About us

Campus Crops is a student run urban gardening initiative at McGill University's downtown campus. We want to grow food on campus, by students, for students. We have been running garden behind the School of Environment building at 3534 University since 2007. In 2009 we started a terrace garden behind the James Administration building. We're really excited to keep improving these two spaces, and need lots of helping hands for the summer ahead! Get in touch and get gardening!

Saturday, May 17, 2014

Pest management

This article is based on a workshop given at La Ruche d’Art St-Henri (go check it out if you live in the neighborhood) in 2013. The workshop was built around the philosophy that pest management is not about killing insects, but rather knowing the different insects that can end up in your garden and managing the garden itself in consideration of those insects and what they might bring you (benefits, chaos and destruction, nothing, etc.).

Hygiene is important to prevent the spread of diseases from plant to plant, as well as to prevent attracting more pests. It is a measure of prevention.
For container gardens, it is usually recommended to use clean pots every year to prevent the reappearance of diseases and pests (e.g. aphids lay eggs that will overwinter in the soil and in confined spaces in the pots). The pots need to be washed with warm soapy water (1-2 tbsp per bucket of water) and then left to dry thoroughly before usage. The soil can be composted at high heat or used for something else than gardening (or for plants not susceptible to the disease/pest that might have survived in the soil) or simply dropped in nature, and replaced by fresh sterilized potting mix. In an ideal world that’s how things should be done, but many (like we at Campus Crops) can’t really afford the time and/or money to do this every year, so we only do it by necessity once every few years.
For all types of garden, tools (scissors, knives, etc.) must be cleaned and sprayed with a 70% alcohol solution (rubbing alcohol) before being used. Hands must also be washed if a diseased plant has been touched.

Growing conditions
Also a measure of prevention. Good growing conditions allow the plants to become and stay strong and healthy, which is essential for them in order to fight pests and diseases, and also to improve resilience.
1- Good growing conditions can mean placing the right plant at the right spot. This is where finding information about the plants you grow gets useful, because it allows you to know, for example, that a tomato plant will be much stronger and healthier in a sunny spot than in the shade. It may be better to move a plant that has not been placed at the correct spot in the middle of the season and risk the transplanting shock than letting it grow weak at its original place, where it will probably attract pest and catch diseases (both of which could spread to other plants).
2- Another strategy is soil building and fertilizing. Sick plants should not be fertilized, except if 
using seaweed emulsion (supposedly it stimulates protein synthesis and that’s pretty much the problem with sick plants). Normally, a good potting mix will be 3 parts compost, 2 parts peat moss and 1 part coco fiber (the latter two ingredients are not very eco-friendly, though). Perlite (drainage), sand (drainage, finer grains) and vermiculite (nutrient retention) can also be added, though it’s better to wear a mask when using perlite and vermiculite, as they are small, light pieces of rock and this is not too good for your lungs.

3- Crop rotation! By rotating crops, you make sure that it’s not always the same nutrients that are taken up from the soil at the same place from year to year. Plants have different needs and do not all take an equal amount of nitrogen, phosphorus or potassium (or trace minerals), so planting the same thing at the same place exhausts the soil faster than rotating crops. Here, knowing what was planted in a given location the preceding year, as well as knowing which plants got sick, is essential to plan crop rotation.
4- Pruning is a necessary but delicate operation in a garden. Some diseases are easily contracted in badly aerated and overcrowded conditions and pests are generally attracted by cuts, bruises or wounds on a plant. Both diseases and pests also spread much more easily in overcrowded conditions. Pruning can thus help aerate plants, prevent pests and diseases, and hinder their propagation across the garden. But pruning, by creating an open wound, also creates the conditions for developing diseases and attracting pests, so it must be done in a way that reduces the likelihood for those things to happen.
To prune properly, cut only the top third of a stalk (the third of the length starting from the tip) or of the plant, in the case of naturally dense plants like chives, in order to limit the expansion of the plant. For purposes of aeration, whole stalks may be cut, and pruning in cases of damage to the plant depends on where the damage has been done. If cutting can be done near a budding region, make sure you cut close to the bud while leaving it intact on the plant, as plants tend to naturally scar rapidly there. In any case, clean and sterilized tools must be used (wipe out the alcohol before cutting, as it would damage the plant), and pruning must be done at a 45° angle through the stem (a beveled cut).
5- Flowers! Flowering plans attract beneficial predators, such as wasps, bumblebees, birds, etc. For birds, berry-producing plants can be added to the garden in order to attract them, though this means you’re not planning on eating the berries (birds will get them before you do, unless you’re an early… bird). But flowering plants (including flowers) do not flower for the same period of time or for the whole summer (some flowers do, of course, which means they’re a good addition to a garden). Therefore they should be selected in order for there to be flowers in the garden at all times throughout the season. Flowers do not attract the same beneficial predators, so a bit of research might be useful here. Rules of thumb : (1) bigger flowers = bigger pollinators (bees, birds, bats, mice) ; (2) colorful flowers = bees, white flowers = nocturnal pollinators ; (3) long flowers = pollinators with a long "mouth" (butterflies, moths, hummingbirds)
6- Companion planting. Companions can help a plant get stronger, mask its odor from pests, attract predators, act as a trap crop (so the pests attack this plant and not another one), hide the plant from predators (some beetles, for example, have very bad vision and can be confused by a wall of bushy plants surrounding the plants that you want to protect), etc.. If companion planting is not your cup of tea, consider letting a patch of your garden go wild in order to attract all kinds of insects (it could backfire as extra weeding for the following years, though).

When hygiene and growing conditions have failed to prevent an infection, it’s time to intervene. Intervention should occur AS SOON AS you see signs of pests.
First thing to do, if there are few pest individuals and if you can see them: squash them. With your hands. Or something. This may not work for pests that are brought by other insects (e.g. ants farming aphids). You can keep to this method as long as the situation is under control.
If the bugs are growing in numbers despite your regular squashing, it’s time to spray. Sprays will not act instantaneously and need to be used throughout the life cycle of the pest in order to actually get rid of it for the rest of the season. Insecticidal sprays are almost never good for the plants, though, so they must be used on a regular schedule, so as to make enough damage to the without damaging the plant too much. Day 1 being the first day you use the spray, spray again on days 4, 8 and 14. That should do the trick.
Do not spray seedlings! They’re not strong enough and they’ll die.
Dusk might be the best time to spray, as a lot of beneficial predators are inactive at the end of the day and there will be no risk to also hurt them when spraying the pest.

1- An alcohol spray can be used on soft-bodied insects (i.e. not beetles). Here’s the recipe: 20mL dish soap + 15 mL 70% alcohol + 1 liter of water.
2- For molds (mildew), the spray recipe goes as such: 1-2g baking soda + 5 mL dish soap + 1 L water. Molds will never go away with this spray, though, as the spray only stops their growth and development. Diseased leaves should be removed and burned (or at least not left anywhere near or in the garden, and certainly not composted). The schedule is once a week or after a rain (and then once a week starting from there). It’s important to spray both over and under the leaves in a light mist without allowing droplets to form; droplets of this spray could damage the plant and weaken them.
3- For hard-bodied insects, trap crops, finger squashing and companion planting are the best strategies. Row covers can also be used but must be installed before the insects come and be removed for plant maintenance only when the pest is away doing something else (sleeping, reproducing, whatever).
4- For slugs and snails, attracting birds, installing beer traps, and sprinkling calcium or diatomaceous earth (after every rain episode) can help.
5- For mammal pests, putting dog, cat or human hair, as well as using hunting gear like deer scent, will normally deter raccoons, squirrels, cats, skunks and other furry friends.

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