Colony losses continue to plague beekeepers
by Dr. Dewey M. Caron — University of Delaware
I have been asking Newsy Bee readers about their colony losses and what they are doing to adopt IPM management for Varroa mite control for the past nine seasons. The percent return has varied from 12-percent to nearly 50-percent of active beekeepers. I summarized the first eight years in the March/April 09 Newsy Bee. Although returns were not robust this spring (only 32 beekeepers responded, owning slightly over 200 colonies from over 80 requests), I herby report the most recent results.
The loss rate this past over-winter period was 23.5-percent (48 of 203 colonies died over-winter). Thirteen beekeepers (40-percent) had no losses. An additional 4-percent of colonies (nine total) died during the season. Loss rate from a survey of 20-percent of colony owners nationwide was 28.5-percent. Nationally about one quarter of the losses exhibited CCD symptoms but no CCD symptoms were reported for any of the Delaware or Maryland losses.
Of respondents, 50-percent had one to five years experience, while 20-percent indicated 10 or more years of beekeeping experience — median was four years of experience which was also the mode (most common response). The number of bee colonies managed by these 32 individuals varied from one to over 40; 90-percent of respondents were managing less than 10 colonies with middle number and mode (most common number) was four colonies. Beekeepers with less than three years experience lost about the same percentage as those with more and beekeepers with four or fewer colonies had a rate of loss similar to those with a greater number of colonies.
Comparing this loss rate with previous seasons would suggest the widely fluctuating losses of the beginning of the century have stabilized to between the 20-25 percentage range. Other surveys similarly peg postmite (but non-CCD) losses in the same 20-25-percent range.
The survey has included questions regarding IPM practices. When asked if they practice IPM, 55-percent of beekeepers indicated that they did. The number of beekeepers monitoring mite levels (33-percent) was considerably lower than past responses. More than half the percentage of beekeepers use screen bottom boards (55-percent), but drone removal or use of resistant queens remains less than 25-percent. Use of essential oils (25-percent of beekeepers are using) exceeds use of Apistan (18-percent) but powdered sugar (10-percent) , formic/oxalic acid (10-percent) or other chemical treatments are utilized by 10-percent or fewer beekeepers.
Thirty seven-percent of beekeepers used Fumigillin (for Nosema) this past season with about the same number using grease patties. None reported use of coumaphos for mite control. Although the survey does not represent the response level hoped for, it is encouraging that the trend toward reduced chemical dependence, as reported in the earlier Newsy Bee, is continuing.