles plenty of job security.)

Purple loosestrife went from an epidemic that many assumed would just become the new normal, to a manageable irritant. Unfortunately for area marshes, just as PL started its precipitous decline, a new monster was rapidly gaining a foothold . . .

(I told you that I loved cliffhangers!)

Dig deeper:

Invasive Plants of Ohio Fact Sheet
Biological Control of Purple Loosestrife