Monday, October 23, 2006

Invasion of Ladybugs: Friends or Foes?

Lady bug, lady bug, fly away home
Your house is on fire and your children aren’t home

As with many homes near wooded lots, our house is prone to the little lady bug invasion just about now. A recent article in the Washington Post, highlights the challenge of this invasive species. For me, the challenge is sorting through competing societal understandings and confusion.

I learned that the ladybug was my friend, that it devoured plant pests, which is very good if you are in the nursery business. Then I learned that there were many ladybugs, followed by the revelation that the bug in the rug inside the house was most likely not the native. In addition there were actually bad lady bugs, such as the Mexican bean beetle and the squash beetle. Now the question for some was whether any bug in the house was good, and for others whether the house guest was the native or the non native. I wanted to know if the non-native devoured aphids too, as well as the native did. Already things were getting out of hand.

Can an invasive species be both good and bad? If the alien devoured food crop pests reducing the need for pesticides, wouldn’t it be good? And the invasion of the house, which itself is invasive as far as natural areas are concerned, is that of concern as far as the invasive species discussion goes?

So first an abstract from Iowa State University “the multicolored Asian lady beetle (Harmonia axyridis), has become common throughout the United States and all of Iowa. It is well known for the annoying habit of accumulating on the sides of buildings and wandering indoors during the fall. Asian lady beetles are a beneficial biological control in trees during the summer, and in fields and gardens during the fall, but can be a severe household nuisance during late fall and winter. Wooded residential and industrial areas are especially prone to problems.
The origins of the Asian lady beetles are not clear, although it appears the current pest species was not purposefully released in the United States or in Iowa. Beetles that arrived by accident in ports such as New Orleans in the late 1980s have crawled and flown all by themselves to all corners of the country. “ Notice the reference to beneficial, except as a pest for the non-agriculturally inclined. Now recall that the newspaper article mentioned invasive in the article, and one begins to see confusion rise like early morning mist. Is invasive bad? Is it neutral? Is it good?

Trying to educate the public as to which beetle is good and which is bad is an exercise in futility. Trying to pin the spot on the beetle as to how it came to live in North America is an ongoing lively game. Compare the article above with the following from a Purdue University website: “The species found so abundantly is the multicolored Asian lady beetle, Harmonia axyridis, common in Japan, Korea and other parts of Asia. The name "multicolored" refers to tremendous color variation in this species, ranging from black with two red spots, to red with 19 black spots, and about every combination in between. They were introduced by USDA Agricultural Research scientists in the late 1970's and early 1980's as a biological control agent for pear psylla and other soft bodied insects.”

And wouldn’t you know it but my friends at USDA get the spotted finger pointed at them. I guess I will meander over there in the next few days and see what they have to say at BARC (Beltsville national Agricultural Research Center). Of course, in an earlier posting I noted that you must be very cautious when using the web as your sole source of information.
So a review; there is an invasion by a bug which purportedly kills our enemies in the garden, but, is also our enemy, even though it looks from afar like our friend, which, also kills our enemies in the garden, but does not move into our house as a winter guest, and, therefore, is both benign and native, and not subject to the vacuum cleaner.

So we have confusion over benefit and identification, as well as conflict between a beneficial use versus a domicile pest. I am making light humor about a serious topic and hope I have shown the challenge I find in getting audiences to stay with me when I try to explain invasive species. However I also hope you can see why the entirety of the question so intrigues me. And one more thing, even the old nursery rhyme seems to be exotic and not native: “The English word ladybird is a derivative of the Catholic term " Our Lady". The tradition of calling this rhyme was believed to have been used as a seemingly innocent warning cry to Catholic (recusants) who refused to attend Protestant services as required by the Act of Uniformity (1559 & 1662). This law forbade priests to say Mass and forbade communicants to attend it. Consequently Mass was held secretly in the open fields. Laymen were subject to jail and heavy fines and priests to execution. Many priests were executed by the terrible death of being burnt alive at the stake or, even worse, being hung, drawn and quartered. The most famous English recusants were Guy Fawkes and the Gunpowder Plot Conspirators.