Maine beekeepers are thinking about their bees and parasitic mite controls, spurred by the arrival of this year’s beekeeping supply catalogs, coupled with the recent snow melt after January’s rain and wind event. Already, there are reports of hive mortality and requests for information and post mortem inspections. So far, most of the inspections reveal mortality due to Varroa and several cases attributed to queen issues. A number of beekeepers were amazed at the levels of mite infestation, given that the hives in question were established in 2012 via packages and nucs. In contrast to last winter, this year’s herd will be thinned based on bee health in the fall and colder winter weather.
Last April, The Bee Line featured an article, “Beware of the Ides of March,” that reviewed the consequences of a mild winter and early spring. In short, the article stated that when the bees are flourishing, so are the Varroa mites. The article cautioned beekeepers of the potential for a repeat of 2010′s experience and urged them to monitor and control Varroa populations before it was too late.
The advice offered last April still applies for this year, although bees and mites are not building at the rate experienced in 2012. Manage honey bees according to weather conditions and plant phenology — not calendar date — since for the most part, that is what the bees are doing. Early spring management should include the usual: feed if necessary, unwrap when weather moderates, and then do brood inspections for queen performance and disease/mite presence. Treat for Varroa if necessary with the appropriate pesticide or management strategy.
This year, beekeepers will have seven approved pesticides for Varroa control, two of which are under EPA-FIFRA Section 18 Emergency Exemption. It is important for beekeepers to consider the pros and cons of each material prior to use. For example, ambient temperature, the presence of supers, time of expected honey flow, and bee toxicity of the pesticide should be considered during the treatment period. All pesticides are not equal with respect to bee toxicity, human toxicity and performance.
Currently, there are three synthetic pesticides and four organic (“soft”) pesticides available to beekeepers for Varroa control. Each group is as follows, in order of introduction to the market:
active ingredient: fluvalinate
Apistan is a pyrethroid and one of three synthetic pesticides formulated in a plastic strip. This pesticide has been available to beekeepers since the late 1980s and worked exceptionally well until repeated use and illegal use of unregistered formulations selected for Varroa with resistance to fluvalinate. With few exceptions, Apistan is no longer effective against Varroa mite.
active ingredient: coumaphos
CheckMite is an organophosphate insecticide formulated in a plastic strip that has been used by beekeepers since the late 1990s. This product also worked well at controlling Varroa mite until repeated and illegal use of unregistered formulations rendered it ineffectual. Varroa are resistant to this pesticide with few exceptions.
active ingredient: amitra
Apivar is a triazapentadiene compound, a member of the amidine chemical family. It is currently approved under EPA-Section 18 Emergency Exemption and was previously sold as a Varroa control strip by the trade name Miticur in the late 1980s through early 1990s before its use was discontinued by the manufacturer. This pesticide has been reintroduced by Arysta and is again formulated in a plastic strip. The pesticide can be used a maximum of two applications per year (spring and/or fall). Apivar cannot be used while bees are making honey and supers are present. In addition, Apivar strips must be removed two weeks before the honey flow starts, in order to prevent contamination of honey. Amitraz, the active ingredient in Apivar, belongs to IRAC Group 19 and is highly susceptible to resistance development by Varroa. Over time, resistant Varroa will reproduce and dominate the mite population. Resistance can be delayed by rotating this pesticide with other Varroa controls in different chemical classes. Like all pesticides, use should be based on integrated pest management (IPM) strategies that include monitoring; record-keeping; and taking cultural, biological and other chemical control practices into consideration. Using IPM with strict adherence to label directions (specifically the removal of strips after 42 days or a maximum of 56 days) on approved treatments reduces the risk of encouraging the development of resistant Varroa populations. It is important to monitor treated hives for resistance development and report performance issues.
Organic (“Soft”) Pesticides
active ingredients: thymol, eucalyptol, menthol, camphor
ApiLifeVar is a contact/vapor action pesticide formulated on a vermiculite tablet. It is considered to be an organic pesticide and is dependent on optimum temperatures. It requires three successive applications when bees are not making honey and supers are not on hives. This pesticide can cause adverse effects to hives in a weakened state.
active ingredient: thymol
Apiguard is a contact/vapor action pesticide formulated as a gel. It is also considered to be an organic Varroa control and is effective in controlling Varroa under optimal conditions, like ApiLifeVar. The product is only effective within a limited temperature range when bees are not making honey and without supers in place. Apiguard can cause bee mortality if used in high temperatures and may incite robbing behavior to hives undergoing treatment.
Mite-Away Quick Strips
active ingredient: formic acid
Mite-Away Quick Strips is an organic vapor-action pesticide formulated in a pre-soaked pad. This product is effective within a certain temperature range and can be hazardous to the applicator. The MAQS can be used while bees are making honey with supers on colonies. This pesticide is associated with queen loss, adult bee and brood mortality, and absconding when used during hot temperatures. The product’s efficacy is inconsistent and influenced by the amount of brood present and size of the hive being treated.
active ingredient: beta acids
Hopguard is authorized under EPA-FIFRA Section 18 Emergency Exemption. It is an organic pesticide formulated on a cardboard strip. The product may be used while bees are making honey and supers are in place. It performs well in hives with minimal-to-no brood and provides control for approximately three days (while strips are wet). The current formulation necessitates multiple applications when hives are actively rearing brood. The manufacturer is currently developing an improved delivery that will provide control for 10 – 14 days. In 2012, Hopguard applications in Maine during cold temperatures resulted in some adult bee mortality due to continual contact with clustered bees. This situation also occurred with CheckMite applications during cold temperatures while bees were clustered.
It is important for pesticide applicators (beekeepers) to read the entire pesticide label prior to use. Following the label instructions is crucial in order to ensure safety to the applicator, bees, and honey destined for human consumption. Proper pesticide usage will also slow the development of Varroa resistance to the active ingredient, thereby extending the long-term efficacy of the compound. Finally, remember that just because a pesticide is considered “organic” does not mean it is not toxic to the bees or applicator. Pesticide labels have signal words that convey toxicity to the applicator. They are:
- Caution: slightly toxic, over one ounce needed to kill the average person);
- Warning: moderately toxic, one teaspoon – one ounce needed to kill the average person; and
- Danger: highly toxic, a few drops – one teaspoon needed to kill the average person).
Pick your poison prudently!
Tony Jadczak, State Apiarist
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- Varroa Treatment Comparison - March 23, 2013