IMPROVEMENT OF FIELD MANAGEMENT OF OSMIA-CORNUTA (LATREILLE) (HYMENOPTERA, MEGACHILIDAE) TO POLLINATE ALMOND

Trap-nested populations of Osmia cornuta were reared in the laboratory at room temperature, over-wintered at 4-degrees-C, and released in almond orchards in NE Spain in 1989 and 1990. Bees emerged over a longer period and over-wintering mortality was higher in 1990 than in 1989. These results are associated with the over-wintering period to which bees were exposed, which was longer in 1989 than in 1990. Females preferred to nest in small nesting shelters rather than in large ones, and significantly selected holes with 8 mm id and 21 cm long as nesting cavities. Dispersal rates of pre-nesting females were higher in 1989 than in 1990, but in both years the bee population obtained at the end of the bloom period notably increased with regard to population released.