abstracts: mycology 329 



and Virginia region are either identical with or allied to species now 

 occurring in comparatively shallow water in the same general region. 



R. W. Stonb. 



MYCOLOGY. — Rhizoctonia in lawns and pastures. C. V. Piper and 

 H. S. CoE. Phytopathology 9: 89-92. February, 1919. 



Brown patches in fine turf have long been known, and, as they com- 

 monly occur in midsummer, have usually been ascribed to "sun scald." 

 Observation of the spots as they occurred in 19 14 near Philadelphia 

 furnished strong evidence that the cause was an organism, but the 

 pathologists who studied specimens failed to disclose the causal agent. 

 The abundant occurrence of the trouble in the vicinity of Washington 

 in 191 6 and since gave opportunity for study. The brown spots usually 

 appear in summer with the advent of hot moist weather and are most 

 conveniently studied on well-kept turf. The spots are at first small, 

 but increase rapidly in a concentric fashion, reaching a definite size 

 varying from a few inches to 2 or 3 feet in diameter, and then cease 

 spreading. In the early morning a fine white mycelium may be ob- 

 served over the discolored turf. Cultures from this as well as from 

 sclerotia on the stems proved the fungus to be the well-known Rhiz- 

 octonia solani. From artificial culture it was easy to induce the forma- 

 tion of brown patches in grass turf under favorable weather conditions. 



The fungus is known to attack an enormous list of herbaceous plants, 

 but strangely enough has never been reported as attacking any grass, 

 although there is one record of the occurrence of the mature form of the 

 fungus (Corticum vagum) on maize. 



Rhizoctonia is, however, very common in lawns and pastures and has 

 been observed by the authors in many places from Minnesota to Maine 

 and southward to the Ohio and Potomac Rivers. Among the plants 

 attacked are redtop, red fescue, Rhode Island bent, carpet bent, velvet 

 bent, Kentucky bluegrass, rough-stalked meadow grass, as well as many 

 lawn weeds. Crab-grass and Bermuda grass seem perfectly immune, 

 as is also white clover. 



Most of the grasses slowly recover in the brown patches with the 

 advent of cool weather in fall, but some are completely killed. Certain 

 strains of carpet bent and velvet bent grown in pure cultures near 

 Washington are especially injured by the disease but others are com- 

 pletely immune. Spraying at intervals with Bordeaux mixture helps 

 protect the grass tiu^, but such applications need to be frequent. 



C. V. P. 



