THE DAMPING OFF OF TOBACCO AND ITS CONTROL IN PUERTO RICO

Resumen en inglé

MANGO WITHER-TIP (Colletotrichum gloeosporioides Penz.)

Resumen en inglé

THE ANTHRACNOSES OF CITRUS FRUITS, MANGO AND AVOCADO

(1) Colletotrichum glocosporioides Penz. appears to be the cause of the anthracnose diseases of mango, orange, grapefruit, lemon, avocado, and sometimes of lime. (2) Lime wither-tip may be caused by either G. gloeosporioides or Glocosporium limetticolum Clausen. (3) Collelotrichum gloeosporioides Penz. frequently causes spotting of lime blossoms and the wither-tip. It is also the cause of the spots on lime thorns. The latter is demonstrated by cultures L 9- L, 13, inclusive, which behaved like other G. gloeosporioides cultures and very distinct from cultures of G. limetticolum. (4) Glocosporium limetticolum Clausen is the cause of wither-tip· ancl leaf spot of limes. (5) G. limetticolum appears to be the only cause of fruit canker or fruit spot of limes. (6) Under artificial conditions the various cultures of G. gloeosporioides and G. limetticolum exhibit distinct cultural characteristics. (7) Cultures from the avocado differ somewhat from cultures obtained from other hosts in cultural characteristics. The difference may not furnish enough evidence for their separation into a new species. (8) There are such differences between most cultures from the lime and all cultures from the other hosts that Clausen's (5) separation of the former into a distinct species appears to be justified. (9) The four most salient growth characters in which cultures of C. gloeosporioides varied from cultures of G. limetticolum or such cultures among themselves are: (a) size, number, and arrangement of acervuli; (b) color of acervuli and substratum; (c) character of aerial mycelium; (d) size of colonies. (10) C. gloeosporioides can resist slightly more acid or alkaline concentrations than G. limetticolum. (11) Setae are occasionally present in C. gloeosporioides and absent in G. limetticolum. (12) Variation in spore size is induced by the culture medium. (13) There is great morphological similarity between G. limetticolum and C. gloeosporioides. (14) Environment induces variation in form and shape of spores. (15) The character of conidia appears to be rather uncertain for distinguishing between Gloeosporium limetticolum gloeosporioides

THE DAMPING-OFF OF TOBACCO AND ITS CONTROL IN PUERTO RICO

1. Damping-off of tobacco is a very severe disease in Pu erto Rico. 2. The disease is caused by Pythium debaryanum and Phytophthora Parasitica var. nicotianae. 3. The agents of transportation of the fungus are water currents, laborers, animals, burrowing insects, etc. 4. Leaves are infected by zoospores of Phy. Parasitica var. nicotianae but apparently not by those of P. debaryanum. 5. Environmental conditions are important factors influencing the spread and severity of the disease. The disease seems to be equally severe during all seasons provided the proper moisture relations are maintained. Organic manures seem to influence favorably the incidence of the disease. The disease is severe on thickly-sowed beds. 6. Control of damping-dff of tobacco is today one of the most serious problems with Puerto Rico tobacco growers. 7. When the disease appears in small areas only, it may be checked by drenching these with a 1-30 formaldehyde solution. 8. Soil disinfestation by means of steam or with formaldehyde does not seem to be practicable under Puerto Rican conditions. 9. Phy. Parasitica var. nicotianae is probably slightly less susceptible to the sterilizing action of formaldehyde than P. debaryanum. 10. Mercury compounds have been found injurious to tobacco seedlings, and ineffectiYe against the clamping-off pathogenes. 11. In preliminary trials two applications of Corona Copper carbonate of four grams per square foot, before seed sowing, and at the same rate a week after germination, were fairly effective. Two applications of copper carbonate in the field did not give effective control probably due to the heavy rains and to overcrowding of the seedlings. Two late applications of copper carbonate on heavily infected beds were unsuccessful. Two 4-gram applications of copper carbonate resulted in good control of the damping-off of tomato, pepper, and eggplant. 12. Copper stereate, in two applications of 4 grams each, seemed to control P. debaryanum but did not have any effect on Phy. Parasitica var. nicotianae. 13. Bayer dust and Uspulun were injurious when applied to the foliage and proved to be ineffective in the control of the disease. 14. Copper sulfate solutions (4 and 5 pounds to 50 gallons) applied at the rate of 1/2 gallon per square foot before sowing the seed were ineffective. 15. Effectiveness of copper fluosilicate is doubtful. 16. Acetic acid does not control the disease under conditions of high infection. 17. Two applications of 4-4-50 and 5-5-50 Bordeaux mixture at the rate of 1/2 gallon per square foot, one before sowing the seed and the other a week after germination, were effective in controlling damping-off. The treatment was not very successful when applied to beds in the field in which the disease had made its appearance. 18. Injury to seedlings resulted when copper carbonate was applied to a tobacco seed-bed on the site of an old bed. It was proved by experiment that the injury was not clue to dryness. Soil reaction appears to have little to do as a direct cause of the injurious action. No injurious action of formaldehyde or acetic acid was found under similar conditions. Charcoal was not effective in preventing injury from the copper compounds. Recovery from injury resulted in one case when a sodium nitrate solution was applied. It is suggested that the injurious action is connected with nitrification which would be hindered by the lasting effect of the copper treatments. 19. Continuous cultivation of infested soils for periods of six to twelve months does not eradicate the disease

Contenido polínico de la atmósmera de Cataluña: resultados año 1983

Se presentan al gunos de los resultados obtenidos hasta e l momento en el Programa de estudio del contenido en polen de la atmósfera de Cataluña y Bal eares: gráficos de pol en total y de al gunos taxones i mportan tes de Barcelona, Bellaterra (U ni v. Aut ónoma de Barcelona), Girona ( aeropuerto ) , LLeida y Tarragona; gráfico de comparación de resul tactos obtenidos a partir de dos metodologías distintas de captación aplicadas a una misma estación y calendario polinice para la estación de Barcelona. Todos e l l os correspond en al año 1983.The r esults we present here are t he preliminary e nes (year 1983) o f a Study Program about atmospheric pol l eo content at severa! s i tes in Cataluña and Baleares. The annual trends of al! taxa considered coll ecti ve l ly and for sorne of the most important enes for Barcelona , Be l laterra (Univ. Autónoma de Barcelona) , Girona { airport), Lleida and Tarragona are compared. In addition we compare the effici ency of two di f ferent designs of pollen traps f rom the same local i ty. Final ly we provide the pollinic calendar of Barcelona

Ampurias en la Antigüedad Tardía. Una nueva perspectiva

Traditional historiography has always maintained that during the Late Antiquity period, the city of Ampurias represented no more than a faint shadow of its former greatness. However, a careful reading of the data and a body of new evidence, both textual and archaeological, allow us to establish the facts in a very different way and to recognize that this stage in its history was a very important one for the city, which was an episcopal see and the most active port in a very vast territoryLa historiografía tradicional ha venido sosteniendo que durante la Baja Antigüedad la ciudad de Ampurias no era otra cosa que el fantasma apenas tangible de su lejana grandeza. Sin embargo, una lectura atenta de los datos y un conjunto de nuevas evidencias, textuales y arqueológicas, permiten plantear los hechos de manera bien distinta y reconocer, para esta etapa histórica, un período de gran importancia para la ciudad. sede episcopal y el puerto más activo de un vastísimo territorio