Follow the link to an interesting article on how neonictinoids affect honey bees. .
Saturday, November 7, 2020
Saturday, October 31, 2020
As part of my evaluation of my breeder queens I was also tracking the mite fall of two mixed breed hives. For the past week the two mixed breed hives have been having a daily mite fall of zero mites.
Previous readers know that my mite control plan is to treat my hives 3 times. One half dose of formic in mid-June, then a full dose of formic the last week of July and then a final fall cleanup treatment with oxalic acid vapor. On October 28th I performed the last oxalic treatment; a single treatment of 2 grams of oxalic. These hives were broodless at this time. Note: a single oxalic treatment of a hive, when broodless, should kill 95% of the mites in the hive.
In the three days following this treatment one hive has dropped 75 mites to the witness board and the second 29 mites. This shows that although the daily mite drop was low (actually zero) that there was still a large quantity of mites in the hive.
This end of season mite treatment will greatly improve the chances of these hives surviving winter.
Friday, October 23, 2020
Until recently mite resistance from grooming/chewing has received little attention in the national bee magazines. I had previously used Purdue Mite Biter stock with this trait. Last fall I became aware of the availability of feral bee stock that also exhibited this trait. I find it fascinating that wild/feral bees had naturally developed a resistance to mites. NOTE: All honeybees exhibit chewing/grooming to a limited extent. The PMB line and this feral stock show enhanced chewing/grooming.
In 2020 I purchased two breeder queens from Dorothey Morgan in Kentucky. One was of Purdue Miter Biter (PMB) stock and the other of feral stock from mountainous areas in Kentucky. Both stocks are known for “chewing” on varroa mites. Dorothey has not treated her bees for the past seven years since converting her entire apiary to PMB stock. The feral stock came from members of the Kentucky Queen Breeders Association. Testing by Dorothey and Dwight Wells had shown this feral stock met or exceeded the level of “chewing” exhibited by the PMB stock. Dwight is knowledgeable about the subject of feral bees. NOTE: In 2020 Purdue University did not produce PMB breeder queens for distribution due to the COVID19 shutdown of their campus.
Dorothey also credits some of her overwintering success to not purchasing packaged bees and thus avoiding importation of any viruses floating around the general bee population (read that as from bees that were held in the California holding yards prior to almond pollination). Also, PMB and feral bee lines do not eliminate the mites, but reduce their numbers sufficiently so that hives can overwinter without need for mite treatments. Reaching an equilibrium between the parasite and host is how the Apis Cerana (the Asian honeybee) evolved to live with the varroa mite, although not through the same mechanism.
I wanted to assess how these two breeder queen hives were doing in relation to mites. You could say I am from Missouri, the “show me” state. I wanted those two hives to show me that they had reduced mite counts. Utilizing witness boards was intended to fulfill that need. Near the end of June, I began daily inspection of the witness boards. Initially I simply counted and recorded the number of mites on each board. During the rapid growth stage of the hives, I did not want to be removing 300 bees to perform alcohol-wash mite checks. I was already opening the hives on a weekly basis to take brood for queen rearing. Too much stress on a hive can result in queen supercedure.
I also tracked mite counts in two overwintered mixed-breed hives. One hive’s mite drop was rising rapidly by the end of July (already greater than 20 mites/day), and consequently I treated both mixed breed hives with FormicPro. Due to the treatments I did not include their data here. The worst hive needed a second treatment at the end of August when the mite drop again built up to 20 per day. (As a side note I requeened the hive after the second treatment with a f1 PMB queen).
Here is the mite drop from the two breeder queen hives. I am presenting the data as 7-day moving averages to smooth the curves. The maximum daily mite drop for the feral queened hive was 10 mites and for the PMB queened hive 23 mites. The maximum drop for both hives occurred on the same day after the nighttime temperature got down to the low 30s (lowest so far this fall).
A few comments/observations.
1) It must be remembered that these were not overwintered hives which would have a longer time frame for the mite population to build.
2) Recommended sticky board mite drop limits are all over the place. I have found some recommendations that mite drops of more than 10 or 12 mites per day indicate the hive is in trouble and needs treatment. Other sources indicate daily drops of up to 40 or 60 per day in the fall are the treatment threshold. I put the 12 mites per day limit in my graph.
-BetterBee recommended a 12/day limit in August
-Brushy Mountain recommended a 60/day limit in fall
-PerfectBee recommended a 60/day limit in fall
-Virginia Cooperative Extension recommended a 40/day limit
-Ontario Ministry of Ag recommends a 12/day limit in August
3) I performed two alcohol-washes (Aug. 21st and Sept 25th) which yielded either 0 or 1 mite. These values are good for that time of year. Limits of 3% or 9 mites per 300 bees are normally deemed acceptable. These two alcohol wash checks show these chewing/grooming bees were controlling varroa mites as desired.
4) I haven’t found any literature stating how to compare alcohol-wash results versus mite drop counts.
6) This uncontrolled test was a small sample of only two hives. I would not jump to the conclusion that “feral” queens, in general, are better than “PMB” queens. It may be true, but the small size of my test prevents me from stating this is so. I can’t determine whether the feral hive or PMB hive is doing a better job of removing mites. Is the lower daily drop of the feral hive a sign of better grooming performance or is the higher spike during the cold spells a sign the PMB hive is doing a better job. I can’t wheedle the answer out of my limited data. The IMPORTANT thing is that the varroa levels of both hives are staying below both the alcohol-wash and sticky board limits.
7) My initial thought was that the two spikes in the mite drop at the end of the summer were attributable to the end of summer decline in brood rearing and cooler nighttime temperatures resulting in the bees clustering. But after looking at the nighttime temperatures it seems that nighttime temperature was the primary factor in both spikes. The first spike occurred when the temperature dipped to the high 30s (Sept 19th, 39F). The second bigger spike occurred when nighttime temperature dropped to the low 30s (Oct 2nd, 32F). Mite drop rose following each cold spell, usually several days in length, and began declining as the nighttime temperatures warmed again. The maximum height of the bump up occurred a few days after the cold night due to the damping effect of the 7-day moving average used to smooth the curve. I assume the colder temperatures are causing the bees to cluster and results in enhanced grooming/chewing. A third cold snap (Oct 19th, 25F) did not result in a mite drop spike. Why the difference?
At the end of July, I started gathering all mites from the witness boards and examining their legs for evidence of chewing. I have had no formal training in this process, but simply looked for severed legs or missing edges on their carapace (shell). I was using a low cost/low magnification digital microscope which may have hindered the accuracy of my observations. In addition, I did not think of looking for severed antenna that are located between the eight legs. About 5% of the dropped mites were alive and moving their legs, 45% were dead, and 50% had chewed legs and dead. Both the PMB and feral hive drops exhibited roughly the same 50% chewing rate. If I assume all of the dead mites were due to natural mortality (this assumption is highly questionable), then I could surmise that the “chewing behavior” had roughly doubled the mite mortality.
The onset of colder nights (~ <40F) also resulted in finding no live mites on the witness board the following morning. When nighttime temperatures warmed back up live mites again appeared on the witness board. My thought is that the live mites that are on the witness board die of exposure during the night without the warmth of the bee cluster. Are the live mites falling to the witness board simply because they lost their footing or due to grooming? I can’t answer that question. So if mites are dislodged by either “chewing” or grooming or simply losing their footing they will probably die during the winter if they drop to the floor of the hive.
Now playing with the data a little. The graph shows a daily mite drop of roughly 8 mites per day (average of the two hives). Taking away the 50% of mites showing chewing that leaves 4 mites per day which would be considered natural mite drop do to mortality. Natural mite mortality runs about 0.5%. Therefore, there is about 800 mites in each hive (4/0.005=800). Based on Randy Oliver’s mite program a hive with 800 mites in mid-October should NOT have a varroa induced crash. That makes me very hopeful about this potential solution and confirms in my limited way that these bees can survive with no treatment.
Overall, I am happy with the performance of both hives/queens and will be taking these two hives through winter untreated. Assuming they survive (and with these low mites loads they should survive), I will track mite drop through another year to see how they cope with the longer period for mite reproduction.
I would say both the PMB and feral queened hives have controlled the mite build up as advertised. My only reservation of my observations is that they were not of overwintered hives. Given the fact that Purdue’s and Dorothey’s apiaries have been untreated for years puts that issue to bed and these queens will continue to be my focus for mite control next year.
From these breeder queens I have put about 50 queens into winter nucs. Next year I will monitor a few of these f1 queens (first generation) to see if they control the mites to the same extent. I would expect them to be not as good because this year’s drone population in my apiary was not all of PMB/feral genetics and therefore there would probably be a dilution of the “chewing trait”. I expect it will take several years to improve my entire apiary to equivalent performance and for me to be able to stop mite treatments. This problem of dilution also occurs with all improved bee lines (VSH, Minnesota Hygenic, Russians, etc.). Once you make the decision to improve your apiary you need to stick with it for several years to counter the genetic dilution effect that occurs due to the honeybee queen’s mating behavior. Purchase of package bees/queens also adds to the dilution. Its everything or nothing.
Thursday, October 15, 2020
This article was found on the US National Library of Medicine website. Written by a Chinese doctor this article provides anecdotal information that Chinese beekeepers near Wuhan, China have not contracted COVID-19. The implication is that bee venom somehow provides immunity to the virus.
Sunday, October 11, 2020
Next Saturday, October 17th, will be the October ECWBA meeting. The meeting will be about winter preparation. The meeting will be at the Rushford Meadery near Omro starting at 9:30AM. Due to a spike in Covid19 masks are strongly recommended.
PS-the next 3 days appear to be the last opportunity for pre-winter feeding. After that temperatures will be too cool for syrup uptake.
Friday, October 9, 2020
Dan Ziehli, the state apiary Inspector, for our area has been replaced by Charlie Koenen. Charlie's contact information is:
Charlie Koenen 608-444-3209 Email: firstname.lastname@example.org
The following link may also be useful:
Note: It costs $50 for a visit by the state inspector.
Wednesday, October 7, 2020
Many beekeepers perform a one time varroa mite treatment using oxalic acid in addition to a late summer treatments. The idea is to perform this last of the season's (also called a cleanup treatment) treatment AFTER the queen has stopped laying and all brood has emerged. When this occurs no mites are hidden inside brood cells and are therefore exposed and susceptible to the oxalic acid vapors. Up to a 95% mite kill is possible at this time. The bees will go through winter as mite free as possible.
I had occasion to be inside several hives and nuc yesterday, October 6th. All still had capped brood. So it is still not time perform the cleanup treatment. It is better to wait to the last week of October or first week of November.