This time last year, I talked about work done at Guelph that looked at the advantages of “strip cropping” in field vegetables.
This time last year, I talked about work done at Guelph that looked at the advantages of “strip cropping” in field vegetables. Strips of crops seemingly offer several advantages including:
- Increased crop and insect biodiversity in the fields.
- Reduced concentration of one crop type, so less opportunity for targeted pest attack.
- Increased number of natural enemies present, particularly during peak pest populations.
- While pondering how this could be applied to greenhouse crops, I was at the same time looking at the new biological control agents (BCAs) that have been introduced recently or are about to come on stream. While not all are suitable for use in Canada (e.g., because they are not native here), newer ones include:
- Two new larval parasites (one of the genus Necremnus) from Koppert against the tomato pest Tuta absoluta.
- The whitefly predatory beetle Delphastus catalinae, introduced by Applied Bionomics and being further developed by Koppert.
- The soil mite Macrocheles robustulus for thrips control (Koppert NL).
- The predatory mite Amblyseius limonicusprimarily for thrips and whitefly control (Koppert).
- Development of a new aphid predator Praon humulaphidis by Dr. Dave Gillespie at PARC Agassiz.
- Gaeolaelaps gillespiei (Beaulieu), a new fungus gnat predator being developed by Brian Spencer at Applied Bionomics. (Incidentally, G. gillespiei was recently named after PARC researcher Dave Gillespie, since it was originally an unidentified mite found by him some 30 years ago while doing IPM work.)1
BROADER THE RANGE OF PLANTS, BROADER THE RANGE OF INSECTS
■ So what? Well it’s interesting that many (but by no means all) of these new BCAs have been found while researchers are out looking for new species – not in the greenhouse – but out in the bush. (G. gillespiei was actually found at Sun Wing Greenhouses in Saanich on Vancouver Island1). That’s not really surprising, since that’s where there is the greatest range of plants (biodiversity), and it stands to reason that there will be a wider range of insect species there, too. Some will no doubt be potential beneficials. This is all the more reason to increase plant diversity in and around the greenhouse.
Many growers already use “banker plants” in their crops to support the establishment of BCAs. Cereal plants growing in pots or hanging baskets among sweet pepper crops are typical examples of this. Years ago, Les Wardlow (an enterprising U.K. entomologist) constantly encouraged growers to raise beds of nettles near or in the greenhouse for “home-reared” lacewing production.
Other growers use “trap plants” (such as eggplants placed in poinsettia crops by OMAFRA floriculture IPM specialist Graeme Murphy) and “sentinel plants” to improve the monitoring process.
The concept of sentinel (or “guardian”) plants was developed by Michael Brownbridge (now a researcher at the Vineland Research and Innovation Centre in Ontario) and Margaret Skinner (University of Vermont), starting with the marigold guardian concept for thrips management. The system is now used in many ornamental biocontrol programs with exceptional results. Sweet pepper plants growing in rose crops (or other cut flowers and bedding plant crops) are another common example. This isn’t really new, but if you haven’t tried it yet, talk to your biological control supplier and see how it can help your pest control.
Increasing plant diversity can also help with rearing BCAs. For example, many years ago Don Elliott (Applied Bionomics) developed the Bush bean system for managing spider mites in tomatoes. It’s now used worldwide and has expanded into ornamentals very successfully.
Many commercial producers are increasingly finding success in employing techniques that rely on natural systems. At the same time, some “unconventional” growers are seeing the benefits of streamlining their production techniques along the lines of those used by large-scale “conventional” producers. Perhaps the divide between mainstream and niche growers is narrowing. Maybe the time has come for less of a “them-and-us” attitude and we should see more opportunity for a spirit of co-operation?
Numerous groups in society are now concerned about food security. Trouble is, all of these sectors seem to think there is only one way to achieve that – their way, of course. But perhaps the developments in pest control strategies are a mirror of how to move forward with food security in general.
1 Thanks to Brian Spencer, Applied Bionomics.
Gary Jones is chair of Production Horticulture at Kwantlen University, Langley, B.C. He serves on several industry committees and would welcome comments at Gary.Jones@Kwantlen.ca.
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