MISCELLANEOUS 433 



deformed, and may rot completely. The best remedial measure for stop- 

 ping spread of the disease is removal and burning of all diseased portions of 

 plants. In greenhouses disease-free soil should be used and plants grown 

 at low humidities and without over-watermg. Sulfur fungicides, copper 

 lime dust, and Bordeaux are effective if the plants are sprayed before the 

 disease starts and frequently enough thereafter to maintain a protective 

 cover. 



Besides the lily pests mentioned in Guterman's summary, the follo\\ing 

 were later studied and reported upon under this fellowship : Penicillium rot 

 of lily bulbs,^^ a cecidomyid larva of lily stems, ^^ bulb rots of lilies, ^^ and 

 some insect pests of Ulies.^^ Some other work done has not yet been pub- 

 Ushed. 



Dahlia mosaic. A survey showed that dahlia mosaic "-^^ jg prevalent 

 throughout Connecticut, New York, and New Jersey. It is probably dis- 

 tributed widely. All members of the genus are susceptible, but there are no 

 suspects outside the genus. Mosaic is not synonymous with "stunt " which 

 is applied to the less tolerant varieties that are stunted by mosaic and by 

 certain insect injuries. The symptoms of the disease on the less tolerant 

 varieties are chlorosis, leaf distortion, shortening of internodes and flower 

 stems, and vein necrosis. The more tolerant varieties that are not stunted 

 by mosaic had been overlooked as carriers of the disease by the earlier 

 American work on dalilia stunt. The mosaic is carried in the tuber and 

 other vegetative parts of the plant but is not transmitted through the seed ; 

 also it has not been transmitted mechanically. It can be transmitted to 

 all varieties by grafting and manifests itself with marked or shght symp- 

 toms on the various varieties in line ^A-ith their tolerance. 



Myzus persicae seemed to be the specific insect vector of the disease. 

 Other insects tested did not transmit the disease. Its symptoms appear in 

 the plants four weeks or longer after insect transmission. Since dahlia is 

 not a preferred food of the insect, the disease spread is at the rate of 10 

 to 25 per cent of the crop per year. The disease is controlled by selection 

 and isolation of disease-free plants along with control of aphids during 

 early growth and roguing during later growth. Tolerant varieties, if 

 growTi at all, should be isolated from those showing marked s^inptoms 

 of the disease. Seedlings are free from the mosaic untU infected by 

 the insect. The infected tuber, of course, carries the disease to the plant 

 gro^^•n from it. Ring spot, yellow ring spot, and oak leaf are three other 

 virus diseases of the dahlia studied by Brierley. The researches indicate 

 that they too are specific dahha diseases. 



Propagation of Trailing Arbutus and Lycopodium 



Abundant moisture, protection from excessive sunlight and probably 



the presence of a mycorrhizal fungus in the soil are necessary for rooting 



trailing arbutus.^ Vigorously growing plants bore well-developed coils of the 



endophytic fungus in the roots; stunted plants showed little or no fungus 



