Food and Fertilizer Technology Center - publications

Nov. 30, -0001

Biological Control of Pests and Weeds


Ipm and Biocontrol


For many years, the Center's pest control programs have focused on integrated pest management (IPM) systems suitable for small-scale farmers in the Asian and Pacific Region. Over the past ten years, biological control has been emphasized in IPM systems, as a sustainable and environmentally friendly substitute for chemical pesticides. Biological control holds great promise for small-scale farmers in the Asian and Pacific region, particularly in South Pacific nations. Most of their pest species are introduced from overseas. Many of these nations have already been carried out a number of successful biological control programs for pests and weeds.


A training course on both the basic strategy and current advanced technology of modern biological control was organized for the benefit of junior researchers and extension specialists from 11 Asian and Pacific countries. It was held at the Cooperative Research Centre for Tropical Pest Management in Queensland, which has a high level of expertise in biological control and one of the most advanced quarantine insectaries in the world.


Besides the lectures, the course provided practice in computer simulations of IPM. Participants made field trips to quarantine facilities, and to field trials where practical IPM programs are being implemented.


Putting Biocontrol into Practice


Biological control is defined as "the actions of parasites, predators and pathogens in maintaining pest density at a lower average population density than would occur in their absence". It is based on the idea that the most effective natural enemies are likely to be found in the places where the pests originated, and where systems of natural control might be expected to have evolved over time. There are three different ways of applying biological control: classical biocontrol, conservation and augmentation.


Classical Biocontrol


This is based on the importation and release of exotic biocontrol agents, with the expectation that the agents will become established and no further releases will be necessary. Classical biocontrol is thus unlike the other two methods, in that it is permanent. Once successful control of a pest has been achieved, the control will continue indefinitely unless disrupted by the introduction of hyper-parasites. It is therefore much cheaper than other methods in the long run. Also, it does not require action by farmers, so that extension and adoption in the field is not a problem.


The problem is that introduced exotic biocontrol agents may not be successful in a new environment, and may not become established. Even if they do become established, they may not have much impact on the target pest. Classical biocontrol is most effective when it is used to control introduced pests, rather than endemic ones. It is also most effective when it is used in isolated and clearly defined areas, as in the case of small islands. The Pacific island nations are thus ideally suited to classical biocontrol programs.


Conservation


This is the protection or maintenance of existing populations of biocontrol agents.


Augmentation


This is regular action to increase populations of biocontrol agents, either by periodic releases or by environmental manipulation.


Current Biocontrol Strategies


In most of the world, current biocontrol programs have been shifting away from classical biocontrol towards conservation and augmentation. It is these last two methods which were the focus of the FFTC training course. However, the principal strategy of modern biocontrol is in practice almost identical to that of classical biocontrol. The first step must be identification of the pest. The next step is exploration for natural enemies of the pest. Finally, appropriate natural enemies are imported for release, and augmented as necessary. Evaluation of the effectiveness of control by the natural enemies must continue for many years after release, until the target pest is exterminated or a stable equilibrium has been reached.


The training course emphasized the importance of accurate identification of both pests and beneficial organisms, since most beneficial organisms are host specific at the level of the genus, or even of the species. For example, scale insects or mealybugs are often incorrectly identified, and the importation of the wrong parasite results in failure of the biocontrol attempt. Specimens may need to be sent to the International Institute of Entomology or a similar international taxonomic service. The dangers of importing exotic organisms were also emphasized, along with the need for prior authorization by governments and quarantine clearance.


Biocontrol Agents


Various types of beneficial organisms, including pathogenic microorganisms (viruses, bacteria, fungi, protozoa and nematodes), mites, spiders, and insects were discussed. Lectures covered not only the taxonomy and morphology of beneficial organisms, but their practical application as biocontrol agents. For instance, in the case of
Bacillus thuringiensis
, one of the most promising bacterial agents, formulation and utilization as a bio-pesticide were explained in detail. Another common biocontrol agent is
Trichogramma,
a small parasitoid wasp often used to control corn borer and other moth pests.


As a key technology of augmentation, issues in mass production of beneficial agents by the private sector were also presented. Before embarking on the commercial mass production of a biocontrol agent, many issues have to be considered: whether the proposed biocontrol agent is effective against the target pest, whether the agent will need to be released repeatedly, and whether there will be a strong enough demand for the product among growers to make the venture profitable. A common problem is contamination during mass rearing. For example, the grain moth used as the host in the rearing of
Trichogramma
can be infected by mites which destroy the colony in a few weeks. Since biocontrol agents are living organisms, storage is another problem. The end product must be given quality checks to ensure that it has not deteriorated during storage. Handling and distribution systems must be carefully designed so that the biocontrol agent is delivered in good condition to growers when it is needed.


Methods of Conservation and Augmentation


The major concerns of modern biocontrol are maintaining adequate populations of existing beneficial organisms, the application of biocontrol agents in IPM (the timing, quantities, application method, etc.), and evaluation. Trainees were introduced to several computer simulation models of interactions between pests, biocontrol agents and crops. The helothis/NPV(virus agent)/sorghum Dymex model was one of the models provided to trainees for computer simulation practice. Trainees could use a PC to run the simulation models, while at the same time viewing the lecturer's monitor on their own screen.


FFTC Training Course


Biological Control of Pests and Weeds





Location
: Brisbane, Australia


Date:
October 13-17


No. participating countries:
11 (Australia, Papua New Guinea, Solomon Islands, Western Samoa, Fiji, Japan, Korea, Malaysia, Philippines, Taiwan ROC, Thailand)


No. papers:
16


No. participants
: 10 trainees, 17 lecturers


Co-sponsors:
South Pacific Commission

Cooperative Research Center for Tropical Pest Management, Australia


List of Papers


1. Introduction to biological control

- Gordon Gordth

2. Should we use biological control?

- Graham White

3. Insect pathogens

- David Holdom

4. Hymenoptera in biological control

- Gordon Gordth

5. Spiders: Anatomy, and role in pest management - Jan Green

6. Mites in pest management sytems

- David E. Walter

7. Diptera in biocontrol - David Yeates

8. Ecological theory and biological control: The distribution and abundance of a species

- Myron Zalucki

9. The heliothis/NPV/sorghum Dymex model -Peter Timmers and Myron Zalucki

10. ENVIROFEASTTM and preservation of natural enemies- David Murray

11. The importance of egg parasitoides in
Heliothis
IPM: A case study of sweet corn

- Brad Sholz

12. Commercial production of beneficial organisms

- Richard Llewellyn

13. IPM issues in brassica vegetable crops in Queensland- Browyn Houlding

14. Integrated pest management (IPM) in citrus

- Dan Smith

15. Biological control of spider mites in strawberries using the "pest- in-first" technique

- Geoff Waite

16. Classical biological control

- Rachel McFadyen


Index of Images




  • Figure 1 Chestnut Gall Wasp (Dryocosmos Kuriphilus) Laying Its Egg in the Bud of a Chestnut Tree (Photo by S. Moriya)


    Figure 1 Chestnut Gall Wasp (Dryocosmos Kuriphilus) Laying Its Egg in the Bud of a Chestnut Tree (Photo by S. Moriya)



  • Figure 2 Parasitoid Wasp (Torymus Sinensis) Attacking a Gall of Dryocosmos Kuriphilus


    Figure 2 Parasitoid Wasp (Torymus Sinensis) Attacking a Gall of Dryocosmos Kuriphilus



  • Figure 3 the Predator Orius SPP. Feeding on Thrips


    Figure 3 the Predator Orius SPP. Feeding on Thrips



  • Figure 4 The Wasp Tamarixia Radiata, a Parasitoid of the Citrus Psyllid Which Transmits Citrus Greening Disease


    Figure 4 The Wasp Tamarixia Radiata, a Parasitoid of the Citrus Psyllid Which Transmits Citrus Greening Disease



  • Figure 5 Wasp Larva Feeding on the Psyllid Host


    Figure 5 Wasp Larva Feeding on the Psyllid Host



  • Figure 6 Dead, Mummified Body of Psyllid Host


    Figure 6 Dead, Mummified Body of Psyllid Host

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