Small Infestations of Seymeria cassioides (Scrophulariaceae) Reduce Growth of Potted Slash Pine. William F. Mann, Jr.,, Chief Silviculturist, USDA Forest Service, Southern Forest Experiment Station, Alexandria Forest Center, LA. Lytton J. Musselman, Department of Biological Sciences, Old Dominion University, Norfolk, VA 23508. Plant Dis. 65:748-749. Accepted for publication 20 January 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/PD-65-748.

Slash pine seedlings were grown alone and with one, three, five, and seven seymeria plants per pot to determine how seymeria affect pine growth in the first year. Each host had 16–233 haustoria. A single parasite did not affect growth of pines, but three or more reduced dry weight by 65% and also reduced diametric growth. Height was not affected. Many pines were chlorotic.

Keyword(s): parasitic weed, phanerogamic parasitism, Pinus elliottii, root parasite, semiparasite.