Many honey bee health issues show symptoms in the brood nest. Learning to inspect the brood carefully is critical to identifying problems early enough to remedy them without losing the colony. The Bee Informed Partnership website (http://beeinformed.org/author/rob-snyder/) has some great photos to help you diagnose diseases in brood, such as this one, which shows varroa symptoms, including damaged larvae, partially removed larvae and deformed wing virus.
Best Management Practices (BMPs) for beekeeping
A best practice is a method, process, activity, incentive, or reward which conventional wisdom regards as more effective at delivering a particular outcome than any other technique, method, process, etc. (Wikipedia definition). In beekeeping, like in most things, there is no one way of doing things that works best for eveyone. There are, however, general guidelines for bee health that will likely provide useful for most beekeepers and will provide a good starting point for anyone getting into beekeeping. For Hawai`i, a brief list of beekeeping BMPs could look like this:
- inspect colonies once per month and document observations
- document any pest sampling/treatments
- keep colonies in a sunny location
- keep colonies off the ground
- control tall vegetation around colonies
- replace frames/comb every 5 years
- remove burr comb at each monthly inspection
- contact Apiary Program with questions
- become a member of the HI beekeeper registry
A more comprehensive list of BMPs from Project Apis m. can be found here.
Of course the two most obvious bee health problems facing Hawai`i beekeepers the past few years have been our unwelcome new residents: varroa mite and small hive beetle. Nosema and American foulbrood are other common problems. Following BMPs can help reduce the imact pests and diseases have on your bees.
In 2007, varroa mite (Varroa destructor) was detected in Hawai`i; first on O`ahu, then on the Big Island. To date, it has not spread to any other islands - let's keep it this way! Just a reminder that it is illegal to move bees or used beekeeping equipment between islands without prior inspection by the Hawai`i Department of Agriculture.
Damage: Considered the most damaging pest of bees, varroa mite is now found almost worldwide. Damage to honey bee colonies can be slow and subtle - but without monitoring and treatment, infection with varroa will almost always end in the death of the colony. Mites weaken developing bees through their feeding activities and can spread several different viruses throughout the colony. One virus that is spread by varroa and found in Hawai`i is called Deformed Wing Virus or DWV, which causes bees to emerge with small, twisted, useless wings. Affected bees can sometimes be found crawling on the ground in front of the colony; they cannot fly and do not live very long.
Life cycle: Varroa mite begins its life as an egg, which is laid inside a honeycomb cell that contains a developing baby bee (larva). When the egg hatches, the young mite latches on to the bee larva using its piercing mouthparts. The mite stays here, feeding on the bee larva and developing as the bee develops. When the bee finally emerges as an adult, the adult mite also emerges - female mites are then free to go lay eggs on new bee larvae or to hitch a ride to a new location on an adult bee. Varroa mite is an obligate parasite of honey bees, meaning that it cannot survive without its bee host. A more detailed account (along with some excellent pictures) of the varroa mite life cycle can be found here.
Control: You cannot control varroa mite without knowing 1) if you have it in your colonies or not; and 2) at what level it is occuring if your bees do have it. Monitoring for varroa levels is the best way to approach varroa control - monitoring helps you treat when you need to and avoid treating when you don't. This approach will save both your money and your bees and is part of an Integrated Pest Management (IPM) strategy for varroa control. The goal of IPM is to manage pest damage by the most economical means and with the least possible hazard to people and the environment. Two methods recommended for use in Hawai`i to test varroa levels are: 1) using a sticky bottom board; or 2) do an alcohol shake. See the FAQ page for more information. Other options include examining drone brood or doing a sugar shake.
Pesticides, both natural and synthetic, are available to control varroa mite. Be sure to use products only as indicated on the label and be aware that many treatments cannot be used with honey supers in place. Rotating products is a good idea and may help avoid pesticide resistance in varroa mite populations (think IPM again!). The products that are licensed in Hawai`i for varroa control are:
Small hive beetle (SHB)
Small hive beetle (Aethina tumida) was first detected in Hawai`i at Pana`ewa on the Big Island in April 2010 and was found on O`ahu later the same year. SHB is now widely distributed on both of these islands and was also detected on Maui and Moloka`i in 2011. In May 2012, SHB was first detected on Kaua`i.
Damage: Small hive beetle invades beehives, where it lays eggs. Both larvae and adults feed on pollen, honey, wax, and even the baby bees (brood) inside the hive. SHB activity causes honey to ferment, drip out , become slimy, and develop a smell like rotten oranges. Bees often desert the hive at this point and beekeeping equipment may be unsalvageable. SHB is also attracted to stored honey and other hive products. Adult beetles are very strong fliers and can locate bees and/or honey from miles away.
Life cycle: After hatching from eggs laid inside the hive, SHB larvae stay there to feed. When fully grown, larvae exit the hive and drop to the ground below. Here, they bury into the soil, pupate, and eventually hatch into adult beetles, which again enter a hive to lay eggs. Although SHB prefers to live with honey bees, it can also complete its life cycle on fallen fruit when necessary.
Control: Although damage from SHB is dramatic and can occur very quickly, this beetle is considered a secondary pest of honey bees. This means that SHB is far more likely to cause damage to a hive that is already stressed by the presence of other pests (e.g. varroa!) or diseases. Following BMPs as descibed above can also go a long way toward SHB control. Hives placed in the sun and/or on surfaces with little available soil tend to be a little more resistant to SHB. A hive can tolerate a certain amount of adult beetles - if you notice eggs or larvae - beware!
Traps: Most beekeepers in Hawai`i use a variety of traps filled with vegetable oil to catch and kill adult beetles inside the hive. See these links for some examples: oil tray for the bottom board and an oil trap for use between frames. Commercial traps can be expensive - many folks are also finding ways to make their own.
Chemicals: Chemical control is usually not considered an efficient way to control SHB. There are two pesticides, however, licensed for use against SHB in Hawai`i:
- Checkmite+ - used inside the hive
- Gardstar - a drench used for soil beneath the hive
Not much was known about nosema in Hawai`i until recently, when Hawai`i was one of 13 states that provided samples for the USDA's 2010-2011 National Honey Bee Pests and Diseases Survey. The survey report showed that nosema was more prevalent in Hawai`i apiaries than in any other state and that nosema loads were also higher than the national average.
Damage: Nosema causes a kind of bee diarrhea. Bees that are infected when they are young cannot digest food properly and therefore cannot produce food for the brood. Their lives are shortened as they become foragers at an early age. Symptoms can include specks of feces inside the hive or on the front of the hive or you may see no symptoms at all. Colonies infected with nosema are weakened, may produce less honey., and may be more susceptible to pests like varroa or small hive beetle.
Life cycle: Nosema disease is caused by a microscopic fungal parasite (Nosema apis/ceranae) that infects a bee's gut. An infected bee's feces contains infective fungal spores. When these bees defacate inside the hive, other bees can ingest these spores and develop nosema disease.
Control: Testing for nosema can be done free of charge by the Hawai`i Apiary Program. If your nosema levels are above an acceptable threshold, your colony can be treated with Fumigilin-B.
American foulbrood (AFB)
American foulbrood (or AFB) is a serious bacterial disease - it is contagious and very difficult to control. AFB almost wiped out beekeeping in Hawai`i in the 1930s. Click here for more information on AFB.