You’re a home gardener and the cost of of buying; the labour of applying; and the difficulty in sourcing beneficial insects seems – all together – like a mountain to climb. You’re not alone. And while it is my goal to make beneficial insects better understood and more readily available to you, this is still a major hurdle for our industry. Fortunately, with minimal effort and little-to-no cost you can have your yard buzzing with beneficial insects using the age-old technique: Conservational Biocontrol.
(To see some of this in video form, click here.)
First, let me introduce the loosely-used classifications of Biocontrol:
Classical Biocontrol: This is one of the primary methods we use for targeting and controlling invasive pests (after we’ve tried and failed to use chemistry). Classical Biocontrol is the introduction of a foreign natural enemy to target a specific pest. Historically, what happens is we are suddenly experiencing a new pest from abroad; Then this pest runs-a-muck in this new territory in the absence of its own natural predators. So researchers go looking for its natural predators back where it came from. They find one or more suitable candidates, run some trials to make sure they won’t interfere with non-target species (or at least to an extent we can tolerate), then rear the best option in large numbers and release it around the target area. One such example is the Cabbage Butterfly or Cabbage White (Pieris rapae) which was accidentally introduced to North America. Several wasp and fly species that parasitized the butterfly’s caterpillars in its natural range were thus introduced to North America is hopes of controlling it.
Problems with this: A case-study. Bindweed (a type of Morning Glory) is a disastrous weed in my yard as well as many of yours’. Several years ago a mite that fed exclusively on morning glory was discovered and evaluated as a candidate for a classical biocontrol release to control the invasive morning glory. However, it was found to also kill the non-target, native species of morning glory and was therefore never released. We have become much better at conducting experiments and far more focused on environmental impact than we used to be. So Classical BioControl is becoming (rightfully so) a bit of a rarity. Instead, we do the following:
Augmentative Biocontrol: This is the most common method of biological pest control in the commercial setting. Augmentative Biocontrol is the mass rearing of a natural and native predator in order to release it in its natural territory to regain a balance of pest to predator, or to tip the scale in one’s favour. This is typically the business of Biological Control companies. For example, Anystis baccarum, a predatory mite, is found all over the world and is a major predator of a huge number of pests. But when mass produced and released en mass it has the ability to control aphids and thrips, once the numbers of those pests have gotten out of control. And in protected areas, like greenhouses, adding the predator that would be outside, is important to “fight the good fight.” In its natural state, Anystis is a fierce predator, but rarely seen and heavily fed upon by larger spiders. I am personally involved in Augmentative Biocontrol. There are several native species I have collected from the wild and evaluated as potential Augmentative Bio-Controls. While this used to be government funded, it has increasingly been left to private funding. Read more about Anystis baccarum – including where to get it: here.
Conservational Biocontrol: What you’ve been waiting for. This is the process of promoting naturally occurring natural enemies control common pests by (in part) providing habitat. With this method you are not buying and applying invertebrates, you are welcoming and attracting them.
You’re likely already considering or practicing the promotion of pollinators by selecting specific flowers to incorporate into your garden. Conservational Biocontrol is based on similar practices, but it requires a bit more specific knowlede or just pure luck. Therefore, knowing who the predators are, and what they want and need is central to the success of Conservational BioControl (CBC) but with a few of my recommendations and a bit of luck you may find success without having to become an expert entomologist.
So here’s what you need to get started:
Fundamentals: Some predators need only the pest to survive and continue for generations. For example, there are some parasitoids that eat the host pest as well as parasitize them, so other than water and some plants to hang-out on, they are fairly simple. But this is rare. It is far more common that a predator needs plant cover that provides a particular level of light or protection from light, a specific place to pupate and different diets as adults than as larvae. But no one is expecting you to figure this out on your own, so fortunately there are some general guidelines that can help, and by following these recommendations, you can generally promote beneficials without having to study them:
- Diversity: When in doubt, plant everything. Have annuals, and perennials; evergreens and deciduous plants. Have ground covers, shrubs and trees. Have plants that shade above plants that like shade, and have plants that want to be alone, basking in the direct sun. Just like your pests, some predators feed on a pest in the summer, but overwinter in forests or evergreen foliage, feeding on something else. Diversity will allow you to account for all these things for which we only know the tip of the iceberg. We are still discovering new insects and mites daily, and almost no one goes to any extent to discover their entire life cycle because it is just too difficult. So this is where luck comes in. Provide it all, and the beneficials should show up.
- Water feature: Everything needs water. Some pests don’t drink because they get the moisture they need from the plant they feed on. Some predators also don’t drink because…well, liquified aphids is thirst-quenching! (Don’t try that at home). But most will drink little droplets of dew or rain, and others: directly from standing water. But the water feature is really needed to add diversity. There will be some living in the water, some visiting the water, and some just there for the water plants. The water feature should deep, shaded and cool. And… it should breed mosquitos. And if you live somewhere where mosquitos aren’t likely to kill you, or have adverse reactions to them, this is something you should want. The reason? One example: dragonflies lay their eggs in the water. Their larvae feed on mosquito larvae then crawl out of the water and emerge as flying adults. The flying adults pollinate, but are also predators of other pests. And dragonflies are just one example of this interaction of water features and pest control in your yard. If you’re worried about mosquitos, know that the water feature is seldom the problem because of the natural enemies that will be present. Mosquitos are a problem where standing water is not suitable for predators, like in a watering can left out over night, small pools collected at the joint between leaves and stems or simply in a clogged gutter. In those areas the water will host entire life-cycles of mosquitoes without predation before the water gets too hot for even mosquitoes. Because the mosquito life cycle is so quick, if the predators aren’t already there the mosquitos will exist un-checked. So while I say you should be ok breeding mosquitos, really, I’m asking you to breed mosquito predators by being more tolerant of mosquitoes and providing habitat for those that wish to eat mosquitoes. Again, mosquitoes are just an example. Put-in a water feature, and sit next to it quietly one hot morning and be satisfied with how you have facilitated such an abundance of diversity. (This sounds “flakey”, but I promise, it’s worth it.)
- Be Chemical-Free: This might seem obvious. Most people understand the relationship between brand-name pesticides and the non-target impacts in ones garden. However, most people feel that soaps or oils or “organic pesticides” are fine. But hell-no! I’ll concede: If you need it, you need it; but all of these will indiscriminately ward-off predators. So let me make this abundantly clear: all these home-concoctions are “pesticides.” They work. Use them if you need. But, they have a lasting effect on the plant (chemical response reactions) and on predators (chemical residue, smells…etc). What eventually comes back is the pest, but the predator will not. So to be chemical-free, means just use water or do nothing. This, with an abundance of patience and tolerance, is all you need to get balance in the yard.
*In the case of chemicals, keep this in mind: In North America, some biocontrol companies, and many chemical companies publish graphs and charts or lists about chemical compatibility and how they won’t kill non-target bugs, like pollinators. But in Germany, they force these companies to prove the sub-lethal effects: perhaps the non-target bug doesn’t die, but does it go blind? Can it no longer reproduce? Does it die 31 minutes later (1 minute after a cut-off for the designation “lethal.) And in Germany, most of the chemicals we toss-around because they “don’t kill good bugs” are banned because the tragically reduce the efficacy of those good bugs.
None of this works without the aforementioned Patience and Tolerance. And to get there, we need education. So keep this in mind, when growing in your yard:
- Plant pests seldom kill healthy, established plants. (Not so true of seedlings).
- Pests are food for predators. If left alone and in an area predators can find them, the predators will. As long as they are in more natural population numbers. Large monocultures can often produce such an abundance of pests that predators can’t keep up.
- Nature wants pest populations to increase before the predators. This ensures enough food to increase the predator populations. This is part of the balance.
- Most pest infestations are the result of trying to grow a monoculture; trying to grow outside of natural environment; history of use of soaps, and oils as pesticides; or plants being stressed due to soil chemistry, moisture level, or some sort of immune attack.
- Pests are often the symptom of a stressed plant – not the cause.
In a greenhouse this changes. Anytime you try to protect plants, you are also protecting the pests. All pests need is your plants. But predators need a variety of things, and usually those are found outside. Your tolerance has to be lower indoors. But try this out to help:
- Increase humidity. Forget what your cannabis-growing uncle says. Plants also like humidity and mildews, and molds bloom because of changes in humidity, not “high” humidity. Healthy plants can maintain levels of moisture immediately below their leaves where predators will need to hang-out.
- Decrease wind-speed. This also allows plants to increase and stabilize the humidity on the undersides of leaves. Also, predators will not fly, will not be able to locate their prey using smell and will generally just hang on until wind speeds drop below 2mph.
- Be prepared to augment. You can bring in plants like alyssum to attract predators, but chances are you have a whole lot of plants that bugs want to eat. You may have to provide the predators.
- Sentry plants should be used. This is a plant that is MORE attractive to your target pest than your crop. If it gets aphids, remove the plant and start again or introduce predators.
- Avoid “Banker” plants. The idea of banker plants seems legit: A plant hosts a species of aphids than will not infect your crop. Then, like a sentry plant, predators are established on the banker and able to multiply and spread into the crop. This sounds good, but what is always more effective and less expensive is just treating your crop as the “Banker” and sending predators into the crop. If there are few pests that’s perfect. Predators will find every single one and hang-out or starve if there aren’t enough. If there are more pests, the predators will find them, feed and cycle. The important thing is they are eating the pests in your crop, not just on the banker.
- If you just have a small greenhouse at home, just put the plants outside when it’s warm, let the predators find them, then bring them back inside.
Perhaps the greatest piece of Conservational BioControl is the selection of plants. As I mentioned briefly, you want a variety. But here are some suggestions of plants I have found useful in my climate (South West British Columbia, Canada.) Some of these are effective anywhere, but you may need to select those more suited for your yard:
Sunflowers: Most species produce tons of pollen, which is an essential protein source for many insects. Plus they are made up of lots of small flowers, which is important for many fly species that have small mouth pieces. But, the plant is also edible and attracts both pests and predators. Furthermore, some species have extra-floral nectaries: these are parts of the flower that secrete nectar (or something sugary like nectar) elsewhere on the plant to attract insects! On sunflowers, these are along the stem and favoured by butterflies. And as a bonus: They add some height and colour to your garden.
Because sunflowers are tall and in the lettuce family. I typically grow them in North/South rows amongst lettuces to help give them a bit of a break from the summer sun. Or I plant an East/West row on the south side of the bed to provide lots of shade.
Sweet Alyssum: Careful with this one. There are lots of “alyssum” and some are invasive. I get “snow carpet” which is bred to be low and abundant in flowers. Alyssum is extremely high in nectar. Again, small flowers attract small bugs, and that is ESSENTIAL for biocontrol. What I find disproportionately feeding on alyssum are small parasitic wasps. Because this variety is low, I plant it in and amongst many crops to provide cover. You see it in my onions, garlic, lettuce and even solanacea beds. I start it early, set it out early and it flowers all season.
Buckwheat: Similarly high in nectar with small flowers and attracts parasitoid wasps like Alyssum, but this is a tall plant that I can use successively. In ideal situations, it can flower in as quick as 4 weeks and is a great plant to till into the soil or compost as it is rich in nutrients and breaks down quickly. Buckwheat is in the rhubarb family and has few pests of its own. I plant this for a quick cover crop after pulling one, or in small rows to add diversity to some beds. One example, is after pulling onions or garlic in summer, I will toss buckwheat seeds in for a quick crop ahead of any autumn plantings.
Mustard: This doesn’t seem to promote beneficials any more than it does pests, but the pests like the mustard, so that’s where they go. Just simple “yellow” or “white” mustard (the type used to produce the condiment) are tall and flower with attractive yellow flowers. All mustards will eventually bolt and flower similarly, but most are bred and selected for low, leafy green growth. So pick the tall varieties. Plant them sparsely or a heavy rain will knock them over. And observe. What’s interesting about this plant is it is not “about” the flowers. It’s the pests attracted to the mustard plants, as a whole, that promotes the beneficials.
Stinging Nettle: Caution: Obviously it stings, but it also spreads. It spreads with rhizomes as well as seed, so only use this if you have an area to confine it and are less likely to bump into it. However, this plant is extremely nutritious, succulent and out-right tasty…..and the bugs think so too. It is so good that it had to evolve with the stinging defence to avoid being eaten by larger animals. So what you find is this is a breeding area for beneficials and food source for pests. If you throw on some gloves are turn over some leaves in the summer time you’ll be amazed at how many insects and mites are just happy being there…..or waging war on each other. Either way, it’s off your more prized plants. What’s unique about this plant in my list is that this has nothing to do with the flowers. It is more the nutritious leafy greens and protection from predation by larger animals that makes this so important for the bugs.
Compost: Careful with this one too. Too much “edibles” and you’ll get rats. If it’s not “broken down” enough before you put it in your garden beds then some composting insects can become pests: example being the sowbug. It breaks down compost, but can feed on your plant tissue to get moisture if it’s not getting it from enough composting material. But, unless your compost is cooking, you’ll see a variety of pests like the woodlouse hunter (spider) that will roam around haunting your dreams (and the dreams of unsuspecting soil pests). So keep this compost available in your yard and spread it into your beds as needed. **Bio diversity of invertebrates (good and bad) is exponentially higher underground than above ground – as long as the soil is healthy.**
Trap Plants: For the advanced gardener: Think of a plant you hate because it always gets overrun with pests – maybe its’ one you’ve sworn to never grow again. Now – bare with me – grow it again! But, this time, don’t care about it. Put it somewhere you won’t see it and just simply don’t care. Let it get overrun with pests and don’t shed a tear. The plant will be unsightly, but out of sight. The plant will attract the pests, but also the predators. You are growing the pest, not the plant! Those pests prefer that plant, but the predators will feed there and move elsewhere, so you’re establishing a season-long bio-control battery in your yard. However, this is for the advanced gardener because you must understand plant families and choose these plants carefully. For example, you can use a stressed Lupin to attract the lupin aphid. That aphid will only infect other lupins (and usually only stressed ones), so there is no threat to other plants in the yard, but the predators of that aphid (like aphidoletes) may feed on all species of aphid and go from the lupin throughout your yard decimating other aphid colonies. But, lupins are in the pea family, and you can get pea aphids that spread to other peas. So, if you have a large or important pea crop, you may want to skip this one for another, like Stinging Nettle. Maybe you’ve already planted (or allowed this) for the reasons above but consider this: Stinging Nettle is one of only two growing season hosts of the Hop aphid (the other being Hops…but possibly cannabis as well). Stinging Nettle leafs-out early and gets the hop aphid (which over winters on prunus) early. This also attracts aphid predators early. And even if you are growing hops and cannabis, this is still beneficial, because some predators are species specific: there are parasitoids that will only infect one or a small group of species of aphids. So with stinging nettle, you produce aphid predators and parasitoids. Then when it’s the time of year for aphids to infect your hops or cannabis you already have the controls in place. This can speed-up how well those pests are controlled (depending on how you’re growing those plants: remember if you’re keeping them dry and feeding them fertilizer, you will get sucking insects like aphids, no matter what – and they’ll be multiplying so quickly that many predators won’t be able to keep up, or the dry conditions will make them go elsewhere.)
Keep Doing What You’re Doing: Lastly: You’re a gardener. You’ve got lots of plants, and probably a variety. You enjoy your yard and go out there regularly to work or enjoy the work you have done. Even when we plant things selfishly for food, or aesthetics, or to make money, we are facilitating life and that’s part of the enjoyment. So keep wandering the yard seeing what grows best where and which companion plants look nice together or help one another, and… watch the bugs. Look more closely at an aphid infestation and see what else is amongst them. Have the tolerance to leave it and check day after day to see what predators show up. Have patience with nature. You might lose a growing tip, but you won’t lose the plant and your garden will be better for it.
Want to see some videos? Check out the Youtube Channel “Gardening with Bugs” here.
For more reading:
How to Attract Beneficial Insects to your Garden
Everything you need to know about Aphids including how to Control them.
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