Integrated system approach for managing fruit files

Fruit flies need to be controlled
Fruit flies are serious pests of agriculture throughout the world and represent a threat to the successful establishment of horticulture industries and trade. The existence of fruit fly also ensures that crops that do reach the market are not eligible for export due to quarantine regulations. Countries like California, Japan, and others refuse fruit from exporting countries unless it is grown in fly-free zones. The scale of the problem is vast. Fruit flies in the pacific and South East Asia cause production losses of from 40-100%. Two third of the South East Asia population are small farmers, important in horticultural industries to meet domestic consumption

An integrated system approach for managing fruit flies
Strategies for the control of fruit flies should have the following characteristic: sustainable, suppression and environmental friendly. Most control strategies use a combination of available approaches, integrated into an Integrated Pest Management (IPM) package to manage and suppress the population of fruit flies. These management approaches may include; physical control, cultural control, biological control, the sterile insect technique (SIT), male annihilation technique (MAT), protein bait technology and insecticides cover spray as there is no single, “one-answer” solution to the fruit fly problem.

However, in the absence of government efforts to control exotic fruit fly pests, losses and damage to private and commercial crops would provoke independent control efforts. Lacking the resources or capability to use sophisticated program techniques, such as surveillance and trapping, sterile insect technique and male annihilation technique, the growers or farmers could be expected to use low technology, relying predominantly on cover sprays of insecticides, and cultural control methods. The control achieved is only for the individual grower or farmer farms where the owner makes its own decision on whether or not to implement the control measures, when to implement and how to implement, resulting in variability in the efficacy of fruit flies controlled in the area. It has little effect on the breeding population of flies inhabiting the general area, the states or the country. For a long term sustainable approach to fruit fly management, the area wide control programme should be implemented. The area wide control programme focuses on reducing the fruit flies population within a large target area to a non-economic level. It will involves many farms/producers but conducted by a special operational organization and involves a well define  long term approach and plan. The bulk of the cost of control will be to control the pests away from the  production area before the crops are susceptible –on wild alternate hosts or abandoned orchards, untreated host plants in home owners gardens etc.

SUMMARY ON AVAILABLE CONTROL METHODS

Physical control
The principle of physical control involves providing a barrier between the host fruits and the egg-laying female fruit fly. One method is to build screen -houses, which can produce fruit fly–free crops. The most common method is to bag or wrap fruit before the fruits reach a stage of maturity at which they are susceptible to infestation. Bags made from double layers of newspaper, brown paper, plastic are normally used. This method works well but is labour intensive.

In Malaysia, for example, carambola has been cultivated for over 70 years using this technique. In 1989, 17 000 tonnes of carambola worth 20 million Ringgit (US$8 million) were produced and exported to Europe, Hong Kong and Singapore using the bagging technique (Dept. of Statistics 1989).

Generally, this technique is applicable where relatively small areas of production are involved (e.g. village or subsistence production); where the cost of labour is cheap; where high quality, high value, unblemished produce is necessary; and where no alternative practical methods of control are available.

Cultural control
Cultural control includes practices that may be regarded as part of the normal production system and do not include the application of insecticides.

• Growing less susceptible varieties or resistant varieties
  Some tropical fruits such as mangosteen, rambutan and duku/langsat are not normally attacked by fruit flies. Occasional damage may be observed when the fruit are over-ripe and/or cracked or damaged on the tree and such fruits support complete larval development. No control measures for fruit flies are required in the production of these fruits, although they are frequently found growing in areas with high endemic populations of fruit flies Other crops that may be non-hosts or at least low risk are squash (pumpkin), zucchini, cucumber, some varieties of watermelon, rock melon, limes and paw paw

• Crop hygiene/field sanitation
  The collection and destruction of fallen, damaged, over-ripe and excess ripe fruits to reduce the resident population of fruit flies. In tropical climates, uncontrolled breeding of fruit flies in poorly managed or abandoned orchards and in a variety of wild hosts results in high populations of adult flies. Crop sanitation/sanitation by itself will not be effective in many situations, because fruit flies can fly in from outside areas

• Early harvesting
  Avoidance of fruit fly infestation is possible by harvesting crops early. Fruit flies do not appear to ‘attack' certain fruits such as papaya, sapodilla and banana when they are 100% green. Paw paws, harvested at colour break, are less likely to be infested by fruit flies than if harvested at later stages of maturity. However, some fruits lose flavor when harvested too early, as they will not ripen fully

• Production during periods of relatively low fruit fly activity:

Sterile insect technique
The sterile insect technique (SIT) is a form of “birth control” method based on genetic manipulation. It involves the colonization and mass rearing of the target pest species, sterilization through the use of gamma radiation and releasing them into the field on a sustain basis and in sufficient numbers to achieve appropriate sterile to wild insects over flooding ratios. The sterile males find and mate with fertile females, transferring the genetically modified sperm. No offspring results, thereby causing a reduction in the natural pest population.

This technique has been successfully used in the Mediterranean for oriental and melon fly eradication/control programme, which involves only a single species and on a single fruit. Success on the eradication/control of fruit flies that occur as species complexes infesting a range of host crops has yet to be tested.

Male annihilation
Male annihilation involves the trapping of male fruit flies using a high density of trapping stations consisting of a male lure combined with an insecticide (usually technical malathion), to reduce the male population to such a low level that mating does not occur. The male attractant used is normally methyl eugenol. A different male attractant is used for Med fly (Trimedlure) and melon fly (Cue-lure). The effectiveness of using Cue-lure as the lure for the male annihilation of species attracted to it is not as great as that using methyl eugenol.

Insecticide cover spray
Although insecticide usage has been useful in suppressing the fruit flies population during high outbreaks. The regular use of insecticides as cover sprays for fruit flies control have led to a host of problems such as health hazard to the operators as a result of high exposure during the operation, high residues in food crops and the effect on the environment. Pollinators and other beneficial insects are severely affected by these cover sprays. Orchards that use cover sprays regularly were also observed to have persistent problems with other lepidopteran fruit borers, leaf and flower feeding caterpillars, and mites. Selected orchards that used only protein bait sprays for fruit fly control and conducted only 2–3 cover sprays or none at all in a year, were observed to be free of other pest problems.

Biological control
Despite a large amount of effort being devoted to the use of biological control agents (predators and parasitoids) to control fruit flies, there have been few instances that may be regarded as sustainable successes. Generally, predators have little effect on the populations of fruit flies in an orchard or vegetable production situation. Predators may include spiders, ants, carabid beetles, assassin bugs, staphylinid beetles, lygaeid bugs and probably others.

Protein bait as an alternative to insecticide cover spray
Protein bait used either as spot spraying or with traps provides a safer alternative to the less environmentally friendly insecticide cover spray. It reduces the use of cover sprays of insecticides and provides a solution for environmentally sustainable and sound fruit fly management in different crops. The technique is based on the fact that fruit flies are strongly attracted to bait of protein, but other insects are not. Only a minute amount of insecticide is used and mixed with the protein bait, which is applied as a spot spray to foliage of the trees at scattered points in the orchard. The fruit flies when feeding on the bait will ingest the insecticide as well and are killed. In order to ensure successful adoption of the protein bait technology by farmers and growers, it must be promoted & communicated in the most effective ways. Only then will the economic, environmental and social impact realized.

Post-harvest control of fruit flies
Various method of treatments are available and may be specified by importing countries to ensure fruit flies free horticulture produces from exporting countries. Examples are vapour heat treatment, forced hot-air treatment (which involves drier air than the vapour heat treatment), dipping in chemicals or hot water, cooling and irradiation.