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Disease Note. Two New Ornamental Hosts for Phytophthora cactorum: Trachymene caerulea and Gypsophila paniculata. R. L. Wick, University of Massachusetts Suburban Experiment Station, Waltham 02154. K. K. Rane, and D. P. Sutton. University of Massachusetts Suburban Experiment Station, Waltham 02154. Plant Dis. 71:281. Accepted for publication 1 December 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0281D. The landscape perennials blue laceflower (Trachymene caerulea R.
Grah.) and baby's breath (Gypsophila paniculata L.) are field-grown
for the cut-flower industry. A wilt of blue laceflower and of baby's
breath was found to be caused by Phytophthora caetorum (Lebert &
Cohn) Schroeter. Ten blue laceflower and 10 baby's breath plants were
inoculated with 25 ml (per pot) of a washed and blended mycelial
suspension. All inoculated blue laceflower and four baby's breath plants
died within 6 wk. Under field and experimental conditions, root, crown,
and stem rot developed in blue laceflower and root and corm rot caused
wilt of baby's breath. Morphologically, the blue laceflower and baby's
breath isolates were nearly identical and were identified by the following
characteristics (all measurements are average diameters): homothallic;
sporangium papillate, mostly ovoid, 28.8 X 22.5 p.m (18-40 X 11-30),
I/b ratio 1.3; oogonia light golden brown, 29.2 p.m (25-35); oospores
25.2 p.m (21-33); antheridia paragynous, 11.0 p.m (8-13); hyphae, 4.6
p.m (2-7). When the blue laceflower and the baby's breath isolates were
grown on cornmeal agar amended with 35 mg/L of hymexazol (I),
radial growth was reduced by 50 and 75%, respectively. |