Hayes mentioned some bee die-offs in Georgia that, until then, hadn't seemed significant.
Hackenberg drove back to West Milton with a couple of dead beehives and live colonies that had survived. He handed them over to researchers at Pennsylvania State University.
With amazing speed, the bees vanished from his other hives, more than 70% of which were abandoned by February.
Hackenberg, a talkative, wiry man with a deeply lined face, figured he lost more than $460,000 this winter for replacement bees, lost honey and missed pollination opportunities.
"If that happens again, we're out of business," he said.
It didn't take researchers long to figure out they were dealing with something new.
VanEngelsdorp, 37, quickly eliminated the most obvious suspects: Varroa and tracheal mites, which have occasionally wrought damage on hives since the 1980s.
At the state lab in Harrisburg, Pa., VanEngelsdorp checked bee samples from Pennsylvania and Georgia. He washed bees with soapy water to dislodge Varroa mites and cut the thorax of the bees to look for tracheal mites; he found that the number of mites was not unusually high.
His next guess was amoebic infection. He scanned the bees' kidneys for cysts and found a handful, but not enough to explain the population decline.
VanEngelsdorp dug through scientific literature looking for other mass disappearances.
He found the first reference in a 1869 federal report, detailing a mysterious bee disappearance. There was only speculation as to the cause -- possibly poisonous honey or maybe a hot summer.
A 1923 handbook on bee culture noted that a "disappearing disease" went away in a short time without treatment. There was a reference to "fall dwindle" in a 1965 scientific article to describe sudden disappearances in Texas and Louisiana.
He found other references but no explanations.
VanEngelsdorp traveled to Florida and California at the beginning of the year to collect adult bees, brood, nectar, pollen and comb for a more systematic study. He went to 11 apiaries, both sick and healthy, and collected 102 colonies.
A number of the pollen samples went to Maryann Frazier, a honeybee specialist at Penn State who has been coordinating the pesticide investigation. Her group has been testing for 106 chemicals used to kill mites, funguses or other pests.
Scientists have focused on a new group of pesticides known as neonicotinoids, which have spiked in popularity because they are safe for people, Frazier said. Studies have shown that these pesticides can kill bees and throw off their ability to learn and navigate, she said.
Researchers have yet to collect enough data to come to any conclusions, but the experience of French beekeepers casts doubt on the theory. France banned the most commonly used neonicotinoid in 1999 after complaints from beekeepers that it was killing their colonies. French hives, however, are doing no better now, experts said.
Sniffing out the culprit
Entomologist Jerry J. Bromenshenk of the University of Montana launched his own search for poisons, relying on the enhanced odor sensitivity of bees -- about 40 times better than that of humans.