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An Insect to Root for

Published in the six Nashoba Publishing papers on Friday, 2 August 2002

My lilies came up this year and grew to their full height, looking healthy. I was surprised, after last year the terrible red Asiatic lily leaf beetle stripped them to stems with brown tatters hanging. Those bulbs must hold a big reserve of carbohydrates, to be able to grow another plant without one year's replenishment. The deep red lilies, my favorite, even started to bloom, which they didn't last year before the invader hit them.

That just made the heartbreak worse: I knew the beetles would be back, too. Sure enough, a month later the bright red little things were gobbling up the plants. And even worse, the voracious orange larvae, with their ugly sacs of feces on their backs (probably a bird deterrent).

I held off getting rid of the mess because the Biological Control Lab at the University of Rhode Island is trying to establish a predator to attack the beetle. Last year they failed to overwinter the predator, a tiny wasp that does not sting humans: _Tetrastichus setifer_. It also does not attack anything native to this continent, a desirable quality. We don't need another introduced species upsetting the ecological balance.

Since this insect has long been established in areas of Europe with temperatures like ours (where it controls the lily leaf beetle) the researchers kept trying. They had mulched the bed it was introduced to; _Tetrastichus_, like its prey, winters in the earth. Perhaps the mulch affected the situation? Last winter, in one plot they tried no mulch: success!

However this doesn't mean I will see them in my garden soon enough to save my lilies. U. Rhode Island will be doing more studies to determine the best way to get this predator established -- with the hope of getting the wasp to spread the way the beetle has, by itself. Perhaps next year the Massachusetts Horticultural Society and the North American Lily Society will help get it distributed. But even if that means individual gardeners can get it, I can hardly believe my poor plants will come up again next year.

There are chemicals which kill the beetle -- but they also kill the pollinating insects we need. The organic insecticide Neem will work, if you keep applying it every five to seven days. You can hand-pick them if you're clever (they drop off the plant and turn belly-up, and their black bellies are hard to see on the ground)....

Yay, Tetrastichus! Hooray, Tetrastichus! Go get 'em, Tetrastichus!

Next Date

For more information

Northeast Region IPM Grants — Sponsored by the Cooperative Extension and Land Grant University IPM programs of the Northeast (Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and West Virginia), the United States Department of Agriculture, and the National Science Foundation Center For IPM.

My report when the beetles showed up in my garden last year.

© Copyright 2002 Catherine Holmes Clark