BLACKHEART INJURY IN STARKSPUR-SUPREME-DELICIOUS ON 15 ROOTSTOCKS IN THE 1984 NC-140 COOPERATIVE PLANTING

Blackheart injury was evaluated at 25 cm above the soil surface on tre es in the NC-140 'Starkspur Supreme Delicious' plantings located in Io wa (IA), Kansas (KS) Massachusetts (MA) Maine (ME), Missouri (MU), Nor th Carolina (NC), Nova Scotia (NOS), New York (NY), Quebec (QUE), and Virginia (VA) after 10 years growth. Trees grown in IA, KS, MO and QUE exhibited the greatest amount of blackheart, whereas those grown in M A, NC, NOS, NY, and VA had the least amount of damaged xylem tissue. O verall, trees on B.9. P.2, P.16, and P.22 were more susceptible to bla ckheart injury than those on B.490, MAC.1, C.6, and MAC.39. Tracing th e area of the discolored xylem and the total xylem area and then calcu lating the percent blackheart injury on. weight basis resulted in a be tter separation of injury among rootstocks than estimating blackheart by other methods.