A monitoring study to assess the acute mortality effects of indoxacarb on honey bees (Apis mellifera L.) in flowering apple orchards.

To evaluate the effect of the indoxacarb 300 g kg(-1) WG, Steward 30WDG, on the honey bee (Apis mellifera L.) in apple orchards, a monitoring study was conducted in Dutch apple orchards in April/May 2004. Before apple flowering began, two honey bee colonies were placed in each orchard to investigate honey bee mortality. Each hive was provided with a Münster dead bee trap to collect dead honey bees. The numbers of dead bees found in these Münster dead traps were counted every 3-4 days for about 2 weeks before and after the period of the insecticide treatment. In nine flowering orchards no indoxacarb was applied during the flowering period, which served as control sites. In 30 flowering orchards indoxacarb was sprayed by the fruit growers according to local practice at 170-260 g formulated product ha(-1) (51-78 g AI ha(-1)). In the control orchards the average mortality was 8 honey bees colony(-1) day(-1). The average daily honey bee mortality before and after indoxacarb application was 8 and 10 honey bees colony(-1) day(-1) respectively. At one test site, indoxacarb was mixed with other plant protection products plus plant nutrients, and in this orchard a slight but biologically non-significant increase in acute honey bee mortality was recorded. It was concluded that the application of indoxacarb caused no effects on honey bee mortality, and that the number of dead honey bees counted in the Münster traps in the orchard treated with indoxacarb was comparable with those determined in control orchards.