Microbial Processes Promising Technologies for Developing Countries (1979) / Chapter Skim
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5 Microbial Insect Control Agents
5 Microbial Insect Control Agents
Pages 80-106
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From page 80... ...
Development of Bioinsecticides In planning an approach to the use of microbial control agents, the most significant factors to be considered include production technology, safety and specificity, and efficacy.
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From page 81... ...
Evidence that microbial insecticides pose little human or environmental hazard has been demonstrated by laboratory animal testing data developed to support federal pesticide registration. Nevertheless, safety cannot be absolutely guaranteed for all entomopathogens in every living system, and it is important that potential hazards for new entomopathogens be known prior to use.
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From page 82... ...
FIGURE 5.2 Scanning electron micrograph of entomocidal parasp oral crystals and spores of Bacillus thuringiensis. (Photograph courtesy of C
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From page 83... ...
Some of these approaches may provide levels of control equal to or better than those currently obtained with chemical insecticides, but further research is needed to exploit their potential. The potential for substituting microbial control agents for chemical pesticides can be deduced from the following examples in the United States shown in Table 5.1.
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From page 84... ...
, various Lepidoptera including nun moth (Lymantria monacha) , European corn borer (Ostrinia nubilalis)
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From page 85... ...
sphaericus) have been closely examined as insect-control agents.
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From page 86... ...
thuringiensis (Figure 5.2) is orate of the best-known and most widely used microbial control agents.
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Gypsy moth (Lyw~ntria dispar) European corn borer (Ostrinia nubilalis)
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From page 88... ...
; 2) possibility of integration with conventional chemical insecticides; 3)
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Tissue culture may be a virus-production technology of the future. Insect tissue cell-culture lines have been established in which insect viruses grow and multiply.
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Whitemarked tussock moth (Or~ |
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MICROBIAL INSECT CONTROL AGENTS ~~,~ ~ ~ ~i ~ (a) Nucleopolyhedrosis virus.
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92 PUPAE ADULTS \~As | Bollworm -.~ cycle 26-36 days MATU RE I LARVAE EGGS NEONA TAL LARVAE _ .~ _ LARVAE ~ ingestion multiplication ~ r _ _ _ ~ Virus _ cycle cell ~ _ reinfection _ _ Released 5-7 days _ _ virus Virus _ Cell replication_ penetration vi,,,< MICROBIAL PROCESSES Carbohydrates_ Fats'~Vitamins Proteins—:~' I | I '~ Gel C} ~ 1 ,~ Cooler e n 1Di et / /Concentration\ | Standar dization | ..... n ~ ~ Form~latinn [ - ]
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From page 93... ...
Gypsy moth (Lyw~antria dispar) Spruce budworm (Choristoneura fumiferarza)
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From page 94... ...
Protozoa Protozoa are primarily free-living, but many types are intimately associated with insects in relationships ranging from compatible to harmful. Most of the approximately 300 described species of entomophilic protozoa are included in the orders Microsporidia (Subphylum Cnidospora)
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From page 95... ...
are currently under consideration as insect control agents. Production Almost all protozoa of potential value as entomopathogens must be produced in living hosts.
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Efficacy Field Infestations caused by protozoa have seldom been documented, but the efficacy of protozoa as control agents is readily apparent in laboratory
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From page 97... ...
Limitations The availability of many kinds of protozoa enhances their potential use as microbial control agents. Although protozoa may be significant as natural regulatory agents, their use as microbial insecticides has been limited, especially by the fact that protozoa act slowly on their hosts in contrast to the rapid action of some viruses or bacteria.
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From page 98... ...
Coelomomyces and some Entomophthora species grow poorly in laboratory media, but most pathogenic TABLE 5.7 Experimental Fungi for Insect Control Fungus Infective Stage Insect Hosts Habitat Chytridiomycetes Coelomomyces Motile planonts Oomycetes Lagenidium Motile zoospores Zygomycetes Entomophthora Deuterom ycetes Aschersonia Beau reria Hirsutella Metarhizium Nomuraea Paecilomyces Verticillium Mosquitoes Aquatic Mosquitoes Aquatic Conidia or resting spores Conidia Conidia Conidia Conidia Conidia Conidia Conidia Caterpillars, aphids White flies Beetles, caterpillars Mites Froghoppers, leafhoppers, beetles, mosquitoes Caterpillars Beetles Aphids, white flies Foliage Foliage Foliage Foliage Foliage, soil, aquatic Foliage Foliage Foliage, greenhouses
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From page 99... ...
Plant Design Construction Commercial Production _ Distribution Development of fungal control agent for aphids. (Flow chart courtesy of fungi, particularly species of the Fungi Imperfecti, can be mass produced on sterilized bran, grain, or beans.
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From page 100... ...
Some isolates of Aspergillus paves that infect insects may also produce metabolites the+ are toxic to human beings, but extensive toxicological studies have not been conducted. Since pathogenic fungi usually do not grow in nature except in or on their insect hosts, toxin build up in the environment after fungi are introduced is not expected.
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From page 101... ...
(a) Conidia of the entomopathoge~c fungus Nomuraea rileyi on the surface of mfected cotton bollworm larva (below)
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From page 102... ...
Little is known concerning interactions between soil microorganisms and pathogenic fungi, but mortality rates can be considerably lower in unsterilized than sterilized soil. More information is needed on soil inhibitors in order to select fungal pathogens that have increased ability to infect insects in the presence of soil microorganisms.
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From page 103... ...
Research bleeds Several areas of research need to be explored to develop the full potential of fungal insecticides. These include: · Conducting exploratory work to isolate new entomopathogenic fungi and improving methods for distinguishing fungal species and strains; · Developing bioassay techniques; · Selecting strains with increased virulence or other traits that will increase their effectiveness as fungal insecticides; · Documenting the modes of disease induction and development; · Developing predictive techniques so that insecticide applications can be eliminated where conditions indicate that fungi will soon significantly reduce the pest population; · Developing methods for encouraging natural epizootics; · Improving fungal insecticide production, formulation, and stabilization technology; · Devising field application and evaluation methods specifically for fungal insecticides; · Integrating fungus insecticides into pest-management systems by exploring compatibility and synergism with current chemical pesticides and cultural techniques; and · Initiating more extensive safety tests with fungal insecticides.
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SROP-Section Regionale Ouest Palearctique (Journal published by O.I.L.B.—Organisation Internationale de Lutte Biologique Contre les Ennemis des Cultures, Swiss Federal Institute of Technology, Zurich, Switzerland)
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From page 105... ...
M I~offo, Biological Control of Insects Research Unit, U.S.
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From page 106... ...
Department of Agriculture, Science and Education Administration Insect Pathology Research Unit, Boyce Thompson Institute, Cornell University, Tower Road, Ithaca, New York 14853, U.S.A.
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