ABSTRACT
Table grapes are one of the most important fruits produced and exported by Chile. During the season 1997-1998 more than 490,000 metric tons of this fruit were produced, The last season’s exportation of grapes meant an approximate income of US$ 604 millions. The false grape mite, Brevipalpus chilensis, is a species occasionally found on table grapes, lemons and kiwis. Since B. chilensis is considered a quarantine pest for the Chilean table grapes’ main market (USA), and on the other hand, since the size of this acaride mite (less than 1 mm), the fumigation of this product before the exportation is mandatory. Methyl bromide is the quarantine treatment most used in Chile for this purpose, but it will be phased out during next decade under the term of Montreal Protocol because it has potential side effects on the atmospheric ozone layer. Due to the reason mentioned before it is urgently needed to find a suitable alternative to the use of methyl bromide as a fumigant for Chilean table grapes.
Since some years ago, several potential alternatives are being studied in Chile. At the beginning of 80’s, the Chilean private sector, in collaboration with government institutions such as Comision Chilena de Energia Nuclear, started the studies on the use of ionizing radiation as a quarantine treatment. Sixteen different fresh fruit species, including 3 varieties of grapes were studied, using low doses of ionizing radiation, in order to know a possible effect of the treatment on the commercial quality of these agricultural products. As a result of these studies it was demonstrated that an average dose of 1 kGy do not affect the commercial quality of tables grapes and most of the other fresh fruits.
At the mean time, several studies have also been done from the 80’s up to now, in order to know the effect of ionizing radiation on different stages of development of the acaride mite just mentioned. In the last one of these studies, doses of 0.5, 1.0 and 1.5 kGy were used, combined with 24 hours precold storage before irradiation and an additional period of 15 days of storage at 0-2° C and 90% RH (to simulate shipping conditions from Chile to USA). The doses mentioned were applied on eggs, immature stages and adults of B. chilensis, maintained on Ligustrum japonicurn L. leaves. It was demonstrated that the irradiated acaride mites were unable to continue their cycle and they would not represent a risk to countries importing these products from Chile.
The establishment of commercial irradiation plants have also been analyzed for operation in the three most important Chilean ports from where table grapes are exported. The irradiation process proved economically feasible as well. At present, the possibility of building small irradiation facilities next to fruit packing is also being considered. The Chilean private sectors and governmental institutions are continuously working together in order to find soon an alternative to the methyl bromide treatment and where ionizing radiation is being seriously analyzed 193In summary, low doses of irradiation seem to be a good quarantine treatment for Chilean table grapes from the technological and economical point of view. However, the possibility to apply this technology at commercial scale in the near future will depend not only the national but also the international efforts such as the establishment of an accepted international protocol for the research studies, approval of the technology by government of the importing countries, consumer acceptance and the feasibility of the other alternative treatments.
