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The cascade in the Japanese Garden.
Photo: Jardin botanique de Montréal (Michel Tremblay)

Phytoprotection: Safeguarding our collections

At the Montréal Botanical Garden, our phytoprotection experts work to keep our plants healthy by taking all kinds of preventive action and treating problems caused by insect pests and plant diseases.

It’s not always easy to know how to treat a plant in distress. The Garden has 22,000 taxa, each with its own specific needs and sensitivity to diseases and insect pests. Proper knowledge of plant physiology and their enemies is essential.

Phytoprotection calls for teamwork

The Section Head and supervisors work hand in hand with two horticulturists specializing in phytoprotection – one responsible for the greenhouse complex and the other for the outdoor gardens.

The greenhouses are a closed and protected environment, so plants there are more likely to be attacked by insect pests or diseases. The horticulturist responsible for the Garden’s collection inspects them every two weeks, and takes note of the results. As soon as an infestation is spotted, he or she notifies the person in charge of phytoprotection, to plan the appropriate treatment.

Going green

  • The use of synthetic pesticides in the outdoor gardens and the greenhouses was steadily reduced between 2005 and 2010.
  • Use of acaricides down by 74%.
  • Use of synthetic fungicides down by 38%.
  • Use of synthetic herbicides down by 22%.

The challenges of phytoprotection

Controlling insect pests and pathogens at the Montréal Botanical Garden is no easy task. The way plants are grouped in collections or in production areas actually makes it easier for insects and diseases to spread, and the huge variety of plants grown there leads to an equally diverse range of problems. For many years now, we have been developing different approaches so as to reduce the use of the most toxic synthetic pesticides at the Montréal Botanical Garden.

Policy on pesticide use at the Space for Life

The policy on pesticide use, adopted in 2004 and updated in June 2011, is intended to minimize the use of those pesticides most harmful to the environment and human health by instead using all alternative means of controlling plant pests and diseases while keeping our collections healthy and attractive.

Biological pest control

This is a method of controlling insect pests that uses living organisms (other insects, bacteria, nematodes or fungi) to reduce pest populations. These organisms, known as pest control agents, are natural enemies of the pest to be controlled. This approach is used instead of conventional pesticides.

Biological pest control in the exhibition greenhouses

For several years now, biological pest control has been used successfully in all the exhibition greenhouses. This calls for precise identification of the pest, thorough knowledge of the techniques, and perseverance.

Three pest control agents are used in the greenhouses. Cryptolaemus montrouzieri is an insect that preys on beetles. Amblyseius swirskii is a predacious mite (slow-release packets of mites can sometimes be seen tucked into the plants’ foliage). Between them they rid the greenhouses of scales, thrips and several other kinds of insect pests. Encarsia formosa is a tiny wasp whose larvae are parasites of whitefly larvae. Micro-organisms like bacteria, viruses and fungi can also be introduced in the greenhouses to infect and eradicate insect pests.

Another strategy involves growing indicator plants and banker plants in the greenhouses. Indicator plants attract harmful insects, so that horticulturists can quickly spot any infestation. Sometimes the plant can be destroyed before the pests spread.

Banker plants, on the other hand, serve as hosts for pest control agents. Small groups of indicator plants and banker plants may be dotted throughout the collections.

Biological pest control in the outdoor gardens

Biological pest control is also successfully applied in some of the outdoor gardens:

  • In the Courtyard of the Senses, harmful aphids and mites are controlled by predators (Aphidius, lacewings and ladybird beetles).
  • In the Japanese Garden, two predators (Amblyseius fallacis, Stethorus punctillum) have been introduced to control mites that attack the thujas.
  • In the First Nations Garden, a predator (Stethorus punctillum) is used to control mites.
  • Ladybird beetles control the aphids that attack the annuals in the Reception Gardens.

Integrated pest control

Integrated pest control is a strategy combining several methods to control insect pests, without necessarily eradicating them. It includes preventive methods (plant and site selection, crop rotation), physical and mechanical barriers, biological pest control and, as a last resort, careful and limited use of pesticides – always preferring those with a low environmental impact. Synthetic pesticides are used only when all other control methods have failed. For integrated pest control to be effective, regular screening must be done so that the appropriate action can be taken immediately. The goal is to effectively control insect pests, at a reasonable cost, while respecting the environment and protecting the health of Garden visitors and employees.

Integrated pest control is successfully used in all the outdoor gardens and in the service greenhouses, as follows:

  • Apply various prevention measures (select plants with better resistance to insect pests, and ensure appropriate growing conditions);
  • Identify enemies and allies;
  • Detect the problem and assess its severity;
  • Use intervention thresholds;
  • Adapt the ecosystem;
  • Combine physical, biological, chemical (synthetic) and other control methods and apply them at the right place and time;
  • Assess the effectiveness of the actions and the data collected, and re-assess the situation.

In the Rose Garden, where there are more than 10,000 rose bushes, over 98% of synthetic pesticides have been replaced with low-impact solutions, i.e.:

  • Improved screening and monitoring techniques;
  • Use of low-impact pesticides (insecticidal soap, pyrethrin, biofungicide, baking soda) and clay-based repellent;
  • Use of companion plants.

Based on article by Conrad Bertrand in Quatre-Temps magazine.

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