465 



plant, experiments show that the sucking insects are the most important 

 agents, as they often deposit the bacteria in the punctures they make 

 in the plant tissues. An account is given of experiments to determine 

 the extent to which certain sucking insects act as such agents. Shoots 

 of certain plants were smeared with the agar culture of B. amylovorus 

 and specimens of different insects were caged, first over the smeared 

 plant and secondly over a healthy plant, and the extent of the injury 

 conveyed from one plant to the other was observed. These investiga- 

 tions showed that the bugs, Canipylomrna verbasci, H.S., Orthotylus 

 Jlavosparsus, Sahl., Poedloscytus basalis, Kent., and Adelphocoris 

 rapidus, Say, all spread the bacteria over young apple seedlings. The 

 first two were specially active disseminators, their attacks being chiefly 

 confined to the tips of the shoots. It is however noted that sucking 

 insects may be present in great numbers without the occurrence of 

 much blight, owing perhaps to the absence of cankers to furnish a 

 source for blight infections and the unfavourable condition of the trees 

 for infection. Thus in 1914, one large nursery was seriously injured by 

 B. amylovorus, conveyed from a neighbouring nursery stock ; here, 

 there had been abundant rainfall during July and August. In another 

 nurser}^ similarly situated near an infected nursery, but where the 

 rainfall had been light, practically no blight was observed. Lijgus 

 invitus, Say, is thought to convey the blight on pear trees, and it is 

 suggested that certain species of flies which are attracted to the gummy 

 exudations of blighted trees, also act as disseminators. 



True (A. C). Report on the Work and Expenditure of the Agricultural 

 Experiment Stations during the year ended 30th June 19i3.-~U.S. 



Dept. Agric, Washingfon, D.C., 5th February 1915, 109 pp. 

 6 plates. [Received 9th July 1915.] 



In Alabama, additional data regarding the life-history of the rice 

 weevil {Ccdandra oryzae) were secured and practical means of control 

 worked out. In granaries and mills a temperature of 120°-150° 

 destroyed the insects and their eggs without injuring the grain. Experi- 

 ments conducted with fumigants at the Kentucky Station, indicated 

 that the use of hydrocyanic acid gas, carbon bisulphide and carbon 

 tetrachloride had apparently not affected the germinating powers of 

 the seeds under test. A volumetric method for the analysis of lime- 

 sulphur solutions was devised. In Montana, a complete life- history 

 of Pemphigus betae, the sugar-beet root-louse, was worked out and an 

 effective means of control by methods of applying irrigation water 

 was estabhshed. The subjects given chief consideration by the 

 Nebraska station were insect parasitism, life-history and control of 

 the European elm scale {Gossyparia spuria) ; and by the New Hampshire 

 station, the control of root and apple maggot and black fly, the use 

 of fungicides and insecticides and their effect on plants, and the effect 

 of temperature in the preparation of Bordeaux mixture. Obser- 

 vations on cotton and melon aphis {Aphis gossypii) showed that this 

 insect can be controlled by spraying with 1 part Black Leaf 40 in 900 

 parts of water. The study of the wireworras Ilorislonolus uhlcri and 

 Monocrepidiits vesperlinus was continued in South Carolina. These 

 insects oviposit in June and July and the adult requires loose soil for 

 oviposition. 



(C180) D 



