1901 



GLEANINGS IN BEE CULTURE. 



0)03 



Air. A'. W. Molheral, Horticultural Commissioner, 

 Han/ord, California. 

 Dear Sir : — In fulfillment of my former letter, and 

 in reply to your request, I herewith give the main 

 facts upon which are based the claim that bees take an 

 active part in spreading the disease of trees vatiously 

 known as pear-blight, twig-blight, fire-blight, etc. 



1. rear-blight is a bacterial disease which affects 

 pear, apple, crabapple, quince, and related trees. It 

 is induced through the action of a specific micro- 

 organism belonging to the bacteria, and known as 

 Bacillus aotylovorus (^Burrill), de Toni. 



These facts have been demonstrated by many scien- 

 tific workers by careful inoculation, experiments con- 

 ducted with pure cultures of the bacillus. The cause 

 of the disease has therefore been well known for 

 many years. 



2. The identity of the blight of pear-trees in the 

 Clow and Taylor orchards near Hanford (these par- 

 ticular orchards are cited only for the sake of accu- 

 racy, as there are many others affected) with true 

 eastern pear-blight has been demonstrated at this 

 laboratory. Bacillus amylovorus was isolated in pure 

 culture by the plate proctss from blighted blanches 

 from Mr. Clow's trees, and a young and thrifty pear- 

 tree was inoculated, and died to within a few inches 

 of the gronnd of true pear blight. A control tree 

 treated the same way as the inoculated tree, except 

 that the bacillus was not introduced, remained per- 

 fectly healthy. 



Mr. M. B. Waite, Assistant Chief of this Division of 

 the Depai tment, has kindly supplied the following 

 additional facts bearing on this matter : 



3. " The occurrence oi the blight on the blossoms in 

 great quantities, and the great racidity with which 

 the disease spreads from flower to flower, indicates a 

 normal and very effective method of distribution." 



4. "The germs were found growing freely in the 

 nectar of the blossoms." 



5. "Bees were seen repeatedly visiting the infected 

 flowers, and .some were caught taking infected nectar, 

 and, by means of plate cultures, the pear-blight germs 

 were isolated from their mouth parts." 



6. " By covering parts of the trees with sacks of vari- 

 ous kinds of material, and then artificially infecting 

 certain flowers on the tree, the blight was observed 

 to spread very freely over the uninfected and uncov- 

 ered blossoms, but was entirely absent in the blos- 

 soms covered by mosquito netting " 



7. "Blossoms were infected, and at once covered 

 with sacks, and the blight, in such cases, was retained 

 in the infected blo-soms." 



8. " Pear-blight germs died very soon after being 

 dried up, and lived tor only a brief period on exposure 

 to weather conditions out of doors, hence they can 

 not live in dust, and be blown around to any great 

 extent by the wind." 



9. " Pear-blight virus, particularly that which occurs 

 on blossoms, is a very sticky substance, and is readily 

 carried by insects, birds, or other animals, but can 

 not be blown by the wind." 



This brief presentation will, I believe, furnish 

 your board with the main facts needed to show the 

 connection existing between the visits of bees to pear- 

 flowers and the spread of pear-blight. 



Sincerely yours, Newton B. Pierce, 



April 23, 1901. Pathologist in Charge. 



Prof. Pierce happened to be in the city at 

 the time, and in an interview which we had 

 with him he gave utterance to substantially 

 the statements as are given above. If any 

 thing, his verbal statement incriminating the 

 bees was even stronger. So far as I could 

 judge, he seemed to be a competent scientist, 

 and a fair-minded gentleman ; but, uncon- 

 sciously, he is prejudiced, I think, in favor of 

 the pear men, with whom he has come much 

 in contact of late. I asked him if it were not 

 true that wild bees, insects, and birds, over 

 which man has no control, could do all the 

 mischief ascribed to the bees. He admitted 

 that this was possible but not probable. Did 

 he not think that bees were valuable as fertil- 

 izers of the blossoms, especially of those of 

 the Bartlett pear? He thought they were. 

 Well, did not this service of the bee, year in 



and year out, more than counterbalance the 

 alleged mischief done by them in the occasion- 

 al year when pear-blight was so prevalent? 

 He could not say, although he was of the 

 opinion that, by a certain alteration of varie- 

 ties, the services of the bee might be dispensed 

 with entirely ; but of this he was not sure. 



From Prof. Waite's statement it would ap- 

 pear (to express it in common parlance) that 

 the bees have been caught "red-handed," 

 bearing the marks of the alleged criminal act. 

 If I undei stood Prof. Pierce he had not found 

 the bacteria of pear-blight on the tongues of 

 the bees, nor had he himself seen the mi- 

 crobes in the nectar. If this be true, we have, 

 as the only real incriminating chain of evi- 

 dence, the statement of Prof. Waite. With- 

 out detracting in the leatt from the skill of 

 the professor, it is proper to remark that even 

 the best of scientific men make mistakes, and 

 we as bee keepers can not accept the unsup- 

 ported statement of Prof. Waiie without fur- 

 ther investigation by some of our men equally 

 competent and fair. 



This is a nice question, as a lawyer would 

 say, and we need to go at it carefully and can- 

 didly to get at the truth, cut where it may. 



There is some evidence that goes to show 

 that Prof. Waite is mistaken. For instance, 

 there are young pear-trees, acres and acres of 

 them, that have never been in bloom, and yet 

 these young trees are blighted to death. How 

 in the name of reason did the bees carry blight 

 to these trees when it is apparent that they 

 never went near them ? And then there are 

 little shoots that have pushed up from the 

 ground since the big trees were in flower, and 

 yet these shoots are blighted like the rest. As- 

 suming, for argument's sake, that bees may 

 carry the blight on old trees, we must admit 

 that there is some agency, possibly the wind. 

 Prof. Waite to the contrary, that carries the 

 destructive microbe to the young shoots and 

 the young trees. There are some things that 

 are not explained yet. 



Again, I believe we have the right to i-nsist, 

 for the present, until we have more corrobora- 

 tive evidence that wild bees, other insects, and 

 birds, over which man has no control, may be 

 able to spread the blight just as much as the 

 bees under the control of man. For example, 

 this illustration was used : If a barrel full of 

 water has two plugs in it near the bottom, the 

 larger plug, represented by the tame bees, and 

 the other plug (the small one) by insects, 

 birds, and wild bees, will not the small plug 

 exhaust the barrel just as surely as the large 

 one ? If this be true the removal of the bees 

 controlled by man would not bring the relief 

 expected, by a long way. 



In conclusion, let me say that I visited the 

 worst-affected large pear-orchards in the vi- 

 cinity of Hanford, Cal. The large pear-grow- 

 ers were fair, intelligent men. While they 

 thought the bees were to blame, ihey also 

 thought the pear-men had some responsibility 

 in the matter. 



I visited one orchard of 120 acres, and every 

 tree was badly blighted, and no mistake ; but 

 in this orchard we found the badly blighted 

 little shoots I have referred to. 



