Biological control is approached in a variety of ways. The three most common approaches are classical, augmentative, and conservation biological control. These approaches are used to achieve various management objectives. The first biological control approach that we will introduce is called classical biological control. This method involves the introduction of non-native biological control agents to control invasive or exotic pests. Exotic pest species that become established outside of their natural range often reach high population levels because of the absence of natural enemies. In these cases, natural enemies of the pests can be identified in the past native fridge, and studied to determine their potential as biological control agents in the introduced range. Before these natural enemies are released, they must be evaluated for their effectiveness at controlling the pest, as well as the potential impact they could have in the new ecosystem. Once suitable biological control agents are identified, they are imported under strict government regulation. Efforts are then made to ensure that these introduced populations become self-sustaining. Classical biological control is the preferred mode of biological control against invasive pests on non-uncultivated land. It is used to control, but not eradicate a single dominant invasive pest species. The introduced agents become a self-sustaining population that continually regulates the pest population. A good example of a successful application of classical biological control involves efforts to control the alfalfa weevil in the United States. This pest beetle species was introduced to North America from Europe in the early 20th century. By the 1970's, had spread across the continental United States. To manage the spread of this pest species, a control program was initiated in 1957, in which 12 species of parasitoids that specialize on the alfalfa weevil were imported from Europe. Six of these parasitoids became established and have since managed to suppress alfalfa weevil populations in the Eastern United States. Augmentative biological control. Unlike the classical approach, involves active manipulation of populations of biological control agents to control the pest species. In this case, the pest species can either be an introduced or a native pest. This often involves the mass production and release of natural enemies in a managed ecosystem. Augmentative biological control can be applied in two different ways. The first is called inoculated, and is characterized by frequent well-timed introductions of natural enemies. These control agents may become established and some control may be provided by their progeny. However, additional releases of biological control agents are generally required to augment these populations for continued control. The second is called inundated, in which large numbers of natural enemies are released at once in a single setting. Unlike the inoculative approach, the goal is for the natural enemy application to overwhelm the pest population quickly. As such, these control agents are not expected to become established or reproduce. An example of inoculative augmentative biological control is the use of the parasitoid wasps in Encarsia formosa for whitefly control in greenhouse agroecosystems. Whiteflies are pests of vegetables and floriculture. As soon as whiteflies are detected on crops, low densities of the parasitoids are released with the intention for parasitoid populations to persist throughout the growing season. The female wasp lays eggs in the developing whitefly, and the wasp larvae go through four larval instars within the host before pulpation. Adult wasps merge within the whitefly host and chew their way out. This new generation of parasitoids provides ongoing control of whiteflies within the crop. The primary goal in the release of these control agents is to keep whitefly population densities from reaching damaging levels in a preventative approach. An example of inundative control includes Bacillus thuringiensis or Bt formulations. As we previously learned, Bt is a soil-borne bacterium which produces a toxin with insecticidal action. Application of Bt can rapidly reduce or eliminate the pest population, which is particularly important for control of insect pests on high-value crops. Crops can be sprayed with the formulation of the bacteria, with the goal to quickly kill pest populations. The bacteria and its toxin are susceptible to degradation by sunlight, though the bacteria can survive in the soil for more than a year. In both inoculative and inundative biological control, the control agents need to be commercially available. Bacillus thuringiensis can be maintained outside of its host. So mass production is possible. Arthropod control agents like in Encarsia formosa are bread enlarge numbers at insectaries, and shipped to producers prior to release into manage ecosystems. Biological control in the future may include natural enemies that are genetically modified with recombinant DNA technology. We can genetically introduce beneficial traits into biological control agents, such as pesticide and disease resistance, temperature hardiness, and manipulate sex ratios, especially in cases where only one sex attacks the pest. Now, let's talk to Dorian Rondeel, the head of Biological Control at Doef's Greenhouses in Lacombe, Alberta to hear about how biological control is used in commercial greenhouse operations. The main crops we grow here in this greenhouse are primarily cucumbers, peppers, a little bit of tomato, eggplant, and melons. The pest that causes us the most issues right now is definitely aphids. We do have a little bit of issue with other things but over the last few years, that's been the big one. The pests that we have in the greenhouse other than aphids, a lot of thrips, spider mites, caterpillars can be an issue. I think those are the big ones. We use mostly predatory mites or parasitic wasps in general for our problems. If we're using insecticides and we have to worry constantly about developing resistances to what we're using, as well as focusing on the product that we're delivering to people in stores, we want to provide the cleanest produce possible. So because of sustainability, we don't need to use near as much control when we're using bios, especially if we can establish a relatively naturalized ecosystem for them like providing supplementary food, things like that really allow us to have very minimal input while getting amazing results out of what we put in. We try our best to make it 100 percent, but there are always issues, your biologicals depending on whether in the greenhouse and outside of the greenhouse may not perform as well as you'd like. So we do keep sprays on the back burner, but we do treat everything with bios. Most of the biological control agents are sprinkled onto the leaves of the crop or placed at the base of the plants. The companies that we buy them from put them in carrier material so they get here safely, and otherwise, we can blow them into the crop over large areas. We actually release biological control agents every single week. So none today. But usually every week, I'm putting something in because we have to stay preventative with what we're doing. At any given time, we only really use one or two for thrips which are the predatory mites and a bug called Orius. For peppers, we use those same two, and then we add in more stuff for spider mites like persimilis and californicus. We probably use, I would say upwards of 20 different things throughout the year depending on the time of year. Banker plant, it is a plant aside from what you're trying to grow that the pest will find very desirable, so you can make a high number of them and basically feeds your predator or parasite population, so that you are getting a constant release of high numbers without putting cost in. Not entirely. But every once in a while, you will see a few come back from previous populations, and sometimes we actually get the benefit of what's coming from outside as control for free. Last year we had a lot of aphids coming in from outside, to the point where our weekly applications weren't doing anything and syrphid flies or hoverflies were coming in and laying eggs, and they're young, eat just hundreds of aphids. So there's a lot of well needed free control for us. Not for our biocontrol agents, because they require a population of pests that is their food. So they're fairly naturalized here, anyways. The only thing that we have to restrict letting get outside is the bumblebees that we use for pollination, just because they are not a native species and they don't want them to breed with the native ones here. Again, that probably depends year to year and what the conditions are. I'd say 90 percent effective, generally. There are the odd times where something will get away from us and it's just because we can't have eyes everywhere in the greenhouse at all times. So hidden pockets growing and when they're visible we deal with them. Aphids can be a problem, but usually it's spider mites, because they're so small and it takes quite a few numbers for them to actually be visible, where aphids are bright-colored and sit at the head of the plant usually, so you can find them fairly easily. If our products are successful, then we can tell people we don't have to spray our product which is a huge thing today. Everybody wants clean produce. Otherwise, that's the biggest benefit really for us. My favorite insect in general is probably the hoverfly, just because the way they come up and decimate aphid populations, that's a huge boon to our business here. The last type of biological control we will examine is Conservation Biological Control, an approach in which specific variables in the environment are modified to enhance the efficiency and persistence of natural enemies already present in the ecosystem. This can be achieved either by reducing factors that interfere with natural enemy success, or by enhancing resources for the natural enemies in the managed system. For example, natural enemy populations can benefit from reduced pesticide applications and reduce disturbances from practices such as tillage and weed removal, provisioning natural enemy habitats with additional resources such as access to alternate hosts, food resources like nectar, or favorable overwintering habitats can promote their success and effectiveness as biological control agents. Most heavily managed ecosystems provide few resources for natural enemies. Because the dispersal capability of many parasitoids is limited, it can be difficult for them to forage for resources outside of the managed area. Floral resources close to the crop can provide carbohydrates from nectar to increase the longevity and fecundity of parasitoids. Synthetic versions of attractive semiochemicals can also be placed within the agroecosystem to attract natural enemies to forage within the crop. Many natural enemies and biological control agents require specific habitat conditions to complete their life cycles. Enhancing certain habitat features can provide refuges for protection and resources for energy for these natural enemies. For example, forested edges around cornfields act as a refuge for [inaudible] wasps that parasitize European corn borer in corn crops. Because the forested areas have a cooler micro-climate than within the crop, wasps seek shelter in the forests and only move into the corn canopy later in the season once the plants have matured and shaded habitat is available. Parasitism rates are consistently higher in corn crops located close to these types of shelter resources. However, these habitats can potentially provide refuge for pest species as well, allowing them to survive when the crop host is unavailable. So the pros and cons of planting the crop close to this refuge must be considered. Natural habitats can also be a source of additional prey items for predators and alternative hosts required by some parasitoids to complete their life cycles. A simple example is given by parasitoids in the genus Anagrus which tack the eggs of the grape leafhopper. Grape leafhoppers overwinter as adults. So the parasitoid needs an alternative host that overwinters in the egg stage, which it parasitizes to survive the harsh conditions each winter. Other non-pest leafhoppers that overwinter as eggs act as the alternative hosts for these parasitoids. Non-crop plants that support these other leafhopper species are planted close to vineyards to increase the overwintering success of parasitoids in the area. This approach is similar to the use of banker plants in managed systems. Banker plants are non-crop plants that are deliberately infested with a non-pest herbivore that helps to support the natural enemies of pests in the cropping system. Natural enemies can be introduced, as with augmentative biocontrol, but the concurrent Introduction of extra resources to support the biological control agents makes this method sustainable for relatively long-term control. Banker plants can help managers use a single species of natural enemy rather than a suite of enemies that may compete against each other and even predate on each other. This type of approach however, can only be used if the alternate hosts of the natural enemy are known. This highlights the type of research that is necessary to support biological control programs. We talked to Dr. Ken Fry, a horticultural professor and entomologist at Olds College here in Alberta to see what he has to say about biological control in horticultural systems. I'm an instructor in the horticulture program and my instructional role is for the most part pest management. Well, in horticulture, it can be segregated into SOD production, nursery production, which is tree propagation and cultivation, as well as field vegetable, greenhouse vegetable, field fruit, field flower production and greenhouse flower production, mushroom production. So anything that isn't a cereal, or an oil seed, or a forage is essentially a horticultural crop. They're very much like you would find in any kind of agricultural production system. So some of the estimates are like 10 percent crop loss due to insects alone, 30 percent crop loss to disease, weed competition, things like that. They're very complimentary, but where you might draw away from what is considered to be typical losses associated with agricultural crops, you have to look at the high value of horticultural crops. So the losses that can accrue in some horticultural systems whilst not large in terms of tonnage or that sort of measure, but the value of those crops are that much higher that the losses can be considerably more severe. Well, the latest census of agriculture numbers that we have is 2015 countrywide in horticulture comes up I think second behind beef production in terms of dollar, about $7.5 billion. But I would say spider mites, aphids, thrips, white flies, fungus gnats across both commodity groups, ornamentals and vegetables. In Ontario where the best data are from is you're looking at 85 percent of vegetable growers, about 50 percent of floriculture growers. The vegetable growers, it wasn't so much a philosophical decision, oh I want to go green, and I want to do bio-control. It was like, none of my chemicals work and I can't afford to have my people out of the greenhouse for that re-entry interval after a spray. They need to have people in harvesting, or training the plants, or maintaining the plant. So it was more of a logistical issue than anything else and bio-control was exceptionally conducive to having people, staff in their production system full-time. So that was one thing. Then of course, the consumer desire for no or low pesticide residues on their foodstuffs. So from a safety point of view, from an ecological sustainability point of view, it's increasingly being adopted by growers. Many of the upsides are clearly worker health, customer or client health, environmental health. You're looking at, I think, hopefully the customer, the ultimate end customer that purchases the product is more aware and made more aware of environmental sustainability and an ecosystem function. As it were, I think that'd be a really nice side effect of producers showcasing how they produce their food. You have a captive audience. So if your events are closed, you have the opportunity to retain those animals that you release and have them cycle within that controlled environment. So you can get inoculated biological control where you're relying on not just the animals you release, but then subsequent generations of that population. So that's one of the major benefits I suppose of having a controlled environment. You can also adjust the temperature, relative humidity, the lighting through LED systems that might better favor the biocontrol in the plant rather than the pest. If you get some generalists getting in there, one, their searching efficiency isn't necessarily as high as a specialist. So it is ideally adapted to host seeking for that prey item or host. Generalists maybe indiscriminate as to who they munch on. If it is parasitized and then a lady beetle comes along and eats it, you just killed it twice and so you've lost some efficiency. Sometimes with application technologies, I know that there's cold foggers, there's hot foggers, electrostatic sprayers. You can get droplet sizes, they'd be very small, you can get smoke bombs and things like this. There are small particle sizes that you can get into a dense canopy, but strictly speaking, that's probably one of the biggest handicaps of spraying is getting that canopy penetration, getting product deposition where the pest is and especially adult thrips, if they go deep into a blossom or a flower, brutal to try and get at them, but that's exactly where Orius goes. So in terms of the more cryptic habits of some of the pests, then the biocontrol agents can overcome a lot of that. Similarly, something like white flies which will have waxy buildups, so a very very thick layer of wax on their cuticle, which will shed. It's quite hydrophobic and it will shed a lot of the aqueous formulations especially of pesticide, and [inaudible] goes, I don't care, doesn't bother me. They can parasitize that very simply. Forest tent caterpillar. It's going to raise a few hackles, and it's totally self-indulgent. When I was a kid growing up in Edmonton, we had two big poplars in our backyard. As a little child, I loved to go climbing them. I was small enough that I wouldn't break the limbs, and if I fell from most moderate height, I would just bounce, no harm, no foul, but my parents didn't see it that way and so every time I got caught climbing the tree, I would get in trouble. Along comes a forest tent caterpillar outbreak. Ken, get up the tree. Get those egg bands. So I love that animal for the very fact that it allowed me to climb that tree with my parents' blessing. In this lesson, we explored the three main types of biological control: classical, augmentative, and conservation biological control. These three approaches have distinctive methods associated with them and are applied to achieve specific management objectives. In the next video, we'll examine the advantages and limitations associated with the use of biological control to combat pests.
