FURTHER TRIALS WITH NAPHTHALENE ACETIC ACID 

 (NAA) FOR TREE TRAINING 



William J. Lord and Duane Greene 

 Department of Plant and Soil Sciences 



It was reported in 1977 that 11 NAA in latex paint is an ex- 

 cellent tree training aid when applied as a painted band around 

 the stem o£ newly-planted apple trees (after heading) to cover the 

 second, third, and fourth buds. The first bud below the heading 

 cut, which was not painted, became a vigorous central leader. This 

 treatment eliminated the cluster of vigorous shoots in the top of 

 the trees which compete with the central leader and increase the 

 number of favorably positioned branches on the newly-planted trees, 

 and improve crotch angles of these branches. If for some reason 

 the bud selected for the central leader died, a strong leader report- 

 edly developed from the NAA-treated area. Basically, the suggested 

 NAA treatment is a replacement for the current training procedures 

 which involve removal by hand, in June, of growth that is in com- 

 petition with the shoot favored as a central leader. 



Directions for use indicated that the 1% NAA in latex paint 

 should be applied after heading the newly-planted tiee to the desired 

 height but before growth begins. The treatment is not effective if 

 made after start of growth. 



We tried the NAA-tree training technique on Marshall Mcintosh, 

 Macoun, and Redspur Delicious in 1977. In the May/June, 1978 issue 

 of Fruit N otes we reported that the treatment was a complete disaster. 

 The f irs t ~bud~below the heading cut, which was supposed to develop 

 into the leader, was with only one exception either severely stunted 

 or killed. When the bud selected for the central leader died, no 

 strong leader developed from the NAA-treated area. 



Further tests were conducted in 1978 on 1-year-old Redspur Deli- 

 cious trees after heading, using concentrations of 0.25%, 0.50%, or 

 1 . 0% NAA in latex paint. Applications of 0.50% or 1.0% suppressed 

 leader growth, although the reduction was less than recorded in 1977. 

 Leaders on trees painted with 0.25% NAA in latex were shorter than 

 those on the headed control, deshooted, or disbudded trees when mea- 

 sured on August 8, 1978 but not on September 9, 1978. Thus, it appears 

 that trees may overcome the inhibitory effects of NAA if concentrations 

 applied are not excessive. 



Thus, we concluded from our 1977 and 1978 trials that NAA, ethyl- 

 esr.er at 0.5 to 1.0% in latex may suppress leader growth when applied 

 as a band on newly planted or 1-year-old apple trees after heading. 



Furthermore, it has at least 4 obvious drawbacks. Spring is an 

 ex',, erely busy season and chances are good that the NAA will not be 



