When University of Illinois entomology Professor Lawrence Hanks was working on his doctorate, looking at an insect destroying mulberry trees in Maryland, inspiration hit him.
Trees standing alone - in the mulch beds and in other decidedly undiverse habitats commonly found in landscaping along urban streets, sidewalks and parking lots - were infested.
But trees in mixed, woodland-like settings were essentially free of the pest. Hanks wanted to know why.
?A light went on in my head,? he said recently. ?There were tons of natural enemies in the woodlot that basically just eradicated (the mulberry pests).?
Now, an ongoing study by Hanks and Purdue University colleague Clifford Sadof is indicating that the idea was correct.
Eventually, the research, funded by the U.S. Department of Agriculture, could lead to a set of criteria that landscape architects can follow to create landscapes that look good and control pests without pesticides.
?We're a long way from being able to make specific recommendations,? Hanks said. ?But at least with our preliminary experiments we show the potential is there.?
The researchers' ultimate goal is to reduce the use of pesticides in urban settings.
That would be good for the environment and for insects and animals we like having around, such as birds and butterflies, as well as good for us.
In addition, it could save the money spent continually spraying just to keep ornamental landscaping alive.
Hanks said the method also could work for yards and gardens, although there's a psychological barrier to overcome: more bugs, the good along with the bad.
?People have to get used to the idea that ?Wild Kingdom' is happening right out in your yard,? he said.
Hanks didn't get much chance to test his idea until he arrived at the UI following his post-doctoral work.
He and Sadof have been studying identical test plots they planted at the UI and at Purdue.
The plots contain Scot pines, which are common in urban landscaping like parking lot buffer zones and are very susceptible to pests, especially pine needle scales.
Some of the pines are in a typically ?bleak urban landscape,? in the words of Hanks, with little diversity in the plant life. Others are surrounded by a few flowers, and still others by a lot of flowers.
The researchers' hypothesis was that the flowers would attract natural enemies of the pine needle scales, particularly a tiny non-stinging wasp, aphelinid, that feeds on floral nectar.
The trees with flowers in their plots would suffer less damage as a result, the theory went.
The results were disappointing the first year. Isolated trees and trees with flowers suffered similar damage.
But things changed the second and third years, and the mixed plots yielded marked improvement. Hanks said it simply took time for the natural enemies of the pests to colonize the new habitat.
They did a similar experiment with dwarf shrubs susceptible to attack by bagworms - a problem that can be found throughout communities like Champaign-Urbana - and flowers attractive to a parasite deadly to the worm.
This year, the researchers will be comparing plots with flowers and plots with the flowers removed but the green part of the flowering plant still in place too see what happens.
Hanks said it was fairly obvious which plants would be likely to attract the scale-killing wasps and the bagworm parasite. It's going to be more complicated to learn how to draw generalist predators, like crickets and certain beetles and spiders, that work for a variety of pests, he said.
?The tricky part is to figure out what it is about woodlots that encourages natural enemies to hang around and do what they're supposed to do,? Hanks said. ?That's the challenge.?
You can reach Greg Kline at (217) 351-5215 or via e-mail at firstname.lastname@example.org.