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Understanding biological control of insects
The summary will encapsulate the understanding of insect biological control.
The manipulation of beneficial organisms remains a very important tool in integrated pest management programs of insect pests worldwide. This chapter describes the approaches to using biological control and a historical perspective of each. Recent developments in genetics, systematics, population dynamics, pesticide chemistry, and public opinion have led to increased scrutiny and inclusion of beneficial insects into IPM programs. This chapter describes these developments and the variety of approaches that have been used to implement biological control as a useful tactic in IPM. It also describes how biological control interacts with other IPM tactics, and the potential for better integration into IPM programs.
In natural world not all insects are pest but all pests have their natural enemies and the pest populations especially in tropic are always kept below the threshold level their natural enemies. For example, the brown plant hoppers N.lugens have not less than 188natural enemies to keep them in check (Ooi, 1988). Since ancient time, human have start to learn to utilize natural enemies in combatting the insects pest. However, the term biological control was only first introduced in 1919 by the late Harry Smith of University of California (Smith, 1919). Nowadays, despite there are many methods have been introduced to control insects pest population there is no single method that could effectively control of insects pest, so entomologist come out with an idea which is the integrated pest management (Ooi, 1988). Biological control is one of the components in integrated pest management. Biological control is a method of managing pests by using natural enemies such as predators, parasites, and pathogens and it’s normally involve human activity to protect, introduce and propagate them. Predator of insects pest can be either arthropods or vertebrates. Insectivorous birds, frogs and mammals are some of the important vertebrate predator while insects and spider are the example of important arthropods predator (Khoo, Ooi and Ho,1991). An insect parasites that are smaller than their host, developed inside or attach to the outside of the host’s body and consuming the tissues and in the end eventually killed the host is known as parasitoid. Pathogens are microorganisms including certain protozoa, bacteria, fungi, nematodes, and viruses that can infect and kill the host. The criterias of a good and effective natural enemy are it is host specific, can feed and reproduce when the pest population is low and can attack a broad range of life stages of the target pest.
History of biological control in Malaysia
In the history of biological control in Malaysia, we have carried out three type of biological control method which are the conservation, classical and inundative biological control. In Malaysia, it have been observed that the severe outbreak crisis of native insect such as bagworm in oil palm and the brown plant hopper in rice field that arise from the overuse of insecticides that destroy most of its their natural enemies. Therefore, scientists have identified conservation biological control to solve these problems. The natural enemy population is conserved by using a management practices which selecting and minimizing the use of insecticides. However in some other pest outbreak that involve exotic insect in which there are no natural enemies that could be found in Malaysia that will control their population, classical biological control is used to establish the new natural enemy species. For example, 3 species of hymenopterous parasites have been identified and selected from the area of origin of diamondback moth, Plutella xylostella, and imported into Cameron Highlands, Malaysia (Khoo, Ooi and Ho,1991). But, there are sometime where both conservation and classical biological control are not effective thus we have to go for inundative biological control which is expensive. It is expensive because it involve the continuous mass culture and release of natural enemies to control either native or exotic pest insects. Inundative biological control have been successfully used in the management of sugar cane borer in Malaysia(Khoo, Ooi and Ho,1991).
How does biological control contribute to sustainable agriculture?
The three main principles in sustainable agriculture are economic profitability, environment health and social and economic equity. Conservation biological control is the key biological control in Malaysia this is because in most of the time even without classical or inundative biological control, the pests population in the agro-ecosystem is often keep in check by the rich and dynamic array of natural enemies that (Ooi and Kenmore,2005). The success that we enjoy now in the oil palm and rice is the best example of the importance of biological control in Malaysia. But, not all the crop enjoy same succes like oil palm. For example, we are facing the stagnation in food production and have rekindled food security concern as horticultural crop culture development could not follow the growth rate of human population in Malaysia. One of the reason is there is horticultural crop culture in Malaysia are having many problem with insects. The lack of research on biological control for horticultural crop have force the farmer to be heavily depends on the use of insecticides. The use of insecticides in horticultural crop is not sustainable as the consumer nowadays have increases awareness on the negative effect of pesticides and have increased demand on organic product and the development of resistant in the target pest toward pesticides.. The increased demand from the consumer for a safer food will become a driving force in determining a better pest management practices from farmer. We will fail to sustain the horticultural crop industry if the requirement for a better pest management practices cannot be fulfilled by the farmer. Therefore, biological control will be key for a sustainable agriculture because unlike pesticide that will lead to the development of resistant in target pest, in the history of biological control it seldom leads to the development of resistant. The only documented case of target pest developing resistant to a biological control agent is the larch sawfly, Pritophora erihsonii, against the parasitoid Mesoleius tenthredinis Morley in Canada (Pschorn-Walcher, 1977). This statistics in fact have proven that a biological control is a sustainable practice for insects pest management. Furthermore, biological control is relative safety for the environment and human health as it doesn’t cause pollution and hazardous. In addition, biological control is also a form of biodiversity of major economic importance that must be preserved as it provides free services in controlling insect pest population. The only cost money during the process of introducing or encouraging them. Once they are established in the agricultural system, they will keep on multiply and sustain as long as there are insects pest. This kind of biodiversity must be preserved or else we will repeat the famous incident in Malaysia agriculture sector where the agriculture sustainability is challenge by the outbreak of brown plant hopper outbreak in Tanjung Karang, Selangor. This outbreak has cause million dollar loss to the rice farmer.
Well, now we know biological control is very important to Malaysia agricultural as it has many benefits but how we could promote the biological control? The contribution of biological control to sustainable agriculture is often escape recognition and been take for granted as it effects is not as obvious and dramatic like pesticides. Thus, no matter which biological control we would like to promote, the key is on the farmer education. The farmer field school would help in educate farmer that lack of scientific knowledges like the role of natural enemies in the field so that they could manage their crop better. Besides that, if we want to implement any biological control especially conservation biological control, the success or failure is lies on the farmer understanding in the mode of action of the natural enemies and conserve them (Kenmore 1996; Matteson et al. 1994). To convince the farmer that biological control would be a better option than insecticides in insect pest management, the comparison of profitability between two methods will be the best answer for it. From the data that obtained from the EU funded and FAO implemented Cotton IPM project, it showed that the average gross margins have increased by $228 per hectares for farmer field school farmer and $67 for exposed farmer if compare with control farmer (Ooi and Kenmore,2005). The increase in profit margin is due to the reducing used of insecticides and this is very important in reducing rural poverty.
Besides that, to promote biological control we would need to develop an effective biological control for pest management so that we could remove the doubt from the scientist community that oppose biological control. They doubt the effectiveness of biological control due not every time the introduction of biological control will end up successfully. The crucial procedure in develop an effective biological control is we must correctly identify the pest, their biology, distribution, nature and important natural enemies (Muniappan, Shepard and Ooi, 2012). Besides that, the identified of the crop and the insect pest origin would also be helpful in developing a successful biological control. In some occasion, the insects pest problem is cause by the introduction of exotic pest from one region to another region without the natural enemies to control their population. For example, the introduction of the papaya mealybug Paracoccus marginatus from Mexico to several countries however in the end the problem is solved when a parasitoid was identified to control the papaya mealybug in its center of origin and have save the papaya industry from collapse (Muniappan, Shepard and Ooi, 2012). In Malaysia, we are rich in biodiversity and we have a huge advantage in exploring the potential market in biological control. For example the potential market that we could explore are the inundative biological control in green house.
In classical biological control, it is important to research on the potential risks such as predation, parasitism or competition of the biological control agent towards the non-target species. This research is crucial as these potential risks might lead to the extinct of the native species and have adverse effect to the local ecosystem. Thus, to avoid these problem, we need to focus on a relatively host specific insects such as parasitoid rather than general predator such as spiders. The famous example of the classical biological control is the ladybeetle Harmonia axyridis Pallas that was released in North America and Northwest Europeas as a predator of aphid pests have become a pest (Roy and Wajnberg, 2008; Koch and Galvan, 2008) . Lastly, to support the conservation biological control more studied should be carry out on how to increase the population of natural enemies others than manipulation of insecticides to suppress number of pest insects. These could include synchronization of their life cycle, modification of cropping pattern, manipulation of non-crop vegetation and management of water and soil. For inundative biological control, more research should be made on how to improve the quality and quantity of the released natural enemies. It is very often the poor quality and incorrect quantity lead to unsatisfactory pest suppression and contribute to the unpredictability of inundative biological control (Hoy et al., 1991).
In the past 100years, through a lot of research and hard work done the scientist we have seen a better understanding on how the biological control agent work and how they could be utilized and manipulated for a more safe and effective pest management system. This trend could be boost by the modern technology such as molecular biology and internet as a useful tool in encouraging biological control in Malaysia. The advanced in molecular systematic would be useful on the classification, behavior and the reproductive biology of the natural enemies would reveal the surprisingly complexities in their life cycle. By untied the complexities behind, we could lead to a better and potential new method of these beneficial insects and the information can be shared widely and quickly through internet.
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