EFB Alarm Bells – tested

I have been watching two colonies in two separate apiaries carefully this spring. Neither has been developing as quickly as others in the same apiary and have begun to show signs of gaps in the brood.

I have been looking for the tell-tale signs of European Foulbrood (EFB) or even American Foulbrood (AFB).

Larvae infected with EFB appear twisted in their cells, sometimes forming an unnatural C-shape along the sides or in the bottoms of the cells. The infected larvae turn yellow and then brown eventually drying to rubbery scales within the cells.

Larvae infected with AFB die in the late larval stage with the body stretched out. As the dead larva decays, it eventually dries to a dark sticky “scale” which becomes gelatinous. If the cadaver is probed with a matchstick or something similar, the body can be “roped-out” – a key diagnostic symptom of AFB.

Neither colony showed these symptoms, but the symptoms were closer to EFB, so I used the Vita EFB test kit to see if it might show up positive.

The test, somewhat like a pregnancy test kit, is very easy to use. It’s important to select the most suspect larva. Remove it from the comb and put it in the supplied solution, shaking well for 20 seconds. Then with the small pipette supplied, put a few drops on the well in the test device. After 1 to 3 minutes, a test line will appear. If EFB is found, a second line will also appear. (Full details and video here.)

Thankfully, even the most suspect larvae (which to the naked eye were not convincingly infected by EFB) showed up negative in the test.

I would have suspected varroa as a second possible culprit, but bees with Deformed Wing Virus were not obvious.

Nonetheless, I have taken the precaution of shook-swarming both colonies on to new foundation. The oils seed rape nectar flow is well underway, so with reasonable weather forecast they should be able to build up quite quickly. Because of plentiful nectar, they are unlikely to take feed at this stage, but as soon as the flow eases, I will consider using VitaFeed Gold to hasten their build-up.

I will be watching them very carefully to see if their health improves.

Turlough
Vita’s Guest Beekeeper Blogger