Table 5.

Annual xylem ring increment (mm) for the year prior to treatment and for 3 years after treatment with paclobutrazol in April 1996 using the soil injection method on eight tree species growing in Indiana, with total reduction expressed as a percentage of untreated controls.

TreatmentYearTotal 1996–98Percentage reduction
PriorAfter treatment
Black walnut
Within crown
Control1.36 a1.38 a1.06 a1.08 a3.52 a
Treated0.82 a1.28 a0.99 a0.94 a3.21 a9
Mid-trunk (2—4 m high)
Control2.05 a2.44 a1.46 a1.67 a5.57 a
Treated1.74 a1.54 a1.14 a1.40 a4.08 a27
Base of trunk (10 cm above ground line)
Control1.86 a1.42 a1.25 a1.66 a4.33 a
Treated2.06 a1.61 a1.05 a1.04 a3.70 a15
European black alder
Within crown
Control2.06 a1.84 a1.46 a1.50 a4.80 a
Treated2.59 a1.20 a1.11 a1.29 a3.60 a25
Mid-trunk (2—4 m high)
Control5.80 a5.00 a3.90 a6.27 a15.17 a
Treated3.15 a2.16 b1.27 b2.40 b  5.83 b62
Base of trunk (10 cm above ground line)
Control5.19 a3.85 a3.30 a4.45 a11.60 a
Treated5.00 a3.25 a2.73 a2.25 b  8.23 a29
Red oak
Within crown
Control3.14 a2.16 a2.07 a3.36 a7.59 a
Treated4.54 a2.38 a1.80 a2.85 a7.03 a7
Mid-trunk (2—4 m high)
Control4.32 a2.82 a2.37 a3.38 a8.57 a
Treated4.17 a2.23 a1.79 a2.60 a6.62 a23
Base of trunk (10 cm above ground line)
Control5.87 a4.39 a3.39 a4.91 a12.69 a
Treated5.97 a3.19 b2.04 a3.57 a  8.80 a31
Within crown
Control4.68 a4.23 a3.78 a4.26 a12.27 a
Treated4.18 a1.99 b1.66 b1.54 b  5.19 b58
Mid-trunk (2—4 m high)
Control4.50 a4.42 a3.51 a3.58 a11.51 a
Treated3.54 a2.46 b2.17 b2.07 a  6.70 b42
Base of trunk (10 cm above ground line)
Control4.10 a4.44 a4.97 a4.93 a14.34 a
Treated3.78 a3.37 b3.45 b4.13 a10.95 b24
White ash
Within crown
Control1.55 a1.63 a1.95 a2.07 a5.65 a
Treated1.09 a1.27 a1.32 a1.48 a4.07 a28
Mid-trunk (2—4 m high)
Control2.21 a2.11 a2.21 a2.15 a6.47 a
Treated1.39 a1.62 a1.55 a1.66 a4.83 a25
Base of trunk (10 cm above ground line)
Control2.03 a2.25 a1.92 a2.25 a6.42 a
Treated1.67 a1.57 a1.30 a1.71 a4.58 a29
White oak
Within crown
Control2.42 a2.17 a1.84 a2.68 a6.69 a
Treated2.46 a1.08 a0.80 b0.97 b2.85 b57
Mid-trunk (2—4 m high)
Control3.02 a2.98 a2.69 a3.26 a8.93 a
Treated2.30 a1.04 a0.90 b1.11 b3.05 b66
Base of trunk (10 cm above ground line)
Control4.11 a2.94 a2.91 a4.36 a10.21 a
Treated3.63 a1.40 a0.95 b1.16 b  3.51 b66
White pine
Within crown
Control4.71 a4.95 a8.67 a10.50 a24.12 a
Treated5.35 a5.67 a4.42 b  5.29 b15.38 b36
Mid-trunk (2—4 m high)
Control9.77 a9.05 a10.39 a10.77 a30.21 a
Treated8.48 a8.79 a  8.42 b10.17 a27.38 a9
Base of trunk (10 cm above ground line)
Control9.17 a11.32 a9.84 a12.08 a33.24 a
Treated8.95 a  9.33 b8.22 a11.46 a29.01 a13
Yellow poplar
Within crown
Control2.83 a2.64 a2.98 a3.65 a9.27 a
Treated2.74 a1.92 a2.57 a3.83 a8.32 a10
Mid-trunk (2—4 m high)
Control3.28 a2.55 a2.71 a3.99 a9.25 a
Treated2.68 a1.88 a2.33 a3.62 a7.83 a15
Base of trunk (10 cm above ground line)
Control2.47 a2.25 a2.20 a3.90 a8.35 a
Treated2.25 a2.16 a2.63 a4.16 a8.95 a(−7)
  • Pairs of values for each set of control and treated trees followed by the same lowercase letter are not significantly different at the P ≤ 0.05 level.