IPM Strategy for Varroa Mites Lance Cuthill Slide Info and Background: Dewey M. Caron University of Delaware

IPM – Integrated Pest Management I=INTEGRATED – ideally use of more than pesticide chemical control P=PEST – mites sure but applicable to any of the 3 P’s M=MANAGEMENT – as you mange the bee population you manage the P’s “Several techniques are employed simultaneously to solve specific pest problems”

IPM IPM is a decision-making process for control of PESTS PEST = pathogens, parasites, predators of honey bees, their colonies &/or products Bee Mites have changed the face of beekeeping – no longer bee-havers We are management specialists!

Four Fundamental Strategies for Varroa Management Do nothing Reduce numbers of pest Reduce susceptibility of the host Use combinations of the last two

Goals to Focus on When Developing a Varroa Management Plan Reduce pest status Accept tolerable pest densities Improve net profits Timing…NOT calendar treatments

Implementation of Varroa Management Strategies Pest identification Pest population assessment Economic evaluation* Timing of controls * Is economic damage possible/imminent?

How to Achieve These Goals Efficient sampling methods Valid decision guidelines Integrating a number of effective tactics for an overall plan of attack Acceptance of higher mite levels

IPM in Practice MONITORING Mite levels fluctuate within & between seasons. We must carefully sample (=scout or monitor) and then use best estimates to determine risk level – if risk elevated we control! We MUST - Understand bee/mite life cycle - be able to ID mite & predict #

Varroa mite – a pest or vector?

enters larval cell as it completes development. She hides on side wall Adult female mite enters larval cell as it completes development. She hides on side wall as pre-pupa spins cocoon Illustration series from Martin IN: Mites of Honey Bees Dadant & Sons, Inc 2001

In 60 hours she lays 1st egg (male). After 24 hours she lays female egg one every 24 hours

Her son (male) develops feeding on pupa & mates w/ sister as she matures

When adult bee emerges 1.3 adult female mites are mature – if eggs on drone 3X are mature

SOLUTION?

Control Collapse w/ Pesticides “Resistant” mites increase with each generation Due to: (1)selection pressure (2)Sub-optimal exposure

Economic Threshold EIL ET Pest density Average density Time 80 70 60 Avoid exceeding economic injury level 70 EIL 60 Apply controls 50 Pest density ET 40 Average density 30 20 10 Time

Mite Numbers Increase seasonally

Mite Numbers High mite yr Low mite yr Vary between colonies & years

Detection On brood - worker - drone On bees - ether roll - powdered sugar - alcohol wash In colony - Sticky board

IPM THRESHOLD Monitoring can supply a number - a “guesstimate” One or more numbers can be obtained - use number(s) to evaluate mite population - one mite in sample = X mites in colony Determine an appropriate risk level - one mite vs 100 vs 1000? Assumption: 3000 mites in fall represents a minimally acceptable conservative risk??? Balance of costs vs benefits Basics of the rational of IPM. It assumes a pest situation (host honey bee) can function with some base level of pests (mites) and still function normally. We determine a threshold, test the threshold and then can assign some level of risk to exceeding the threshold level of pests.

Threshold An acceptable level of pests [mites] – determine necessity of further controls A number to use to evaluate mite control efficacy efforts Allows estimation of risk if no pesticide chemical is integrated into the control The basis for IPM – a decision process utilizing modern pest control practices

Threshold Spring/summer (April or May or Mid-June) Sticky boards – over 5-10 Adult bees – over 3-4 Brood – over 5% Exceeding threshold means additional control may be useful Pre-fall (mid-August, Sept too late!) Sticky boards – over 50-60 means additional control Adult bees – over 10-12 Brood – over 5-10% Exceeding threshold means additional (chemical) control needed

IPM THRESHOLD Monitoring can supply a number - a “guesstimate” One or more numbers can be obtained - use number(s) to evaluate mite population - one mite in sample = X mites in colony Determine an appropriate risk level - one mite vs 100 vs 1000? Assumption: 3000 mites in fall represents a minimally acceptable conservative risk??? Balance of costs vs benefits Basics of the rational of IPM. It assumes a pest situation (host honey bee) can function with some base level of pests (mites) and still function normally. We determine a threshold, test the threshold and then can assign some level of risk to exceeding the threshold level of pests.

Threshold An acceptable level of pests [mites] – determine necessity of further controls A number to use to evaluate mite control efficacy efforts Allows estimation of risk if no pesticide chemical is integrated into the control The basis for IPM – a decision process utilizing modern pest control practices

Threshold Spring/summer (April or May or Mid-June) Sticky boards – over 5-10 Adult bees – over 3-4 Brood – over 5% Exceeding threshold means additional control may be useful Pre-fall (mid-August, Sept too late!) Sticky boards – over 50-60 means additional control Adult bees – over 10-12 Brood – over 5-10% Exceeding threshold means additional (chemical) control needed

IPM Mite Control Triangle

Varroa Mites – cultural control Apiary site location Comb culling Small-sized cell base Requeening w/ Resistant (tolerant) stock Hygienic queen stock SMR (surpressed mite resistance) Russian stock Cultural control is less interventive and non-chemical type of approach. Each of the alternatives have been shown to offer some level of control but must be used skillfully. From Martin: In Mites of the Honey Bee

Varroa Mites – physical control Screened bottom boards (season long) Drone brood trapping (1X to 8X) Heat (104-110◦F for 4 hrs) Physical control is use of traps or devices (something physical) and is non-chemical. The top two are effective but vary widely in amount of effort needed – drone trapping is lots of work.

Varroa Mites – physical control Screened bottom boards are about 10-20% effective depending upon circumstances. The bottom screens can be left on colonies year-round but requeening and smaller nuc colonies do not do as well with open screen bottoms. The debris that falls below the bottom screen is an ideal location for development of hive pests so they must be incorporated into a management system. Screened bottom board

Varroa Mites – biological control No identified control agent so far Best choice seems to be a virus or fungus Biological control (biocontrol) has not yet been shown to be feasible. Varroa mites are susceptible to a fungus and a nematode is found in the mites but neither have yet been utilized into effective management for control.

Varroa Mites – Chemical control Miticides - Apistan®; Checkmite+®; Amitraz® Formic acid - Apicure®; Mite-Away II® Other acids (acetic; oxalic) Essential oils Thymol Api Life VAR® [thymol + others]; ApiGuard® Others -thyme, citronella, clove, camphor, eucalyptol Semiochemcials – Nasanov gland pheromones + others Mineral/vegetable oil (FGMO), esters Grease patties; oil machines, Sucrocide ® Drying agents Diatomaceous earth, talc, powdered sugar Chemical control is therefore usually necessary once mite populations exceed threshold levels (measured in mid-August) if colonies are to overwinter and be healthy to expand in the spring buildup. Chemical control can utilize various types of chemicals from relatively non-toxic (to host, applicator and sometimes to pest too) such as drying agents (bottom of list) to chemicals sold as killers (XXXcides=killers)

Varroa Mites - Chemical Control Pesticides – natural/synthetic need to be approved (registered) for legal use Emergency registration (i.e. Apivar) means emergency – temporary answer Natural doesn’t mean less toxic DUMB chemicals (less toxic, not pre-packaged) need SMART beekeepers