Epidemic of Lophodermium Needle Cast of Scotch Pine in Michigan. G. C. Adams, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. D. L. Roberts, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 72:801. Accepted for publication 28 June 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0801D.
A severe epidemic of needle cast caused by Lophodermium
seditiosum Minter, Staley & Millar (1) became evident in May 1987 in
Christmas tree plantations of Pinus sylvestris L. The disease was more
damaging on Scotch pine than any recorded Lophodermium epidemic
in Michigan in that some plantings of Scotch pine were uniformly
defoliated from the terminal to ground level. Trees in 34 counties in the
Lower Peninsula were damaged, with the most severe defoliation in
southwestern and southeastern counties. Counties that were inland or
north of Oceana County had more moderate levels of disease incidence
and severity. Climatic factors favoring this disease included abnormally
high precipitation in September 1986 (30 cm vs. the 7.6-cm average for
September [30 yr mean]). The repeat frequency for the unusual
September 1986 precipitation is a 200-yr period. Seed sources of P.
sylvestris varied in susceptibility, as evaluated by severity of defoliation,
and are ranked in order of decreasing susceptibility as follows: Pike
Lake, Turkish, Spanish, French, East Anglia, and Highland.
Identification was by G. Adams; voucher is deposited at MSU