Osmia cornuta management in pear orchards

Abstract

Osmia cornuta (Latreille) (Hymenoptera Megachilidae) is a well-known pollinator of pear and several rosaceous plants. If the pollinator cocoons are released in the orchard at the start of pear flowering and the nests are retrieved at petal fall, both its pollinating and reproductive potential are limited. The two-years' study (2004-05) carried out in north-eastern Italy aimed to optimise O. cornuta pollinating potential and to enhance its field reproduction. Two aspects have been considered: 1) the use of ecological infrastructures (hedge of Prunus spinosa L. and strips of Brassica sp.) as complementary food sources in order to anticipate the release of pollinator cocoons in the pear orchard; this technique could allow the female to initiate the nesting/foraging activity before the pear bloom starting; 2) the comparisons among various safety measures to be adopted in order to reduce the impact of noxious treatments; this technique could allow females to extend their activity after pear bloom end. Data showed that both the ecological infrastructures can be functional to anticipate the female activity before pear blooming. The complementary food sources sustained the females and allowed them to increase the number of pedotrophic cells with respect to previous studies concerning females released at the beginning of pear blooming. The most effective safety procedure was: (i) close the nesting boxes after sunset, (ii) store them at cool temperature during the night, (iii) perform the spray treatment in the evening and (iv) relocate the boxes at the same place and orientation.