Polinização do meloeiro (Cucumis melo L.) por abelhas melíferas (Apis mellifera L.): requerimentos da cultura e manejo das colônias

Abstract

This work was carried out from July to December, 2001 at the irrigation project of Baixo Acaraú in the county of Acaraú, state of Ceará, Brazil. The experiments were installed in commercial areas cultivated with yellow melon (Cucumis melo L.) AF-646. Colonies of honcybces (Apis mellifera L.) were introduceds to the orchards aiming to study the use of honeybees to pollinate melon. The investigation was split in four phases: first, floral biology and pollination requirements of melon plants were studied; second, honeybee foraging behaviour for pollen and nectar at melon flowers was assessed; third, honeybee colony introduction was tested considering number of colonies, its distribution at the orchard and period of the melon cyclc for colony introduction; fourth, managcmcnt of colonies to enhance pollen col1ection was investigated by feeding sugar solution and using pollen traps. Data collect were analysed by ANOVA and means compared a posteriori by Tukey test or, depending on the data, by Mann-Whitney or Kruskall-Wallis non-parametric tests. First hermaphrodite flowers appeared on the 23rd day of melon cycle at the plants stern showing high rate of fruit set, and later at branches with lower fruit set rate. Only flowers which received biotic pollination set fruits, while flowers prevented from their visits failed to set fruits. Greater bee activity at melon flowers occurred early in the mornings (05:00 - 07:00 h), mainly for pollen collection. Total fruit production increased with the number of colonies used in the area up to four hives/ha. There were no significant differences on the number of bees foraging melon flowers and total fruit production when colonies were placed the orchard's central row ar at side rows 30 m out of the cultivated area. The period of melon cycle in which colony introduction produced the highest fruit production was at the 23rd day. However, the greater arnount of fruits reaching export standards was produced when colonies were introduced to the orchards at the 33rd day. The greater number of bees collecting pollen on melon flowers was achieved when colonies were red regularly with sugar syrup. Considering the use of honeybees to pollinate melon plants cultivated at open fields and during the dry season in NE Brazil, it is possible to conclude that: the melon plant can produce fruits from the 23rd day of its cycle, it depends on biotic pollinators and the first hermaphrodite flowers set and mature higher proportion of fruits than later ones. Iloneybees visit melon flowers mainly early in - the morning for pollen collection. Time spent per visit for pollen collection is greater than for nectar collection, and a bee needs to visit dozen of flowers to complete a pollen load. Four strong honeybee colonies per hectare are enough to obtain adequate levels of pollination and fruit production. Colonies can be arranged in a side row up to 30 m out of the melon orchard shaded by native vegetation. Colony introduction can take place at the 23rd day of melon cycle, when producing large frnits are not a lirniting factor, and at the 33rd day when fruits have to be of srnall size. Pollen collection should be stimulated feeding honeybee colonies with 500 ml of 2: 1 sugar syrup every other day.