Variegated Cutworms and Forest Tent Caterpillars
The first damaging news to share is the destructiveness that caterpillar species are imposing on our crops this year. We suspect that you may be aware of this challenge due to the news articles that were highlighted in local papers and the egg masses many of you likely found on your own homes. Variegated Cutworms, Yellow Striped Armyworms, and Forest Tent Caterpillars have invaded the fields and forest of NE MN. The Variegated Cutworms and Yellow Striped Armyworms, new species to northern MN, are nocturnal and live at or below the soil line making them hard to find. Unlike the other cutworm species that climbs the stem of plants and cut it off at the base leaving it to die, the Variegated Cutworm and Yellow Striped Armyworm, along with the Forest Tent Caterpillar, feed on leaves consuming most of the plant material leaving little left for the plant to survive. For forest species, the trees are big enough to survive the defoliation. In vegetable crops, particularly young, freshly germinated plants, the survival and recovery rate is low.
So what are we doing about this? Lots! We have not quit the battle with this army of worms. Our main defense is hand-picking caterpillars off crops and keeping an organically-approved treatment regimen utilizing Btk and Pyganic. Before planting our 2000 tomato plants, we picked off around 6 to 20 caterpillars per plant before putting them in our field. When we planted squash and cucumber seeds, we found a cutworm in nearly every other hole we dug and destroyed them. Currently, our lettuce and other spring greens, one of our proudest crops year after year, is being hammered the hardest. We pick and pick, hoping to gain an edge on this fight, but the greens are currently our losing crop. In a 2-day window of picking, we easily found 40 caterpillars in every 4’ row; many of them so tiny and hidden in the soil that the population returns within a couple days. What we are planning to do this evening is night pick; since they are nocturnal feeders, we will wake after midnight and pick by headlamp to see if we have a greater impact on their population. As if farmers weren’t tired enough!
The Btk and Pyganic treatments are naturally-derived and organically approved, listed by the Organic Materials Review Institute (OMRI). We are being proactive with these expensive and time-consuming treatments, staying on top of a schedule that is made difficult due to rain (which washes the treatment away). As organic farmers, we are pleased that there are some controls that we can utilize to help the combat. These controls won’t kill the pests in whole, but will hopefully knock the population back just enough to let us get ahead and get us through the season with less loss of crops. That said, as organic farmers and one’s who practice Holistic Management, our goal is to not simply replace nasty chemical controls with more benign or naturally-derived chemicals, but to better understand the organism and it’s role within the ecosystem, so that we can disrupt it’s lifecycle and habits in order to minimize the damage. Forest Tent Caterpillars and Variegated Cutworms will prove difficult at best with this holistic approach, but this quest for knowledge and understanding is the ongoing story of an organic farmer’s life. All in all, we will continue to be proactive and vigilant. Our main hope will be a normal, cold winter that pushes the Variegated Cutworm back to southern MN where they have natural predators (they typically can’t survive the winters of NE MN) and for the 10-year cycle of Forest Tent Caterpillar to hit its peak (possibly next year) and begin to decline for another quiet decade.
Flood Impact
As if our fight with caterpillars wasn’t trying enough, the flooding definitely dealt another blow of harsh and risky reality for the farm and its members. Given our location along the North Shore, we don’t think it will come as a surprise that we were hit hard with water. We received close to Duluth’s rainfall at 9.71” with all roads around us closed due to wash-out or flowing water. At midnight on Tuesday evening, the field was under water. We went to bed in a dramatic state, fearing that all crops would be lost.
As we watched the water recede the following day, to our great surprise, many of our crops held. We believe this is directly due to production and management choices we made this season to improve our ecosystem function to include sub-soiling our land, adding 30 yards of compost, and raising our crop beds (we will share more about these highlights in the future). The field is currently too wet to fully inspect each crop; to work in a field this wet will do more long-term damage to the soil than what the flooding itself caused. For now, we look out to see rows of crops, stunted and waterlogged, but rows none the less. From this point on, the real test will come as the plants decide if they can weather this storm or will succumb to root rot and fungal disease, common to flooded fields and prolonged periods of wetness. Our hope is the plants will weather the storm. That life isn’t going to throw us more than we can deal with this summer. That we have positive outcomes out of a tough start to a season.
We are hopeful! And with that hope, the rain clouds that threatened when I started this post have passed with only a nominal shower. The sun has come out. Farming is a risky business; it’s a beautiful thing to have our CSA members sharing the risk with us!