Index

Introduction

Types of biopesticides (biochemical and microbial pesticides)

Types of microbial pesticides

Bacteria

Viruses

Nematodes

Fungi

Protozoan

General advantages and disadvantages of microbial insecticides over chemical insecticides

Some examples

INTRODUCTION

BIOINSECTICIDES AND PESTICIDES: Pest management tools that are based on beneficial microorganisms (bacteria, viruses, fungi, and protozoa), beneficial nematodes or other safe biologically based active ingredients.

Biopesticides are an important group of pesticides that can reduce pesticides risks Biopesticides in general: Have a narrow target range and very specific mode of action Are slow acting Have relatively critical application times

Suppress, rather than eliminate, a pest population Have limited field persistence and a short shelf life Are safer to human and the environment than conventional

pesticides Presents no residue problem

Two types of biopesticides are biochemical and microbial

Biochemical pesticides may have a similar structure to and function like naturally occurring chemicals and have non-toxic mode of action Insect’s pheromones for example are naturally occurring chemicals that insects use to locate mates. Men made pheromones are used to disrupt insects mating by creating confusion during the search for mates, or can be used to attract male insects to traps. Pheromones are after used to detect or monitor insect’s population, or to control them.

Microbial insecticides come from naturally occurring or genetically altered bacteria, fungi, algae, viruses, or protozoan. They suppress pests by -

Producing a toxin specific to pest Causing a disease Preventing establishment of other microorganism through

competition `Other modes of action

Microbial insecticides:

Microorganisms that have been made commercially available to control orthopods pests.These products must compete with their synthetic counter parts in pest management marketplace.Major pathogens groups are

BacteriaMost pathogenic entobacteria are found in families bacillacea, pseudomonadaceae, enterobacteriacea, streptococcaceae. And micrococaceae.Bacillus is by far most important microbial pesticide genus.Bacillus thuringiensis has been the most widely used and successful microbial pesticide ever registered. The only non-bacillus bacteria microbial insecticide is serratia entomophila currently registered for pasture land grub control in Newzealand.

Bacillus thuringiensis:Members of family bacillaceae are gram positive motile or non motile rods that can produce endospores the larvicidal activity of the bacterium is due to the parasporal crystals procedure by bacterium at the time of sporulation. Protein toxin in parasporal crystal collectively called delta endotoxins must be ingested in order to be active. After being eaten crystal is solublized in alkaline environment of midgut and enzymatically activated. Portion of the toxins molecules responsible for larvicidal activity, binds to specific sites on membrane of midgut cells and disrupture osmotic balance of midgut cells.cell swells and rupture allowing gut contents to enter body cavity,insect dies afterwards

Factors influencing the larvicidal activity of BT

Age of targeted larvae ie younger larvae are more susceptible

Temperatureo Spray rateo Coverage of plants o Timing and number of applications o Inactivation by sunlight

Advantage of BT formulation over chemical pesticides: Safely for application and field workers

Lack of activity on non targeted organisms including natural enemies.

Drawbacks of BT formulation Still expensive when compared to many synthetic

pesticides Media must be optimized for each new strain put into

commertial production.

Other bacteria:

Two other species of bacteria currently registered as microbial insecticides are:Bacillus sphacricus and serratia entmophila, B.sphaericus: strict aerobic spores former, registered for mosquito control particularly effective against membrane of genus culex.S.entomophilaNon spore forming, gram negative ,anaerobic,rod shaped bacteria,commonly found in nature as saprophytes in soil and water .S.Entomophila is the casual agent of amber disease in Newzeland grass grud, costelytra zealandica .it is registered for control of C.zealandica in Newzealand pasture.

Viruses:

Number of currently registered viral insecticides are made up of a relatively small no of entomopathogenic viruses exclusively from family baculoviridae.

Baculoviruses-

Viruses that infect insect, mostly of order lepidoptera hymnoptera, celeopreta. They are rod shaped and have circular doubled stranded DNA as their genomes. In nature they are found occluded within proteinaceous crystals known as POLYHEDRA on plant faliage,plant debris or soil.Insect larvae get infected when they feed on plant foliage and after a few days, show feeding cessation and ultimately die.

Baculoviruses primary infect insect larvae and adult insects are not susceptible to them .the insect larvae while feeding on plants foliage accidently feed upon the polyhedral with then gets solubilized in midgut thereby releasing the virion. These virions replicate within the nuclei of epithelial cells lining the midgut to produce more virion which are released in budded form by 10-12 hr pi or get occluded in polyhedra late in infection cycle tissue liquefication and death of these cell upon death of infected larvae liberate masses of these polyhedra in soil environment from here they are again ready to be ingested and infected their host.

Advantage of baculoviruses over chemical pesticides:

Have a narrow host range ie don’t harm beneficial insects.

Because of their persistence in environment, they are suitable for long term, ecologically sound control progammer

Can be produced easily locally.

The global use of baculoviruses has been hampered by various constrains:

Slower speed of kill Narrow hast range Product stability Registration and patentibility.

Inactivated by UV, Brays of sunlight.

Efficacy of baculoviruses is measured in lad. By an insect bioassay. Occlusion bodies are quantified under microscope using haemacytometer.

Some registered or commercialized baculoviruses as insecticides are:

Country product name active againtUSA Elean cotton bollworm Brazil multigen velvet bean catterpiller

Nematodes:

Entomopathogenic nematodes (EPNS) are being recognized as important biological control agents for a wide variety of insect pests. EPN’S are insect parasitic nematodes. They are simple roundworm with cylindrical shaped bodies, ranging in length from .4 – 1.1mm

Attributes that makes EPNS commercially suitable as biological control agent of insect pests:

They have a host range that includes majority of insects orders and their families and kill their host in 48 hr of infection

They can be easily cultured on a larger scale in an artificial media (in vitro culture) and infected juvenile stage obtained can be stored for longer time.

Infective juvenile stage can withstand high pressure and can be applied in field using conventional spray.

Advantage of EPNS over chemical insecticides:

There will be a reduction in social costs that incur from accumulation of chemical insecticides in food chain and water

Reduce formwork health risk associated with application of chemical insecticides

Broad activity of EPN based bioinsecticides allow for the target of several market.

Mode of action:Nematodes parasitizes their host by direct penetration either through the opening in host integument ie mouth spiracles or through cuticle. An insect death is due to a symbiotic becteria that is released by juvenile into host.

Fungi:

Entomopathogenic fungi are found in division eumycota in the subdivisions: mastigomycotina ,zygomycatina,ascomycotina and deutromycotina

Toxicity from entomopathogenic fungi most often occurs from contact of fungal conidia with host cuticle this necessitates through coverage of pest and foliage

The first registered myainsecticides was Hirsutella thampsanii procedure by abott labs under trade name Mycar

Currently most widely used fungal insecticide is Beauveria bassiana .it has been produced by several companies and market for control of calorado potato bettle that several other insects.

Using Fungus toFight Locustsseveral years of research involving fungus trials have culminatedthe development of an environmentally friendly way of controllinglocust plagues, i.e. through the use of a new fungal bioinsecticide.This form of plague control is to be marketed as a commercial productwithin the next two years.In the past, locusts have resulted in significant losses for farmers andgraziers throughout Australia. The rainy weather in many parts ofQueensland and northern New South Wales (NSW) has createdconditions ideal for locust breeding. Currently, chemical insecticidefenitrothion is being used to reduce locust numbers. However, the useof this insecticide as well as several alternative chemicals (e.g.endosulfan), has caused residue problems, contaminating waterwaysand organic farms. This has led the Australian Plague LocustCommission (APLC) to impose buffer zones, where pesticide sprayingis banned. In areas such as these however, the locust population isallowed to multiply since no form of control is used. As this neworganic bioinsecticide uses the naturally occurring fungal insect diseasepathogen Metarhizium as the active ingredient, it can be used toeffectively control locust plagues without polluting the environment.The fungus bioinsecticide is formulated in such a way that live fungalspores can be air-sprayed on vegetation. Once the insects come intocontact with the fungal spores (either by direct contact or throughingestion of treated vegetation), they become infected with the disease,and die in a matter of days. The stabilized oil-based formulation ofMetarhizium was tested against the migratory locust (Locustamigratoria) in the Central Highlands and proven to yield excellentfield results. Other trials have also shown its effectiveness against thewingless grasshopper and the plague locust.

SFactors that effect its larvicidal activity includes:

Temperature Humidity Age and stage of insects Timing and number of application Dosage agricultural practices Deactivation by sunlight

Advantage of fungal pathogens used in microbial control Less expensive Broad host range Able to grow and sporulate on any generalized media Can adapt to a variety of growing conditions

Despite of advantages there are numerous constrains on ability of fungal pathogens to infect their host these includes:

Desiccation U.V light Host behavior Temperature Pathogen vigor and Age

Protozoan:

Entomogenous protozoan are extremely diverse group with relationship ranging from common Sal to pathogenic, generally slow acting rather than quick and acute .

Currentely in U.S one registered protozoa insecticide Nosomea locustae targeted against grasshopper. it is soled in U.S as NoloBait by W and R Durango. Products are formulated on bran that is consumed by grasshopper. Death follows shortly after lethal infection and egg production reduced by 60 – 80 % in surviving adults

Demerits of protozoa as microbial insecticides They can be extremely effective at reducing fitness and fecundity of insects so that they may have e real negative effect on microbial insecticides (viruses etc) produced in vivo.

Advantages of microbial pesticides over chemical insecticides. Specificity to the target organism or to a limited number of

host species. Little or no direct impact upon parasitoids and invertebrates

predators. Harmless to vertebrates and plants. No toxic residues. Little or no environmental pollution. Little or no development of resistance by target organism. No secondary pest outbreak. Compatibility with other biological control agents. Possibility of long-term control. Ease of application. Adaptability to genetic modification through biotechnology

Disadvantage of microbial pesticides

Specificity only to target organism Strictly timing of application for maximal effect Long period of lethal infection (little or no knock down effect Inactivation by environmental factors (e.g. U.V, dissection)

and difficult to formulate Short shelf life. Possibility for development of resistance by target

organisms, especially to bacterial toxins. Uneconomical. Except for niche markets. Risks associated with genetically modified organisms.

The real issue is that a strategy to constitutively express an insecticidal compound in large-scale crop monocultures and thus expose a homogeneous subecosystem continuously to the toxin, seems bound to create Bt-toxin-resistant pests because of heavy selection pressure. Sooner or later we will likely see Bt-toxin resistance in those insects that are continuously in contact with these monocultures and feed on them. If or when this occurs, we will have lost the use of a valuable bio-insecticide.

Bt toxin has been found to leak through the root system of Bt-toxin GM maize into the soil, which could possibly affect a myriad of insects in the soil and give rise to horizontal gene transfer, for example, through soil bacteria

EXAMPLES OF SUCCUSSFULLY USED BIOINSECTICIDESProduct Crop(s)

Bacillus thuringiensis (Bt) All (Label Expansions)

Gibberellic Acid (GA) Strawberries & Blueberries

Bacillus popilliae Pastures

Methyl Eugenol (w/ Malathion) All

Grape Berry Moth Pheromone Grape

Codling Moth Granulosis Virus Apple, Pear, Walnut & Plum

Pseudomonas fluorescens Strain NCIB 12089

Mushroom

Lagenidium giganteum Rice

SOME RECENT EXAMPLES

1. LPE - 97 and 98S formulations on 13 fruit crops (EUP) – promote ripening and

2. Extend storage shelf life.3. Cinnamaldehyde – for mite/powdery mildew control on 39 crops.4. Chitosan (Elexa 4) – for powdery mildew control on grapes, roses

and strawberries.5. Messenger (Harpin Protein) – for disease control on apples &

grapes.6. Milsana – for powdery mildew control on ornamentals.7. Sucrose Fatty Acid Esters - on all commodities for insect and mite control (pending)8. Macleaya Extract - for ornamental disease control (pending)