The American Bee Journal, Vol. VI, No. 4, October 1870

In No. 11 of the Bienenzeitung for 1870, the Baron of Berlepsch urges bee-keepers to make diligent observations, to ascertain the origin of honey dew. I have for many years given special attention to the subject, as it is one of great interest, not only to bee-keepers, but also to pomologists. My observations fully corroborate the remark of the Baron, that honey dew occurs, in most cases, independently as a vegetable excretion, and only occasionally as the product of aphides. On last Sunday, June 19th, I had an opportunity to assure myself definitely of the correctness of this position. On that day, as early as seven o’clock in the morning, I received a visit from Mr. Heuser, of Westom, one of the intelligent apiarians who compose the Ahrweiler Association for Bee-culture. While we sat conversing about bees, a lad came to inform us that he had, the evening before, seen a fine swarm clustered on a large pear tree. We naturally hastened to the spot, but found that the swarm had already decamped. A loud humming among the branches, however, led us to suppose there might be a hollow limb somewhere, into which the bees had retreated, and friend Heuser was induced to climb up in search of it. He found none, but observed a multitude of bees busily engaged licking up the honey dew with which the leaves of the tree were covered—being evidently an exudation, for on the most careful examination we could not find a single aphis, though on the morning of the next day thousands of aphides were observable there.
It remains for me to mention the state of the weather at the time, for according to my observations this chiefly conditions the production of honey dew. On Saturday, June 18th, the weather was oppressively hot. Towards evening the wind began to blow from the northwest; and the night was cool, though without dew on the grass. This necessarily checked the circulation of sap, which I regard as the primary cause of honey dew, for I may state explicitly that I never saw any, except when hot days were followed by a sudden and great reduction of temperature. The same observation was made, many years ago, by an aged bee-keeper in Niederheckenbach, who, whenever he notices in summer a sudden change of weather, at night, from great heat to cold, will rise at three or four o’clock in the morning and close the entrances of his hives; as he is firmly persuaded that the honey dew certain to come, will be injurious to his bees. I must confess that honey dew has not always proved beneficial to our bees. In some cases they seemed to be sickened by it, and to remain so for nearly a week, as indicated by their inability to fly. This was more especially the case at an apiary which I had in an oak forest, where bark was largely stripped and dried for tanners’ use. I am unable to account for the occurrence, and must leave chemists to determine whether the consumption of tannin had aught to do with it. Whenever honey dew occurs in my neighborhood again I will strip leaves from various trees affected by it, and send them for examination to Dr. Keermrodt, of Bonn, the chemist of the Agricultural Experimental Union of the Rhine province.