154 EXPERIMENT STATION KECOED. 



A list is also given of the plant diseases observed during 1914, the list being 

 arranged alphabetically according to host plants. 



Department of botany, C. R. Okton (PennJiylvania Sta. Rpt. 1913, pp. l-'fl- 

 151). — A progress report is given of a study of the apple collar rot and its con- 

 trol, winter blight or spring disease of tomatoes, the effect of soot and included 

 gases on growing plants, apple rust, chestnut blight, a plant disease survey of 

 Pennsylvania, and an investigation of the practical value of asphaltum as a 

 dressing for cuts and wounds on fruit trees. 



In connection with the apple collar rot investigations, some organisms have 

 been isolated, and inoculation experiments ai*e luider way for the determination 

 of their connection with the disease. As a result of investigations on its con- 

 trol, the author recommends cutting out the wounds and dressing with asphaltum, 

 provided the injury is in its early stage. 



The winter blight or spring disease of tomatoes seems to be limited to green- 

 house growing of this vegetable, and experiments in which root material, soil, 

 and lesions of stem, leaf, and fruit were tested as causes of this disease, were 

 carried out without definite results. The study of the soil suggests that there is 

 a possible correspondence to the amount of acidity in the soil rather than any 

 particular element. 



An attempt was made to determine the length of the period of germination 

 and sporidial formation on the red cedar, with weather conditions influencing the 

 same, and also, if possible, to determine the susceptible period of infection l)y 

 apple rust for the apple leaves and fruit. Bagging experiments were carried out 

 on wild cral>-apple trees in close proximity to re<l cedars abundantly infected 

 with Gyninosporangium. Tliere appears to be a fairly definite period in the de- 

 velopment of the leaves when tliey are most susceptible to infection from the 

 cedar. AVhether this is primarily due to an inherent resistance in the apple 

 leaves at certain periods, or whether it is caused by atmospheric conditions 

 favorable to the germination of the rust spores has not been determined. 



In the investigations with asphaltum as a dressing for cuts and wounds, 7 

 different forms were used and compared with G forms of dressings more or le.ss 

 in conmion use. Particular attention was paid to the healing, persistence, fun- 

 gicidal value, waterproof qualities, and the ease with which the compound may 

 be applied. The conclusions drawn from the preliminary observations indicate 

 that serious checking tonds to prevent healing; if small wounds are not smoothly 

 made, healing will be arrested; innnediate application of asphaltum prevents a 

 tendency of the bark to pull away from the cambium, and healing rosults very 

 quickly ; applications made in the stimmer did not heal as quickly as cuts made 

 in the spring; in general, results favor this substitute as offering a cheaper and 

 more effective Avound dressing. 



Sulphur arsenical spray injury and its prevention, J. P. Stewakt {Pcnn- 

 s}/lvonia Sta. Rpt. 1VJ2, pp. 571-578, pi. 1). — This is a reprint in sliglitly modi- 

 fied form of the address previously noted (E. S. R., 28, p. 48). 



Perennial mycelium in species of Peronosporacese related to Phytophthora 

 infestans, I. E. IMeliitjs (f'. S. Dcpt. Agr., Jour. Afir. Rcsrarrh, 5 (IP 15). Xn. 2. 

 pp. 50-70, pi. 1, fig. 1). — The author gives results of experiments and observa- 

 tions on several North American species of Perono-sporacere, viz, Pcrnnospnra 

 parasitica, P. ficario', P. ririo', Ci/stopus raHfiidu.'i, and Planmopara halstcdii, 

 comparisons being made with Phytophthora infcMan.i. The results obtained 

 indicate that several species of these four genera may be perennial in the tis- 

 sues of their hosts, the mycelium passing the winter either In the aerial or In 

 the underground organs of winter annuals, biennials, or perennials. 



A list of literature cited is given. 



