Insectes : changement de tactiques

L'agriculture et le jardinage biologique retournent en arrière pour intégrer à nouveau les méthodes d'un passé presque oublié, non sans créer et exploiter de nouvelles innovations, pour cultiver sans utiliser de produits chimiques nocifs. L'auteure, Beth McMahon offre aux lecteurs des conseils utiles pour attirer biologiquement les insectes bénéfiques dans votre jardin tout en décourageant les nuisibles.

Pour minimiser les ravages de certains insectes dans votre jardin, McMahon suggère de : 
o Planter des plantes qui résistent aux maladies et aux insectes. 
o Introduire la diversité dans votre jardin. 
o Planter des variétés dans différents endroits. 
o Faire la rotation de vos plantations. 
o Protéger vos semis. 
o Utiliser des paillis. 
o Sacrifier des plantations au périmètre de votre jardin.

Bugs: Changing Tactics 

Beth McMahon
ACORN

May 2008

"A good gardener always plants three seeds - one for the bugs, one for the weather and one for himself." - Leo Aikman

here is overwhelming evidence in favour of eliminating unnecessary chemicals, which have impacts on humans and the broader ecosystem, from our lives. Organic agriculture and gardening is reaching back to recapture methods from the nearly forgotten past, all the while creating and exploring new innovations for growing without the use of harmful chemicals.

Over and over, we're told that gardeners have to pay attention to the whole system, by creating good spaces for vegetables, flowers, and … bugs. Believe it or not, bugs aren't bad; in fact, the vast majority of them have a key role to play in your garden. Some estimates say that only 1-2% of bugs cause garden troubles - and far more are considered beneficial insects. Bugs are essential to the success of your gardens - pollinating, preying on other problem pests, and aerating the soil (ants are great at this!). What's key is to create a balanced ecosystem and to prevent problems before they start.

Good growers think about how to attract beneficial insects to their gardens, a practice often referred to as "farmscaping." In order to host beneficial insects, you have to consider what practices will entice them settle in your garden. Bugs need water (ever thought about a "bug bath" - a miniscule version of a bird bath?), a good home (e.g., some like to live undercover, so try leaving patches of leaves under big bushy plants), and food. Bug-friendly plant varieties often include those with small, shallow flowers, and those with bright colours, nectar, and pollen (e.g, lavender, cosmos, butterfly weed, marigolds, and many types of herbs and wildflowers).

Beneficial insects should be viewed as mini-livestock.  They will be healthier, reproduce more readily, and be more effective biocontrols when provided habitat with an adequate and easily available diet of nectar, pollen, and herbivorous insects and mites.

In order to minimize bug damage to your garden, think about variety selection; start researching plants that are resistant to disease and pests. Selective breeding has been taking place for millennia - it's completely natural (we're not talking about gene splicing here). You might also want to consider heritage and native varieties; many have inherent resistance to local pests. With the help of the Internet, selecting the right variety has never been easier.

Think about designing for diversity, even within a particular species, whether it's roses or carrots. And, while you're thinking about diversity, don't forget to consider the biggest crop you have surrounding your gardens: the lawn monoculture, which, like any crop will attract particular kinds of pests (i.e., leafhoppers).

Plant your varieties in different locations, so if problem pests find one, they might not locate the other. You also shouldn't plant the same plant family in the same place as last year. Include crop rotation in your garden planning, which confuses potential pests and improves the soil too.

Protect your seedlings. Some people find that putting tubes (paper towel and toilet paper rolls) or the tops of disposable cups around seedlings works well to discourage bugs from eating fresh shoots or transplants. I've also seen clear water jugs placed over squash seedlings acting for climate regulation and protection from cucumber beetle.


Frances McGinnis examines new salad greens, which have been protected from bugs by using row covers.
(Photo: Beth McMahon)

Use mulch. This is very beneficial for the soil, water retention, and it also does a good job at confusing pest-y bugs (even Colorado potato beetles can have a hard time finding potatoes with a good amount of straw around the plants). The exception here is that cucumber beetles like mulch, so avoid it on your melons and cucumber patches. Make sure the mulch you're using is "clean" - you don't want to bring in more weed seeds or herbicides from grass clippings.

Try using "trap" crops, which are planted around the perimeter of your garden. These plants are your sacrifice to bugs; they also function to lure them away from the preferred plants you don't want to sacrifice. Often, trap crops are planted earlier than the real crop to head off the pests. When you become aware of destructive pests, you should kill them to control their populations.

Companion planting is another key to preventing bug problems. This is where combinations of plants are put together to benefit each other. For example, white flies and aphids dislike nasturtiums. There are many known combinations that you can find in books (e.g., Roses Love Garlic by Louise Riotte) or on-line. Companion plants also result in added garden diversity.

At this time of year, your gardens should be growing strong, so make sure they flourish by performing preventative maintenance. Be good to your soil - reduce tilling and add well-composted material - this will help ensure strong plants. Clean up your gardens and keep your compost piles away from the garden. Scout for bugs and eggs daily (remember to look under leaves) and handpick them out. If you find a bad infestation in a plant, pull it out.

Despite all of these great bug-friendly activities, there may still be times when you need stronger tactics. My first suggestion is the Internet, as there are so many great ideas and forums that you can access for advice. There are also strategies that may be new concepts for gardeners, which are used in farming. For example, using row covers is very effective for controlling flea beetles. Then there are "natural" insecticides to be found at garden centres (e.g., Ecosense by Scott's) or homemade concoctions, which still require moderation and smarts (don't spray the soil, which may kill micro-organisms and good bugs). Finally, change your expectations, accept imperfection (you can cut out the worm hole), and embrace the nature of your backyard!

Additional resources:
ACORN Organic Insect Directory
Insect Control
Trap Cropping
Companion Planting 1 2 3
Farmscaping (PDF - 1.36 MB)
Natural pesticides

Beth McMahon is the Executive Director of ACORN.  ACORN promotes organic growing and consumption in Atlantic Canada. 

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