Regular and thorough colony health inspections are critical for successful beekeeping and arguably the most important part of keeping colonies healthy. As all experienced beekeepers know, the health of colonies can change quickly. Therefore, consistent, periodic inspections are required to ensure timely management and to ensure that past management has worked.

Maryland is a relatively small state at roughly 12,400 square miles; however, according to the Maryland Department of Agriculture, we have around 1,800 beekeepers managing approximately 14,000 colonies. This means that we have over one colony per square mile in our Old Line State. Foraging can take place up to six miles from the hive. Suffice it to say, there is a LOT of shared forage, and transmissible mites and disease can rear their ugly heads at any point throughout the season.

Just like in people, early detection of disease in our bees allows for interventions that can help reduce the negative long-term impact of the disease, as well as the chances the disease will spread to neighboring colonies or apiaries.  

One sign of disease all beekeepers should be aware of is the presence of young bees with crumpled and malformed wings (see image above). This is caused by high levels of infection of deformed wing virus (DWV), which is transmitted between bees in several ways: by trophallaxis, by mites feeding on bee larvae, pupae, and adults, and by vertical transmission from queen to offspring. The tell-tale “deformed wing” has been shown to be more commonly observed when introduced during development as a pupa via an infected Varroa mite. Not all colonies show visible signs of disease. However, when one sees bees with crumpled wings, as in the image above, it's a likely indicator that Varroa mite populations are high. The beekeeper needs to take immediate action to reduce the infestation.

Once a relatively rare disease, DWV is considered one of the leading causes of colony mortality and most commonly seen in colonies infested with Varroa mites. In fact, according to the 2023 APHIS National Honey Bee Pest and Disease Survey, Maryland colonies had an average of 4.3 mites/100 bees, and 92% of colonies tested positive for DWV. This emphasizes the importance of monitoring your colonies for mites regularly.

“I didn’t see any mites…,” is often the reply of beekeepers who hear this advice. Oftentimes you won’t see mites unless you use a standardized test to look for them, such as collecting a known quantity of bees and performing an alcohol wash of the sample. Beekeepers should make it a routine practice to check mite populations once a month during the active season, to ensure they remain low.  When mite loads remain high, DWV levels in the colony also increase, sometimes manifesting with signs of deformed wings. This is why routine mite checks are a best practice in beekeeping.

If you see this sign, you should assume you have or recently have had high mite loads in your colony. While there is no treatment for DWV, you can prevent it from becoming a major issue in your colonies by monitoring mite loads and managing them when they exceed thresholds (1% or higher in spring, and 2% or higher in summer). Remember to do a follow up mite wash after your treatment period to confirm a successful treatment.

A beekeeper’s year starts in the spring. Timing of spring management is critical to healthy productive colonies, and it is not a simple task. This is especially true for the Maryland beekeeper and her colonies. A typical overwintered Maryland colony has a large amount of stored pollen. When weather allows, this ready protein source permits colonies to start rearing brood, and about a month later, adult bee populations start to grow. Strong early spring colonies pose both opportunity and risk for beekeepers. By anticipating colony development, the best beekeepers can predict and prepare for the time-sensitive and critical beekeeping activity of splitting. At UMD, weekly inspections of our colonies (weather permitting) began early this year when winter was still with us. By the early days of springtime, we had started making stand-alone splits, as soon as we knew we needed to control swarming. As is typical, our overwintered colonies are not all the same size. We first tackled several overwintered colonies that were very strong, and we made queenless splits. Next, we made several more splits using purchased queens on other colonies that had just grown a bit in size. Still other colonies remained small and unsplittable. Those were left to requeen last in our sequence.

While in the yards near the end of March, we saw two distinct kinds of queen cells. When looking at Figure 1 and 2, can you guess which frame came from a walk-away split? And which from an overwintered colony?

Figure 1, showing an emerged queen cell (circled in purple), is typical of emergency replacement queen cells. These cells appear on the face of the comb, extending out from a worker comb cell.  This is from one of our walk-away splits, and it is a welcome sight, as it means the colony successfully reared a queen from a young larval worker bee. Typical of emergency queen-rearing activity, there are many queens cells on the frame; these, however, remained unhatched.

Figure 2 depicts typical swarm cells: many long, extended queen cells at the bottom of the frame. This frame came from an overwintered colony whose population had grown quickly. This frame made a great addition to a stand-alone split that had failed to make a queen.  

Bald brood is a glaring indicator that something may be amiss in a colony. Many different things can cause bald brood, including infestation with pests like wax moths (as evidenced in the first photo) and small hive beetles.

When wax moth larvae move through the brood comb looking for food, they sometimes move just below brood comb cappings. Worker bees can detect the larval  passage and uncap those affected cells, creating a characteristic squiggly line tracing the wax moth's route. While not a cause for alarm, this sign does suggest the colony may be weak. If you see something like this on one of your frames, try gently tapping the frame with your hive tool and see if one of the little buggers pops out!

In the case depicted in the image below, however, the likely culprits are the bees themselves.

One way bees are able to fend off disease is through hygienic behavior. This involves bees sensing diseased or dead pupa under the cappings, uncapping the suspect cells, and removing the contents. In this picture, you can see many pupal bees exposed where the cappings have been removed. Also visible are several brood areas where both the cappings and the pupa missing, after the pupa have been removed or cannibalized. While various diseases can cause this behavior, in this case, we think it was a result of cold weather (chilled brood). During a cold snap, the population of adult bees in this colony was not large enough to cover all the brood the colony had produced. So, we suspect, after a cold night, the bees clustered but were unable to cover all the brood in the colony to keep them warm. As a result, some died and were removed. However, happily, the next visit showed this colony as healthy and with no signs of bald brood!