5.0 DISEASES, POISONING AND PESTS
The candidate will be:
5.5 able to describe ways of controlling Varroa using integrated pest management techniques;
NOTES
There are several methods of controlling varroa and these should be used in combination, at different times of year, in order to keep varroa levels as low as possible and avoid using single techniques that could cause a build up of resistance or excessive use of chemicals. This is known as Integrated Pest Management (IPM).
There are two main categories of varroa control – chemical treatments and “mechanical” procedures.
Chemical treatments include:-
1. Pyrethroid impregnated strips (Apistan). These were originally highly effective but now mites have developed resistance to these. Mites can be tested for pyrethroid resistance and if found these chemicals should no longer be used. The manufacturers advice on dosage should be followed exactly in order not to increase the likelihood of resistance developing.
2. Thymol based products (Apiguard). These require an optimum (warm) temperature to be most effective as they rely on evaporation.
3. Oxalic acid. There are 2 main ways of applying this treatment- in solution or by gas sublimation. The treatment is usually carried out in the winter when there is no brood. Oxalic acid cannot penetrate sealed brood cells and therefore is of limited use during the brood rearing season.
Trickle treatment of oxalic acid solution is done by dribbling the solution over the “seams” of bees clustered between their brood frames.
Sublimation is done by placing the acid crystals on a metal plate attached to a battery. The plate is heated inside the hive until a gas forms. Great care should be taken when using this method as the fumes are highly toxic.
Oxalic acid in its raw state is not legally authorised as a veterinary treatment although until recently this was widely used in practise. Now, approved medicines are readily available, such as Api-bioxal, oxybee and Varromed (a combined oxalic and formic acid solution).
3. Formic acid. This is usually supplied in the form of absorbent pads impregnated with the acid. When the pads are taken out of the packaging and placed on the top of brood frames the formic acid is released into the hive.
Formic acid, in contrast to oxalic, will penetrate brood cell cappings and therefore can be used effectively at any time of year. However there is a minimum temperature required for effective treatment – approx 10C.
Approved medicines for formic acid include MAQS, Formic Pro and Varromed (a combined oxalic and formic acid solution).
4. Amitraz impregnated strips (Apivar). These strips are hung between the frames of the brood box where the varroa are likely to come in contact with the active ingredient. The strips stay in the hive for 6-10 weeks. These are usually used after the honey supers are removed in the autumn but can be used at any time.
Manufacturers instructions should always be followed when applying any medicines.
It is a legal requirement to take records of all veterinary medicine treatments applied to bee colonies.
Mechanical procedures include:-
1. Using an open mesh floor. Any live mites that fall through the mesh will not be able to get back in the hive. Easy but not effective control.
2. Drone brood removal. Mites prefer the larger capacity drone cells to breed in. Drone cells can be removed with their contents of larvae and mites. Fairly easy but limited in effect.
3. Dusting the bees with icing sugar. This makes them groom themselves and each other and can cause mites to be dislodged.
4. Comb trapping. Queens are restricted to laying on certain frames by vertical queen excluders and then that frame is removed “trapping” the varroa. Effective but complicated and time consuming.
5. Artificial swarm. Combine swarm control with varroa control by trapping the virgin queen in the parent colony then using “bait” frames of brood when all the parent colony brood have hatched.