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Susceptibility of Pinus strobus and Lupinus spp. to Phytophthora cinnamomi. H. Walker Kirby, Former Graduate Student, School of Forest Resources and Department of Plant Pathology, North Carolina State University, Raleigh 27607; L. F. Grand, Associate Professor, School of Forest Resources and Department of Plant Pathology, North Carolina State University, Raleigh 27607. Phytopathology 65:693-695. Accepted for publication 25 January 1975. DOI: 10.1094/Phyto-65-693.

Two-year-old Pinus strobus seedlings were highly susceptible to Phytophthora cinnamomi in greenhouse and shadehouse tests. Symptoms include stunting of new growth, chlorosis, necrosis, drooping of necrotic needles, and decay of feeder and small lateral roots. Seedlings were inoculated by dipping roots into a water suspension of inoculum, or by incorporating infested oat grains into the soil. There was no difference in disease development between root-dip and soil inoculations. Seedlings grown in a saturated soil expressed symptoms earlier and died faster than seedlings grown in a nonsaturated soil. Lupinus albus ‘Tifton A-10’ and Lupinus angustifolius ‘Rancher’ were found to be reliable indicator plants for P. cinnamomi. Lupine seeds planted in pots with inoculated P. strobus seedlings often failed to emerge. Lupine plants which did emerge developed lesions at the root collar, became partially defoliated, blackened, and collapsed within 40 days after planting.