Document Type

Article

Journal/Book Title/Conference

Acta Phytopathologica

Volume

3

Issue

1

Publication Date

1-1-1968

First Page

59

Last Page

71

Abstract

On the basis of their flight period, wild bees might be divided into three main groups: species with short, medium, and long flight period. Among the species with a short flight period, spring, early summer, and high summer animals are known. The long flying group contains bivoltine, solitary, and continuously developing social insects. The main participants in the pollination-of lucerne are the short flying summer species, as well as some medium and long flying taxa. The short flying pollinators of lucerne build their nests in the lucerne fields but since they fly from the end of June to the end of August, the application of insecticides administrated up to the middle of June and later than the middle of August does not affect them. The other species do not nest in lucerne and visit the fields only for food, i.e., in the period of blossoming. Assuming weedless fields, these species are not poisoned by treatments applied prior and subsequent to flowering time. However, the period lasting from the middle of June to the middle of August is dangerous for all pollinating insects. According to our investigations Melipax and Thiodan applied in this period are toxic to the wild bee species in the field. Treatments before and after the dangerous period defined above are also advisable to be made by spraying or wet dusting, because a certain rate of poisoning of the nesting sites and of food providing areas is unavoidable when done by simple dusting. Weed control decreases the feeding possibilities of the wild bees, causing on the one hand a diminishing of their numbers and, on the other, a decrease of their off springs owing to the shortening of the flight period. This situation is especially striking in cultivated areas, therefore also in the vicinity of the lucerne fields. Feeding conditions must therefore be assured by artificial means in these areas.

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