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 trees in the NC-140 'Starkspur Supreme Delicious' plantings located in Iowa (IA), Kansas (KS) Massachusetts (MA) Maine (ME), Missouri (MU), North 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 MA, NC, NOS, NY, and VA had the least amount of damaged xylem tissue. Overall, trees on B.9. P.2, P.16, and P.22 were more susceptible to blackheart injury than those on B.490, MAC.1, C.6, and MAC.39. Tracing the area of the discolored xylem and the total xylem area and then calculating the percent blackheart injury on. weight basis resulted in a better separation of injury among rootstocks than estimating blackheart by other methods.