Greenhouse grower notes: Starting a biocontrol program?

January 11, 2010
Written by Graeme Murphy
Back in the summer of 2009, I wrote the first in what was to be a series of articles on how to plan, set up and implement a biocontrol program in your greenhouse. The original plan was that each article would follow quite closely on the heels of the previous one. However, the best laid plans.… 

Now the new plan is to revive the series of articles with “Part Two – Planning for Success,” and for those of you who don’t remember “Part One,” it discussed the importance of gathering information, resources and expertise before the program is put into place. The article can be found in the August 2009 issue of Greenhouse Canada, or online at

This article deals with the next step, planning the actual program – what crops will be included, which pests will be targeted, when to start, how to get the most out of the program, what to expect, which biocontrol company should you use, etc. One of the last things I said in “Part One” of this series is that a biocontrol program should be a team effort and an important part of that team is the biocontrol company you will be working with. So this is probably where you should start.

Your supplier is actually much more than that; they should be an integral part of the program’s development and decision-making process. The Ontario greenhouse industry is in the very fortunate position of having access to all the major producers of commercial biocontrol agents. Their product quality is excellent and they have technical specialists in the field whose job is to work with growers to make their biocontrol programs successful. Make your decision as you would with any other product or service. Talk with them, discuss your program and expectations, get their feedback and develop a comfort level with the specialist with whom you will be working.

Crop scouting is a key element in a successful program.
Ontario is in the very fortunate position of having access to all the major producers of commercial biocontrol agents.

These two questions often go hand in hand. If dealing with a crop such as poinsettia, there is really only one pest that growers are concerned about. Yes, there are other poinsettia pests (e.g., Lewis mite, fungus gnats), but, in general, whitefly dominates pest management discussions from August to December. In spring crops, thrips and aphids are the predominant pests for most growers while mites and whiteflies have a narrower host range. In chrysanthemum or gerbera, be prepared to deal with thrips, aphids, mites, leafminer and (for gerbera) whitefly.

If we forget about the specific crops for a minute and think of the pests, thrips is often the driving force behind growers switching to a biocontrol program; ironic really, when you consider that only two to three years ago, thrips was often the main obstacle to growers making the change.

The difference is resistance to pesticides. Currently, there are very few, if any, products that growers can rely on for effective thrips control. And with thrips being such a widespread problem across the whole industry, biological control has for many growers become their primary pest management strategy.

If you are basing your biocontrol program on a particular crop (e.g., poinsettias), then the starting time chooses itself. The only comment to add is that in almost all cases, the program should be started as soon as the crop is in the greenhouse, even on the rooting bench.

If the plan is to implement a broad-based biocontrol program for all crops and pests, then there are other things to consider:

Perhaps most importantly, the pesticide history of the crop plays an important role in your starting point. Murphy’s Law (no relation) states (among many other things) that pesticides kill biocontrol agents more effectively than they kill pests. That includes their residues, which in some cases can remain lethal for several months. So forward planning is important and in some cases it may mean that introductions of biocontrol agents have to wait until pesticide residues are no longer an issue. In the meantime, pest control programs may need to be adjusted so that pesticides with a much shorter residual period are used until the biocontrol program can be started.

In many cases, the fall is often the best time to start a program. There is usually a natural decline in pest populations at this time of year as daylength shortens and light quality and quantity are reduced. This allows time for biocontrol agents to establish in the greenhouse without too much pressure from a rapidly increasing pest population (as often happens in the spring). However, it should be noted that the same factors that slow the development of pests in the winter will do the same for biocontrol agents and a residual pest population can still increase rapidly in the spring ahead of the biocontrols.

Apart from pesticide residues in your own greenhouse, residues on plant material entering your greenhouse can also affect a biocontrol program. If possible, ask suppliers for a list of pesticides applied to stock plants prior to cuttings being taken. If that is not possible, be aware that it could be an issue and pay close attention to how well the program establishes on new plant material.

Biological control is very different from a pesticide-based control program. It is based much more on anticipating problems and taking steps to deal with them before that happens, rather than following the reactive approach of pesticides. It requires a greater understanding of the biology of pests and how they interact with the crop and with the biocontrol agents. How we make use of pest biology in dealing with some of the major greenhouse pests will be the subject of the next article on setting up a biocontrol program.

Graeme Murphy is the greenhouse floriculture IPM specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs at Vineland. • 905-562-4141, ext. 106, or This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

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