990 



SCIENCE. 



[N. S. Vol. XV. No. 390. 



a very rapid growth of six to ten inches, and 

 three or four new full-grown leaves had devel- 

 oped on each twig, which were, of course, un- 

 protected by the spray. In a few cases these 

 leaves had become infected with fungi, prob- 

 ably the bitter rot fungus. At the time of the 

 fourth treatment, these leaves were, of course, 

 thoroughly covered with the mixture and pro- 

 tected from further infection, but it is inter- 

 esting to know that the two weeks' interval at 

 this period of rapid leaf formation was long 

 enough for leaves to form and become infected 

 with the fungus before they could be pro- 

 tected by the spray. The inference is that 

 the interval between the third and the fourth 

 spraying should in this case be shortened. 



Mr. Wm. A. Taylor called attention to some 

 field experiments recently made, to ascertain 

 in a practical way to what extent bees are 

 responsible for the spread of pear blight. In 

 these experiments, which were conducted by 

 Mr. Charles Downing in Kings County, Cal., 

 where blossom blight was very destructive 

 last year, the members of the association of 

 bee keepers agreed to remove their bees to a 

 minimum distance of two miles from the pear 

 orchards for the blooming season. It was 

 found during the blooming season that a con- 

 siderable number of swarms were left in the 

 area in question, including one lot of thirty 

 or forty swarms that had been overlooked. 

 Certain trees of P. Barry, Clairgeau, and 

 Bartlett pears were covered with mosqiiito 

 netting before the blossoms opened, to exclude 

 all the larger insects, including bees. When 

 the trees blossomed it was found that the trees 

 of P. Barry and Clairgeau, which blossomed 

 early, when nearby orchards of apricots and 

 peaches were in bloom, were little visited by 

 bees. Both covered and uncovered trees of 

 these varieties, to the number of 3,000, set a 

 full crop of fruit, with no blight infection 

 except on a few late blossoms. The un- 

 covered Bartletts, which blossomed later, 

 beginning just before the peaches and apri- 

 cots were through blooming, were well cov- 

 ered with bees almost from the start. The 

 blossoms on the uncovered Bartlett trees were 

 badly blighted, and very little fruit set on 

 them except from the first blossoms, which 



opened before the bees began their visits. On 

 the covered Bartlett trees more fruit 

 set than on any other Barlett trees in the 

 orchard. Some blossom blight appeared on 

 the covered trees, but upon examination some 

 dead bees were found inside the netting, which 

 had been slightly torn by storms. 



Mr. Downing estimates the financial loss on 

 his Bartlett pears last season due to blossom 

 blight at $10,000, and his loss on the same 

 variety this year from the same cause at 1,000 

 tons of fruit on 9,000 trees. He concludes 

 that so long as there are blight-infected pear 

 trees in his locality the crop of Bartletts will 

 be destroyed if the bees have access to them. 

 The fact that the covered trees set fair crops 

 of fruit appears to indicate that cross-polli- 

 nation of Bartletts was not necessary in that 

 locality this season. 



In the discussion of pear blight in Califor- 

 nia, Mr. Waite stated that the blight bacteria 

 were usvially carried from the gummy exuda- 

 tion of hold-over cases by flies and wasps, flies 

 being the principal agents in the transporta- 

 tion of the virus. After the first blossoms 

 have been infected in this manner, the regu- 

 lar flower-visiting insects, of which the com- 

 mon honey bee and the sweat bees, belonging 

 to the genera Halictus and Andrena are exam- 

 ples, earrj' the disease from one blossom to 

 another. These flower-visiting insects are 

 very efficient in transporting the disease, and 

 other things being equal, the later a pear 

 blooms the more complete its infection. If 

 our pomaceous fruit blossoms continued to 

 open during the summer, the destruction by 

 pear blight would doubtless be almost com- 

 plete. Ordinarily the closing of the bloom- 

 ing period terminates the multiplication and 

 distribution of the disease. 



Mr. M. A. Carleton discussed 'The Spread 

 of Smut and Bunt in Wheat as affected by 

 Dry Seasons and the Earliness of Varieties.' 

 It has been pretty well known for some time 

 that smut and bunt in cereals are much more 

 prevalent in dry seasons and in dry regions. 

 Experiments and observations made by the U. 

 S. Department of Agriculture have also shown 

 that these fungi, when attacking wheat par- 

 ticularly, are more likely to appear in earl.y 



