Cultural control or ecological management unlike biological control does not rely on the manipulation of natural trophic interactions. Instead, it involves the purposeful manipulation of environmental factors to reduce the number of pests present and to mitigate the damage they cause. Like biological control, cultural control requires a thorough understanding of pest ecology, behavior, and biology. This allows us to target and exploit vulnerable parts of the pest's life cycle. For example, we can manipulate a pest's access to food and shelter, target them during vulnerable dispersal periods or manage environmental conditions such as temperature and moisture to disrupt the growth and development of the target pest. Some cultural control methods aim to reduce pest reproduction and survival by changing the physical environment, thus reducing the suitability of an ecosystem for a pest. This can be achieved by eliminating or modifying pest habitats. For example, potential egg-laying sites for mosquitoes can be removed by draining flooded fields or eliminating standing water. Thorough cleaning and sealing any cracks within a resident's can help reduce the number of refugia available to cockroaches and bed bugs. Another approach is to change the physical conditions within the environment. Tillage for instance, can physically harm or kill pests while simultaneously exposing them to the elements and potential predators. Tillage is a technique used in agriculture to prepare the land for cultivation and to reduce the germination of weeds by mechanically disturbing the soil. As this soil is turned over, soil dwelling life stages of insect pests can be exposed. The use of tillage as an agronomic tool however has declined in recent years in an effort to reduce soil erosion and nutrient loss. In indoor managed systems, temperature can be adjusted for a short period of time to render the habitat inhospitable to the target pest. In fact, temperature manipulation is a common approach to bed bug management. The final method that emphasizes manipulation of the habitat is to remove the pests access to essential resources. For example, we can eliminate habitats that pest required to complete development or survive over winter. The removal of crop residue is a classic example. Removing unharvested crop residue is a common approach to control the apple maggot, a significant pest of apples in North America that renders infested fruits unmarketable. In the fall, apples on the ground are removed before the developing larvae within the fruit emerge and pupate in the soil. The fallen apples must be destroyed or discarded away from the orchard so that the emerging flies do not find their way back the following spring. Uncontrolled infestations can damage more than 80 percent of the apples in an orchard, but adequate management substantially reduces impact on the crop and can prevent apple maggot flies from spreading to new areas. Another approach to eliminate pest access to resources is to destroy alternate plant hosts. These are host that the pest depends on when the target host is unavailable. For instance, the removal of volunteer weed plants early in the season helps to prevent the buildup of mite populations that vector the wheat Streak Mosaic Virus. This preventative measure mitigates the spread of this plant virus to the main wheat crop later in the season. We can also control pests by upsetting the chronological continuity between the pests and their hosts. Crop rotation, the practice of planting different crops in the same area over consecutive seasons, is a widely employed pest control method in agriculture that disrupts this continuity. Crop rotation mitigates the buildup of pest populations that specialize on one type of crop. This practice works best against pest species that have an immobile life stage during the transition between cropping seasons. Crop rotation is an important part of integrated pest management for the Western corn rootworm, an important beetle pest of corn in North America. After overwintering is eggs in the cornfields, newly hatched larvae emerge from the soil in the spring and feed on the roots of young corn plants. Continuous cropping of corn in the Midwestern United States has promoted the pest status of the Western corn rootworm, since it is a specialists that survives best on corn. By alternating corn with a different crop, farmers can reduce larval populations of the Western corn rootworm. Interestingly, some populations of the Western corn rootworm have evolved resistance to crop rotation. These populations can remain in diapause over the entire year and through the next winter to avoid the alternate crop in the rotation. This is another reminder of the importance of using many different pest management tactics in an integrated pest management system. The temporal synchrony between hosts and pests can also be manipulated to reduce pest pressure. This approach requires a clear understanding of the phenology of both the pests and their hosts. Many insect pests not only prefer certain host species, but also targets specific stages of host development. In agricultural settings, a change in the planting or harvest date of annually produced crops will alter crop phonology and subsequently crop insect interactions. This can help to reduce pest success and population growth. Altering planting dates to mitigate pest damage is a common practice in the cultivation of wheat. In early summer, aphids that vector barley yellow dwarf virus appear on young wheat plants. Because the aphids prefer young plants, seeing earlier in the season means the vectors will encounter less attractive mature plants. This reduces the incidence of aphids on the crop plant and subsequently reduces the spread of the plant virus. With passive humans and animals, periods of outdoor exposure can be managed to reduce pest encounters. Recreational activities can be organized at times or during seasons when serious arthropod pests are least active. For example, different species of mosquitoes are active at different times of the day. Most mosquitoes bite primarily from dusk until dawn. So outdoor activities can be organized around these times. Similarly, livestock can be released into open pastures when pest activity is at its lowest. For example, some ranchers may choose to keep livestock indoors during the daytime during peak horse fly activity. Cultural control also involves tactics that divert pests from the target resource. Such tactics include trap cropping and inter-cropping. Trap cropping involves planting crops adjacent to the main crop that are attractive and susceptible to the target pest. These attractive plants serve to divert pest infestation and thus dilute damage to the main crop. The insects can be controlled in the trap crop to reduce the possibility of movement into the main crop. Trap cropping forms an important component of programs to control major pests of soybeans such as the bean leaf beetle and several species of stink bugs. The truck crops in this case are not a different type of crop, but rather early planted and early maturing soy beans that are attractive to the mobile stage of the insects. A section ranging from 1-10 percent of the total cropping area can be sufficient to attract up to 85 percent of the pest population. Truck cropping is often combined with the use of semiochemical lures to help attract insects to the truck crop. Targeted and appropriately timed insecticide applications to the insects within the truck crop can also help control and prevent the spread of the pest. Intercropping, on the other hand, involves planting multiple crops in this same cropping area. While the goal of intercropping is often to increase yields by making the most efficient use of resources in the field, it can also be used to make the field less attractive to pests and mitigate damage to the crop. The mechanism behind this approach may be as simple as making the host plants less apparent to the past by planting crops with different canopy heights. In other cases, the intercrop may be planted because it is repellent to pest insects. For instance, when molasses grass is intercropping among corn in African fields, the terpenoids produced by the grasp deter stem borer moth from seeking over position sites on the corn plants. As with all control methods, there are challenges that occur with intercropping on a large scale in the harvest of different crops, at different times, and with different types of machinery. On a smaller scale, we can even reduce pest damage in our own gardens by intercropping, which is sometimes called companion planting. When onions are planted next to your carrots, for example, the onions can diter carrot rust fly. If a gardener would like to deter the Colorado potato beetle, they may grow eggplants or tansy next to the potato crop. Outside of agriculture, blood feeding insects can also be diverted away from their animal hosts. Insect repellents like DEET provide personal protection by making humans and animals less attractive to biting insects. Recent research has shown that some bacterial formulations may also be repellent to mosquitoes. In some instances, semiochemical lures can be used to divert pests away from a protected resource. In some cases, bark beetle control in infested forest stands can be achieved by baiting trap trees with synthetic pheromones and kairomones. Beetles are attracted to the lure so the attack is concentrated on the trap tree. The beetles are controlled either with insecticides or by removing the trap tree after it is invested. This protects the surrounding trees from subsequent attack. Physical barriers can also be used to keep pests away from vulnerable plants, animals, and humans. Insect netting can protect crops from herbivorous insects or protect people from mosquitoes and other biting flies. In fact, insecticide treated nets are one of the main ways to protect people from contracting malaria, which is vectored by night flying mosquitoes. The emphasis in many pest management programs is to kill pests. This one-sided approach can lead to the overuse of insecticides, which causes further problems down the road. Some argue that the emphasis of IPM should shift from targeting pests to managing host plant stress. This approach to pest management involves reducing host injury to acceptable levels while simultaneously using pest management techniques at reduced frequencies. Host resistance to insect pest activity can be considered a cultural control tactic in IPM. The idea is to manipulate crops and livestock through selective breeding or genetic engineering in order to increase the expression of traits that enhance resistance to pass damage. For example, certain livestock have been bred for resistance against insect bites by selection for traits such as variable skin thickness, coat type, coat color, hair density, and skin secretions. These traits make the animals less attractive to biting insect pests. Many crop plants are bred to express physical and chemical defense traits that deter pests from finding or accepting the host plant. This type of host plant resistance is called non-preference defense. Other plant defenses can interfere with an insect's metabolism after ingestion, a process called antibiosis. Plants in the family Brassicaceae have been selectively bred to enhance their resistance to pests through antibiosis. Breeders select Brassicaceous plants that deter herbivores with secondary plant metabolites common in the Brassicaceae called glucosinolates. Glucosinolates are a great defense against generalists herbivores. However, they are also exploited by specialists Brassica feeding insects, such as cabbage white butterflies to signal host location and acceptance behaviors. Interestingly, while glucosinolates are toxic to most insects, they are not toxic to humans and even have antimicrobial properties. Some Brassicaceous crop residue is even added into soil mixtures as a natural defense against pathogens. Another form of host plant resistance is tolerance. By increasing host plant tolerance to pest damage, crop yields can be maintained despite the presence of an insect pest infestation. A good example of host tolerance is the response of hybrid corn varieties to feeding by corn root worm larvae. Feeding damage increases root growth by inducing compensatory growth in the corn plant. Damaged corn plants with greater root mass actually produce higher yields than undamaged plants. An important advantage of host tolerance compared to other types of host resistance is that no selection pressure is placed on the past as a result of host tolerance. Therefore, the pests that feed on the host plant are unlikely to evolve resistance to the traits that confer tolerance. However, the effectiveness of tolerance is dependent on host and environmental conditions. Animals or plants that are stressed tend to be more vulnerable to pest activities compared to healthy individuals. Sometimes, increasing host tolerance can be as simple as using fertilizer to strengthen crops and provide good growing conditions. That being said, host plants are better protected against pests if we actively select for genetic traits of host resistance. Treats of host resistance are incorporated into plant and animal varieties by selective breeding and through genetic modification. Selective breeding involves the selection of desirable characteristics that are passed from parents to offspring. Selective breeding is a slow process and can take several generations to achieve the desired traits in a particular crop or animal variety. Most modern day crops and livestock have historically been selectively bred for quality such as taste, high yields, pest resistance, and tolerance. Genetically modified organisms or GMOs are genetically engineered individuals whose DNA has been modified to achieve certain desired characteristics. Unlike classical breeding, genetic engineering allows us to effectively manipulate targeted genes using molecular processes. More importantly, genetic engineering allows the incorporation of genes from one species to another creating what is called a transgenic organism. The genes targeted for pest management usually have a variety of functions ranging from increased pest defense, to insecticide production, and herbicide resistance. There are many ways these desired genes can be transferred into the host genome. The desired DNA can be injected into a fertilized egg at the single cell stage, which allows the DNA to integrate into the genome of the cell. A common method to introduce desire genes is to use a bacterial vector, whereby genes are introduced by bacteria and integrate into the DNA of the target organism. Current efforts to genetically modify farm animals for resistance against pests and pathogens remain economically infeasible. This is because there is still no cost efficient way to transfer foreign genes into large animals. Conversely, genetically modified plants have been commercially available for some time. Let's take a closer look at two types of transgenic crops, Bt crops and RNAI crops. Bt crops are produced by inserting the genes that express the delta endotoxin of Bacillus thuringiensis into plant genomes. As a result of genetic modification, the plants produce the Bt toxin and all of their cells, which depending on the type of toxin, can be deadly to a variety of insect pests. All Bt crop plants express the insecticidal toxin which exerts strong selective pressures on the insect pests active in the transgenic crop. This can lead to the evolution of resistance to Bt toxins in populations of the target pest. Fortunately, the development of Bt resistance can be mitigated through the use of refugia that are planted next to susceptible plants in a portion of the cropping area. In this way, some of the past population does not get exposed to the Bt toxin and avoids the selective pressure that leads to the evolution of resistance. Preservation of susceptible insects in the population slows the evolution of resistance. This approach functions well because the allele for Bt resistance is a recessive trait. As such, its effect can be suppressed by the presence of a dominant susceptible allele. The heterozygous offspring between susceptible and resistant individuals will not exhibit Bt resistance. RNAI or RNA Interference is a newer technology used to develop a transgenic crop and is an alternative to BT crops. RNAI involves RNA molecules that interfere with gene expression by binding to mRNA strands produced by cells during the early stages of protein synthesis. Since mRNAs are templates used in protein production, this approach is referred to as post transcriptional gene silencing because it happens after the genes are transcribed into RNA. RNAI can be designed to inhibit the synthesis of enzymes in insects that normally help them detoxify defensive plant chemicals. This renders the pests more susceptible to the plants natural toxins. The first successful trial of such a transgenic plant involved cotton that produced ingestible RNAI that silenced the expression of a gene for a certain enzyme in Cotton Bollworm caterpillars. Without the gene product, the lepidopteron passed was unable to detoxified the defensive chemical gossypol, produced by cotton which caused larval mortality. Transgenic plants that encode ingestible RNAI remain in the early stages of development. While this biotechnology has great potential and can provide defense against multiple insect pests, further research is necessary before pest control through RNAI becomes economically feasible. Another use of genetic engineering is in the sterile insect technique, whereby members of the pest species are modified to become reproductively sterile. When wild pest insects mate with these genetically sterilized individuals, it can significantly reduce the population size of the next generation. For example, the release of genetically sterilized male mosquitoes may be used to manage wild vector populations and in turn reduce rates of disease transmission. Trials of SIT programs using genetically modified mosquitoes in Brazil, Malaysia and the Cayman Islands have successfully reduced the local mosquito population levels by up to 95 percent. As you can see, the development of IPM programs can be extremely complex as many factors must be taken into consideration. However, the challenges associated with developing an IPM program are well worth the effort as they have significantly less impact on the environment and are often more cost effective than traditional pest management tactics in the long run. Dr. Hector Carcamo, a research scientist studying insect pest management at Agriculture and AgriFood Canada told us about pest management systems in the Prairie provinces. Let's hear from him now. My title is research scientist, I'm in the area of insect pest management. Yes, IPM and conservation are linked through the concept of biodiversity. Because biodiversity is essential for a solid IPM program and conservation aims to enhance diversity of organisms, so the two actually work quite nicely and they go hand in hand because you do need to have that diversity of organisms to have a more sustainable, more ecologically based crop pest management program, and the concept in conservation actually help us in Applied ecology to achieve that goal of having greater diversity. You need to keep producers operating in the short term, people have to have an income, so whenever a pest arise in our prey ecosystems and poses a threat to production of a crop, we have an obligation to help the growers stay in business and maintain productivity. So usually, the initial focus is economical, so we like to help the growers make sound decisions on control options, once we get them in staying in business and able to produce the crop, economically, we start thinking about more sustainable ways to protect that crop and that's where it becomes a bit more fun I guess to be an ecologist and start applying some ecological concepts and learning more about the basic biology of the insects and learn more about the ecology, the habitat, what biotic factors and what abiotic factors are having an impact on the population of those insects. The priorities, we can start thinking about environmental aspects of the integrated pest management program, and in that case, we need to consider what natural enemies are part of the ecosystem of the habitat and we make efforts to learn more about the biology of those natural enemies, their phonology, their seasonal activity, so that we can integrate them better into that integrated pest management program. The first step when a new insect pest comes is to learn the biology of that insect. That phrase, know thy enemy, it applies really well to integrated pest management, so you have to prioritize and say, okay, what is the number one aspect that I need to know and that will be the phenology. When does it occur? What are the best times to sample that organism and what are some of the methods that can be used to sample that organism? First step you have done with biology then develop a sampling program and then the next step is to actually validate the economic thresholds. So it's really important to show what levels are actually causing you losses, and it's only when you reach those levels where you have raised the economic thresholds. We have shown using cages something like what we have behind me where if you have a few lygus bugs feeding on a canola plant, canola plants actually will be bigger and they will have bigger stems and will produce a little bit more yield. This idea that you need to have a clean field, like, I think it's no longer very common, but sometimes people feel, oh I don't want to have any insects in my field, let's spray them and get rid of them. It's actually not a very valid idea. The stakeholders that need to be considered, first of all, are the growers. We are doing this work to help the growers and we need to help them stay in business and find practices that are sustainable and economical so they are the number one stakeholder. We also need to consider the industry, there are companies that are involved in very much part of agriculture and they provide the excellent tools to help growers. I guess the third stake holder to keep in mind is the Canadian public because they are going to consume the products, they're going to benefit from the agricultural activities, so those are the three stakeholders that we need to keep in mind. Depends how you define IPM. Some people define IPM, integrated pest management, simply monitoring, having a threshold and spraying on insecticide. If you use that definition you have widespread adoption but I don't think that is truly integrated pest management system. So in reality, I think we still have some ways to go, and part of it is that we haven't done the research that is required and another part is that is it's complicated, is very knowledge intensive and it often requires more work on the part of the producers or the agronomist to actually implement it. When I give these talks to growers, I tell them every one of you in the audience that farms you have an army of natural enemies in your farm working for you freely, every day and every night, various times of the days. In general, I've heard as a rule of thumb that if you have around 30-35 percent mortality caused by beneficial organism, by a parasitoid or predators, that you are likely not going to reach the economic threshold. So if you get say 30 percent mortality for natural enemies you're probably doing quite well. For a wheat stem sawfly, using wheat that has a solid stamp is actually the key strategy to manage the wheat stem sawfly. That along with biological control, those are the two pillars of IPM for wisdom wheat stem sawfly. Well, my favorite research insect I think it would have to be a lygus bug. I say my research subject because it's a fascinating insect with a very complex biology, it's also a complex of species, the life history is quite flexible, it varies on where you are and you will eat almost anything.
