Apple trees, Blackheart Injury, and rootstocks

A Review of the Literature by Dr. Curtis E. Swift, Area Extension Agent, Horticulture
Colorado State University Extension
Tri River Area

Wholesale nurseries bud graft apples onto rootstocks for resale to nurseries and garden centers. At times, retailers are unaware which rootstocks were used to produce their trees, or what effect rootstocks have on the survivability of the tree. With new dwarfing apple rootstocks being developed every few years, nursery personnel need to stay abreast of research being conducted and request wholesale nurseries provide the best quality trees available.

Blackheart injury is a debilitating factor effected by both rootstock and apple cultivar. Blackheart, a form of winter injury resulting in the killing and plugging of xylem tissue, is so named due to the resulting oxidative brown or black discoloration of the xylem. Blackheart may not cause the outright death of the tree but has been implicated in tree decline and reduced productivity. It has been reported that damage may not be apparent when less than 20% of the xylem is injured, while trees sustaining greater than 50/% injury may not recover (Steinmetz, 1937). Due to the weakened condition caused by Blackheart injury, insect and disease pests may invade and cause irreparable damage to these damaged trees.

The susceptibility of various apple rootstocks to Blackheart was reported in 1991, 1996, and 2001. These 10 year, multilocation site studies culminated with the trunks being severed 8 to 10 inches above ground and the amount of Blackheart injury determined. The authors found winter hardiness is a function of rootstock as well as cultivar. The following tables should help you select the best rootstocks and cultivars for your clients.

Table 1: Average Blackheart injury based on rootstock
  • Rootstock % Blackheart
    Seedling 36.9
    B.9 25.5
    M.4 29
    M.7 EMLA 29.1
    M.9 16.7
    M.9 EMLA 21.5
    M.26 EMLA 26.7
    MAC.1 32
    MAC.9 20.8
    MAC.39 47.4
    Mark 26
    O.3 18.2
    OAR.1 22.2
    P.1 49.6
    P.22 50
Table 2: Average Blackheart injury based on cultivar
  • rootstock Golden Delicious Jonagold Empire Rome Beauty
    M.9 EMLA 15% 25% 17% 35%
    B.9 17% 26% 19% 23%
    Mark 21% 26% 18% 37%
    O.3 15% 26% 16% 25%
    M.26 EMLA 15% 22% 19% 24%
    Mean 17% 25% 18% 29%

reference.gif References:

Domoto, P.A., Autio, W.R., Brown, G.R., Ferree, D.C., Hirst, P.M., Mullins, C.A., and Schupp, J.R. 2001. Blackheart injury in 'Golden Delicious', 'Jonagold', 'Empire' and 'Rome Beauty' apple trees on five rootstocks in the 1990 NC-140 cultivar/rootstock trial. Journal American Pomological Society 55(3):146-153.

Steinmetz, F.H. 1937. A historical evaluation of low temperature injury to apple trees. Me. Agr. Expt. Sta. Bul. 388.

Warmund, M.R., Autio, W.R., Barden, J.A., Cummins, J.N., Domoto, P.A., Embree, C.G., Granger, R.L., Morrison, F.D., Schupp, J.R., and Young, E. 1996. Blackheart injury in 'Starkspur Supreme Delicious' on 15 Rootstocks in the 1984 NC-140 Planting. Fruit Varieties Journal 50(1):55-62.

Warmund, M.R., Ferree, D.C., Domoto, P., Barden, J.A., Mullins, C.A., and Granger, R.L. 1991. Blackheart injury in 'Starkspur Supreme Delicious' on nine rootstocks in the 1980-1981 NC-140 planting. Fruit Varieties Journal 45(4):219-223.

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Placed on the Internet 10/25/2001 10:03:50 AM