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1. INTRODUCTION
Integrated Pest Management (IPM), implies the integration of various approaches and methods into a pest management system. It takes into consideration the ecology of the environment and all relevant interactions that pest management practices may have upon the environment. Cultural practices and the use of chemicals can significantly influence the balance of crop pest populations and their natural enemies. For instance the populations of natural enemies can be enhanced by selective use of cultural practices or decimated by indiscriminate use of pesticides. As interest in environmental issues expands, the impact of cultural and mechanical pest management practices is receiving greater attention. Since IPM considers all applicable methods, it is assumed that emphasis on chemical methods may be reduced when effective non-chemical options are made available.
For the effective implementation of the IPM strategy, the following conditions are required:
v an understanding of the ecological interrelationships within a farming system (e.g. plant, pest and factors in the development)
v an understanding of the economic factors within a production system (e.g. economic threshold, infestation and loss levels)
v an understanding of the sociocultural decision-making of producers/farmers( e.g. traditional preferences, level of education)
v the involvement of farmers in the analysis of their plant protection problems and the elaboration of solutions
v the successful creation of the appropriate legislative, administrative and agricultural policy framework favouring IPM
The rest of the paper would analyse the introduction of an IPM strategy for the control of the Mediterranean Fruit Fly (Ceratitis capitata).
2. CASE STUDY: MEDITERRANEAN FRUIT FLY MANAGEMENT
2.1 DESCRIPTION OF THE PEST
The Mediterranean fruit fly, commonly known as Medfly (Ceratitis capitata), is one of the most devastating pests of fruits and vegetables. It attacks more than 300 plant species, ranging from citrus to peppers. The adult fruit fly is smaller than the housefly. The top of its back is mottled with yellowish-white and black areas. The abdomen has two distinct white cross bands. The front edge of the wing has many small dark/clear areas. The fully grown larva is opaque white in colour and the pupa is elongated and dark, reddish-brown. Medflies are not strong fliers and cannot fly more than a few miles, but will disperse when the adult population density or climatic conditions are favourable. Most dispersal of the Medfly, is caused by movement of larvae-infested fruit. Medfly originated in Africa but is now found in most tropical and subtropical areas of the world.
2.2 LIFE CYCLE
Females attack the fruit by piercing, and laying their eggs just beneath, the skin of the fruit. After about 2 to 3 days, the eggs hatch into larvae, which feed inside the fruit pulp. Generally, the damage by the larvae leads to premature ripening, rotting and early fruit drop. The larvae then leave the fruit, burrow into the soil where pupation takes place. After 10-11 days, the adult fly emerges. The complete Medfly life cycle takes 20 to 60 days depending on the environmental conditions. In the wild, adult fruit flies generally feed on various yeast and bacteria species, which supply the protein necessary for sexual maturity and for female flies to produce eggs.
2.3 ECONOMIC IMPORTANCE
The damage is caused by the larvae, which live and feed on the fruit of the host plant. In addition, ovipositional punctures by the female allow decay-causing micro-organisms to enter the fruit. A Medfly infestation is often devastating to the fruit and vegetable industry, particularly as a result of trade restrictions imposed by other countries making it necessary for a high level of investment in reinforcing quarantine restrictions and eradication programmes. Countries with established Medfly populations have typical crop losses of up to 50% if no effective pest management system is established. The Mediterranean fruit fly has an extensive list of preferred cultivated and wild hosts, including apple, apricot, nectarine, citrus, cherry, mango, pear, peach, plum, guava, coffee, lychee, grape, passionfruit, tomato, capsicum and eggplant.
2.4 IPM APPROACH FOR MEDFLY CONTROL
The IPM Medfly control strategy makes use of a series of methods. Some may be suitable only for fairly small areas whereas others can be classified as area-wide techniques needing the collaboration among many stakeholders. The main methods included in such a management strategy for Medfly include the following:
2.4.1 PHYSICAL, MECHANICAL AND CULTURAL TECHNIQUES
Cultural control includes practices that may be regarded as part of the normal production system and do not involve the application of insecticides. When combined with protein bait sprays in an IPM program, it results in very effective fruit fly management.
2.4.1.1 SOIL CULTIVATION
In small areas, e.g. heavily-infested crop of tomatoes or capsicum, soil cultivation immediately after harvest can bury larvae and pupae or expose them to the sun and predators.
2.4.1.2 AVOIDANCE/SOWING AND HARVESTING TIME
The production of certain crops (e.g. tomatoes, capsicum) can be restricted to periods of relatively low fruit fly activity. The harvest of crops at a stage of maturity when fruits or vegetables are not susceptible to fruit fly attack is a useful avoidance technique. It is also important to avoid growing crops which ripen consecutively close together as fruit fly will move from one to the other as fruit ripens.
2.4.1.3 GROWING LESS SUSCEPTIBLE CROPS/VARIETIES
Growers could select crops or varieties that are less susceptible or not susceptible at all to fruit flies (e.g. certain capsicum varieties)
2.4.1.4 COMPANION PLANTING
Some plants grown around the susceptible host can be used to deter or repel fruit fly. In addition some wild or cultivated plants support a range of natural enemies against the Medflies.
2.4.1.5 DESTRUCTION OF SUSCEPTIBLE WILD HOSTS/WEEDS
The destruction of wild hosts and weeds, on which the fruit fly pass part of the year before coming back to the crop, can be very useful in suppressing the fly population.
2.4.1.6 SANITATION
Not adopting sound crop sanitation places unnecessary pressure on other components of control systems. The collection and destruction of fallen, damaged, over-ripe and any excess of ripened fruits is very important to destroy mainly the larvae and pupae. Fallen, over-ripe, damaged or rotting fruits may be destroyed by deep burying (at more than 50 cm deep), burning, boiling or feeding to animals. Alternatively, they may be sealed inside plastic bags and exposed to direct sunlight for several hours or immersed in water or kerosene. Putting such fruits or vegetable residues into compost heaps or rubbish dumps is not recommended.
2.4.1.7 EXCLUSION
Fruit wrapping and bagging is used in some countries However this is labour- intensive and difficult to practise on large areas. Home-made or commercial fruit fly waxed paper or cloth exclusion bags are used. Some farmers also use lightweight fabric such as mosquito netting, shadecloth or nylon flyscreen material supported by a frame to cover the susceptible crop.
2.4.2 BIOLOGICAL CONTROL
The main advantages of using biological control are that it is non-toxic, cheap, specific/selective and compatible with the other methods. Natural biological control agents include braconid wasp egg parasitoids, ants spiders, dragonflies, robber flies and birds, free-range poultry and several other organisms. Maintaining the biodiversity is thus important. The most important parasitoid against Medfly is Fopius arisanus.
2.4.3 TRAPPING
Monitoring is the most common application of pheromones followed by lure and kill and mating disruption. Pheromone trapping can be used to determine the abundance of the pest as a tool to determine the judicious application of the various IPM control techniques. A wide range of insect attractant traps is used as a quarantine tool, for early detection of flies in an area, for monitoring and for mass trapping. This generally makes use of a combination of pheromone and pesticides or the insect dies by drowning or by being glued to the trap (e.g.baited yellow sticky board trap). Trimedlure is commonly used in traps for male annihilation technique. Alpha-copamine is more effective but is much more expensive and breaks down more easily than Trimedlure. Some traps are also used with protein hydrolysate bait to catch males and females but research more to develop lures effective for both male and female flies is being undertaken.
Yellow home-made traps of coloured Styrofoam balls covered with a non-drying glue may catch a lot of fruit flies. Researchers have also found coffee bean juice from ground up ripe coffee berries a great success as bait for female Medflies.
2.4.4 PROTEIN BAIT/ SPOT SPRAY APPLICATIONS
Protein bait containing hydrolysed protein or autolysate yeast and a small amount of toxicant chemical (e.g.malathion) attract both male and female fruit flies. The bait is applied in the form of a very coarse "squirt" with maximum droplet size and virtually no drift. The bait spray method is more economical and environmentally friendly than full cover (blanket) foliar pesticides sprays for the following reasons:
v reduced amounts of chemical are applied
v the chemical does not contaminate the whole plant or its fruits
v residue problem is negligible
v the development of pest resistance or resurgence is reduced
v there is limited adverse effects on non-target organisms
v very simple and inexpensive equipment is used
v only a small proportion of host plants need to be treated
v the application cost and time can be significantly reduced
A very promising new control will be improved bait using very low levels of insecticide in a gel formulation so it doesn't wash off in rain.
2.4.5 PESTICIDES
Farmers value pesticides for a variety of reasons, including the ease of application, rapidity of the effects and convenience for farm management. An over-use of pesticide resulting from too frequent and heavy use can only be discouraged through the greater adoption of an IPM programme. More selective use of chemicals applied within an IPM programme will lead to a more rational use of pesticide and reduce their harmful effects to beneficial organisms and toxic residue problems. Pesticides used in IPM must have the following features:
v selectivity for the target pest/disease
v safety to non-target organisms and the environment
v effectiveness at very low dosage to keep input into the environment as low as possible
v biodegradability
v compatible to other IPM techniques
Most insecticide sprays aim to cover the foliage and fruit as completely as possible so that the adults are killed through direct contact. At the same time, the larvae may be destroyed either by the chemical penetrating the fruit (systemic action) or through contact when they exit the fruit to pupate. Chemical treatments used in the past include products such as Malathion and Dimethoate for foliar sprays or Diazinon for soil drenches. Research with extremely fine mist sprays of botanical products such as neem is being made. Research is on-going with a new insecticide based on a very low toxicity phytoactive dyes ("Sure dye") used in splash baits.
2.4.6 STERILE INSECT TECHNIQUE (SIT)
Large quantities of sterile flies (irradiated or sterilised by a chemosterilant) are released in infested areas to ensure that wild females are mating with sterile males irradiated in laboratories. This is often used for area-wide suppression or eradication programmes.
2.4.7 LEGAL, QUARANTINE AND POST- HARVEST MEASURES
Many countries have established quarantine systems against the Medfly and will not permit importation of products from infested areas. The risk of introduction of quarantine pests/diseases depend upon the commodity involved, its origin, the tolerance of the organism to transportation conditions and conditions at the destination area favouring the establishment and proliferation of the new pest. Harvested fruit may undergo irradiation, fumigation, heat and cold treatments to destroy any egg or larvae. Refrigeration of fruits for several days is often sufficient to kill Medflies inside fruits.
SUMMARY SHOWING IPM STRATEGY FOR CERATITIS CAPITATA
3. CONCLUSION
As stated in the introduction, Integrated Pest Management makes use of a holistic approach encompassing a combination of strategies. For the above system to work there is a need for a precise understanding by stakeholders of the economical and ecological conditions. Moreover, an area-wide approach is necessary to achieve maximum impact. This means that for an effective Medfly IPM strategy, there must be cooperation and coordination of everyone involved in production of fruits and vegetables and the legal and administrative measures enforced by the government. The IPM system may not totally eradicate the Medfly or eliminate the pest problem, but the pest population can effectively and efficiently be reduced to a point at which it is no longer perceived as a problem.
References
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§ GTZ (1994). Integrated Pest Management: Guidelines. Typo-Druck, Rossdorf
§ Horsefall, M.(1996) Organic Fruit fly control. On the Net at: http://www.netspeed.com.au/cogs/cogint13.htm
§ Jutsun, A.& Gordon, R. (Eds.). (1989). Insect Pheromones in Plant Protection. Wiley & sons, Surrey
§ Kumar, R. (1984). Insect Pest Control. E. Arnold Publishers, London
§ Ohio State University (1992). Integrated Pest Management. On the Net at: http://ohioline.osu.edu/icm-fact/fc-01.html
§ Pacific Community Secretariat(2001). Cultural control of fruit flies in Pacific island countries and territories (PICTs). On the Net at http://www.pacifly.org/Control/Cultural-control.htm
§ Reuveni, R. (Ed.) (1995). Novel approach to Integrated Pest Management. Lewis Publishers, London
§ Smith, E. Fruit fly control by protein bait application.(1998) No.766-147 Agnote, Australia. On the Net at: http://www.nt.gov.au/dpif/pubcat/agnotes/766.htm
§ University of California. (2001). A research summary of Mediterranean Fruit Fly. On the Net at: http://ucce.ucdavis.edu/counties/ceve...of_Mediterranean_Fruit_Fly.htm?$=754
§ Van Emden, H. & Peakall, D. (1996). Beyond Silent Spring: Integrated pest management and chemical safety. First Edtion. Chapman & Hall, London
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