Dysentery is a condition resulting from a combination of long periods of inability to make cleansing flights (generally due to cold weather) and food stores that contain a high proportion of indigestible matter.
As a bee’s gut becomes engorged with feces that cannot be voided in flight as preferred by the bees, the bee voids within the hive.
When enough bees do this, the hive population rapidly collapses and death of the colony results. Dark honeys and honeydews have greater quantities of indigestible matter.
Occasional warm days in winter are critical for honey bee survival; dysentery problems increase in likelihood during periods of more than two or three weeks with temperatures below 50 °F (10 °C).
When cleansing flights are few, bees are often forced out at times when the temperature is barely adequate for their wing muscles to function, and large quantities of bees may be seen dead in the snow around the hives.
Colonies found dead in spring from dysentery have feces smeared over the frames and other hive parts.
In very cold areas of North America and Europe, where honey bees are kept in ventilated buildings during the coldest part of winter, no cleansing flights are possible; under such circumstances, beekeepers commonly remove all honey from the hives and replace it with sugar water or high fructose corn syrup, which have nearly no indigestible matter.
Chilled brood is not actually a disease, but can be a result of mistreatment of the bees by the beekeeper. It also can be caused by a pesticide hit that primarily kills off the adult population, or by a sudden drop in temperature during rapid spring build-up.
The brood must be kept warm at all times; nurse bees will cluster over the brood to keep it at the right temperature.
When a beekeeper opens the hive (to inspect, remove honey, check the queen, or just to look) and prevents the nurse bees from clustering on the frame for too long, the brood can become chilled, deforming or even killing some of the bees.
Honey bees are susceptible to many of the chemicals used for agricultural spraying of other insects and pests. Many pesticides are known to be toxic to bees.
Because the bees forage up to several miles from the hive, they may fly into areas actively being sprayed by farmers or they may collect pollen from contaminated flowers.
Carbamate pesticides, such as carbaryl, can be especially pernicious since toxicity can take as long as two days to become evident, allowing infected pollen to be returned and distributed throughout the colony.
Organophosphates and other insecticides are also known to kill honey bee clusters in treated areas.
Pesticide losses may be relatively easy to identify (large and sudden numbers of dead bees in front of the hive) or quite difficult, especially if the loss results from a gradual accumulation of pesticide brought in by the foraging bees.
Quick-acting pesticides may deprive the hive of its foragers, dropping them in the field before they can return home.
Insecticides that are toxic to bees have label directions that protect the bees from poisoning as they forage. To comply with the label, applicators must know where and when bees forage in the application area, and the length of residual activity of the pesticide.
Some pesticide authorities recommend, and some jurisdictions require, that notice of spraying be sent to all known beekeepers in the area, so they can seal the entrances to their hives and keep the bees inside until the pesticide has had a chance to disperse.
This, however, does not solve all problems associated with spraying and the label instructions should be followed regardless of doing this. Sealing honey bees from flight on hot days can kill bees.
Beekeeper notification does not offer any protection to bees, if the beekeeper cannot access them, or to wild native or feral honey bees.
Thus, beekeeper notification as the sole protection procedure does not really protect all the pollinators of the area, and is, in effect, a circumventing of the label requirements. Pesticide losses are a major factor in pollinator decline.
Colony collapse disorder
Colony collapse disorder (CCD) is a poorly understood phenomenon in which worker bees from a beehive or western honey bee colony abruptly disappear. CCD was originally discovered in Florida by David Hackenberg in western honey bee colonies in late 2006.
European beekeepers observed a similar phenomenon in Belgium, France, the Netherlands, Greece, Italy, Portugal, and Spain, and initial reports have also come in from Switzerland and Germany, albeit to a lesser degree.[Possible cases of CCD have also been reported in Taiwan since April 2007.
Initial hypotheses were wildly different, including environmental change-related stresses, malnutrition, pathogens (i.e., disease including Israel acute paralysis virus), mites, or the class of pesticides known as neonicotinoids, which include imidacloprid, clothianidin, and thiamethoxam.
Most new research suggests the neonicotinoid hypothesis was incorrect, however, and that pesticides play little role in CCD compared to Varroa and Nosema infestations.
Other theories included radiation from cellular phones or other man-made devices and genetically modified crops with pest-control characteristics,.
In 2010, U.S. researchers announced they had identified a co-infection of invertebrate iridescent virus type 6 (IIV-6) and N. ceranae in all CCD colonies sampled.