FLUVALINATE RESIDUES IN BEESWAX, BROODFOOD AND HONEY
Stefan Bogdanov, Anton Imdorf, Verena Kilchenmann and Luzio Gerig.
Bee Departtment FAM CH- 3097 Liebefeld Switzerland.
Translated from the Schweizerische Bienen Zeitung
by A.E. McArthur MIL
The regular use of Varroa chemotherapy causes the danger of contamination of the hive produce. In the struggle against Varroasis the long term application of acaricides must be taken into account. Most acaricides become concentrated in the wax but however only slightly contaminate the honey. This condition arises due to the fat soluble nature of these substances. The possibility of acaracide accumulation in beeswax due to this factor has been little researched.
Apistan is not allowed to be used in Switzerland today. Its use as a treatment against Varroa is forbidden (at time of paper being published!). In France, Austria and Italy, however the treatment is allowed and due to its ease of application it is widely used.
The effective ingredient of Apistan, fluvalinate belongs to the pyrethroid groups which are widely used in the agricultural industry as insecticides. Fluvalinate in the form of Apistan is impregnated into a plastic strip. In the course of time the effective substance is released by the plastic strip and distributed throughout the whole colony by the bees themselves. The recommended application time is four- six weeks. In order to assess the contamination levels in the bee colony and in particular in the beeswax from long term annually repeated applications, a trial was carried out, where Apistan strips were left for extended periods of time in colonies
Material and Methods
Application of Apistan
The experimental colonies were hived in Dadant 12 comb hives. On the 7th September 1988, three Apistan strips per colony were inserted (approx. 900 mg effective substance per strip). Due to the larger volume of the Dadant type hive one strip more than the normal number in the Swiss type hive was inserted in this trial.
The following three procedures were used:
A - The Apistan strips were removed after four weeks
B - The strips were left in place for 13 months
C - The strips were renewed every four weeks over a 13 month period.
Accumulation in Wax
When the Apistan strips were removed after four weeks (procedure A, which is the recommended application method) the amounts of residual fluvalinate in the brood combs remained relatively small. The values varied between 0.2 and 7.3 mg/kg, the average value amounted to 1.9mg/kg.
When the same strips however were left in the colony for a complete year (procedure B), the residues in the wax at the start of the breeding season (February - April) increased dramatically.
During May, June and July the residues did not increase further. This could be due to the “diluting effect” resulting from the increase in virgin wax. However when new strips were inserted each month (procedure C) the increase in fluvalinate residues was smaller. In 1989 the fluvalinate residues using procedure B were on average 44% higher than the residues resulting from procedure C. This difference was significant using the t-test (t = 3.02, 2P = 0.02). This means that the effective substance diffuses more effectively from the strip when it is resident for a long period of time in the colony. The fluvalinate diffused in lower amounts from new Apistan strips. The expectation that old strips would yield less fluvalinate due to propolisation was thus refuted.
Distribution in the Colony
Around the end of the experiment (July 1989) samples of honey comb wax, cappings, pollen and bees in addition to the brood comb samples were removed from the colonies subjected to the Apistan strip procedures B & C. As a further measure we harvested the summer honey from each colony separately. These values give an indication of the distribution of fluvalinate in the colony. The honey contained no measurable fluvalinate, titlehough the wax of the honey comb and cappings showed quite high concentrations.
In the brood comb with the highest fluvalinate residue levels of 64.8mg/kg, the brood food in these combs showed only 0.016mg/kg. The fluvalinate concentration in brood food and honey was 2800 - 12,100 times smaller than in the corresponding comb wax! This indicates that fluvalinate is an extremely fat soluble substance.
The fluvalinate levels found in the collected pollen of both colonies (procedure B & C) on June 15th, 1989 were higher with on average value of 15mg/kg.
The results of this experiment can be interpreted as follows:
The differentiation between brood comb wax and honey comb wax is made. The acaricide residues in wax after a treatment according to correct instructions fall within the same band of values as the fluvalinate values which we found. Folbex VA is the single exception, where the contamination values are higher by a factor of 10 to 50.
In France fluvalinate is used in the form of Apistan in apiculture and as Klartan (liquid formula fluvalinate) in agriculture. Tests on pollen and bees from all over France have shown that fluvalinate was the most frequently occurring insecticide, (Fleche and Faucon, 1989). This acaricide is often found in honey bee colonies which have never been treated by it. The bees therefore have carried the fluvalinate into the hive from the surrounding vegetation. These results show that fluvalinate either only decays slowly or not at all, that it has persistent qualities. Moosbeckhofer and Kohlech, (1990) found that the varricidal effect of fluvalinates, even after the removal of the Apistan strips persisted for up to three months. The authors fear that the residues of below-lethal doses of fluvalinate remaining on the bees could promote resistant Varroa mites. Apistan is today not permitted in Switzerland and its use as a varroacide is prohibited.
During the treatment with Apistan the levels of fluvalinate increase in the comb wax.
The wax contamination increases with the length of the treatment.
The honey and brood food compared to the wax are much less contaminated.. Here the values of fluvalinate lie mostly below the traceable level of 0.003mg/kg.
The bees and in part, also the pollen collected from foragers at the hive entrance are contaminated by fluvalinate. The residues are however less than that in the wax.
Faucon and Flamini (1988) reported similar values in wax after a five week treatment with two Apistan strips to those we found in our trials after a four week period. The values for honey at a level of between 0.01 and 0.02 mg/kg were higher than ours by a factor between five and seven. (The traceable limit of their methods were not given).
Our results confirm the current results, which have been found with fat soluble acaricides. For the acaricide treatments Folbex VA (bromopropylate) Perizin (Coumaphos), Malathion and 1.4 dichlorobenzene (used as a moth deterent)the residues in wax were found to be much higher than those in the corresponding honey (Kleen et al 1986, Hansau and Pererson, 1988, Thrasyvoulos and Pappos 1988, Binder et al, 1988). In these experiments, in order to qualify Apistan properly the following questions ought still to be clarified:
The use of Apistan leads to the accumulation of residues of fluvalinate in wax. In brood food and honey however only trace levels of the effective substance are present.