, 1989 , 1991 ; Worley, 1979a , 1979b ). Other work suggested that inhibition of return bloom by developing fruit was incited by phytohormones or other growth regulators ( Amling and Amling, 1983 ; Smith et al., 1986 ; Wood, 2003 ; Wood and McMeans
regulating return bloom. For instance, Wood et al. (2003) reported that there was no association between alternate-bearing intensity and fruit ripening date or nut volume. In addition, as the postripening foliation period increased, alternate bearing
” year, but results vary with cultivar ( Schwallier et al., 2006 ; Singh, 1948 ). Research has shown that blossom thinning is more effective than fruitlet thinning alone to increase the potential for return bloom ( Byers, 1997 ; Johnson, 1995 ; Preston
The optimum time for removing pecans [Carya illinoinensis (Wangenh.) K. Koch] to enhance return bloom was determined. Fruit were removed from part of `Mohawk', `Giles', and `Gormely' trees five times during the season as determined by fruit phonological age: immediately after postpollination drop, at 50% ovule expansion, at 100% ovule expansion or water stage, during the onset of dough stage, and 2 weeks after dough stage. Return bloom of all cultivars was increased by fruit removal during ovule expansion. Removing `Mohawk' and `Giles' fruit shortly after pollination induced the greatest return bloom. Return bloom in the small-fruited `Gormely' was equally stimulated by fruit removal at any time during ovule expansion, a result indicating that early fruit removal may be more important for large-than for small-fruited cultivars. If a commercially feasible method to thin pecans is developed, our studies indicate that the optimum time for fruit thinning would be during ovule expansion.
This research was undertaken to document the extent of biennial bearing in flowering uprights by American cranberry (Vaccinium macrocarpon Ait) cultivar and growing region. Seven cultivars were studied: three found in all states considered (Massachusetts, New Jersey, Wisconsin, Oregon), two common to Massachusetts and New Jersey, and two other commercially grown cultivars, one each from Wisconsin and Oregon. There were significant cultivar, region, and cultivar × region interaction effects for both percent return bloom (%RB) and percent return fruit (%RF). Percent RB ranged from 74% for `Ben Lear' in Wisconsin to 14% for `Howes' in New Jersey. `Ben Lear' differed the most in %RB among regions, from 74% in Wisconsin to 14% in Massachusetts. However, in some regions, especially in Wisconsin, many blossoms did not set viable fruit. There was no significant difference in %RB among cultivars grown in Massachusetts or Oregon; however, cultivars grown in these regions did differ in %RF.
blossom or fruit thinning chemically, by hand, or a combination of the two. Blossom thinning is a standard procedure for improving fruit size, increasing return bloom, and promoting regular bearing ( Byers, 2003 ; Jonkers, 1979 ). Reducing the number of
Pecan trees, Carya illinoensis, often exhibit a strong alternate bearing pattern. The presence of a heavy seed crop inhibits terminals from fruiting the following season. This study was developed to discover at what point in the development of the pecan fruit does this inhibition take place. Six nut removal times were evaluated: (1) after pollination but before fertilization, (2) one-half ovule expansion, (3) full ovule expansion or water stage, (4) dough stage, (5) 3 weeks after the initiation of the dough stage, and (6) no fruit removal until harvest. The cultivar `Mohawk' was used for this randomized block experiment.
Return bloom was significantly enhanced by the removal of fruit prior to the initiation of kernel filling (dough stage). Less than 10% of terminals that supported pecans through the dough stage were able to produce distillate flowers the following year. Twig mortality was significantly higher for terminals that completed kernel filling. These results indicate that nut thinning prior to the water stage may reduce the alternate bearing tendency in pecan.
In 1997 and 1998, we determined the effects of defoliation on return bloom and fruit set following a light cropping year. In one study, `Braeburn' trees were hand-thinned to a crop density (CD) of 3 fruit/cm 2 trunk cross sectional area (TCSA) in late May 1997, and then either completely defoliated or half of the tree defoliated by hand on one of five dates between June and Sept. 1997. Compared to a nondefoliated control, both whole and half-tree defoliation on all dates reduced fruit count and yield efficiency (kilograms per square centimeter of TCSA) and affected fruit weight, starch, firmness, and soluble solids in 1997. In 1998, return bloom and fruit set were reduced by most 1997 defoliation treatments. Compared to other dates, defoliation on 3 July caused the greatest reduction in return bloom in both whole and half-defoliated trees. In another study, `Braeburn' trees were hand-thinned to a CD of 5 in late May 1998; complete defoliation by hand on 1, 15, or 29 July reduced return bloom and fruit set in 1999; the 1 July treatment resulted in zero return bloom. `Golden Delicious' and `York' trees were thinned to a CD of 3 in late May 1998 and were hand-defoliated on 21 July or 12 August by removing every other leaf or removing three of every four leaves over the entire tree. In 1999, return bloom and spur and lateral fruit set were reduced by all defoliation treatments. Fruit set was most reduced by the 12 Aug. treatment. Fruit set for `York' was lower than for `Golden Delicious' in all cases.
Thidiazuron (THI) applied at full bloom (FB) at 10 or 50 mg·liter–1 thinned `McIntosh' apples (Malus domestica Borkh.) and reduced return bloom. The same concentrations applied at 22 days after FB (DAFB) thinned excessively and inhibited return bloom even more. THI at 1, 5, or 15 mg·liter–1 did not thin `Empire' at FB, but when applied 18 DAFB, these concentrations achieved thinning, with 5 mg·liter–1 reducing crop load to near ideal commercial levels. Return bloom of `Empire' was not influenced by THI at these concentrations. THI increased fruit weight, flesh firmness, soluble solids concentration, and fruit asymmetry on `McIntosh' and `Empire' and reduced red pigmentation and seed count on `McIntosh', especially when applied 22 DAFB. A FB application of CPPU and THI, each at 5 or 10 mg·liter–1, on `Delicious' increased the fruit length: diameter (L: D) ratio and flesh firmness (at harvest and following 26 weeks of refrigerated storage and reduced return bloom). CPPU at either 5 or 10 mg·liter–1 increased the fruit L: D ratio more than 25 mg Promalin/liter. Chemical names used: N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron); N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU); N-(phenylmethyl)-1H-purine-6-amine plus gibberellins A4+7 (Promalin).
Heavily cropping `York'/M.27 trees sprayed with seven multiple low doses of ethephon (135 mg/L each) did not cause greater return bloom in 1999 unless foliar fertilizers (either 18–18–18 or Ca N03) were added to the ethephon sprays. Foliar fertilizer sprays alone did not promote return bloom. `York'/M.7 trees selected for very little bloom in 1997 (“off year” of the biennial bearing cycle) and sprayed with 160 mg/L GA3 or 320 mg/L GA3 had significantly less return bloom in the 1998 (“on year”) (61% and 46% spurs flowering, respectively, compared to control trees that had 99% of spurs flowering). Trees sprayed in 1997 (“off year”) with GA3 return bloom and cropped in 1999; but trees in the “off year” in 1997 that were not sprayed with GA3, did not crop in 1999. Sprays of GA3 provided some control of alternate bearing of `York'/M.7 trees when applied in the “off year” of the biennial bearing cycle. Leaves taken from `Braeburn'/M.27 trees in 70 °F rooms evolved ethylene through out the 12 days of the test. A moderate ethylene peak occurred on about days 5 and 6. Leaves from trees in the 40 °F room did not evolve detectable ethylene levels until trees were put in another 70 °F room on day 6. Ethylene levels were about the same from day 6 through day 12 for all treated trees at 70 °F. Nontreated control trees in rooms at 40 or 70 °F did not produce detectable ethylene levels during the experiment (except for a very small amount detected only on day 2 from leaves seal for 24 h at 70 °F.