Earthworms gone wild

Nearly everyone loves earthworms. I don't remember my first childhood encounter with earthworms, but I imagine it had something to do with wet sidewalks after a rain, and rescuing "wormies" from the hot sun. As I grew older I learned to respect earthworms less for their delightful slimy "squirmy-ness" and more for their practical roles in helping gardeners and farmers, and providing food for wildlife... and other good things like fishing.

No one denies that earthworms provide hefty environmental services in the form of improved soil aeration and water penetration, and composting.  But it turns out that there are some bad guys in the earthworm community. And sometimes earthworms just show up in the wrong places at the wrong time.

Extreme earthworm excavation can lead to boggy soil and weak
turfgrass stands. 

Let me explain. Some types of earthworms are notorious for leaving excessive amounts of castings on the soil surface. The spongy soil and excess castings produced by these worms can make it difficult to mow, or even walk across an infested lawn. Earthworm tunneling can also disrupt grass roots and reduce turf quality. And don't talk to golf course superintendents about earthworm castings on putting greens. Besides disrupting play, earthworm activity dulls mower blades used to keep greens short and fast.

Also, it turns out that earthworms are not very welcome at airports. With the number of reported bird strikes increasing over six-fold between 1990 and 2013, airport managers are eager to look for ways to reduce bird activity around airport runways. Therefore, high earthworm populations, which attract birds, are not desirable close to airplane landing and takeoff sites.

Of course the overall benefits from earthworms on turf is great, but there are places and times where earthworms are pests.  Until now, there has been little to be done about earthworms.  A few insecticides and fungicides are known to be highly toxic to earthworms; but there are currently no pesticides (vermicides) registered for earthworm control in the U.S. And by all accounts the U.S. EPA, which regulates such things, does not appear eager to register worm-killing pesticides.

Research reported in 2010 from the University of Kentucky documented that an organic, plant-produced mixture of natural soaps called saponins could effectively be used to control earthworms for at least five weeks. The best commercial source of saponins turns out to be a byproduct of tea manufacturing called tea meal.  While the research has not resulted in anyone registering tea meal as an insecticide, a company called Ocean Organics has started importing tea meal from China and using it as a base for a new organic fertilizer.

Early-bird 3-0-1 organic fertilizer, described by some as "a fertilizer with benefits", uses a tea seed base.  Though not sold as a pesticide, it happens to be toxic to some earthworms. It is labeled for application at 6 lbs/1000 ft sq or 5 bags per acre. A 50 lb bag retails for around $55, and cost of application is around $275/Acre (it can be found at Winfield Solutions--Land O Lakes in Texas, and possibly other suppliers).

I know that any suggestions on ways to kill earthworms will be viewed with alarm by many, but there will be situations when at least short term control is desirable. On the other hand, as one researcher thoughtfully concluded, earthworms are highly adaptable creatures that are difficult to manage, and to some extent we will have to learn to take their bad along with the good.  Think about that the next time you go fishing.

Recreational pursuits of flies

If you haven't seen it yet, a silly new email is going around. The premise of the email concerns what you can do when you're bored at the office (this never happens in my office of course). According to the email, all it takes is a few dead flies, some paper and pencil, a little imagination and a digital camera. I've attached a few of the nine examples.

The email (which I predict may go viral) ends with a question: "Makes me wonder, though: where does someone work that there are this many flies???"

The entomological answer appears to be: "almost everywhere but where I live". The flies in the pictures appear to be cluster flies, Pollenia rudis. These rather large, sluggish flies are identified by the sharp bend in the medial vein on the wing, and the characteristic golden hairs visible on the thorax in some of the pictures. Cluster flies are common in northern areas including Europe, Canada and the northern United States. I first encountered cluster flies as a graduate student at Purdue University in Indiana. They were common there in the fall and winter, sneaking in around the drafty windows of my office in old Entomology Hall. Cluster flies are best known for their annual fall migrations into homes and offices, where they "cluster" in windows and attics similar to the behavior of paper wasps, Asian multicolored lady beetles and other fall invaders in Texas. Curiously, I've not seen a single cluster fly since moving to this state over 25 years ago.

One of the things that always fascinated me about cluster flies is that they are parasites of earthworms. Who knew that earthworms even needed parasites? Don't they have enough to worry about with robins and moles and other predators? And what harm could earthworms possibly cause anyway?

I learned from my mailbox this week that some people, at least, think that earthworms are still a little too abundant, even with all their plagues and problems. A just-published paper by Dan Potter et. al at the University of Kentucky reports on problems with over-abundant earthworms in golf courses and sports fields. Too many earthworms can lead to uneven playing surfaces, and messy turf areas. In Texas we get occasional calls from homeowners complaining that earthworms turn their lawns into mush, making it difficult to push a lawn mower and even walk over the spongy ground. As Potter and colleagues pointed out in their article, earthworms can also pose a hazard at airports by attracting flocks of birds to feed on the oozing populations that creep on runways, especially after a heavy rain.

People ask me all the time, "so what good is that insect?" The cluster fly shows us that even the most humble insect can be invaluable to society. Fighting earthworms and boredom at the same time is no small accomplishment.