DYNAMICS OF DOMINANT BEES - POLLINATORS AND INFLUENCE OF TEMPERATURE, RELATIVE HUMIDITY AND TIME OF DAY ON THEIR ABUNDANCE IN FORAGE CROPS IN PLEVEN REGION, BULGARIA

The knowledge of bee preferences to different flowering forage crops (birdsfoot trefoil, alfalfa, sainfoin, and a mixture phacelia, alfalfa, sainfoin, red clover and cocksfoot) and the influence of temperature, relative humidity and time of day on their abundance in forage crops in Pleven region, Bulgaria have important environmental implications and allow predicting of effects of abiotic factors on the abundance of pollinators. The pollinator density and species composition were recorded by "sweeping" with an entomological net from the beginning of flowering to the flowering end. The number of bees that visited the flowers of forage crops was counted by visual observation starting from 8:30 AM to 9:30 AM and from 12:00 to 14:00 PM. Dominant species of wild bees in sainfoin, alfalfa, and mixed crops were halictid bees, Halictus quadricinctus Fabricius, 1776 (Hymenoptera, Apidae), square-headed furrow-bee, H. maculatus Smith, 1848 (Hymenoptera, Halictidae), long-horned bee, Eucera longicornis Linnaeus, 1758 (Hymenoptera, Apidae), thick-margined mini-mining bee, Andrena falsifica Perkins, 1915 (Hymenoptera, Apidae) and short-fringed mining-bee, A. dorsata Kirby, 1802 (Hymenoptera, Apidae). Species reached a maximum number in a full flowering stage as with the passing of flowering their number considerably reduced. The observation time of 08:30 - 09:30 AM had higher abundance of bees in compared with 12:00 - 14:00 PM. Temperature and relative humidity had a significant influence on the bee number as the temperatures had a negative influence while relative humidity was positively correlated with the bee density. There is a need to harmonize agricultural practices like pest control operations with pollination and bee activity in such a way that it saves bees and other insect pollinators. Such operations should be applied at times when bees’ activities are very much reduced.