Cooperative Extension: Garden and Yard

I’m so sorry to hear you’ve been hit by the worms, but if it’s any consolation you’re not alone. And your hypothesis for how you got them is reasonable–purchased product is unfortunately a common method of exposure, though the industry is adjusting to the situation. For things like annuals, it’s often tough to get much information about the details of the growing medium, but if you get any bulk soil, compost, or mulch, I would talk to them about this issue beforehand and see if they do heat treatments.

So, for the first question, you are definitely going to want to avoid planting in the spring/early summer and solarize the beds instead, though depending on how things go you *might* be able to plant some late season crops next year. No promises. This is definitely the best method at the moment, as to my knowledge we still have no EPA-approved treatments and the approach has been shown to be effective. According to Purdue Univ Extension, 104 is the target temperature to sustain for 3 days or so to kill off adults and (more importantly) eggs, and you’ll hit that pretty easily with clear (not black) sheeting on a few sunny days next year. I would go ahead and follow the solarization advice in the UNR link above and keep the plastic in place for 4-6 weeks, just to be sure. Start early in the season, as you don’t want the eggs to hatch into adults (the solarization should kill them, too, but they might try to escape, whereas the eggs are immobile). If all of that’s effective and you don’t see any adults by mid-summer, you could try pulling back the plastic and planting some late season crops.

Going into your second question, the compost, this will be more of a project, I fear. If the worms are in your finished and/or finishing compost, they’re likely to serve as a reinfection vector. I would certainly stop moving any compost to other locations for now. These worms are annual in our climate, meaning the adults die in the cold but the eggs survive to hatch another generation next year. The early solarization kills those eggs before they hatch and you (ideally) break the cycle. Depending on the size of your operation, the compost heap *might* be warm enough deep to keep some of the adults alive and to allow earlier hatching of the eggs–the data is out on this, but I’ve seen it mentioned a couple of times and I find the reasoning compelling enough to consider. If it’s true, I worry you’d just be moving the worms back into the solarized beds with your compost, which is a non-starter. Regardless, you have eggs in there for next season.

So your ideas of 1) solarizing the finished compost, and 2) altering your composting practice temporarily–by moving the finished pile and probably pausing the finishing pile temporarily–are both good. I don’t actually know the extent to which the worms might invade unfinished scraps, but I’d err on the side of being sure your compost source isn’t contaminated, so poke around at the bottom of the finishing pile, too–you may wind up wanting to solarize it, too, if you find some. If either pile is too large and you aren’t sure the solarization is getting into the middle of it, rake it out a bit to make sure it’s only a few inches deep before putting down the plastic (if it’s too big to rake into that thin a pile, just do the best you can, knowing that the thinner the layer, the more effective the treatment).

Happy gardening.