46 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



them. On the same date, transfers were made by a sterile needle from 

 a pure culture of the organism to lesions in the succulent growth of 

 several other twigs. Although observations were made on all of these 

 trees until the 13th of October, no traces of blight were noticed. On 

 the 25th of August, infected aphids were placed on four Yellow Trans- 

 parent and four Jonathan trees, but the results were similar to the first 

 experiment. 



During the month of September, the average maximum tempera- 

 ture was 80.3° and the total rainfall was 8.12 inches. The apple trees 

 now began to put forth new, tender growth, producing conditions more 

 nearly approximating those of spring w^hen blight is ordinarily more 

 prevalent. 



On the 25th of September, infected aphids were placed on nine Yellow 

 Transparent, two Jonathan, one Delicious, one Winesap, and one Ben 

 Davis apple trees. Although brown spots appeared on the leaves and 

 terminal buds of some of the Yellow Transparent trees, no clear cases 

 of blight were discovered. On the 7th of October, the Jonathans 

 began to exhibit signs of blight, which became well developed cases by 

 the 10th of October. The other varieties did not blight. 



During the first thirteen days of October, while observations were 

 being made on these trials, the average maximum temperature was 

 77 degrees and the total rainfall for that period was .9 of an inch. 

 The apple trees developed considerable new growth during the early 

 part of the month. On the 3d of October, infected aphids were placed 

 on three Jonathan and four Yellow Transparent trees. The blight 

 made' its appearance on October 5 when the leaves began to turn 

 brown, increasing daily until, on the 13th of October, all of the twigs 

 showed well-developed cases of fire-blight (PL 2, Figs. 3 and 4). 



Summary 



1. The blight developed only in the tender succulent growth on the 

 twigs. 



2. By hatching from eggs laid in blight cankers, the aphids come in 

 contact with the fire-blight organism. 



3. Aphids can and do inoculate trees with the bacteria of fire-blight. 



4. The amount of fire-blight infection in an orchard may be materi- 

 ally jiecreased by destroying all of the aphids which may appear there. 



Vice-President G. A. Dean: This paper is now open for discus- 

 sion. 



Mr. M. T. Smulyan: I would like to ask what species of aphids 

 were utilized in these experiments. 



Mr. J. H. Merrill: Green. 



