dijous, 8 de maig de 2008

NOSEMA CERANAE

DARRERES NOVETATS SOBRE NOSEMA CERANAE


CATCH THE BUZZ
This information was gleaned from Eric Mussen's UC Davis Newsletter. Information below on how to subscribe. It is one of the best there is. This article has good information on treating Nosema cerane. You need to know this.
Colony Collapse Still Around

Stories of collapsing colonies are still coming in. As in the previous year, they started in late summer and continued right through almond bloom. Involved beekeepers varied from some who never had problems before to others who were hit hard two years in a row.

As in previous years, samples taken after the collapse don’t tell us too much, because whatever happened occurred earlier. What we see is empty hives with no sample bees left to take.

Something that quite a number of beekeepers have noticed is that Nosema infections are much higher than they anticipated. When I arrived fresh from the University of Minnesota, I really emphasized the necessity of controlling nosema disease, especially if a beekeeper was going to sell queens and bulk bees to other beekeepers. That made quite an impact, especially on our
Bee Breeders. Sales of fumagillin rocketed up in California.

Our Bee Breeders have been using fumagillin for decades to control Nosema apis with very good results. They had their treatment schedules worked out and samples sent to me for spore counts were nearly always ND (not detected).



This year, Dr. Marla Spivak and her crew began a project, with the assistance of Sue Cobey, to help the Bee Breeders select breeder queens whose workers demonstrated elevated hygienic behavior. Marla was pleasantly surprised to observe how well that trait already is established in many of the stocks.

During those visits to the beekeeping outfits, samples also were taken of worker bees and analyzed for Nosema spores. A few years ago, ND was the norm. This year, ND was a rare exception. Most colonies had levels of infection that required treatment, according to the old guidelines. Some counts were as high as we see in laboratory studies of caged bees.

How did this happen? Did our old friend, Nosema apis, become resistant to the fumagillin? I doubt it. The few studies that have been conducted over time showed no problem of that sort.

Perhaps this isn’t Nosema apis. It is likely to be Nosema ceranae, according to verbal reports of the CCD researchers. The European studies suggest that N. ceranae is susceptible to fumagillin, but they use it at dosages up to four times stronger than we use for Nosema apis.

The Bee Breeders are not the only ones to see increased Nosema infections this year. Other California beekeepers are reporting high spore counts. Some are reporting globs of bee feces on the fronts of hives and on the ground in front of the colonies. Last fall, Randy Oliver was taking
some samples from his colonies. He found that returning foragers, captured around noon and especially if they were writhing around on the ground, had elevated levels of spores. However, workers taken from the brood nest (nurse bees?) did not have demonstrable spores.

This follows the pattern that Dr. Higes presented at our MegaMeeting in Sacramento a few months ago. He stated that the nurse bees would appear to be uninfected during the spring and summer, but as late summer and fall approached, the bees inside the hive would start top build up spore levels, as well as the foragers. When nearly all the “house bees” were infected, the adult population would abandon the hive. Is this what we call CCD?

As our beekeepers try to resolve this nosema disease problem, they have to con-sider three important factors. The first is that worker honey bees infected with Nosema ceranae apparently will not take feed, either syrup or patty. Thus, the bees have to have the medicated syrup applied onto their bodies to force them to clean themselves off and take their medicine. Since you can only apply a small amount of syrup per treatment, the researchers in Spain suggest four treat-
ments at one week intervals.

The second difference between treating Nosema apis and N. ceranae concerns the dosage of the medication. Without saying much about experimental trials, the Spanish have decided that the
dosage should be about 2.5-3.0 times higher than that used for N. apis. Thus, they would
mix the 95 gram bottle into 40 gallons of syrup, instead of into 100-120 gallons.

The third interesting factor is the formulation of the fumagillin that now is available to us. Fumagilin-B® is imported into the Unites States from a Canadian company, Medivet. The product is not “registered” as such, but the FDA has worked out a type of memorandum of
understanding so that the product can be imported and used in the U.S.

The numbers on the label differ from those on the label of the old Fumidil-B®, but
the mixing instructions are the same for Nosema apis. However, since it is not likely
that we have Nosema apis in our bees anymore, you should pay attention to the instructions for use against Nosema ceranae.

The Medivet label divides its instructions into fall and spring uses. Fall isn’t difficult, because they are the same instructions as for the old Fumidil-B in the fall. It is the spring use that demands careful study.

The instructions say to feed “at a rate of 30 mg fumagillin activity per colony, 4 times at 1 week intervals.” For our purposes, the next set of instructions is better. “Dissolve 454 g Fumagilin-B (one large bottle) in 40 US gallons of sugar syrup and feed each colony 1 pint (treats 320 colonies). Repeat 3 times at 1 week intervals.” Schedule to complete treatment at least 4 weeks before adding honey supers.”

Yes, this means that the dosage is about 2.5 times stronger than we used to use for Nosema apis. Yes, this means many additional visits to the bee yards. And, if you notice that the bees in the colony just are not taking up medicated syrup, you may have to pour it on the bees. That is the procedure used by the Spanish researchers. Spraying the applications on the bees is being tested, currently, by Medivet.

There are a few other Medivet suggests that bear repeating. Make sure the fumagillin is well blended into the syrup. This formulation blends into syrup much more readily than the old Fumidil-B – do not get the syrup very hot or the fumagillin will be inactivated. Check to see if the bees are taking the syrup. Nosema ceranae-infected bees often stop feeding, all together.
You can subscribe to Eric Mussen's electronic Newsletter by visiting the address below. It is one of the best there is.
http://entomology.ucdavis.edu/faculty/mussen/news.cfm


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