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Inside View: February 2010

January 28, 2010  By Gary Jones

Early last year at an organic conference, Geneviève Labrie, of the
University of Québec in Montreal reported results of some work she had
been doing on field vegetables (hang on in there with me if you’re a
greenhouse flower grower).

Early last year at an organic conference, Geneviève Labrie, of the University of Québec in Montreal reported results of some work she had been doing on field vegetables (hang on in there with me if you’re a greenhouse flower grower). She’d compared field-grown crops of soybean, corn and wheat grown in conventional “full-field” systems (one crop per field) to a system using different strips of each crop, each strip 18 metres wide. Her results suggested that the “strip system:”

  • Increased crop and biodiversity in the fields.
  • This reduced the concentration of pests’ food supplies by not having just one crop species present.
  • Reduced the concentration of one crop type in a field, so reduced opportunity for pest attack on that crop.
  • Reduced olfactory attraction of the crop for its pest species.
  • Increased the number of natural enemies present in the field, particularly during peak pest populations.

Further, the project demonstrated that in the strip system:

  • Natural enemies in strip-cropped fields were more synchronized with times of high pest populations.
  • Natural enemies were able to move around the fields more easily to control pest outbreaks.
  • More winged aphids were found in fields of single crops than in strip-cropped fields.

The basic principles of this should come as absolutely no surprise to organic producers, but it does add scientific weight to the concept that mono-cropping makes pest control more difficult in many situations; if not more difficult, certainly more fragile.

Fast forward to the poinsettia season. Like most things Christmas-y, the season seems to start earlier every year. It was the last week of October or the first week of November for the first shipments to box stores in British Columbia this year. (Does “climate change” mean an “AYR” poinsettia season? Or is it all just marketing again?) And just like the days when I was growing them in England, whole glasshouses, or at least complete sections of glasshouses, are set aside for production. Of course, this approach makes a lot of sense – greenhouse environments can be set to meet specific environmental (temperature, lighting, blackout, and irrigation) requirements of early, mid and late varieties. And when it comes to shipping, there is nothing as satisfying as an efficient “clear cut” of uniform plants all meeting customers’ specifications, labelled, tagged and packed quickly into pot covers, sleeves and boxes. Job done – what’s next?

The other advantage of this “field system,” of course, is that it makes crop and pest management easier – we can schedule our applications of growth regulators, Encarsia, and fungus gnat control across whole blocks at once. Plus, earlier shipping means that the greenhouse is emptied earlier, freeing up space the grower can utilize to get going with the spring crops of bedding and other potted crops.

But hang on a minute. What if Geneviève Labrie’s “strip cropping” system could be applied to poinsettias? Perhaps that’s the way to manage pests and diseases? How much easier could it be than to let a well-balanced ecosystem take care of its own pest and disease issues rather than justify a fragile mono-crop system by claiming ease of pest management as one of the reasons? How about “strips” of poinsettias growing alongside another crop that could be a super early spring bedding or potted crop species (or more!). Of course, there might be greenhouse environment challenges (what else likes the same temperature conditions as poinsettias at that time of year?). But no doubt this is just something to figure out and you may already have the ideal crop combinations. Sure, it’s nice to turn the heat down to basic “frost protection” once a greenhouse is emptied of “points” for Christmas – but what if the greenhouse were heated with a profitable, early spring crop inside?

It’s just a thought. But why should landscape folks have all the fun with eco-system “bug Gardens,” or field vegetable growers enjoy “strip farming.” Surely, there’s opportunity for bio-diverse greenhouse systems that don’t compromise quality, and that maximize production efficiency while at the same time increasing natural pest management options. There would be plenty here to keep researchers busy, no doubt, but “strip farming” in greenhouses. Perhaps there’s an idea. ■

Gary Jones is chair of production horticulture at Kwantlen University, in Langley, B.C. He sits on several industry committees and would welcome comments at

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