Sporulation on infected tissues, and presence of airborne Verticillium albo‐atrum in alfalfa fields in New York

The phenology of Verticillium albo-atrum (Vaa) sporulation on infected tissues and the presence of Vaa in the air were investigated in alfalfa fields affected by verticillium wilt (VW) during the 1983/84 growing season. Few and scattered Verticillium conidiophores developed on stubble by the end of May, but abundant Verticillium sporulation was found on necrotic leaflets and petioles by the beginning of June at the first appearance of symptoms. Abundant conidiophores developed also on necrotic stems and leaf tissues sampled later. Sporulation was never found on entirely green stems. Concentration of airborne colony-forming units (cfu) of Vaa ranged from 0.0 to 15.3 cfu/m3 above fields with a VW incidence of 2.2-33.0% in June and August, and from 5.9-25.9 cfu/m3 during mowing of the crop in August. The ratio of Vaa to other airborne fungi above sampled fields was less than 5 x 10-3, Airborne fungi were even more abundant at the time of mowing. Our results suggest that airborne V. albo-atrum may not play an important role in the epidemiology of VW of alfalfa.

[1]  E. Kokko,et al.  Role of the leafcutter bee in dissemination of Verticillium albo-atrum in alfalfa , 1986 .

[2]  D. L. Stuteville.  First Report of Verticillium Wilt of Alfalfa in Kansas , 1986 .

[3]  R. Jiménez-Díaz,et al.  Lack of systemic colonization of alfalfa plants after inoculation of uninjured leaves with conidia of Verticillium albo-atrum , 1986 .

[4]  A. Keinath,et al.  Persistence of an alfalfa strain of Verticillium albo-atrum in soil. , 1986 .

[5]  C. Grau,et al.  Importance of Verticillium Wilt of Alfalfa in North America , 1985 .

[6]  A. M. Harper,et al.  Contamination of Insects by the Plant Pathogen Verticillium albo-atrum in an Alfalfa Field , 1984 .

[7]  R. Howard,et al.  Aphid transmission of Verticillium albo-atrum to alfalfa. , 1983 .

[8]  A. A. Christen.  Incidence of external seedborne Verticillium albo-atrum in commercial seed lots of alfalfa. , 1983 .

[9]  A. A. Christen.  Demonstration of Verticillium albo-atrum within alfalfa seed. , 1982 .

[10]  R. N. Peaden,et al.  Verticillium wilt in alfalfa. , 1981 .

[11]  J. Sheppard,et al.  Verticillium wilt of alfalfa in Canada: Occurrence of seed-borne inoculum , 1980 .

[12]  J. H. Graham,et al.  Verticillium wilt of alfalfa found in the United States. , 1977 .

[13]  H. C. Smith.  The morphology of Verticillium albo-atrum, V. dahliae, and V. tricorpus , 1965 .

[14]  J. B. Heale,et al.  Wilt of Lucerne caused by species of Verticillium. IV. Pathogenicity of V. albo-atrum and V. dahliae to Lucerne and other crops; spread and survival of V. albo-atrum in soil and in weeds; effect upon Lucerne production. , 1963 .

[15]  P. Talboys.  A CULTURE‐MEDIUM AIDING THE IDENTIFICATION OF VERTICILLIUM ALBO‐ATRUM AND V. DAHLIAE , 1960 .

[16]  A. T. Lloyd,et al.  WILT OF LUCERNE CAUSED BY SPECIES OF VERTICILLIUM.: II. SEASONAL CYCLE OF DISEASE; RANGE OF PATHOGENICITY; HOST-PARASITE RELATIONS; EFFECTS OF SEED DRESSINGS , 1959 .

[17]  R. Davies,et al.  Dissemination of Verticillium albo-atrum through the Atmosphere , 1958, Nature.

[18]  I. Isaac.  WILT OF LUCERNE CAUSED BY SPECIES OF VERTICILLIUM , 1957 .