Colony collapse disorder refers to a phenomenon which entails a sharp, unusual decline in the number of bees in a colony. This phenomenon has raised great concerns in the USA in the recent past given that honey bees are a significant part of the US economy. Honey bees are involved in pollination therefore contributing to about one third of the US diet. Several causes have been identified as triggers of the phenomenon; most of which are under investigation. Among the causes identified are: genetically modified foods, pathogens, pesticides and antibiotics. Pesticides in particular are deemed to be a leading cause since pesticides such as neonicotinoids can accumulate in nectar and pollen. Prolonged exposure to these pesticides can eventually be detrimental to the bees therefore leading to losses in colonies. This paper shall examine the phenomenon of CCD from a toxicological standpoint with particular focus on antibiotics, miticides and neonicotinoid
Introduction
Honey bees play a critical role in contributing to US economy. Pollination which is carried out by the honey bees is said to contribute to about one third of the US diet since it is involved in the production of wide range of fruits, some special crops, forage crops, food crops and fruits. There has been a sharp and unusual decline in the number of commercial honey bees since late 2006. This phenomenon has baffled the scientific community; the phenomenon is known as Colony Collapse Disorder (CCD) (Johnson , 2010). Losses occur often in nature mainly due to the failure of the bees to return to the hive but the recent losses have been in large numbers. Efforts by the scientific community to understand the phenomenon have led to discovery that CCD is not a phenomenon that has a single cause rather it is a result of “a combination of factors working synergistically (Johnson , 2010).” This phenomenon is characterized by the following symptoms: a decline in the number of dead bees found in the hive, a sudden loss of adult worker bees, presence of immature bees and stores of honey and pollen in the hive. All these symptoms are deemed as unusual given that the honey bees are highly organized and social creatures (Johnson, 2010).
Several causes of CCD that have been identified. The first cause is pesticides which are believed to have a negative impact on the bees. It is also speculated that a virus or a parasite such as Nosema ceranae might be attacking the bees therefore resulting in the sharp decline of the honey bees. It is also possible that a number of stresses may be negatively impacting the immune system of the bees therefore making them susceptible to disease. This could ultimately lead to the collapse of the social system of the honey bees and eventually the decline in the numbers. Some of the stresses that could lead to this include: stress as a result of migration, increased competition for food due to apiary overcrowding, scarcity of nectar or pollen or scarcity of high quality nectar or pollen and contamination or scarcity of water supplies.
Background information on the chemicals
Neonicotinoids pesticides
For the longest time, there has been concern that pesticides may have an effect on the honey bees: the effect is not necessarily death but it is speculated that the pesticides have a negative impact on the growth and the development of bees. Neonicotinoids are often used on field, ornamental and turf crops; they are applied as both seed and soil treatments. Unlike other pesticide, these group of pesticides are systemic hence end up the nectar and pollen. The active ingredient of neonicotinoids is imidacloprid. Along with other chemicals such as clothianidin and thiamethoxam, these chemicals are thought to gradually accumulate in plants eventually working their way to the nectar and the pollen. The doses that are taken by the bees are not lethal but eventual accumulation of these chemicals is thought to have an effect on the foraging behaviour of the honey bees hence negatively impacting navigation, coordination, recruitment, olfactory movement and flight. However, there has been conflict on the effect of neonicotinoids since CCD has been observed Europe where the use of the pesticide has been banned. On other hand, the Organic Consumers Association reports that farms that practice organic farming do not report cases of CCD.
Antibiotics
Honey bees can get bacterial infections from time to time hence the need to use antibiotics for treatment of the infections. One of the most common infections is the American foulbrood which can wipe out an entire honey bee population if left untreated. The use of antibiotics such as oxytetracycline has been found to have a negative impact on the bees. The antibiotics have been found to interfere with the ability of the bees to excrete pesticides. Pesticides often have to be used by apiary owners in order to prevent the destruction of hives by pests. In a study conducted by University of Maryland, it was found that honey bees that were pretreated with oxytetracycline were more sensitive to exposure to pesticides as compared to honey bees that had not been treated with oxytetracycline. It is speculated that the antibiotics interacts with multiple drug resistance protein transporters therefore interfering with their efficacy. As a result of the interference, the honey bees are more prone to exposure to pesticides.
Miticides
Varroa mites can be detrimental to a hive; they cause the death of bees since they suck blood, are transmitters of viruses and result in a reduction of the vigor of bees. There are several miticides that are used by apiary owners to keep the mites in check. The first antivarroa miticide to be used in controlling the Varroa mite was Apistan which comprised of two strips impregnated with tau-fluvalinate. The strips are hung between the brood frames for a period of 6-8 weeks. Apistan was highly recommended because it is nontoxic to the bees but highly effective in keeping the mites in check. However, mites eventually became resistant to tau-fluvalinate. Checkmite+ is one of the miticides that is highly recommended as a substitute for Apistan. Its active ingredient is coumaphos which is an organophosphate. Organophosphates have been found to be highly toxic to bees. Studies indicate that a quantity as little as 300 nanograms of coumaphos is two times more toxic to bees than tau-fluvalinate. It is therefore possible that treatment of a hive with Checkmite+ would result in the death of honey bees.
Analysis of key causes of Colony Collapse Disorder
One of the leading causes of colony collapse disorder is genetically modified foods. In order to confer genetically modified foods with resistance to insects, they are engineered with insecticidal proteins which are produced by Bacillus thurigienesis. The endotoxins that are produced by Bacillus thurigienesis result in the formation of pores in the insect gut after binding to receptors in the mid gut. The pores let out the contents of the mid gut hence resulting in a rise in the osmotic pressure in the mid gut which could eventually lead to the death of honey bee. This contributes to losses in the colony. Evidence also indicates that poor nutrition contributes to losses in colonies. It has been found that honey bees that are well nourished are less susceptible to Nosema ceranae as compared to their undernourished counterparts. It is therefore recommended that a variety of crops ought to be grown in the area near the apiary. Parasites and pathogens are also a cause of colony collapse disorder albeit indirectly. Varroa mites may transmit viruses to the bees therefore leading to the death of the bee. Nosema ceranae has been identified in the digestive tracts of some of the bees isolated from hives exhibiting CCD.
In my opinion, the most likely cause of colony collapse disorder is the use of pesticides. Pesticides are widely used on farms including those owned by apiary owners. Some of the pesticides that are used on farms include: fungicides, miticides, herbicides and antibiotics. This is because bees are exposed to the pesticides in small doses while feeding on nectar and during pollination. The accumulation of the pesticides over time may have a negative impact on the bees therefore disrupting their flight, feeding, navigation and coordination eventually resulting in losses in the colony.
References
Frazer, M., Mullin, C., & Ashcraft, S. (2008). What have pesticides got to do with it? American Bee Journal , 521-523.
Hawthorne, D. (2011). Killing them with Kindness?In Hive medications may inhibit xenobiotic efflux transporters and endanger honey bees . PLoS ONE, 2679.
Johnson, R. (2010). Honey Bee Colony Collapse Disorder. New York: Congressional Research Service.
Johnson, R. M., Ellis, M. D., Mullin, C., & Frazier, M. (2010). Pesticides and honey bee toxicity – USA. Apidologie, 23-65
