Seminar Presentation on Ecological

7/28/2019 Seminar Presentation on Ecological

1/22

SEMINAR PRESENTATION ON

ECOLOGICAL IMPLICATIONSECOLOGICAL IMPLICATIONSOF BIOLOGICAL CONTROLOF BIOLOGICAL CONTROL

PRESENTED BY

OPAYELE ADEWALE VICTOR

ENTOMOLOGY UNITDEPARTMENT OF ZOOLOGY

([email protected])


2/22

INTRODUCTIONINTRODUCTION Biological control is the use of living organisms

advertently to suppress the population of a specific pestorganism, making it less abundant than it would

otherwise be (Eilenberg et al., 2001).

When a species becomes established outside its natural

range, it may achieve pest status because its natural

population regulators (natural enemies) did not also

become established (Keane and Crawley, 2002).

Entomologists are often deployed to find the geographicorigin of the pest and to identify its naturally occurring

predators, parasites, and pathogens.


3/22

Biological control agentsBiological control agents

Predators and Parasites

Predators are usually larger than their victims andtend to be polyphagous. They may have chewing orsucking mouthparts, may hunt their prey on theground, on vegetation or in flight or may trap it byvarious means, they range from vertebrates to

invertebrates Parasitic insects, often called parasitoids lay their eggs

in or on the bodies of other arthropods and developat the expense of the host eventually killing the host.

Most belongs to the order Hymenoptera and Diptera Microbial Control

This involves the use of viruses, bacteria, protozoa,fungi, and nematodes in Biological control


4/22

METHODS FOR USING NATURAL ENEMIESMETHODS FOR USING NATURAL ENEMIES

1.INTRODUCTION

Classical biological control involves the

importation and establishment of natural enemies

of exotic pests (Altieri, 1991)

Neoclassical biological control, involves the

importation of non-native species to control native

pests.


5/22

2. Augmentation

Augmentation is the supplementation of existing

natural enemies, including periodic release ofthose that do not establish permanently butnevertheless are effective for a while afterrelease.

3.Conservation

Conservation is another broad strategy ofbiological control that aims to implement practices

that maintain and enhance the reproduction,survival, and efficacy of natural enemies(predators, parasitoids, and pathogens) of pests(Barbosa, 1998).


6/22


7/22

Unfortunately, the species that are most likely to

be effective biological control agents are also

those most likely to be a threat to non-target

species

Gillot, 2005 Observed that it is often difficult to

properly explore the delicate balance between

pests, their natural enemies, and other insect

species in a community before embarking onbiological control.


8/22

EcologicalEcological EffectsEffects ofof IntroducedIntroduced AgentsAgents onon

OtherOther OrganismsOrganisms inin thethe EcosystemEcosystem

EFFECTS ON NON-TARGET ORGANISMS

The released biological control agent might affect

the abundance of native non-target species in

natural or semi-natural ecosystems. Direct negative effects can occur when the agent

attacks other species in addition to the target

species. Knowledge on host specificity is thereforeessential.


9/22


10/22

ECOLOGICAL REPLACEMENT This occurs when a biological control agent is used

against a pest that has become integrated into the

native community by physically or functionally

replacing native species.

For example, biological control of exotic European

rabbits Oryctolagus cuniculus in the UK is believed

to have resulted in the extirpation of the large blue

butterfly Maculina arion through a series of

indirect effects that fatally linked this species tothe rabbits (Moore, 1987).


11/22

The large blue required nests of the ant Myrmica

sabuleti for the development of their larvae.

These ants in turn were dependent upon rabbitgrazing to maintain open habitat for their nests

Biological control of the rabbits with theMyxoma virus initiated a cascade of interactions

believed to have led to the extinction of the

large blue. (Dean and Ragan, 2003)


12/22

COMPENSATORY RESPONSESPlants can alter the outcome of biological controlherbivory through compensatory growth orincreased production of secondary compounds.Herbivory by the root-boring biological controlmoth Agapeta zoegana on the invasive forb

Centaurea maculosa might deleteriously affectnative grasses, such as Festuca idahoensis(Callawayet al., 1999). The mechanism for this unusualindirect effect can be explained with two non-

mutually exclusive hypotheses.


13/22

1 C. maculosa exhibits a very strong compensatorygrowth response to herbivory (Callaway et al.. 1999),and resource competition might intensify with

increased resource uptake.

For example, the application of A. zoegana did notsignificantly decrease C. maculosa biomass butactually stimulated small but significant decreases inF. idahoensis biomass.

2 Herbivory can stimulate increased production of

harmful exudates (Bais et al., 2002), that can affectbeneficial organisms


14/22

FOOD-WEB INTERACTIONSIntroduced biological control agents that gotestablished have the potential to be superabundant

within the host environment when they encounterplentiful food, little competition and few naturalenemies of their own. If biological control agents arestrong enough to control their host populations, their

superabundance will be ephemeral since it will declineas it depletes its food resource. On the other hand, ifan established biological control agent is ineffective atreducing its host densities, its population are likely to

remain abnormally high. The superabundantintroduced agent could indirectly present a lucrativeopportunity for native consumers to blossom (Goedenand Louda, 1976; Story et al., 1995; Dray et al., 2001).


15/22

The Urophoracase study

In the early 1970s, two species of gall flies, Urophora

affinis and U. quadrifasciata, were introduced to western

North America for the biological control of spotted and

diffuse knapweeds Centaurea maculosa and C. diffusa

(Julie and Griffiths, 1998). The Urophora spp. which

successfully established, but failed to control the hostplant population, and as a result, becomes

superabundant, occurring at densities of 3000 larvae m-2

(Harris, 1980). Studies have shown that these gall flies are

readily exploited by deer mice Peromyscus maniculatusand these larvae now comprise 85% of the deer mouse

winter diet in grasslands invaded by knapweed (Pearson et

al., 2000).


16/22

The presence of the introduced agent has resulted

in an increase in overwinter survival that has

elevated deer mouse populations two to three fold

in knapweed invaded grasslands. Maron and

Simms, (2001) found the ecological role of deer

mice to include the aggressive predation of seeds

and insects, compete with other small mammals,and are important prey for larger predators. The

failed biocontrol might exacerbate the impacts of

knapweed on the native community throughindirect effects. For example, seed predation by

deer mice can significantly reduce recruitment in

native plant populations.


17/22

COMPETITION

When the biological control agent is attacking and

reducing an organisms population (target or non-target) this may negatively affect other naturalenemies that attack the same pest.

When the biological control agent and the other in

situ natural enemy are effectively exploring the sameresource ultimately only one of both may survive.

If the introduced agent survives the competition atthe expense of the in situ natural enemy, and in thelong run prove not to be as effective as the in situnatural enemy, the ultimate aim of control will not beachieved.


18/22

ENRICHMENT AND VECTORING The released biological control agent may not only

attack some organisms but may also be attacked

by other organisms within the ecosystem.

This will have positive rather than negative effects

on these populations, but it may indirectly have

negative impact on victim species.


19/22

HYBRIDIZATION Apart from causing ecological changes, a released

biological control agent may also cause geneticchanges in other populations in the ecosystem.

One specific mechanism is hybridization between

the biological control agent and indigenousbiotypes of same or very closely related natural

enemy species. This can result in the production of

sterile hybrids that will ultimately crash the

population of the local biotypes or the hybrids

may be less aggressive in host seeking behaviour.

CONCLUSION


20/22

CONCLUSION Biological control agents has a lot of effects on the

ecosystem and most of these effects manifest

themselves slowly and are irreversible. Wrongapplication of biological control agents has done a lotof ecological damages on our ecosystem and is stillcapable of doing more if lessons are not learnt from

already concluded biological control projects. The ecological problems that do arise from biological

control methods is due to the fact that the projectssuffers from insufficient assessment of the risks

associated with release of the biological controlagent, in particular, failure to carry out sufficientlybroad host-specificity studies.


21/22

RECOMMENDATION Workers in this field are to be given enough time to

do their evaluation as most effects do not show upearly.

Enough information should be collected and

documented to serve as data base for scientists towork with, especially about the organism in the

new environment where the biological control

agents are to be released.

Research institutes, cooperate bodies, NGOs and

the government should be more committed to

sponsoring research in biological control works.


22/22

THANK YOUTHANK YOU

Documents

Seminar Presentation on Ecological