Honey bee brood ring-test in 2002: method for the assessment of side effects of plant protection products on the honey bee brood under semi-field conditions

Benth.) were used for the different treatments. The crop was sprayed in both treatments on the same day during bee-flight activity of the bees. The effect of the reference substance Insegar 25 WG was examined on small bee colonies (“Mini-Plus-Beuten”) placed in the tents before the application. The bee colonies were exposed to the treated crop for 7 days. Special attention was turned on the assessments of the condition of the colonies and the development of the bee brood during the trials. The assessments were carried out at least once before the application and four times after the application on fixed dates. The time schedule of the assessment dates was chosen in order to check the bee brood at different expected stages during the development. For the evaluation of the condition of the colonies the strength of the colony, presence of a healthy queen, areas with the pollen and nectar on combs and areas containing eggs, larvae and pupae on combs were assessed. The development of the bee brood was evaluated by using transparent acetate sheets to mark single cells on brood combs with its content on different assessment dates during each trial. Additionally the flight intensity in the tunnels and the mortality was checked before as well after the treatment. In all trials of the reference treatment an increased number of dead pupae was noticed in the dead bee traps with malformations as typical for the active substance fenoxycarb (Insegar 25WG). The pupae mortality occurred approximately 14 days after application and was on a different level in the trials. For special interests on the honey bee brood development the detailed assessments with transparent acetate sheets were evaluated by calculation of brood termination-rates in % and brood indices. The termination rate of brood ranged from 94% to 100% in the reference treatment of the trials, which confirms the sensitivity of the test method. In the control treatment a wide range in the termination-rate was noticed in the trials (8% to 43%). The increased brood termination in the control treatment in single trials could be explained by weather conditions in Germany in 2002. It was rainier than in the previous years and therefore the food supply for the bee brood during the exposure in tents was reduced. It should be discussed, above which level of control mortality the test should be repeated.