HAUSTORIAL FREQUENCY OF SOME ROOT PARASITES IN CULTURE

Summary Seventeen root parasites representing nine genera in three families native to the southern United States were grown with 19 tree species to determine host preference and host susceptibility. Trees were grown in pots with a single parasite. After about 12 months the plants were removed and the number of haustoria noted. The number of haustoria or haustorial frequency were interpreted as a rough index of the suitability of that tree to serve as a host. All parasites showed a broad host range indicating little host specificity. In addition, none of the hosts were immune to parasitism. A few plants behaved as complete autotrophs, even though host roots were in physical contact with those of the parasite.