Using NAA to reduce growth in tops of super-spindle apple trees where a heading cut is used to

correct tree height

•Wes Autio and Jon Clements, UMass Amherst

•Win Cowgill, Rutgers University

•Northeast PGR ‘Classic’ March 2008

• target the base of 1-year old wood

•use a flexible, paint-like carrier

•NAA at a final concentration of 1.5%

•paint a 3 inch band around the trunk

•apply at or near bloom

NAA can differentially reduce growth in the tops of

dwarf apple trees

Cameo/B9

Cameo/G16

2007 treatments1.UTC – UnTreated Control

2.PRN – heading pruning cut made into two or three year old wood

3.PRN+NAA – heading cut made into two or three year old wood, then covered with NAA plus tree wound healing paint at 1.5% final concentration NAA

Varieties

•Golden Supreme/M.9-Pajam 2

•Cameo/G.16

•Buckeye Gala/G.16

•Lindamac/M.9 (NJ only)

Golden Supreme - NJ

b

a

ab

b

aa

Table 1.

Golden Supreme - NJ

146 b 583 a 466 a

total shoot growth (top 5 branches)

Golden Supreme - MA

ab

a

b

Table 2.

Golden Supreme - MA

UTC314

PRN322

PRN+NAA136

total shoot growth (top 5 branches)

Cameo - NJ

a

bb

aa

a a

b bb

bb b b b

Table 3.

Cameo - NJ

65 b 439 a 11 b

total shoot growth (top 5 branches)

Cameo - MA

bb b

a

aab

Table 4.

Cameo - MA

UTC206 b

PRN568 a

PRN+NAA510 a

total shoot growth (top 5 branches)

Buckeye Gala - NJ

Table 5.

Buckeye Gala - NJ

91 b 791 a 275 b

total shoot growth (top 5 branches)

Buckeye Gala - MA

Table 6.

Buckeye Gala - MA

UTC124 c

PRN304 a

PRN+NAA218 b

total shoot growth (top 5 branches)

Lindamac - NJ

b

ba

a

a

bab

b b

Table 8.

Lindamac - NJ

39 b 235 a 94 b

total shoot growth (top 5 branches)

Shoot Growth- NJtotal of all 5 branches

Shoot Growth - MAtotal of all 5 branches

ab

c

Shoot Growth- NJone-year shoots originating from

trunk

preliminary conclusions•treatment of pruning cut(s) with NAA

reduces amount of reactionary growth, however, with some caveats:

• varieties may react differently

• the effect appears to be more prominent on new leader

• effect may diminish down the trunk – some pruning (thinning cuts) of lateral branches is still necessary

•more work is warranted to fine tune application details to achieve all-around desired reduction in growth - adjusting concentration and placement of material are likely starting points?