May 1, 1920 Artificial and Insect Transmission of Mosaic 133 



houses at Washington. The insects used were those at hand which 

 were known to feed on sugar cane. Provision has been made by coop- 

 eration with the Bureau of Entomology to collect im'ormation leading 

 to the identification of the particular insect or insects responsible for 

 secondary infections in the infested cane regions. ]Mr. George N. Wol- 

 cott, of the Bureau of Entomology, is at present working on that phase 

 of the problem in Porto Rico. 



EXPERIMENTS AT GARRETT PARK, MD.i 



Seed pieces from diseased parent stock were received from time to 

 time during 19 18 and 1919 and planted in the greenhouse, which was 

 screened with physician's cloth so that insects could not escape. On 

 August 10, 1918, a shipment of diseased Crystalina cane from Ensenada, 

 P. R., was planted. Yellow Bantam sweetcorn and Sugar Drip, Early 

 Amber, and Japanese Ribbon sorghum were planted August 13, 1918, 

 in the same greenhouse. On September 24, 1918, a shipment of dis- 

 eased Rayada cane from Rio Piedras, P. R., was planted. Diseased 

 seed pieces of Morado, Yellow Caledonia, Crystalina, and Rayada 

 varieties from Arecibo, P. R., were planted on April 24, 1919. Similar 

 pieces of Selangore, D.-117, and Rayada from Mayaguez, P. R., were 

 planted on April 25, 1919. Lastly a shipment from Yauco, P. R., con- 

 taining diseased seed pieces of G. C.-701, G. C.-1486, B.-3922, B.-6450, 

 and P. R.-260 were planted May i, 1919. 



Through the kindness of Dr. Erwin E. Smith, cuttings of Lahaina cane 

 were secured from plants which had been growing in one of his green- 

 houses at Washington for more than six years and showed absolutely 

 no signs of mosaic. These cuttings were planted in pots in a third 

 greenhouse at Washington on December 10, 191 8. All the cane, diseased 

 and healthy, sprouted and grew well. All cuttings from diseased par- 

 ents produced mottled sprouts, without exception, and all cuttings 

 from Dr. Smith's healthy cane produced in great contrast healthy plants 

 with leaves of uniform dark green color. 



Experiment i. — This was a preliminary experiment to determine 

 whether infection could take place by natural means, merely by exposing 

 healthy plants in the same greenhouse with diseased plants. On May 10, 

 1 91 9, 5 healthy cane plants, 5 months old, in pots were taken from the 

 greenhouse in Washington and placed in the quarantine greenhouse at 

 Garrett Park, Md., in such a way that the leaves did not come in contact 

 with the leaves of diseased plants. At that time the corn aphis (Aphis 

 maidisY was abundant on the sorghum. The wild grasses, a few clumps 

 of which came up as weeds in the greenhouse, were infested with red 

 spiders {Tetranychus hinaculatus) . Both these insects were seen occasion- 

 ally in the cane. A small leafhopper was also seen but was not captured 



' Thanks are due Dr. Caroline Rumbold, who was in charge of this work during the writer's absence 

 on trips to the Tropics. 

 '' Identified by Dr. A. C. Raker, of the Bureau of EntomoIo£y, United States Department of As,rictilture. 



