Dear Miss Floribunda,

My new next-door neighbor has come up here from Georgia. She has been bagging the leaves she’s raked for pickup, rather than composting them. She says in Georgia they only use pine straw as mulch, to deter “jumping worms.” She says they are as invasive and destructive as kudzu down there, and like kudzu, have moved north and west. Unlike kudzu, however, they don’t mind cold weather and are unstoppable. I don’t like to panic, but I would like to know how much of a threat they are.

Is there any way to recognize them when they aren’t jumping? Could they possibly hurt me or my family? 

Worried About Worms on Madison Street

Dear Worried About Worms, 

The jumping worm, Amynthas agrestis, arrived on our shores from Asia back in the late 19th century in dirt used for ship ballast, as well as among imported plants. It advances very slowly on its own, but continued use of these worms as bait by fishermen, as well as sale and gift exchange of plants across state lines, has helped spread them. 

This worm is particularly prevalent in unsterilized mulch and has presented a serious problem in southern forests and gardens for awhile. Over time, the jumping worm has gotten as far north as Minnesota and as far west as Kansas.

The jumping worm is not difficult to identify. It is larger than the earthworm, about 6 inches long, and instead of having a pinkish-orange, slightly raised band (clitellum) around its middle, it has a flatter, whitish one. 

You need not worry about it attacking you, although it could startle you when it jumps. 

The real problem is what it does and does not do to the soil. Our beneficial earthworms burrow down deeply and break up the soil, aerating it and improving its texture, while incorporating nutrients from the organic matter they ingest and excrete. Jumping worms do not go far into the soil but stay near the surface and leave their highly erodible castings on top of the soil. These look like coffee grounds and are a sure sign of the presence of these invaders, who reproduce at an alarming rate and displace beneficial worms. Soil fertility and moisture retention is reduced, and these worms and their castings are toxic to the microbial subsoil ecosystem — with far-reaching consequences. 

This degraded soil is then taken over by invasive plant species that do not support beneficial insects and animals. For some still undetermined reason, few birds will prey on these worms. Possums, moles and snakes will eat them, but there are any number of reasons you might not want to invite them into your garden. 

I consulted an expert in helminthology, Dr. Vermicelli Dolitter. When asked if pine straw mulch was an effective deterrent, Dr. Dolitter replied that all mulch attracts them, and that it is advisable to heat-treat whatever mulch you do use before spreading it.  

Of course, unlike Dr. Dolitter, we don’t have a laboratory with special kilns. Although you can heat soil to 150 F in your oven in covered pans, this is painstakingly slow and potentially messy. If you can afford it, you might invest in a portable steam or electric sterilizer. Another method, traditionally used by golf courses, is to apply tea seed meal from camellias  to eliminate worms. This also destroys earthworms you want to keep, so it isn’t to be recommended. For the same reason, the method of heat-treating soil by placing plastic sheeting on it is not prudent. 

Hand-picking is unpleasant and difficult because of these worms’ wild wriggling, but Dr. Dolitter told me how to bring the worms to the surface of the soil to do so: Mix 1/3 cup of ground mustard seed into a gallon of water and pour it over the soil you suspect might harbor them. They will rise to the surface immediately — but don’t think the mustard mixture will kill them or their eggs. 

Dr. Dolitter told me that because there is no magic bullet for this pest, prevention is paramount. Don’t make piles of leaves to create an attractive smorgasbord for them, but rather leave your leaf litter on the ground. Be careful not to move any plants from an infected area into any other part of the garden, and sterilize any tools you’ve used. Order bare root plants only. If you give or receive plants as gifts, wash their roots before repotting in sterilized soil. Most important, clean your shoes carefully after walks in fields or gardens. While the worms themselves die over the course of the winter, their egg-filled cocoons do not. Peppercorn-sized, they are often transported by means of footwear they attach to. These will hatch in early spring. So, even though the adult worms themselves don’t move very far, you should be careful not to further their invasion of our landscape by spreading their eggs.

Now, as far as I know, this worm has not been spotted in Hyattsville. If you do find any — and they’d be most visible in fall — please report your finding to the University of Maryland extension service. Your photos can be posted to their Early Detection and Distribution Mapping System, eddmaps.org. 

To discuss this, as well as pleasanter gardening matters, please come to the next meeting of the Hyattsville Horticultural Society at 10 a.m. on Nov. 19. It will take place in the garden of Mary Jane Stevens and Bob Meyers, 3925 Nicholson Street, and will feature a wreath-making workshop.