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Globally there are more honey bees than other types of bee and pollinating insects, so it is the world's most important pollinator of food crops. In addition, honey bees play a significant role in the pollination of other important crops such as cotton and flax. ...
Only 13 absolutely require animal pollination, while 30 more are “highly dependent” on it. Production of the remaining crops would likely continue without bees with only slightly lower yields. So if honeybees did disappear for good, humans would probably not go extinct (at least not solely for that reason).
Colony symptoms, commonly called parasitic mite syndrome, include an abnormal brood pattern, sunken and chewed cappings and larvae slumped in the bottom or side of the cell. This ultimately causes a reduction in the honey bee population, supersedure of queen bees and eventual colony breakdown and death.
Contact pesticides are usually sprayed on plants and can kill bees when they crawl over sprayed surfaces of plants or other areas around it.