Eradicating Plant Pests Presents Summer Quandary

Hornworms, mosquitoes, Japanese beetles

By Lorna Carlisle, Beacon Volunteer
Parasitic tachinid fly, called “the winsome fly” or “Sweet and Charming,” helps to eradicate Japanese beetles.

As a follow up to the last article in the August Beacon, Yes, a black light does work to find tomato hornworms.  Now if only it could help us find actual tomatoes!

By now, everyone has probably had their worst gardening year in the last decade.  Tomatoes are as scarce as a sunny day this summer.  Normally, August means abundance.  The only thing abundant is mosquitoes.  Well, Japanese Beetles are a close second.  Most of us grew up with them.  According to a PDF from (title:  The Fly That Attacks Japanese Beetles), the beetles first showed up in New Jersey in 1912.  Like many of our pests, they came in on plant materials.  In 1927, we started introducing a parasitoid wasp (Tiphia vernalis) and a tachinid fly called the winsome fly.  According to the dictionary, winsome means “Sweet and Charming”.

There aren’t many flies I consider sweet and charming, but now I have to worry about killing the good flies!  Bad News.  If you want to get more winsome flies to kill your Japanese Beetles, you will have to separate your beetles.  Look for a white dot/dots on the thorax.  That means it has been parasitized.  I thought I could take these “keeper beetles” and put them in a box and a few of their favorite grape leaves until the flies hatched out.  Sorry.  Here’s how the process works.  The eggs hatch in about 24 hours.  Only one larva goes into the body of the beetle where it starts eating.  (Sound like a horror movie?)  The flight muscles usually are affected first causing the beetle to drop to the ground and bury itself.  Here’s the kicker—after the beetles dies in under a week, the fly larva stays in its host all winter. 

Now, I had to worry about how deep to bury my keepers.  This was sounding too complicated.  Better let nature take over.  As with most insects and predators, we need to provide their favorite plants to encourage them to stay.  Luckily, the winsome flies like many easy-to-grow plants like coriander (cilantro that has bolted), dill, lovage, yarrow, etc.  As with most things, if you spray to kill the Japanese beetle, you will most likely kill the flies too.  Nature really does know best.  We have to stop reaching for the spray bottle every time something annoys us.  While I make an exception for poison ivy, I try to put the bottle down and study the situation.  We have to learn to live with things being less than perfect.  In Mother Nature’s eyes, everything is perfect without us interfering.  Stand back and appreciate how the insects, birds, weather, etc. are all in a “winsome dance”.