ENVIRONMENTAL PROBLEM TARGETED:
The protection from the pest of Med flies in the absence of Insecticides.
Agriculture has a major economic importance in most of the Mediterranean countries and goes hand in hand with a large food-processing industry both up- and downstream. It represents over 15% of the GDP in numerous southern and eastern Mediterranean countries). It thus constitutes an important source of employment, especially in regions where it still remains today the major activity. Conservation of the Mediterranean agricultural potential therefore constitutes a challenge for maintaining the social and economic structure of societies.
The Mediterranean fruit fly "med fly" is considered one of the world's most destructive pests while it has one of the widest host ranges of any pest fruit fly, and is considered the most important agricultural pest in the world. It is rapid colonizer and unlike most species of fruit flies, it can tolerate cooler climates. These traits along with its' broad host range make the med fly to be a worldwide key economic factor in fruit production.
The damage caused by larval feeding makes fruit unfit for human consumption. In addition, the presence of an established population would cause a severe economic impact via restrictions/prohibitions on the export of fresh fruit both domestically and internationally.
The med fly attacks more than 260 different fruits, flowers, vegetables and nuts. Thin-skinned, ripe succulent fruits are preferred. It can be especially damaging to citrus, stone fruits, pome fruits, peppers, tomatoes and figs. Although several species of cucurbits including watermelon and musk melons have been recorded as hosts of the med fly, they are considered to be poor hosts. However, host preferences vary in different regions and what may be considered a good or poor host in one region may be differ in another. Feeding by fruit fly larvae (maggots) damages the fruit internally, causing it to ripen prematurely and rot. Up to 100% of fruit may be damaged by fruit fly when infestations are uncontrolled. Med fly is most active from July to November in Greece and in some places all over the year depending on the seasonal host present like for example in the inland of Crete where a lot fruits can be cultivated due to its semitropical climate. Some activity will continue in warmer periods during the winter months while overwinters as adult flies in sheltered locations. Med fly also overwinters as eggs or larvae in fruit, or pupae in the soil. Adults become active again in spring and begin laying eggs in mature fruit. The adults can live for a few months and lay hundreds of eggs, several at a time, a few millimetres into the fruit. A med fly may lay up to 300 eggs during her life. Eggs hatch in a few days and the larvae eat through the fruit, growing to about 9mm long when mature. Depending on temperature, this takes two to six weeks. Infested fruit often ripen prematurely and drop to the ground. Mature larvae leave the fruit, dropping to the ground and burrowing into the top few centimetres of soil to pupate.
Pupation depth is an important factor for growers who are considering cultivation or livestock as part of their fruit fly management strategy. Results from a range of trials indicate that pupation depth varies with soil texture and moisture content. In moist or dry sand, med fly pupated within 3cm of the surface. In soil, several other species were observed to burrow to a maximum depth of 7.5cm. When med fly pupae were buried in compacted soil or moist loose soil, no adults emerged from deeper than 7.5cm, while in dry loose soil, some med fly adults emerged successfully from as deep as 32cm.
The med flies insects belonging in the Tephritidae family, which infest cultivations of fruit trees of large economical importance, cause large damages on fruits and have a large economical effect on the agricultural production. To accomplish control of this pest in conventional agriculture, insecticides and relevant plant-protection products are used, which however have serious disadvantages, such as development of insect resistance against these agents, harmful effects on the environment by means of decreasing the biological diversity by creating imbalances in the soil, and therefore can make a plant more attractive to insects' pest.
Five kinds of treatment are used alone or in combination to eradicate the med fly.
a. Cover Bait Spray Application -The spray contains minimal amounts of an insecticide and protein/sugar bait attracts the flies.
b. Sterile Insect Technique (SIT) - In the SIT, Med flies are reared in large quantities, sterilized with small amount of irradiation, and released into areas where they mate with wild med flies. Such mattings do not produce offspring. Eventually the wild population is eliminated through attrition. SIT is most effective against low-level med fly populations where a high proportion of sterile to wild flies can be achieved to ensure success. Initial applications of insecticide bait spray and male annihilation are sometimes necessary to bring local populations down to low densities.
c. Insecticide Application to soil under Host Trees - These products will kill some larvae as they enter the soil to pupate and most of the adults as they later emerge. The preferred and most popular eradication strategy is an integrated approach combining all three treatments, with emphasis on the use of SIT.
d. Biological Control - Newly emerged flies need up to 24 hours for their wings to harden before they can fly, so are prone to predation on the soil surface by birds, ants, bugs and earwigs. One of the most used biological control is to cultivate parasitic wasps and released them in the orchards in order to reduce the med fly insects.
e. Mass trapping Control - The mass trapping technique is used for the implication of the control of the med fly for the minimizing the use of insecticides or the complete absence of the insecticides. From the above methods, the most widely used is the Cover Spray Application (a).
Various methods previously developed for the control and elimination of insect enemies of various fruit trees are based on chemical attractants, various hydrolysed proteins, fruit juices, ammonium salts and animal feces [In suspended traps, the proteinaceous baits when decomposed under various conditions release various chemical substances, e.g. acetic acid ammonia and others.
Apart from the protein hydrolysis products, nitrogen fertilizers can also be effectively used for attracting insects of the Tephritidae family, by ammonia release.
Frequently all these above have a negative effect on ecosystems, since they affect a large number of beneficial insects along with the harmful one, disturbing thus the balance of the ecosystem.
In the case of Mediterranean fruit fly, the mass-trapping method with specific attractants (sex attractants) has been used, e.g. the synthetic chemical substances of the TRIMEDLURE type [(1.1 dimethyl-4 (and 5)-chloro-2-methyl-cyclo-hexane-l-carboxylate), which selectively attract the males of the Mediterranean fruit fly. Further, the combination of three chemical substances [4-amino-butane, trimethylamine and ammonium acetate, named Biolure, working as food attractant attracts more females of the Mediterranean fruit fly than the respective males.
Therefore, for a sustainable agriculture there is a great need of an effective food for attracting ONLY female med fly insects. Such a product should be based on low-cost and widely available materials,should have high selectivity
Since the targets are the females, Biolure seems to be the answer of tackling the major problem of med fly infestation in the fruit orchards, nevertheless the attraction of beneficial insects and the relative high cost together with the need of careful handle of this product due to its relative toxicity, remain significant problems.
Therefore, for a sustainable agriculture there is a great need of an effective food for attracting ONLY female med fly insects. Such a product should be based on low-cost and widely available materials, should have high selectivity (with no attraction of beneficial insects), high attractiveness, low production cost and large attractive-action period (e.g. more than three months), preventing thereby the regular replenishment of the mixtures [attractant and insecticide]. Moreover, the product should be harmless to humans and to the environment.
Such a product, named Biodelear, has been developed and patented by the coordinator of this project (see details in the following state-of-the-art section) and since the success of Integrated Pest Management (IPM) programs is usually measured by the overall reduction in the volume of pesticides used to control prevalent pests, Biodelear is the most appropriate product because it offers zero use of pesticides and no adverse effect to the ecosystem.
Thus, the project through its actions will demonstrate the use of this innovative attractant throughout the Med region and will provide farmers, stakeholders and policy makers an Integrated Med Strategy to address med fly by an environment friendly, effective and low cost way.
