Biological Control Agents Lecture Notes PDF

3. NATURE OF BIOLOGICAL CONTROL AGENTS 3.1 PARASITOIDS 3.2 PREDATORS OF INSECTS 3.3 ENTOMOPATHOGENS 3.4 ANTAGONISTS of Pathogens 3.5 BIOCON AGENTS FOR WEEDS  PREDATORS PARASITOIDS 1. Devours and...

3. NATURE OF BIOLOGICAL CONTROL AGENTS 3.1 PARASITOIDS 3.2 PREDATORS OF INSECTS 3.3 ENTOMOPATHOGENS 3.4 ANTAGONISTS of Pathogens 3.5 BIOCON AGENTS FOR WEEDS  PREDATORS PARASITOIDS 1. Devours and kills the prey instantly 1. Kills host gradually, depend and completely survival on their hosts 2. Free-living both as immatures and 2. Only the adults are free-living, the adult stage immatures are parasitic 3.In most cases, stage-and host- 3. May attack all stages of its prey species specific 4. Consume more than 1 individual 4.Usually lives/affects on only one preys in order to complete host during its entire development development  PREDATORS PARASITOIDS 5. With high parasitism may 5. Predator never eliminates its cause death and elimination of prey completely its hosts. 6. Prey-predator interaction/relationship - 6. not very dynamic dynamic equilibrum 7. Preys are usually smaller than 7.Hosts are usually bigger than predators or equal in size parasitoids WHAT IS PARASITOID? WHAT IS A HOST? Parasitoid – a parasitic insect that lives in or on eventually kills a larger host insect (or other arthropods) Host – those animals attacked by parasitoids CHARACTERISTICS OF PARASITOIDS Insects (mostly wasps and flies) Adults are free-living Host –same taxonomic class Eggs laid in, on or near host Parasitoid larva develops in host Initially does little harm to host Eventually consumes and kills host – usually before or during host’s pupal stage Classification of parasitoids 1. Position in food chain Primary-- parasitoid of a non parasitic host (herbivores/pests) Hyperparasitoids- parasite of a parasitic host Secondary—parasitoid of a primary parasitoid Tertiary-- parasitoid of a secondary parasitoid Facultative--species which can develop either as a primary or a hyperparasite  2. Egg placement and larval development Egg away from the host Microtype egg eaten by host, larva develops as endoparasite Planidium larva, hypermetamorphosis, larva develops as endoparasite. Planidium - specialized form of insect larva seen in the first-instar of a few families of insects that have parasitoidal ways of life - usually flattened, highly sclerotized (hardened), and quite mobile  Hypermetamorphosis Chafino et al 2018  Egg on or near host Larva develops as ectoparasite then penetrates host and develops as endoparasite Egg inside host, larva develops as endoparasite. 3. Number of parasitoid individuals per host: 1.Monoembryonic--One embryo gives rise to one individual a. Solitary--One parasite individual develops b. Gregarious--Two or more individuals (from different embryos) of same species c. Facultative --Either solitary or gregarious, depending on the size of the host 2. Polyembryonic --One embryo divides mitotically, producing many genetically identical individuals Host stage(s) utilized 1.Egg-- Complete life cycle in host egg 2.Egg-larval--Parasite egg placed in host egg, parasite larva develops in and kills host larva 3.Larval (Nymphal)--Complete life cycle of parasite in (or on) host larva (or nymph) 4.Larval-pupal 5. Larval-adult-- (rare in nature). 6. Pupal--Complete life cycle of parasite in or on host pupa 7. Pupal-adult--(rare in nature) 8. Adult--Complete life cycle of parasite in adult of host species  5. Host range: Host specific--Parasite is generally restricted to one host species under natural conditions (cf. monophagous) Generalist - successfully complete development in many host species (latter are usually taxonomically related). Stenophagous--Parasite with a narrow host range (cf. oligophagous) euryphagous - wide host range (cf. polyphagous)  Quiz: 1. Example of insect predator aside from a praying mantis and spider 2. Give two common parasitoid orders 4-5. Give 2 ways on how parasitoids differ from predators 6. Type of parasitoid attacking major pests/herbivores 7. Parasitoid attacking #6 8. Tetrastichus brontispae is what kind of parasitoid based on the stage of the Brontispa host? Sex determination/mode of reproduction Thelyotoky - Diploid females give rise to diploid females no males exist only female progeny are produced; “uniparental”  Deuterotoky--A form of thelyotoky a few males are produced unmated females produce both male and female (mostly) progeny “uniparental”  Arrhenotoky - Males haploid develop from unfertilized eggs females (diploid) develop from fertilized eggs facultative parthenogenesis, haplodiploidy, male-haploid system “biparental species”; basic mode:  Adelphoparasitism sibling-parasitism Special form of arrhenotoky haploid males develop as hyperparasites, often on diploid females of the same species Aphelinidae in which the males are parasitoids of females of their own species (the females parasitize Hemiptera) 7. EGG PRODUCTION/OVIGENESIS A. Proovigenic – species which reach the adult stage with a complete complement of mature eggs deposited in a short time All are endoparasitoids No more eggs are produced during the parasitoid’s life Egg production dependent on metabolites retained from the immature stages OVIGENESIS B. Synovigenic – those species which continue to produce eggs throughout the adult stage. Production of eggs dependent on the nutrition of the adult female Adult wasp nutrition – aphid honeydew, plant nectaries  Ovisorption ripe eggs in the ovarioles are absorbed if cannot obtain proteinaceous food or cannot find host Eggs can be produced later Correlated with high searching capacity  8. Sex allocation strategies Variable fitness -- Males develop in smaller hosts and females develop in larger ones Larger females from larger hosts live longer and lay more eggs Local-mate competition (LMC)--Female-biased sex ratio in inbreeding species where sons of same female compete for mates; expect female to allocate the minimum number of males necessary to inseminate Premating period Mating habits – courtship Pre-oviposition period – interval between emergence of the adult female and deposition of the first egg marking pheromone - oviposition deterring pheromone = cues or signals that prevents the females from laying eggs on hosts bearing brood Will avoid competition of the offsprings  9. Host – parasite relationship Koinobiont--A species which allows the host to continue to develop, move about, and defend itself; Idiobiont - halts host activity before the parasite's egg hatches  Regulator-A species which interferes with or alters the host's biochemical processes Conformer - egg or newly hatched larva remains inactive while allowing the host to develop and then are triggered by host conditions to begin their own development Pseudoparasitism-- Oviposition (or penetration with the ovipositor) without the production of offspring 10. Hyperparasitism Direct--Female searches for and oviposits in or on the primary parasite Indirect - female searches for and oviposits in or on the nonparasitic host (herbivorous pest) Obligate--A species whose larva can develop only as a hyperparasite (cf. facultative)  10. Impact on host population a. Density dependent- % parasitization varies with host density either direct (positive) or inverse (negative)  b) Species dependent--Total % parasitization varies with number of parasite species exploiting the host MODE OF DEVELOPMENT OF PARASITOIDS WITH RESPECT TO: 1. The host Endoparasitoid (internal) – in situation where the host is exposed Ectoparasitoid (external) – usually in situation where host lives within protected location 2. The number of immatures/ individual host Solitary parasitoid Gregarious parasitoid Imago or Adult Parasitoid behavior What is an effective natural enemy? 1.High searching capacity 2.Host specific 3.High potential for increase 4.Ability to occupy and survive well in all ecological niches occupied by the host 5.Easily cultured 6.Able to restrict oviposition 7. Host finding behavior - Long range attractants Kairomones – volatile chemicals produced by the host for a purpose or just a byproduct of feeding; - e.g. sex pheromones of parasitoid’s host - Volatile odors from the host’s food  Visual stimuli Sound – e. g. mating calls of hosts Close range chemical stimuli Arrestant kairomones = chemicals may be less volatile produced by the host during feeding and egg laying E. g. larval excrement and secretions Also known as contact chemicals Defense mechanism by hosts Encapsulation – host blood cells surround and suffocate the parasitoid egg or larva Host defenses Major taxa of Parasitoids HYMENOPTERA: Trichogrammatidae Scelionidae Mymaridae Encyrtidae Ichneumonidae Pteromalidae Aphididae Braconidae Chalcididae DIPTERA Aphelinidae Tachinidae Eulophidae Phoridae Examples of parasitoids Order Strepsiptera Minute insects, parasitic on other insects: twisted-winged parasitoids Males free living and winged, beetle-like with protruding eyes Antennae with elongate processes Front wings resemble halteres of Diptera Hind wings large and membranous, fan-like Females wingless, legless, do not leave the host STYLOPIZED  ORDER STREPSIPTERA: Life History Male mates with the female which never leaves its host Male mouthparts are reduced and non- functional Triungulins have well developed eyes and legs, active to locate host escape from the body of the host to the soil and vegetation Hosts: Orthoptera Hymenoptera Thysanoptera Homoptera Elenchus - parasite of leafhopper Halictophagus - parasite of leafhopper DIPTERA: Tachinidae most beneficial groups of Diptera similar to flesh flies (Sarcophagidae) abdomen has a number of very large brittles plus smaller ones parasitize many kinds of insects DIPTERA: Ceccidomyiidae gall midges or gall gnats minute, delicate flies with long legs and usually long antennae reduced wing venation most are phytophagous one example of parasitoid: Endaphis sp. - endoparasite of abaca aphid (Pentalonia nigronervosa) Muratori et al 2010 Hymenoptera Minute to very large; larvae usually legless with distinct head 1.Ichneumonids - large wasps, about Family Braconidae 1/10” to 1 1/2” long, can be nearly 3” long including its very long tail- like ovipositor. 2.abdomen longer than the head and thorax combined; females frequently have an ovipositor (egg- laying organ) that is longer than their body. 3.yellowish to black, or brightly colored with black/brown or black/yellow markings. Braconids resemble ichneumons, but are usually smaller in size and darker in color, although some species have striking coloration Ichneumonidae 1. Family Braconidae 2. Family Ichneumonidae Braconids and ichneumonids differ in wings: Braconidae adults relatively small, many stout bodied Abdomen is about as long as the head and thorax combined Many pupate in silken cocoons on the outside of the body of host Polyembryony occurs in a few species Examples: Cotesia/Apanteles - form small white cocoons outside the body of parasitized larvae Bracon chinensis - parasite of stemborer Opius sp. - parasitize fruitfly maggots, Dacus Superfamily Chalcidoidea  Family Trichogrammatidae very tiny insects: 0.3-1.0 mm in length 3-segmented tarsi hairs on wings arranged in rows short head somewhat concave behind egg parasitoid Examples: T. chilones, T. evanescens  Family Eulophidae 1-3 mm in length; 4 segmented tarsi brilliant metallic coloring, male have pectinate antennae Example: Tetrastichus schoenobii - parasitize eggs of stemborers Family Chalcididae 2-7 mm in length with hind femora greatly swollen and toothed Example: Brachymeria sp. - parasitize older larvae of leaffolders, skippers and satyrids single egg deposited in body of each larva or pupa pupation occurs inside the host 6. Family Encyrtidae 1-2 mm in length; with broad convex mesopleura; mesonotum convex Example: Copidosomopsis - parasitoid of leaffoder larvae wasps lays eggs in leaffolder eggs and develop inside the larva even after the host egg hatches Wasp eggs divide many times and 200-300 wasps are produced from a few eggs à polyembryonic  Abdomen very small and Superfamily Evanioidea oval attached by a slender 7. Family Evaniidae petiole to the propodeum considerably above the base of the hind coxae Abdomen is carried almost like a flag Parasite of egg capsules of cockroaches HOW TO COLLECT PARASITOIDS? 1. Sweeping plants with nets 2. Yellow pan traps 2. Collecting the pest itself and rearing parasitoids from it 3. Collecting “mummies” e.g. parasitized aphids and mealybugs