248 EXPERIMENT STATION RECOED. [Vol. 41 



A fungus disease of prickly pear, G. 1'. Dakneix-Smith and H. Ross {Agr. 

 Gaz. N. S. Wales, 29 {1918}, No. 6, pp. UO, Ul, fig. i).— At Harrington Inlet on 

 the Manning River, a disease affecting tlie pest prickly pear {Oimntia inermis) 

 was studied by the authors, who found many of the young segments dead 

 and older ones rotten and filled with slimy pulp. Others showed a sickly 

 yellow color in areas where diseased segments had been thrown into clumps 

 of healthy plants. The infection usually starts at or near the base of the seg- 

 ments, being marked by concentric dark lines in the latter case. The disease 

 may, it is thought, afford means of control for prickly pear. 



Influence of soil environment on the root rot of tobacco, J. Johnson and 

 R. E. Haetman {.Jour. Agr. Research [U. K.], 17 {1919), No. 2, pp. 1,1-86, pis. 

 8, figs. 2). — A report is given of a study undertaken cooperatively by the Wis- 

 consin Experiment Station and the Bureau of Plant Industry, U. S. Dejiart- 

 ment of Agi-iculture, with a view of determining the environmental conditions 

 which might influence the tobacco root rot caused by Thiclavia basicola. 



There seems to be no variation in the patliogenicity of the fungus secured 

 from different sources, the amount of disease l)eing determined by the suscepti- 

 bility of the host, the amount of infection, and the soil environmental factors 

 surrounding the roots of the host. IMoisture, temperature, reaction, physical 

 structure, and fertility of the soil were investigated, and mider normal condi- 

 tions the amount of injury due to root rot is said to be determined by the 

 sum total of the favorable and unfavorable action of these factors on the 

 disease. Root rot is apparently capable of developing in relatively dry soils, 

 but increasing the moisture content up to three-fourths of the water-holding 

 capacity was not found to materially increase the amount of disease. Saturated 

 soils, however, are considered more favorable to the disease than unsaturated 

 ones. 



Studies of soil temperature carried on for four seasons have indicated that 

 the occtirrence of root rot is determined primarily by soil temperature, the most 

 favorable temperature for the disease ranging from 17 to 23° C. Below 15° 

 the disease is less marked, and above 2G° the severity is gradually reduced 

 until, at about 29 or .30°, the disease has little or no influence. At 32° prac- 

 tically no infection occurs, even in the most heavily infested soils. 



Root rot is said to be checked by high soil acidity, but tests of tobacco soils in 

 Wisconsin indicate that the use of acid fertilizers will not reduce infection by 

 T. haMcola. Organic matter present or introduced into the soil was not found 

 to play an important part in the amount of infection, although a high organic 

 content of the soil is believed to favor infestation and also to aid the fungus 

 in persisting in the soil. Clay soils were found no more favorable to infection 

 than sand and under some conditions possil)ly less so. Clay may, however, 

 favor the persistence of the parasite in the soil. Fertilizers applied to heavily 

 infested soils under practical conditions are considered to be largely wasted 

 except in seasons in which such high temperatures result that the disease is held 

 in check. Field observations, as well as limited laboratory experiments, are 

 thought to show that infested soils when compacted are more favorable to the 

 disease than loose, open soils. Transplanting infected seedlings to an uninfested 

 field is considered a bad practice, allhough recovery from the disease may 

 occur. 



Fruit insect and disease control, L. R. TTeslkk {Ept. N. Y. fitatc Food Com. 

 S<itp., 1911, pp. .'?f»-.'?S).— Brief notes are given of the working of a plan employ- 

 ing, besides ordinary means, an extensive tc^lejihone relay system organized in 

 some counties of New York, over whicli the field agent in Wayne County was 

 able to send out two days before a rain period was due the recommendation 



