Where have all the Honeybees Gone?
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Parasitic mites have nearly wiped out the wild honeybees and have severely decimated the managed honeybee colonies in the United States. Fruit and vegetable growers are now more dependent upon the native bees and the managed honeybee colonies for pollination. The grower should be aware of this and take appropriate action to preserve both sources of pollination.
We on Long Island were actually protected from these mites for a while because we have no migratory beekeepers serving Long Island. The mites were probably brought onto the Island in package bees ordered by new or restocking beekeepers. Upstate New York began suffering major losses several years ago. The winter of 1996 was the second of major losses here on the Island. As many as 80% of the managed colonies may have died over this winter.
The first threat came from Acarapis woodii, the HoneyBee Tracheal Mite (HBTM), first found in the US in 1984. It quickly spread in spite of the destruction of thousands of honeybee colonies in an attempt to eradicate it. This mite is so small it lives within the breathing trachea of the honeybee. This is the mite that is considered to be the cause of the loss of almost all of the honeybees in Great Britain around 1940. To our knowledge, the honeybee is the only known host for this parasitic mite. It moves from bee to bee within a hive and from hive to hive by drifting bees or from bee to bee transfers on flowers in the field. This mite is so small that the only practical detection method is dissection of the trachea under a stereo microscope.
The second mite is Varroa jacobsoni, first found in the US in 1988. The honeybee is not the natural host to the Varroa mite. This mite is natural on Apis cerna, the giant honeybee of southeast Asia and appears to have first transferred over to the honeybee in eastern Soviet Union. Since its introduction, it has also spread very rapidly across the US and into parts of Canada. This mite is large enough to see with the naked eye but can go undetected because they tend to hide under body joints on the bee. The HBTM breeds within the honeybee trachea and fertile females go looking for a new host. In a new host, she penetrates the trachea wall to suck the bee's blood and starts laying eggs. Many generations can occur before the bee dies so that the breathing becomes difficult for the bee and it is unable to perform strenuous activities, such as fly and heat the hive. Most losses from HBTM are in the winter because of the colony's failure to maintain the survival temperature within the cluster. The short six week life of a worker in a major honey flow, due to plain wearing out, reduces the number of successive generations of the mite possible within a single host and thus the impact of this mite. The wintering bees do not have this advantage.
Varroa mites reproduce within the protection of the capped cell of the pupating larva. A fertile female enters the cell of a larva shortly before capping. She lays several eggs including one male and the remaining females. The eggs hatch and begin sucking the blood of the larva as they develop in parallel with the bee larva. The mature mites mate with the siblings or progeny of additional mites laying eggs within the same cell. The mated female mites leave with the honeybee, which can be so severely deformed from the loss of nutrition that it may never serve the colony. The mites attach themselves to a passing bee as temporary host until ready to lay eggs. Severe infestation occurs when brood rearing is at its highest, during nectar flows, so that colonies often crash with abundant honey right after a flow.
Treatment for the mites is difficult because of the biological similarities and requirements of both the mite and the honeybee host. An additional problem is that chemicals used within a honeybee colony must be food safe because they could get into the honey, thus contaminating it.
If you keep honeybees, you probably have both mites and you need to learn how to safely treat your bees to help them fight off these attacks. If you have depended upon wild honeybees for pollination of large blocks of fruiting crops, you need to look at all pollinator activity and take action to achieve the pollinator populations necessary. If you contract pollination, be aware that with the additional costs of fighting the mites, it is estimated that it costs a minimum of $80 to maintain a colony of bees for one year for pollination, an alternative to honey production because of different management goals.
Why all this about pollination?
Fruits are bait produced by plants to facilitate seed scattering. Pollination is required to produce seeds and the seeds produce a hormone causing the development of the fruit. The number of seeds set determine the amount of hormone and thus the fruit size. It has been estimated that it requires 15 visits by a honeybee to a musk melon flower to set enough seeds to produce a #1 melon. Misshapen fruit are often the result of poor pollination.
Pollinators are required by many flowers to move heavy, sticky pollen from one flower to another to produce seeds. In other cases, like strawberries, they are not necessary but can be beneficial because the strawberry is considered to be 80% wind pollinated. The additional 20% of seed set, and thus fruit crop, provided by pollinators represents increased berry size and the uniformity desired or the seeds set when conditions are poor for wind pollination, such as damp weather.
Growers thus need to preserve the pollinators they have by avoiding their destruction by sprays, preserve habitat, and actively encourage pollinators by establishing suitable habitat.
(Ray Lackey has been keeping honeybees for over 25 years on Long Island. He has served as President of the Long Island Beekeepers Association. He often speaks at nature centers, parks, schools, scout troops, and adult meetings on honeybees and pollination. He has earned a Master Beekeeper certification from Eastern Apiculture Society, the principle beekeeping organization in Northeastern USA and eastern Canada.)