Pitch canker ratings of longleaf pine clones correlate with Fusarium circinatum infestation of seeds and seedling mortality in containers

The incidence and severity of pitch canker was rated among 16 clones of mature longleaf pine (Pinus palustris) in a seed orchard and cones were collected from five of those clones across the range of pitch canker disease ratings. Seed were extracted and commercially processed by clone and the percentages contaminated with Fusarium circinatum determined. Seed from each clone were sown either without treatment or with one of three fungicide treatments in a soil‐less mix at a commercial container nursery to evaluate the effects of F. circinatum (syn. F. subglutinans) on seed and seedling survival. The percent of seed with F. circinatum correlated with the pitch canker ratings in the orchard for the year of collection (r = 0.88, p = 0.05) and, when sown without fungicide treatment, with the number of seedlings produced (r = ?0.94, p = 0.01) and with seedling mortality after germination (r = 0.92, p = 0.02). The same orchard clones were more symptomatic of pitch canker through three annual surveys. Fusarium circinatum was isolated from a higher percent of seed from more symptomatic clones and a lower percent of their seed produced plantable seedlings. We propose that removing such clones from seed collections should reduce seedling mortality at the nursery.