And why is it taking so long!
By Josef Gorres
A lot is happening in the jumping worm world, both good and bad. On the bad side, the range of jumping worms has expanded in the US and into Canada. The latest states reporting them are Washington and Oregon, bringing the number of states with introductions of jumping worms to 40. Canadian ecologists have found them in Nova Scotia, New Brunswick, Quebec and Ontario during the last 5 years. So more gardeners are beginning to wonder what is slithering lazily amidst their summer flower bed.
On the positive side: science hasn’t stood still, and more progress has been made towards knowing about these earthworms and how to control them. Pesky as they might be, they are also pretty fascinating. For example, did you know that the three species we have here are also ubiquitous in Japan but they are tough to find in the forests there? However, if you go to the roadside ditches adjacent to the woods, you find plenty. The ditches are where they get washed from the woods during big storm events. Even so, very few were to be had when we visited Japan for a jumping worm safari. We don’t know why yet, but it’s a question we would dearly like to figure out!
The three most common jumping worm species in New England: Metaphire hilgendorfi (left), Amynthas agrestis (middle) and Amynthas tokioensis (right). Photo credit: Maryam Nouri-Aiin
The one thing that every gardener worries about is: how do I control these worms in my garden? Members of the Healthy Soil Collaborative are trying to tackle this issue by doing pesticide trials and studying the life cycle of jumping worms. We know that there are plant-based substances that kill the worms. Tea tree seed meal is the one that most of us have heard about, but it is not registered as a pesticide in North America, and it is very expensive because you have to buy it in bulk from China. Furthermore, there are currently no registered products, including tea seed meal, for earthworm control which makes it technically illegal to use for this purpose.
It is actually incredibly expensive and time-consuming to get a brand new pesticide through tests and past certification at a federal and state/provincial level. Federally, pesticides are regulated by the EPA through the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA for short). In Canada, Health Canada regulates pesticides through the Pest Control Products Act. Those regulations are justifiably strict and any pesticide needs to go through that first hurdle of showing that it is both effective, and not harmful to the environment, humans or other organisms. There must be known, safe methods of applying it. (By safe methods we mean the formulation, the strength, the timing, and the place of the application.) In addition, there are separate regulations in the states and provinces that are typically more stringent than those set by federal agencies. In Vermont, for example, part of the pesticide law enacts strong pollinator protection.
Getting a new pesticide approved by EPA will probably cost on the order of a million dollars and on top of that, we need to convince pesticide producers that it is worth their while to manufacture such products, and convince regulators that this issue matters. And that also means more data on the environmental and societal impact of the pest. Have a look at this paper to understand the breadth of the impact of earthworm invasions. We have a lot of information, but we need even more to pass this hurdle.
All this sounds really difficult, but there are some intentional loopholes in the FIFRA regulations. (These loopholes do not apply in Canada.) The first one of these is FIFRA section (2ee): this section of the law states that if a pre-existing pesticide is already approved for use on a range of pests, then it should be allowed to be used on another pest as long as it is efficacious and used in accordance with the label. So, there is a long list of FIFRA-approved pesticides already that can be tested for their effect on jumping worms. The second loophole includes a range of substances that have been deemed by the EPA as of low enough impact on the environment and humans that they do not need registration at the federal level, so if one of those can be shown to have an impact on jumping worms, they might be easier to get approval for as well. We’re looking into both avenues.
So, there you are, easy-peasy, right? Not so fast! Just because a pesticide is allowed at the federal level does not mean that the individual states allow it. There is an additional layer of scrutiny that is applied to meet standards set by states.
For example, from greenhouse trials, we know that sodium lauryl sulfate is effective at killing jumping worms, similar to tea tree seed meal. Sodium lauryl sulfate is on the EPA list of minimum risk active ingredients. It may be in your toothpaste or shampoo right now as a soapy surfactant. It’s a good candidate because you can bypass the federal FIFRA approval process but not in states that do not recognize the list of minimum risk substances.
Botanigard, a biopesticide based on soil-based fungi, is effective as well and it is a registered pesticide with EPA and deemed not to have any off-target environmental impact when used in accordance with the label. Under section 2(ee) it should thus be all right to use. However, it still needs state approval, so more testing needs to be done.
Tea seed meal is not a registered pesticide in the USA at all, and thus it must go through the expensive FIFRA registration process, plus the extra steps to get it approved in the states.
We’re really focusing right now on trialing substances for efficacy that are either candidates for FIFRA exemptions under section 2(ee) or on the list of minimum risk substances. At least, in theory, this should allow us to go straight to the state regulators for registration and get something safe and approved to users more quickly. These probably would not be appropriate for forests and more complex ecosystems, but they might work very well in regulated settings like nurseries and growers and composters and maybe garden planting beds, all of which can be vectors of jumping worm spread into the forests.
Another question that we need to answer for pesticide labels is when during the life cycle of a jumping worm is the application of a pesticide most effective. This also requires trials of pesticides at different stages of worm development. We found that Botanigard is most effective when the worms are still young. (See figure below, from Nouri-Aiin & Gorres: Biocontrol of invasive pheretimoid earthworms using Beauveria bassiana. PeerJ 9:e11101). The average kill rate of juveniles for Botanigard treatments hovers around 75%. The mortality rate for pre-adults was only around 15% (figure below). Pest age and timing of application is important to consider for other pesticides as well.
Mortality of jumping worms treated with Beauvaria bassiana (Botanigard) for juveniles (A) and preadults (B). Note the low mortality for the preadult worms.
We are working hard to learn more about the environmental impacts of invasive earthworms and the potential treatments that we hope might help control them someday. There is light at the end of the tunnel! We just need to get there. We’ll be posting more and more of our research on this website, and hope to see it become a repository of new findings and resources.
And if you want to help us to keep this effort going, we invite anyone who is interested to make a donation to fund our research at the site as it is still difficult to convince federal and state agencies to fund invasive earthworm research.
