Summer pruning effects on processing peach on fruit quality, light penetration and interception, and % defects was studied in 2 trials. In study A, pillar-trained trees were pruned with the following treatments: a control, summer pruning at stage II fruit growth, summer pruning post-harvest or, pruning twice (all trees dormant pruned). In the first year, pruning prior to harvest significantly increased blush and flesh firmness but reduced soluble solids content (SSC). In the second year, summer pruning reduced yield per tree and fruit drop (weight and % of total) but did not affect fruit size, blush, or SSC. After 2 years, trees pruned post-harvest or twice had significantly smaller height, spread and trunk diameter.1 In study B, 2 cultivars of central leader trained trees were pruned at stage II fruit growth in the following treatments: a control, canopy thinning, and hedging. Thinning pruning improved light penetration and hedging reduced light interception. Thinning pruning reduced % of fungal rotted fruit but did not affect fruit quality.
Curt R. Rom, R. Bourne, K. Kupperman, and R.E. Moran
Alisson P. Kovaleski, Jeffrey G. Williamson, Bruno Casamali, and Rebecca L. Darnell
(SHB) cultivars and rely on high prices obtained for early-season fruit ( Lyrene, 1992 ; Williamson and Lyrene, 2004a , 2004b ). Summer pruning after fruit harvest is used in these areas to stimulate healthy vegetative growth for the remainder of the
Alisson P. Kovaleski, Rebecca L. Darnell, Bruno Casamali, and Jeffrey G. Williamson
the major species of blueberry grown in Florida and other mild winter areas. High temperatures and a long-growing season characterize the climate where SHB are typically grown, and summer pruning after fruit harvest stimulates healthy vegetative growth
Wesley R. Autio and Duane W. Greene
The effects of summer pruning on the yield and quality of apples (Malus domestica Borkh.) from mature `Rogers McIntosh'/M.7 trees were assessed in 1986-88. Summer pruning from 1 July through 1 Sept. enhanced red coloring and increased the percentage of the crop graded U.S. Extra Fancy. Fruit weight was not altered by summer pruning. Total yield was reduced by summer pruning only in 1 year, however, in no year was the harvested yield reduced. The portion of the crop that was picked in the first harvest was increased by summer pruning. Dormant-pruning time was decreased by summer pruning, and the total time required for pruning was increased only 1 of the 2 years where it was measured. Summer pruning and daminozide treatment significantly increased the estimated net returns.
Kuo-Tan Li and Alan N. Lakso
Summer pruning increases canopy light penetration and re-exposes spur leaves of the interior canopy of apple trees (Malus ×domestica Borkh.). However, we hypothesized that leaf photosynthetic ability is determined by the pre-pruning light environment, and the re-exposure intensity after summer pruning is incapable of restoring the photosynthesis efficiency of shaded leaves. To test this hypothesis, a commercial-type thinning-cuts pruning was applied to mature central leader `Empire'/M.26 apple trees. Changes in light availability, leaf net photosynthesis (Pn), photosystem II efficiency, and specific leaf weight (SLW) were recorded periodically before and after pruning. Leaf photosynthesis declined slightly through the growing season and was well correlated with pre-pruning light availability until late September. Although Pn decreased more substantially late in the season on exterior leaves than on interior leaves, Pn of leaves in the inner and middle canopies was lower than exterior leaves until late October. Maximum efficiency of photosystem II of dark-adapted leaves, measured by chlorophyll fluorescence (Fv/Fm), was not related to prior exposure or re-exposure. Specific leaf weight was well correlated with pre-pruning light availability and with leaf Pn in August but not in October. Results suggested that commercial summer pruning significantly increases light environments in the inner and middle canopies. However, light availability at interior and middle canopy sites was still much lower than exterior canopy and, consequently, leaf photosynthetic ability did not increase after summer pruning.
Kuo-Tan Li and Alan N. Lakso
Summer pruning is primarily used in apples to increase the light penetration into inner canopy to improve fruit color. However, summer pruning may reduce fruit size. We hypothesize that removing healthy exterior shoots reduces the whole-tree carbon supply in relation to pruning severity. If the crop load (i.e., demand) is high, fruit size and quality will be reduced. The effects of summer pruning on photosynthetic activity and recovery of shaded leaves after re-exposure were monitored on a range of exposures in canopies of `Empire' apple trees. The photosynthetic ability of leaves was positively related to its prepruning exposure. There was little recovery of photosynthetic activity of shade leaves until late growing season, indicating the re-exposure of shade leaves after summer pruning cannot replace the role of exterior leaves removed by pruning. Whole canopy net CO2 exchange (NCER) was measured on `Empire'/M9 trees with a commercial range of pruning severity. Reductions in NCER were approximately proportional to pruning severity and % leaf area removed and were as great as 60% in the most severe pruning. Canopy light interception decreased slightly. The effects on canopy NCER thus appeared to be primarily related to reduced photosynthetic efficiency and secondarily to reduced light interception.
Charlotte M. Guimond, Gregory A. Lang, and Preston K. Andrews
To examine the effect of timing and severity of summer pruning on flower bud initiation and vegetative growth, 4-year-old `Bing' cherry trees (Prunus avium L.) were pruned at 31, 34, 37, 38, or 45 days after full bloom (DAFB) with heading cuts 20 cm from the base of current-season lateral shoot growth, or at 38 DAFB by heading current-season lateral shoot growth at 15, 20, 25, or 30 cm from the base of the shoot. The influence of heading cut position between nodes also was examined by cutting at a point (≈20 cm from the shoot base) just above or below a node, or in the middle of an internode. Summer pruning influenced the number of both flower buds and lateral shoots subsequently formed on the shoots. All of the timings and pruning lengths significantly increased the number of both flower buds and lateral shoots, but differences between pruning times were not significant. There was significantly less regrowth when shoots were pruned just below a node or in the center of an internode, rather than just above a node, suggesting that the length of the remaining stub may inhibit regrowth somewhat. The coefficient of determination (r 2) between flower bud number and regrowth ranged from -0.34 to -0.45. In young high-density sweet cherry plantings, summer pruning may be useful for increasing flower bud formation on current-season shoots. The time of pruning, length of the shoots after pruning, and location of the pruning cut can influence subsequent flower bud formation and vegetative regrowth.
Roberto Nunez-Elisea and Lilia Caldeira
We tested two severities and four timings of summer pruning in 2-year-old `Sweetheart' (P. avium L.) trees on seedling mazzard (P. avium L.) rootstock to evaluate growth and precocity responses. Trees were planted at 3.6 m × 5.6 m (497 trees/ha). Canopies consisted of three to four scaffolds and about 20 current-season shoots. All shoots on summer-pruned trees (n=6) were either headed or tipped on 24 June, 9 July, 26 July, or 9 Aug. 2004. Control trees were trained as steep leaders, with comparative current season shoots left intact. Trees had no bloom in 2004 and negligible bloom or fruiting in 2005. All 2005 shoots were headed in late July, except for controls, where only leaders were headed. By late Fall 2005, controls were 3.4 m tall with a canopy diameter of 3 m, while headed and tipped trees were about 65% and 75% the size of controls, respectively. Growth modules consisting of the original shoot and subsequent growth showed distinct responses to summer pruning treatments. Control shoots did not branch in 2004 and modules had an average of 17 spurs. Headed shoots branched in 2004 (except those headed 9 Aug.) and produced compact modules with a similar amount (24 June) or about 25% fewer (later heading treatments) spurs than controls. Shoots tipped in 24 June or 9 July branched in 2004 and produced modules with about 50% more spurs than controls. Shoots tipped in 26 July or 9 Aug. produced no new growth in 2004 and modules had about 30% the spurs of controls. Selective summer pruning produced compact trees which are expected (based on spur number) to yield at least 15 kg of fruit in 2006 (4th year) and appear suitable for densities of about 750 trees/ha. Yields, fruit quality, and future canopy management will be discussed.
W.C. Olien, R.E. Williamson, C.E. Hood, D.R. Decoteau, and D.C. Coston
Factorial combinations of ± root pruning (RP) and ± summer pruning (SP) were initiated in 1991 as subplots within a Redhaven/Lovell study of orchard training systems: Open Center (OC), Y-Trellis (YT), Central Leader (CL), and Meadow Orchard (MO) established in 1985. Root pruning was imposed at bloom (March 28) at 76 cm from the trunk to a depth of 45 cm. Summer pruning consisted of preharvest removal of water sprouts (June 5). Canopy density, quantified by transmittance of PAR radiation through the canopy, was greatest in OC and MO and least in YT and CL systems. SP and RP treatments further reduced canopy density by 35 to 80%. There were no main or interactive effects of SP and RP on 1991 yields or fruit quality, and also no interactive effects of orchard systems with SP and RP. Thus, SP and RP reduced canopy density without negative effects on fruit. RP, however, advanced harvest date by ca 4 days. A parallel study was also initiated in 1991 to determine the effects of root pruning distance (30, 60, 90 cm from the trunk, or no RP) on canopy density, yield, and fruit quality of mature, OC-trained Redhaven/ and Jefferson/Lovell. Reduction in canopy density without loss of yield or fruit size was obtained at a RP distance between 60 and 90 cm.
Ray Allen, Curt Rom, and John Aselage
Summer pruning effects on apple tree canopy microclimate, fruit quality, and summer disease were studied in a commercial orchard in eastern Arkansas. Eighteen lo-year-old trees of `Golde n Delicious'/M111 were treated as follows: 1) non-pruned control, 2) moderate pruned, thinning cuts in the canopy, and 3) heavy pruned, thinning cuts in the canopy and heading shoots on the canopy periphery. Treatments were applied on 23-June, 1992. All trees were dormant pruned. PPFD and relative evaporation (RE), measured with Livingston atmometers, were measured at time of treatment, on 15-July, and at Harvest, 9-Sept. PPFD and RE were immediately increased by summer pruning but by harvest had returned to levels near the non-pruned control. Fruit firmness, titratable acidity, starch, and color were not significantly affected while soluble solids were inconsistently affected. Weight was decreased insignificantly by moderate pruning and decreased slightly by heavy pruning. Summer fruit rot incidence was similar among all treatments. PPFD and RE were significantly higher in upper positions of the canopy as compared to lower positions.