Some of the hives which swarmed the first spring began to have only drone brood in late summer, and perished. We attribute this to poor weather in June while the queens were mating.
Many of you have been interested in the results of our experiment using middle entrances in our beehives to combat Varroa mites. We have concluded our field work, and would like to share a brief summary of our results. We expect to provide a more detailed report, which may be posted on the NJBA website later.
We designed a middle entrance board which could be placed between any two hive bodies, expecting that the bees would use it instead of the bottom entrance. Since mites fall off of bees and land on the bottom board, they may be catching rides back to the brood nest on the field bees returning to the hive. By using the middle entrance the varroa load could be reduced. We placed the middle entrance above the brood nest, and below the honey supers.
We set up four types of hives, with and without middle entrances, and using screen bottoms or solid bottoms. We made up nucs for five groups of these four types in July 2008, for a total of 20 hives. Every two weeks we weighed each hive and counted a 24hr natural mite drop rate. We used no other mite controls, and tried to limit our interference with the hives. We fed syrup to the hives the first summer, ant the second fall, and used pollen patties in late winter. For more details refer to June/July 08 New Jersey Beekeepers Association Newsletter
These are the conclusions we reached, in somewhat sequential order. Perhaps you have come to some of the same conclusions in your experiences, but repeating them may be good for all of us.
1: Always put hives in the sunniest location. One group of hives was in a shady location. They grew slower, and did not survive the first winter.
2: Varroa mite drop from November to February is negligible. It may be better to keep the hive warmer with a solid bottom during the winter, so the hive can build earlier. Several hives perished during the unusual cold snaps in March 2009.
3: Solid bottom hives strengthened earlier in the spring. Screen bottoms and middle entrances seemed to slow the colony buildup.
4: Apparent honey flow can vary by a month depending on colony strength.
5: Natural fall varroa mite counts can fluctuate. For a reliable measurement repeat several times.
6: Some hives seem to combat mites during the spring.
7: During, or shortly after the honey flow mite loads can jump from around 30 to over 300.
8: The mite jump was not observed in screen bottom hives. Middle entrances seemed to reduce mite loads slightly, but the experiment was inconclusive.
9: Middle entrance hives extended the honey flow, and produced more honey, but not as quickly.
10: Middle entrances are a slight annoyance when working with the hives, as returning field bees hover where the entrance should be.
11: Using a queen excluder below the middle entrance hinders swarming, as the queen cannot exit unless the bottom entrance is not plugged.
12: Some of the hives which swarmed the first spring began to have only drone brood in late summer, and perished. We attribute this to poor weather in June while the queens were mating.
13: Colonies with heavy mite loads into the fall flew away. There was no brood left in the hive, but that may be due to the seasonal cessation of brood rearing. Perhaps this is similar to CCD, but stores were robbed by other bees.
14: Winter weight loss was about 40 lbs. One hive which had more stores used about 50 lbs. 60 lbs should be sufficient for wintering. No hives perished from lack of honey, but some had no surplus pollen remaining. This could hinder spring buildup. Check for pollen in the fall.
15: During August and September the hives were consuming their stores. Summer feeding could help keep the colonies vigorous.
16: None survived past the second fall. Additional methods are needed to combat varroa and the stress it inflicts.
We hope these pointers may help in your bee yards. Thanks to Tim Schuler and his continued advice.
Dave and Tim Stewart.
Any opinions, findings, conclusions, or recommendations expressed in this article are those of the author, and do not necessarily reflect the view of the U.S. Department of Agriculture.