Small Hive Beetle IPM

by Wm. Michael Hood
Dept. of Entomology, Soils, and Plant Sciences
Clemson University, Clemson, South Carolina

There are many options available to beekeepers to practice integrated pest management (IPM) of small hive beetles which have become a troublesome pest, especially in the southern US when conditions are favorable for their reproduction. Although we do not know all the answers to what conditions favor small hive beetle reproduction, we have developed an arsenal of control recommendations and tools for controlling this hive pest. In this article, we are going to discuss the integrated management of small hive beetles in the context of the eight basic IPM beekeeping principles.

Acceptable Pest Levels

In one of my past articles, I stated that an effective IPM program is based on a treatment threshold system. Although attempts have been made to develop a treatment threshold for small hive beetles (SHB) in managed colonies, there has yet to be one published. Research is also needed to develop an effective beetle sampling tool which will estimate the total number of beetles in a colony without having to conduct a whole colony beetle count. We are somewhat handicapped in our IPM approach to control this hive pest without a treatment threshold system. However, there are a few general guidelines that we need to follow in our IPM of this hive pest.

The beekeeper must resist the temptation of treating the colony with a pesticide when only a few beetles are present in the hive or treating when it is obvious the colony collapse level has been reached. We now have several practical tools in our small hive beetle control toolbox which offer the beekeeper some help in maintaining low beetle populations.

Preventive Cultural Practices

Maintain Strong Colonies. Beekeepers should practice good colony management to help the bees defend their colony from the negative effects of pests such as the small hive beetle. Good colony management starts with a good laying queen that can regulate the colony population to maximize the chances of survival. Her genetic makeup is paramount in that her progeny must be able to sustain the colony in the presence of various diseases and pests, including small hive beetles. In general, a high beetocomb ratio is recommended for SHB control.Another cultural technique recommended for beetle control is the placement of colonies in full sun to create drier soil conditions to help prevent successful beetle pupation in the ground. Beetles need moist soil to pupate and the placement of colonies in a shady, damp location is not recommended. This recommendation runs counter to what most beekeepers were taught in the past: to place colonies in locations that offer early morning sun and afternoon shade, particularly in the hot summer months. Beekeepers should also be careful in placement of their colonies in or near irrigated crops which are often grown in damp soil conditions.

Minimum Manipulation. Honey bees have their own method of defending the colony from small hive beetles. Worker bees chase and corral the adult beetles into confined areas inside the beehive which prevents the beetles from freely roaming the hive and laying eggs on or near stored pollen and bee brood. The beetles need the pollen and brood as a source of protein for sustained nourishment and growth. Without the necessary protein in their diet, beetle reproduction is hampered.

When beekeepers open their colonies, beetles often escape confinement and freely roam the colony again. If the colony is showing signs of stress, the bees may not be able to recorral the beetles, which may lead to an increase in beetle reproduction. Therefore, beekeepers should not open their colonies unless necessary, such times as honey removal from the colony or feeding to prevent starvation. This is particularly true during times of the year when beetle populations tend to increase which begins as early as May in the southern US and may continue till early fall. New beekeepers should resist the temptation to over manipulate their colonies. The queen simply does not have to be checked on a daily basis. Leaving colonies open during inspections can also lead to stress from robber bees from nearby colonies, especially during times of dearth.

In beekeeping operations that have a history of beetle problems, it is recommended not to use hive inner covers or frame spacers as they provide additional hiding places for the beetles to hide and to avoid bee contact and imprisonment.

Monitoring practices

If small hive beetles are present in a colony, their presence is normally obvious when the beekeeper removes the hive top and carefully inspects underneath the top and exposed frame top bars. Beetles do not care for light conditions and will seek refuge quickly. So, the beekeeper can often get a good idea of the number of beetles present in the colony simply by checking for beetles in the top of a hive. If there are many beetles in the top of a hive, a further inspection of the brood chamber is highly recommended to get a better idea of the total beetle population.

Another quick beetle survey tool is to lift the top super off the colony and bounce it gently a couple of times on an overturned telescoping hive top which the beekeeper has placed on the ground. If beetles are present in the super, some will dislodge and fall to the hive top inner surface below.

A telltale sign of a major beetle problem in a hive is when the entrance landing board is soiled with residues of fermented honey which has oozed from frames inside the hive. This is normally a sign that the bee colony has reached the colony collapse level or the colony has succumbed to major beetles activities. “Leaking” is the term that is commonly used to identify this beetle damage stage. Immediate hive removal and treatment of the soil left behind is recommended.

Genetic control. Scientists have discovered that African worker bees readily remove unprotected SHB eggs and larvae. This behavioral trait likely plays an important role in the apparent resistance of African bees to beetle infestation. Cape honey bees which only live in the southern tip of Africa have shown the ability to identify capped bee brood cells that the female adult beetles have made a slit and oviposited their eggs. The bees tear into the cells and remove the cell contents including beetle eggs and larvae. These traits likely occur in our European bees at a much reduced level, however these hygienic behavioral traits may possibly be incorporated in a selection program.

Bees often use prisons constructed of propolis to confine adult beetles. African bees are known to collect and utilize more propolis than other bees races, therefore this activity is another possible reason that African bees show resistance to beetles. Selection of bees that utilize more propolis may contribute to beetle resistance.   

Mechanical control

Several mechanical trapping devices have been developed in the US and Australia to control small hive beetles. Most of these beetle traps use either vegetable or mineral oil as the beetle killing agent. Caution should be used in the use of these oils because they can also be deadly to your honey bees. After use, these oils should be recycled or disposed of properly to prevent environmental contamination.

Beetle traps should play a major role in most integrated management plans because of their safety in providing control without fear of hive product contamination. Traps provide a low cost form of sustained beetle control as long as there is little chance of mass beetle immigration into the apiary. The major disadvantage of most beetle traps is regular trap service is necessary.

A beetle trap has been developed for use outside hives, but it has been used only to monitor beetle movement in an area. The trap was made of a 25.5 cm section of black PVC pipe with 7.5 cm interior diameter with both ends of the pipe covered with 18mesh screen cones. A bait made of pollen dough conditioned by allowing male SHB to feed on it for 3 days was placed inside the pipe which was suspended about 1 meter above ground. The traps were found to be attractive to beetles preferably when the traps were placed in shade. These traps are not marketed and do not likely compete well with bee colonies for attractancy. However, there are many inhive traps presently marketed, but most have not been compared in trapping efficiency with other traps.

The West beetle trap was the first beetle trap marketed in the US. The West trap is a hive bottom trap that includes a removable tray that should be partially filled with vegetable oil that beetles enter and die. The trap is designed to be serviced through the hive entrance. A similar hive bottom trap known as the Freeman trap has been developed recently which also utilizes a removable tray with vegetable oil, but this trap is serviced conveniently from the back of the hive. One big advantage of these bottom hive traps is that they incorporate the use of oils which also kills varroa mites that fall into the oil tray.

The Hood beetle trap was developed at Clemson University and is a plastic box trap with three separate compartments that can be partially filled with various lethal agents and attractants. The best readily available attractant that I have found is apple cider vinegar which should be placed in the middle compartment and food grade mineral oil in the two side compartments. The trap should be secured inside an empty hive frame and placed in frame position number 1 or 10. Beetles enter the oneway beetle trap and become immobilized in the mineral oil and die. Our research with the Hood trap indicates that roughly the same number of  beetles can be trapped in the top super as can be trapped in the brood chamber. However, placement of the trap in the hive body has an added advantage of doubling as a drone brood/varroa mite trap. Bees will construct only drone brood cells in the void area of the frame and the queen will lay drone eggs. When the drone brood is about twothirds capped, the beekeeper simply cuts out the comb and places it in a freezer to kill the varroa which were highly attracted to the drone brood.

AJs Beetle Eater trap was developed by an Australian beekeeper and is marketed in the US. The trap is a two piece longitudinal plastic trap that should be partially filled with vegetable oil and suspended between two frame top bars. Laurence Cutts, former Florida State Apiarist, has recently developed a similar beetle trap, the Beetle Blaster. This trap is also placed between two frame top bars, however his trap has a removable plastic disposable bag that holds the dead beetles. The Beetle Blaster and AJs Beetle Eater traps can be placed between frame top bars in the bottom brood chamber or supers above or both. 

Other forms of mechanical hive measures have been investigated that have not proven to provide beetle control. Bottom screens tend to increase hive ventilation and light conditions near the bottom of a hive, but have not proven to increase or decrease the beetle population. Reduced hive entrances in the form of round plastic pipe entrances did not control beetles. No studies have shown diatomaceous earth to provide beetle control.

Small hive beetles can be present in a colony in low numbers and not be a problem, however, beekeepers are advised to monitor their colonies closely and be prepared to take action especially during certain times of the year when beetle reproduction tends to  increase. Beetles do have the ability to reproduce quickly when conditions are favorable and colonies are stressed. There are many IPM tools and recommendations available to the beekeeper to manage this hive pest. In this article, we will discuss physical control, genetic control, and lastly chemical control.    

Physical control

Beekeepers often smash small hive beetles with their hive tools as a form of physical control. If a beekeeper has the time and patience, this activity can reduce the beetle population and contribute to holding the beetle population in check. Battery operated vacuums are also available for beetle removal, however this form of control is for the parttime beekeeper who only has a few bee colonies. These activities can give the beekeeper a tremendous since of satisfaction, but it can be a futile effort when colonies are overrun with beetles.

In some of our SHB research, we have used vacuums and aspirators to remove beetles from colonies in the fall (before bees begin to cluster) to obtain a total colony beetle count. This is a laborious and time consuming task that requires a minimum of two people, but may pay big dividends for the parttime beekeeper to reduce the number of overwintering beetles. The procedure begins by finding and placing the queen in a cage for safe keeping. Then each hive frame is removed and shaken on an 8x3 feet white plastic table to free bees and beetles. Next, the frame top bar edge is lightly bounced a couple of times on the table top to free any remaining beetles that are hiding in the cells. The frame is then turned over and the frame top bar bounced again on the table top to remove any beetles from the other side. While one person manipulates the frames, another person stands on the opposite side of the table and vacuums or uses an aspirator to collect the beetles from the table top, counts beetles and brushes bees to the side. The boxes, bottom, and hive top should also be bounced on the table to remove and capture beetles. After all the equipment has been processed in this manner, the frames are reloaded into the hive, queen released, and bees remaining on the table brushed back into the hive. For research purposes, we released the captured beetles back into the hive to continue the project.

This radical technique is no doubt very stressful to a colony, but has proven to remove at least 80% of the beetles, as reported by scientists who have used this approach. A few beetles will get by undetected and a few will fly away safely and return to a colony. This technique has been used to only count beetle numbers in bee colonies and its effectiveness as a control tool has not been investigated. As a beetle control technique, simply smashing beetles with a hive tool will likely be preferred as opposed to safely removing the beetles. The beekeeper can expect to kill a few bees during the process of eliminating the beetles.

Another physical control technique is to move beetleinfested colonies to a new location at least a few miles away. Some migratory beekeepers report having few beetle problems, as long as they keep colonies on the move. Moving colonies simply breaks the beetle life cycle by leaving the mature larvae and pupae behind in the soil. Leaving colonies in the same apiary where beetles have been a major problem for years is not recommended.

If it is evident that several hundred adult beetles are present in a colony and beetle larvae are present, the entire hive should be removed from the apiary and treated in a remote location. Or, placement of the hive and its contents into a freezer for a couple of days will kill all beetle life stages. Regardless, the entire hive should be removed from the apiary before more larvae exit the hive to pupate in the soil.

Anything that reduces the ratio of beestocomb surface when beetles are present can lead to major beetle problems. Oversupering and swarming are two examples that can result in increased beetle problems, as well as wax moth problems.

In areas where beetles are problematic, beekeepers should not use a Porter bee escape to remove the honey crop. Honey supers left above a Porter bee escape for more than a day or two stand a high chance of destruction by beetles which thrive in the warm conditions that are free of bee activity. Pollen traps should also be serviced regularly and maintained carefully because the pollen serves as a necessary protein for beetle reproduction and it is unprotected by bees.

Freezing individual frames containing beetle larvae from live bee colonies is recommended, but this will rarely result in successfully salvaging a colony that also shows signs of weakness and low moral. A close examination of these beetle larvae infested frames will often reveal wax moth larvae too. Two measures that may help increase the chance of success are: 1) to replace the larvaeinfested frames with frames with bees from other healthy colonies that show a high beetocomb ratio to boost the bee colony population or 2) to move the remaining frames down to a nucsize (4 or 5 frame) box where the bees can better cover the remaining frames.

When honeyfilled supers are removed from colonies that are beetleinfested, it is highly recommended to extract the honey within 2 days. However, if this is not possible, the beekeeper is advised to maintain a relative humidity of 50% or less inside the honey house. The low humidity results in desiccation of beetle eggs and larvae that were transported into the honey house inside the honey supers. Beetle larvae can cause complete loss of the honey crop inside the honey house, if these guidelines are not followed. Frames of honey which have been used in the past as brood frames are more  vulnerable to beetle problem.

Beekeepers are also advised to practice good sanitation around the honey house to avoid beetle problems. Timely removal of bits of comb, cappings, and pollen is highly recommended because these materials are highly attractive to beetles.

A 50% bleach/water solution has been shown to kill beetle larvae in honey houses and for use in cleaning or salvaging larvaeinfested comb after 4 hours of treatment. Treated comb should be set aside for at least 24 hours to allow the bleach odor to dissipate.

Biological Control

Research investigations have been conducted to find an effective form of biological control for small hive beetles. Infectivity tests under laboratory conditions found that SHB larvae were susceptible to soil infesting entomopathogenic nematodes, but field tests have yet to confirm their reliability in the field. An infectious fungus (Aspergillus flavus) has been identified that infects SHB, however the utilization of the fungus for beetle control has not proven to be safe because of its side effects on bees and fear of honey contamination.

Imported fire ants (Solenopsis invicta) which are found throughout the southern US feed on other soil infesting insects and likely feed on SHB as the beetles enter the soil to pupate. Fire ants are opportunists and may play a role in conjunction with other IPM tools, but they have not been found to be relied upon as a standalone beetle control option, even when ant mounds are present in the apiary.

Chemical control

There are two pesticides that are registered in many states for SHB control. Check Mite + is registered for inhive beetle control but can only be used during a nonnectar flow period. A single strip of the product is cut in half and attached underneath a 4x4 inch piece of corrugated plastic or cardboard and placed near the back of the hive on the bottom board. The piece of plastic or cardboard serves as a hiding place or trap and the beetles receive a lethal dose of the pesticide upon contact. Varying results have been reported by beekeepers using this product. This product stands little chance of controlling beetles in late winter, early spring or late fall when adult beetles are normally inactive or confined to the bee cluster. Beekeepers should carefully use this product only when other forms of control have failed. Beekeepers must follow the pesticides labeled directions and resist the temptation of using the product in other locations in the hive. The product must be removed from the hive in a timely manner according to the directions.

Gard Star is marketed as a soil drench pesticide and is used to kill mature beetle larvae as they exit the hive to pupate in the soil. Care should be taken to avoid spraying this pesticide on the hive entrance which would result in killing bees. Gard Star can also be used to treat the soil underneath deadout colonies to prevent adult beetles from emerging and entering other nearby colonies. Since this product is not used inside the hive, there is little chance of hive product contamination. Therefore, the use of this pesticide may be used more freely in an IPM program until we can find a more suitable and efficient biological soil agent for killing beetles. From a beetle reproductive control approach, Gard Star should be used only when beetle larvae are present in the colony. In my experiences in the SEUS, I have seen very few beetle larvae in colonies in April and May, but June and July are normally the months when beetle reproduction is increasing, so beekeepers need to more vigilant these two months. However, one problem with the use of Gard Star is that we simply do not know how long the product will remain lethal to beetles in the soil, which is likely dependent on temperature, soil type, and rainfall. The other concern is that widespread overuse of Gard Star will likely lead to beetle tolerance or resistance to the product in a few years, similar to the current problem with varroa mite resistance to Apistan in many states.

NOTE. Beekeepers should resist the temptation of using offbrand or unregistered pesticides for SHB control. There are great risks involved when a beekeeper breaks the law (federal and state) when using a pesticide that is not registered for its labeled application. The pesticide label is the law and should be followed carefully by the beekeeper. We have found that beeswax readily absorbs chemicals and may harbor toxic materials for long periods of time. Using illegal pesticides for SHB control may lead to contaminated hive products and can result in injury to the consumer as well as the beekeeper. Our beekeeping industry can ill afford the public outcry over the news of pesticidecontaminated honey.

Summary

Sometimes when conditions are favorable for small hive beetle immigration and beetle reproduction is high, the beekeeper is in for a real challenge to control this hive pest. Large numbers of beetles have been known to enter single bee colonies which can overcome the natural defenses of even a strong bee colony. There are a few reports in the literature of migrating swarms of beetles entering a single hive. Fortunately, this occurs very infrequently, so it is up to the beekeeper to help the bees in maintaining low beetle populations by using a combination of safe and effective IPM tools and recommendations. In most cases, the integrated management of small hive beetles will serve well to control this hive pest.

Winter is a good time for you to sit back and evaluate how well your beetle management efforts worked last year. Maybe the beetle levels increased to the point of negatively impacting your colonies or perhaps colonies seemed to be overrun in some apiaries. On the other hand, beetles may have been present but in very low numbers. Regardless, it is well worth your time to make some decisions now for the coming year. There are many IPM tools available for you to consider and maybe it is time to try a combination of control options and not depend on a single method. Good luck in your beetle management for this year. For a quick review, here are a few recommendations on how to control small hive beetles:

Do’s

  • maintain healthy, strong colonies to promote high beetocomb ratio   
  • monitor colonies for beetle infestation levels
  • trap beetles using one or more of the trapping devices presently marketed
  • physically kill or remove beetles when inspecting a colony, but do not leave equipment exposed for long periods of time which may lead to robbing
  • remove weak colonies from an apiary when infested with beetle larvae and treat the soil
  • extract honey from supers within 2 days of hive removal
  • maintain good sanitary conditions inside and outside the honey house
  • treat soil with Gard Star, if beetle larvae are present in the hive
  • use Check Mite + in the hive as a last resort

Don’t’s

  • do not place colonies in shady, damp locations
  • do not overmanipulate colonies when beetles are present
  • do not leave colonies exposed during extended hive inspections
  • do not oversuper colonies when beetles are present
  • do not hesitate to move colonies to a new location away from an old apiary which has a history of beetle problems 
  • do not use pesticides that are not registered for SHB control