Treatment: outside West Virginia University Greenhouse, 10 April 2009, hive with 8 frames of brood: 5:15 pm, T = 70 F (21 C), sunny; rain was forecast. The students applied 70 ml of 50% formic acid on a Gusmer pad. The pad was placed on 6 gummy candies; on a separate paper towel - 15 ml of HBH; closed the entrance with duct tape, 1.5 by ¾ hole cut in center. After the treatment, the Gusmer pad was wet and heavy and smelled of formic; not dry. Weighed the pad on Saturday, 11 April 09: 63.75 g. Wt of dry pad: 38.54 grams. Difference = 25.21 grams. Divided by 1.110 = 22.71 ml of 50% FA still in the pad. So, 70 ml was too much for this hive. We should have used 50-55 ml or so.
Duct tape was used to close the entrance; they were concerned that expected rain would mess up a paper entrance. Dead bees plugging the entrance may have reduced the effect of fanning.
Dead bees in the field from video; copied from pause of the video player.
Jeff Seese, helping count dead bees from bottom of hive. We took about ½ of the dead bees and counted in 10 s: 632 dead bees.
Estimated 1230 dead adults on this freezer paper taken from the bottom board, plus another 200 dead bees on the ground. Total dead adult bees: 1456. Unacceptable! There were several hundred dead larvae, about 26 dead drones; an excessive kill of
We assayed 106 capped drone cells on Saturday, 11 Apr 09. We found 9 capped drone cells with varroa mites; 9/106 = 8.5% infestation. Total number of mites in cells: 14, all dead. Found 39 mites on paper on bottom board of hive: all were dead. Total of 53 dead mites found, none were alive. 100% control, but lost too many bees. In spring, bees are less resistant to formic acid, or they are more susceptible. Also, they apparently do not fan as well. Probably, there are large numbers of very young bees, and these do not resist FA as well and do not fan. Or, the physiologically different winter bees, early spring bees, are less resistant and do not fan or elevate temperatures, like the summer and fall bees, who are physiologically adapted for curing honey. The summer and fall hives have many more older adults for foraging, fanning.
We checked a drone for semen color. Still too young.
Our treatments of 10 hives in Ft. Pierce, FL, on 16 April, 2007, did not have such drastic results. We had excellent control and few losses; the Florida bees were gathering a crop of citrus honey, and they were physiologically more developed than April bees in West Virginia and Maryland. In 2007, Florida had excellent conditions for buildup in January, February and March, so they were probably at least two months ahead of honey bee hives in April in West Virginia and Maryland. Perhaps, bees in Italy in 2009 were not as well developed as the bees that we treated in Florida. [Beekeepers in Italy, Apr 09, used 85ml of 50% FA on a different pad, in Dadant hives (larger and deeper than our hives); they had enormous losses of adult bees and larvae, and despite using Honey B Healthy, they lost the queen on some of them. One of their hives, using a Gusmer pad had more typical results.] We recommend that spring bees (or developing colonies) be built up with syrup, HBH, Protein, Megabee, etc., and wait until May to be sure the colonies can handle the FA. In Spring, use less FA: 50 or 60 ml per deep chamber.
Dr. Amrine, 12 Apr 09, Easter I just thought I would let you know that I checked my hive today and it is doing quite well. I treated them with formic acid the same day as Jeff, my brother (5 April 2009). I think Jeff told you in class that he treated his hive with formic acid, and you were wondering if the weather was the cause of the loss he experienced. I think it has more to do with the strength of his hive because he only had one frame of brood. His queen was new... he thinks he crushed his last one when he was looking at her earlier in the year. When he inspected his hive after the formic acid treatment the queen was gone and some queen cells were started. He thought I had told him the wrong procedure, but my bees are thriving... so I didn't have the same problem. I had one deep box with at least 5 frames of brood and one deep box of drawn comb and less than one frame honey. I treated with 60 ml of 50% formic acid as you instructed, with the candies, pad, and freezer paper on top the brood box, and then placed the deep box with comb and honey on top of the freezer paper. I couldn't remember if you said to put freezer paper on top the super as well, so I did and it seemed to not be detrimental. Susie Spiker (she has the red collar in above photos)