Chapter 1: The Biological World and its Balancing Mechanism PDF

The Biological World and its Balancing Mechanism Natural ecosystem - Phytophagous insects co-existed in a complex relationship with plant communities that vary in phenology, abundance, and association with other living organisms Plant life Insects are intimately associated with a number...

The Biological World and its Balancing Mechanism Natural ecosystem - Phytophagous insects co-existed in a complex relationship with plant communities that vary in phenology, abundance, and association with other living organisms Plant life Insects are intimately associated with a number of beneficial activities including pollination, or harmful activities like damaging the plants and even cause its death. In biological warfare between plants and insects, harmful insects are suppressed either by other insects or through natural plant defense mechanism. These factors prevent the excessive population growth of harmful insect species. Crop Production Natural ecosystems are disturbed when land is cleared to plant crops. Leads to disturbance of balance between the host and insect communities Example: Kaingin, excessive use of fertilizers and pesticides (DDT) The use of DDT had given us 3 eras: a. Era of Optimism (1946-1962) b. Era of Doubt (1962-1976) c. Era of IPM (1976- present) Broad spectrum insecticides kill both the insect pests and the beneficial insects. Era of Optimism (1946-1962) DDT is a colorless, crystalline, tasteless and almost odorless organochloride known for its insecticidal properties. DDT (dichloro-diphenyl-trichloroethane) was developed in the 1940s. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations and for insect control in crop and livestock production, institutions, homes, and gardens. Era of Doubt (1962-1976) Silent Spring written by Rachel Carson and published by Houghton Mifflin on September 27, 1962. It brought environmental concerns to the American public and led to a nationwide ban on DDT for agricultural uses, and inspired an environmental movement that led to the creation of the U.S. Environmental Protection Agency EPA has banned the registration and interstate sale of DDT for nearly all uses in the United States effective December 31, 1972  Harmful Effects of Pesticides: a. Insect Resistance b. Insect Resurgence c. Harm non-target Organisms 1. increase pesticide residues on crops 2. increase pesticide residues on bodies of animals d. Pollute the environment Era of IPM (1976- present) Integrated Pest Management - An ecological approach to pest control which utilizes a combination of any of the following pest control tactics: a. Host Plant Resistance (Antibiosis, Antixenosis, Tolerance) b. Cultural Control c. Biological Control d. Use of Chemicals (last resort) Review of Ecological Concepts & Principles - basis of Biological Control To reduce a pest population, one must make its environment unfavorable for the pest. Example: use of insecticides, resistant plant varieties, cultural control, etc. Biological control of insect pests is one of the methods of pest control which manipulates the biotic factors to create an environment unsuitable for insect pests to live. Biological control is safe, permanent, cheap and is environmentally friendly. Things to consider in the study of ecology a. Balance of nature – the tendency of the population densities of all species in the same general area to maintain a more or less numerical relations to each other, due to interaction with each other and the physical environment. b. Population equilibrium & equilibrium position Population equilibrium - the average species density when the population fluctuates both positively and negatively. Equilibrium position – the steady density or the average population level of species. A single species may have different average population densities in different habitats due to the following differences in: 1. food 2. shelter 3. natural enemies 4. physical factors Permanent displacement of the equilibrium position of a species classified into 2 types: 1. Disturbances resulting from a major change in habitat Example: change in food, drying of the ponds, etc. 2. Disturbances which result from transferring an insect from its native home into a new habitat where natural enemies are absent. Example: importation of new plant varieties Most insect pests are immigrants thus they are classified into the second type. These introduced species are of less importance in their native home where their population equilibrium is kept at low level by their natural enemies. Examples of Introduced Pest Effects on the Ecosystem Jumping plant lice Introduced by the typhoon in 1980. Has (Heterophylla cubana) affected almost all standing Leucaena leucocephala (ipil-ipil) plantations Leafminer (Liriomyza sp.) Accidentally introduced with the importation of chrysanthemum: major pest of potato and ornamentals. Mealy bug (Pseudococcus sp.) Affects coconut in Northern Palawan. Accidentally introduced in 1990 with the importation of hybrid coconut planting materials. Spiraling whitefly Affected vegetables (Aleurodicus dispeures) and ornamentals. Accidentally introduced with the importation of ornamental kalanchoe in the 1970s. Riceblack bug Major problem for rice in Mindanao and (Scontinophora coarctata) Leyte. Introduced through vessels plying the route between the province of Palawan and countries south of the Philippines. (Golden Apple Snail) Consumes crops like rice, taro, cassava, Pomacea canaliculate papaya, kangkong, and sweet potato was introduced in Asia, specifically in Taiwan from Argentina in 1979 as human food to be cultured indoors (Mochida, 1991). From Taiwan, it spread to Japan in 1981 and to the Philippines in 1983 (Santos, 1987) to boost food production and increase the protein intake of average Filipino families.  (Mango Pulp Weevil) Its establishment in southern Palawan is Sternochetus frigidus attributed to the shipping route and trade activities between southern Palawan and Borneo, which is a native area of the pulp weevil (Basio et al., 1994). (Mango Seed Weevil) Originating from India (Waterhouse, 1993) Sternochetus mangiferae and Myanmar (CABI, 2001), it has often been spotted by the Service of the United States Department of Agriculture (Anonymous, 1988). However, its mode of transfer to the Philippines is unknown. Review Basic Definition of Insect Pests and Their Characteristics Insect pests - injure/cause damage to human’s interest - destroy crops; compete with humans for food & shelter; transmit diseases & reduce availability, quality, and value of human resources. Terminologies: Movement of organisms to new locations is important to Biological Control Indigenous (or native) – those organisms in a specified area, that arose evolutionarily in their current taxa in that location Precinctive – are the subset of the indigenous of a given area that occur nowhere else Adventive- those species in specified location that did not evolve there but arrived there from elsewhere (opposite of native) Immigrants- are those adventive organisms in a specified location that arrived there without the deliberate, purposeful aid of man. Includes both actively dispersing organisms, ones arriving as stowaways on plants or other commodities moved by man. Introduce- those brought to a location by the conscious choice of man (food crop species, ornamentals or forage plants, pets and domestic animals, biological control animals). Biological control attempts to restore the natural balance by duplicating the conditions in the pest’s native home through the importation of its natural enemies. This successful restoration of the natural balance exemplifies the ecological basis for biological control. Insect Pest based on their Feeding Habits: a. Chewing ex. larvae of stemborers b. Rasping-sucking ex. nymph & adult thrips c. Cutting-sponging ex. adult horse fly d. Piercing-sucking ex. nymph & adult green leaf hoppers Major Orders of Insect Pest: – Hemiptera ex. Green leafhoppers – Lepidoptera ex. Rice stemborers – Diptera ex. Corn seedling maggots – Coleoptera ex. Coconut rhinoceros beetles – Thysanoptera ex Thrips – Orthoptera ex. Mole crickets – Blattodea ex. Cockroaches – Phasmatodea ex. Walking sticks – Isoptera ex. Termites – Siphonaptera ex. Fleas Factors that determine the existence of an organism in an ecosystem Ecosystem – any community of living (biotic) and non- living (abiotic) things working together. - Biotic factors include plants, animals and any other living things while abiotic factors include all non-living things in an ecosystem. - Both factors are related to each other in an ecosystem, if one is missing the entire community is affected for the survival of an individual or organisms. - Focus Interactions Host-Parasitoid Predator-Prey Interactions: 1. Single-Species Population - dynamics of populations with discreate or distinct generations - individuals in the population compete for the limiting resource e.x. ovipositional sites (adult), food (larvae) 2. Interspecific Competition -important in communities such as: social insects, insects feeding on ephemeral resources (last for a short time), parasitoids, predatory beetles 3. Interaction between single host or prey and natural enemy Host-Parasitoid Systems Prey-Predator System A. Host-Parasitoid Systems - dependent on host rate of increase Various factors affecting the overall parasitoid performance: 1. searching efficiency 2. max. rate of attack of adult females 3. spatial distribution of parasitoid 4. sex ratio 5. survival of parasitoid progeny B. Prey-Predator System Factors affecting predatory ability: 1. Intrinsic factors a) Limited time available for prey searching b) Limited stomach size c) Time needed for digestion 2. Extrinsic factors a) Competition with another predator b) Environmental disturbances Competition with another predator Resource competition/Scramble competition - when there are many predator & abundant preys available, the predators capture as many preys as quickly as possible Interference competition/Contest competition - as predation causes prey to become more limited, competing predators may interact directly, leading to injuries or limited predatory success. Environmental disturbances (ex. flooding, fire, pesticide use of farming). C. Multispecies Systems - multiple natural enemies should be used if the net impact is greater than that of a single natural enemy. 1. Natural enemy species attacking competing prey/host species 2. Competing natural enemy species sharing a common prey or host species 3. Prey species attacked by both generalist and specialist natural enemies