Dispersal and survival of seed of eastern dwarf mistletoe

Seed dispersal of eastern dwarf mistletoe (Arceuthobiumpusillum) parasitizing black spruce (Piceamariana) in the Fond du Lac State Forest, Carlton Co., Minnesota, U.S.A., began in the 1st week of September and continued until the first frost. Most seeds were discharged during the first 3 h after sunrise. Seed expulsion was a function of rising temperature during that time. The mean horizontal distance travelled by discharged seeds was 1.65 m. One seed travelled 13.7 m. Freezing temperatures on August 31, 1970, caused nearly complete fruit abortion in that year of the study and caused a substantial reduction in seed discharge in the other 2 years. Of 3200 seeds placed on the needles of healthy black spruce in September 1971, only 6.5% of the seeds had germinated by August 1972.