Something to Consider

In November 2005 all my 12 hives were treated with Oxalic acid. This was after being treated with Apistan.

During the summer of 2006 these hives were monitored for varroa drop. Each hive has a mesh floor and tests were started in June 2006 by placing the inserts under the mesh. I do not leave the inserts in for more than 3 days for fear of generating wax moth infestation.

June produced no mite drop as did July. In August, the average was 5 mites per colony and early in September the average was 15.

At the last test the amount of brood in the colonies was considerably more than I would have expected. Some hives had 8 frames of wall to wall sealed brood, with the queen still laying. This was due to the very warm weather, bees having access to loads of pollen from Himalayan Balsam and Ivy.

They were all treated with Bayvarol and a further count was made as soon as the strips were administered. The knock down was between 50 and 200 mites. After 6 weeks the strips were removed and there was still signs of brood, but only in 3 frames and in much smaller amounts.

On Saturday 25th November I examined the first 2 hives and no brood was found, so each hive was treated with Oxalic acid. The solution was ready made up, but no more than 50ml was applied using a syringe by dribbling between the frames. The outside temperature was 12 degrees with no wind. Only the super was removed, the queen excluder being left in position to minimise disturbance, but the bees were not clustered. The floor insert was put in place and the following day I checked the hive entrance and no dead bees were visible.

On Wednesday 29th I removed the floor inserts and the following knock down was found:

• 4 colonies had approximately 150-200 mites
• 4 colonies had approximately 200-350 mites
• 4 colonies had approximately 350-700 mites

I�m of the opinion that due to the queen laying so much later into the season the majority of sealed brood would contain numerous mites not being affected by the Bayvarol treatment and as the brood hatched out so these mites remain active even after the strips were removed.

When treated with Oxalic acid those exposed mites were destroyed.

Had these hives not been treated then the live mites would cause havoc among the adult bees during the winter so much so I will not be surprised if we do not have between 50% to 60% losses before the season begins.

The other problem we are going to face is starvation. Many hives have consumed a large amount of stores and we are only just into December, fondant icing is the answer.

Four other South Cheshire members have carried out the above treatment, all reporting similar results, one even commented �The dead mites were stacked up on top of each other�.

Bob Parsonage

(Other possible explanations for the large number of mites knocked down by Oxalic acid following treatment with Bayvarol are either re-infestation from collapsing wild colonies or pyrethroid resistance in the mites. I recommend carrying out a resistance test next summer � Ed)

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