18 June 2009

If only I had known the trouble I had sown...

Organic and Ecological gardening relies heavily on an intact bio-sphere of pests and their natural predators. There are literally hundreds of insects and natural allies to become familiar with, and not just identify, but to learn their habitats and provide the conditions to attract these beneficials. In my first potato patch, while hunting down potato beetles and their voracious larvae, I squished anything that looked remotely like the larvae, only to realize later I had been destroying Lady Beetle larvae as well. The next year I saw with new eyes that every new bug I encountered was a potential ally, and began a practice of keeping a digital camera in my pocket so that I could snap a picture of unknown insects and identify them at my favorite site http://www.bugguide.net/.

I had read about the importance of keeping a wild or overgrown areas around the garden to provide habitat for beneficial insects, birds, toads and snakes. And yes, this is true, but I have learned, only in moderation, and only with specific habitat plants. I left a large strip of weeds grow up along the garden last summer, and with the worst characteristic of an organic gardener, I lazily called "habitat", and left standing. This spring, we are over-run with cutworms, and I know why. The Dart Moth, the adult form of the Cutworm, is a night flying moth that prefers to lay it's eggs in dense stands of weeds, like Lamb's Quarters, and I provided the perfect habitat.

I have not yet discovered a single beneficial that requires a habitat of standing weeds, but many are attracted by the other "real" habitat stands that we leave around the garden, consisting of Tansy, Goldenrod, and Evening Primrose. And of course, most of the flowering plants in the garden attract beneficials, like Dill or Carrot flowers. So don't let that lazy voice get the best of you and call any overgrown area of your garden that you haven't gotten around to, a "habitat".

The Cutworms are not the type I have read about, toppling Tomatoes and Beans like tiny trees. These ones prefer Onions, Carrots, Parsnips, Beets, Chard, Spinach, Lettuce, and even some Radish and Turnips and one Cabbage. I have had to re-plant many of these crops, and I am blown away by the number of Cutworms in the garden this year. They hide just below the surface, and I have found and hand picked no less than 500 Cutworms from a 3,000 square foot area this spring.

Every morning I look for damage, either wilted seedlings or leaves, as they tend to take off stems above ground.

Nine times out of ten, I find one of these an inch or so below the surface near the root of the damaged plant.

I collect them, and take a rough count, to keep track of the population curve so that I know whether I am getting on top of them.

And then they are breakfast for the hens. What takes me an half-hour to collect, disappears in a matter of seconds. And then they look up for more. We let the chickens scratch over the garden in the fall, but we are looking into building chicken runs, and moving them over the garden in the spring, before planting.I'm not the only one searching out the Cutworms. Fortunately we have most of the natural enemies of the Cutworm in the garden this spring.

The Soldier Beetles are breeding like crazy (they are attracted by Comfrey and Mullein), and are a welcome site. They prey on a number of pest larvae in the soil, including Cutworms and the larval stages of Potato, Cucumber and Flea Beetles when they go under ground to pupate. In fact, there are more Soldier Beetles in the potato patch than Potato Beetles this year. Hooray!

Ground Beetles provide a similar service as the Soldier Beetles, but they are less conspicuous and often go unnoticed.

Firefly larvae also eat Cutworms, and I'm sure they are in the soil because the adults reliably emerge and light up the pasture with their flickering lights in July.

Stink bugs, another Natural Enemy, are just emerging. They also prey upon Potato Beetle larvae and were in abundance in the potato patch last year.

Tachinid Flies and Braconid Wasps are also present in the garden. Just this morning I spotted a cutworm inching along the surface of the garden, a rare occurrence in the daytime. But before I could get to it I noticed a beautiful Ichneumonid wasp (of the Braconid family) swoop down to parasitize the worm. The Cutworm curled defensively and the wasp leaped away, touching down momentarily twice. I don't know how quickly they can deliver their eggs into the worm, but it was definitely on the look out for vulnerable Cutworms such as this one.

This friendly toad was spotted earlier in the spring, most have probably retreated to the cool cover of the mulched areas of the garden by now. But they come out at night and feed on nearly anything that moves, including the night flying Dart Moth.

I hope this Garter Snake, also spotted earlier in the spring, has made a nest in the pile of logs atop a mound of sawdust next to the garden that we leave for snake habitat. Last year we hosted an Eastern Smooth Green Snake, a voracious insect eater.

And last, but not least, our garden is visited by Northern Short Tailed Shews, they also, are insect eaters, and feed on earthworms, as well as other invertebrates. And our tireless kitty prefers to feed on them.

So we have plenty of allies to help control our Cutworm infestation, but as usual, there is a lag between the population bloom of pests and the appearance of predators in sufficient numbers to control the pest. And that's where we, as gardeners, come into the picture. So for now, I will continue to scour the soil, around the problem areas, and keep counts of the number of Cutworms found in 100 square feet, and when I begin to see the numbers decreasing, I will know that my allies have found the feast.


ChicagoMike said...

That is a magnificent post.

Observation, humility, action.

randi said...

I've been meaning to tell you how much I've enjoyed your informative posts. I learn something every time I read one of your entries..thank you!

Anonymous said...

You always provide interesting insights here. Gardening is so full of opportunities to learn!

I wonder about your weed classification. Here in se BC I would not let Tansy, Goldenrod, or Evening Primrose in or very near my garden. But I do let Lamb's Quarters grow as all the animals like it and it is a relatively easy weed to pull.

Is your reasoning based on cutworms? So far I only have seen a few cutworms... I'll look more carefully from now on thanks to your warning.

Throwback at Trapper Creek said...

Great post, it so important to know what each insect's role is, it is so easy to assume that a certain bug is eating our plants when we see them around the dead plants. Sometimes the blame is placed in the wrong place. It is important to know what the insect actually eats. Some insects are part of the clean-up crew, for instance - sow bugs gets blamed for all sorts of damage... .

Sorry to see the explosion of cut worms, that is excessive!

Freija and Beringian Fritillary said...

Chicago Mike, thanks!

randi, I'm so glad you commented, always happy to meet a fellow blogging gardener. And thank you very much for your kind words.

EJ, most nectar producing flowering plants attract beneficials (although some do attract pests, like Lilac attracts the Cutworm moth). Goldenrod attracts Big-Eyed Bugs, Soldier Beetles, Hoverflies. Tansy: Tachinid Flies, Braconid Wasps, Ladybugs, Lacewings. Evening Primrose: Ground Beetles, and they are a favorite of Hummingbirds.

The garden was turned in on an overgrown pasture that had been taken over by goldenrod and tansy, so it has been simple for us to keep a border of these flowering plants along one side of the garden, but they are not allowed to grow within the garden as they are a difficult plant to cultivate once established. Since leaving this border I have noticed an increase especially in the number of Ground Beetles and Soldier Beetles in the garden from year to year.

The Evening Primrose prefers disturbed soils and has introduced itself since we have turned the garden. It is a large plant in it's 2nd year when it goes to flower, so there are few places within the garden I would let a Primrose go, but again, I allow, and encourage their self-sowing around the borders of the garden and herb beds. It was established in North America from Europe as a domesticated vegetable. The first year roots are a vegetable similar to Parsnips, so I will sometimes let the first year roots grow as an annual in the garden and harvest in the fall (similar to the way I treat Dandelion in the garden).

From my research into Cutworms I have found numerous sites linking Lamb's Quarters, Pigweed and the Docs (Curled and Yellow) as favorite egg-laying sites of the Cutworm moth. We also harvest Lamb's Quarters from the garden as animal fodder, but try not to allow the plant to seed, especially as we are growing Quinoa and do not want it to cross. The most important thing I have learned about the link between Lamb's Quarters and Cutworm is not to let the plants overwinter. If we had cultivated the weedy area in the fall, or better yet, pulled and removed the plants, we would not have suffered the same infestation.

Trapper Creak, yes the cutworms are excessive, it is my first experience with a full-blown infestation, and it can be pretty discouraging! I've always been a "bug nerd" since I was a little girl, kind of strange like that. Sometimes I think my garden is an excuse to watch and learn about the insects that live there. And it is certainly true that not all the bugs you see in the garden are pests.