pest and weed control for raspberries and asparagus
Grace Farm’s ”Integrated Plan”
Grace Farm is implementing an integrated pest and weed management program that is now in its third year. Here in McHenry County, Illinois, the most difficult weeds to contend with are various forms of ” garlic mustard,” ”carpet weed”, crab grass, dandelions, and thistles. They are very aggressive, and can grow to be quite large. Unchecked, they soon dwarf and choke out emerging canes and spears, competing with them for light, water, and nutrients. Since we grow asparagus and raspberries, the most destructive pest we encounter is the Japanese beetle. This insect is particularly attracted to raspberries and will eat not only the leaf tissue but also the ripened berry. Although it typically does not emerge here until late June and so does not threaten the asparagus harvest, it will decimate mature asparagus ferns and impact the yield of the bed in subsequent years. In addition to the Japanese beetle, we also contend with earwigs, slugs, squash and asparagus beetles.
Our “integrated” pest and weed management plan includes (1) use of “sodded alleyways” to suppress weeds, retain moisture, reduce soil-disrutive tilling, and provide a natural source of nitrogen; (2) encouraging native birds, such as starlings, robins, kildeer, and finches; (3) a small “insect patrol” of bantam chickens in a mobile coop; (4) multiple applications of “beneficial nematodes” for short-term control Japanese beetle and other grubs; (5) application of “milky spore” powder for long-term control of Japanese beetle grubs; (6) handpicking and Neem oil based insecticidal soap and sprays for control of adult beetles; (7) diamataceous earth and Neem oil based products for control of soft-bodied insects; and (8) pest-repellent “companion” plantings such as marigold, columbine, four o’clocks, etc.
Focus on Efficient Use of Resources
In addition to producing the most naturally grown produce possible, we are also focused on resource efficiency. There are only two of us and we don’t have the resources to hire extra help. We also don’t have a lot of space, and we don’t have an unlimited water supply. Here in Northern Illinois, there are periods of intense drought. When we developed our farming plan, we looked for options that would be manageable over a long period of time with just two of us. Some people call this “sustainable” farming which is valued in its own right as good for the planet, but it so happens that these practices are also helpful to the farmer who wants to be as self-reliant and resource-efficient as possible.
Cover Crop to Suppress Weeds: New Zealand White Clover
Because we believe that the plants we grow ultimately absorb chemicals which are repeatedly applied to the soil or directly onto the plants, we have been trying to find the least toxic way to ensure the health and yield of our little farm. Many of the techniques we are using are “organic” or natural, limiting the use of synthetic pesticides and herbicides. One of these techniques is the use of a low-growing cover crop to suppress weeds while also providing a “living mulch”. Another advantage of cover crops is that one can avoid tilling the soil, preserving its natural ecosystem and structure.
After researching various annual and perennial cover crops, we initially settled on two: buckwheat and New Zealand White Clover. Buckwheat is an annual plant that grows very quickly and can outcompete weeds in our area. We decided to try this on areas that we were not intending to plant in the near future. Our rationale was that it would be easier to plant the next season in such areas than if we had to deal with an unwanted perennial cover crop in a sensitive area. Unfortunately, the buckwheat did not perform as we hoped. It did not germinate quickly without more watering than we could handle, and in the end, wasn’t dense enough for our purposes. We can see how it would be helpful in other contexts, however.
On the other hand, the New Zealand clover has performed very well. We chose it after researching various experiments in using sodded alleyways to control weeds without reducing raspberry yields. We looked for a low-growing, dense, heat- and drought-resistant perennial that would not choke out our raspberry canes and asparagus. There are several varieties of clover used for weed suppression. Some are annuals, however, and again we want to be as resource efficient as possible, so if we could seed a over crop once and have confidence that it would come back in successive years before the weeds did, then we would go with that option. And although there are lower-growing clovers than the New Zealand, including the Dutch white clover, we were concerned that the other varieties would be less heat tolerant and require more frequent watering in our area. Clover and other crops are sometimes called a “living mulch” because they can be tilled under and will fix nitrogen into the soil. We don’t till our sodded alleyways, however. We mow the clover periodically to keep it in check, and we collect the clippings for our compost pile.
We settled on New Zealand White Clover and purchased rhizocated seed (innoculated) from Peaceful Valley Organic Supply (groworganic.com). Even though we applied it a little later than recommended - its recommended application window is as early as possible in the spring - we nevertheless found that with natural rain and minimal supplemental watering it germinated and quickly overtook established weeds. This clover also spreads, and it is crucial to avoid seeding it too closely to the target rows and in between plants. It is easily removed from unwanted areas when young, but you must pull it up from the roots in those areas as early as possible. Once well established, New Zealand White Clover will put down very strong roots in spots from which it then sends out runners, which subsequently develop roots of their own.
This process has been most critical for us with our first and second-year raspberry beds. We found that in the more mature beds, the clover simply does not get a foothold in between established plants because the canes outgrow and block light to clover that may stray into the row. We nevertheless manually groom along the rows to protect the raspberry root structure, as raspberries have shallow root systems. We have not found that it significantly reduces yields. But then again, maximizing berry yield is not necessarily one of our primary goals. We want healthy, productive, manageable beds and as long as we aren’t obviously losing yield, we are satisfied.
The New Zealand White was pleasantly effective with the asparagus beds as well. It is a very hardy clover, but over the winter it turns brown and creates a fairly dense carpet, not unlike straw or pine needles, that blocks light for weeds in the alleyway but is fragile enough to permit asparagus spear emergence in early spring. When the clover begins to rejuvenate, some effort is necessary to keep it from creeping into the asparagus rows, as it will impair spear emergence and development if not timely removed. After harvest, the asparagus ferns should also be monitored and protected from too much clover interference. We aren’t meticulous about it, but we do try to keep the clover at a low density.
And it may seem trivial, but the clover performs well without supplemental watering, is quite drought resistant, and it looks really lush and beautiful between the rows, especially when periodically mowed.
In future posts I’ll talk about the other facets of our “integrated” plan.
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