Actions for Varroa Mite Monitoring and Chemical Resistance Management

Implement the following measures to reduce the impact of varroa mite infestations and manage the growing risk of synthetic miticide resistance.

Recommended Actions

1. Monitor mite levels monthly wherever possible

Regular monitoring is critical for early detection and effective control. The alcohol wash method is recommended as a simple and reliable technique for assessing mite numbers. Keep records of all mite monitoring.

2. Implement an Integrated Pest Management (IPM) plan

All operations should develop and maintain an IPM plan incorporating:

• Cultural controls
• Non-chemical/mechanical controls
• Chemical controls

Synthetic miticides alone should not be relied upon for varroa control. Prepare for the increasing presence of synthetic miticide resistance by implementing IPM at the apiary level.

3.  Treat only when treatment thresholds are reached

Do not apply treatments unnecessarily. Chemical control measures should be based on verified mite counts and established treatment thresholds. This is especially the case for synthetic miticides.

4. Continue monitoring during synthetic miticide treatment

Mite numbers should be checked while treatments are in place. If mite numbers are continuing to rise after 2-4 weeks of synthetic treatment, seek technical assistance immediately and arrange resistance testing.

Early intervention is essential. If resistance is suspected, consider removing synthetic treatments and replacing them with an approved organic option before test results are received. NSW Department of Primary Industries and Regional Development (DPIRD) Bee Biosecurity Officers can assist with this decision.

5.If resistance is confirmed, you must immediately change treatment strategy

Where mites test positive for resistance to amitraz or pyrethroids, remove any remaining synthetic treatments without delay and replace with suitable approved organic options, including:

• Oxalic acid strips (Aluen Cap)
• Oxalic acid dribbling (Api-Bioxal)
• Oxalic acid vaporisation (Api-Bioxal)
• Formic acid (Formic Pro)
• Thymol (Apiguard)

Also consider cultural and non-chemical/mechanical controls under your IPM strategy that might be required in addition to organic treatments to bring down or maintain mite numbers at manageable levels.

Again, if mite numbers are high during synthetic treatment, strongly consider switching to organic options before resistance test results are received. Once mite numbers rise well above threshold, they can be difficult to reduce with organic treatments, so early action is critical.

6.Continue ongoing monitoring of affected loads

Maintain regular and frequent surveillance of mite numbers and overall bee health in all colonies. Monitor mites monthly.

7.Do not select for chemical resistance

Where resistance has been detected, synthetic miticides must no longer be used. Continued use is likely to select for the survival and uncontrolled increase of resistant mites leading to colony loss. This has been observed by DPIRD in NSW.

Evidence from international studies suggests that reducing reliance on a single treatment and lowering selection pressure through rotation of miticides and alternative control methods may help slow the development of resistance and recover some degree of susceptibility in populations containing mites with resistance mutations.

Critical Warning

If action is delayed until mite numbers are uncontrolled, there may be limited ability to save colonies. An early transition to cultural, non-chemical/mechanical and organic treatment options provides the best chance for successful control. You must prioritise varroa management at this point in order to keep your bees alive.

Testing options

It is never too early to test for chemical resistance. It is good practice to have your mite population assessed before a problem arises. This way you can plan for effective varroa mite control. Testing can be arranged through the NSW DPIRD laboratories or through a private provider.

What is IPM?

Integrated Pest Management is an approach to pest management that utilises cultural, mechanical and chemical means to control a pest.