To investigate the effects of bud age on sprouting and flowering, bearing Clementine mandarin trees were hand-pruned at monthly intervals from late spring to fall. This pruning resulted in regrowth bearing axillary buds ranging in age from 9 to 5 months. After winter rest and during the return bloom, sprouting and flowering were assessed on axils on terminally positioned stems of these ages. The proportion of axillary buds sprouting and the number of spring shoots produced by each sprouting axillary site decreased with decreasing bud age. The proportion of axils sprouting one or more inflorescences, and the average number of flowers per stem also decreased with decreasing bud age. The number of axillary sites per stem, also significantly affected sprouting and flowering. Our results demonstrate the potential of hand-pruning to manipulate sprouting and return bloom depending on when in the summer or autumn the trees are pruned.
BA, NAA, and carbaryl at 75, 6, and 600 mg·liter-1, respectively, were applied alone or in combination to `Starkrimson Delicious' in 1989 and `Redspur Delicious' apples (Malus domestica Borkh.) in 1990. BA was effective alone, but when combined with carbaryl it thinned excessively. Thinning failed when BA was combined with NAA because many seedless pygmy fruit were formed and they persisted until harvest. BA and carbaryl were more effective than NAA at increasing return bloom. Return bloom was more closely related to total seed count than to final set. BA improved flesh firmness at harvest and after cold storage. None of the treatments influenced the development of calcium-related storage disorders following air storage. Chemical names used: benzyladenine (BA); naphthaleneacetic acid (NAA).
Postbloom applications of benzyladenine (BA) thinned young fruitlets of mature `Empire' apple trees (Malus domestica Borkh.) as well as or better than NAA or carbaryl (CB). BA increased fruit weight more effectively than either NAA or CB. Promalin (PR) was less effective than BA for both thinning and fruit-weight increase. In 1990, both BA and PR reduced fruit set up to 29 days after full bloom, but PR showed less thinning activity. BA and NAA produced independent and additive thinning responses when tank-mixed. Effects of all thinners on foliar mineral-nutrient concentrations were associated with changes in fruit load. BA increased return bloom as much or more than NAA or CB. PR did not affect return bloom. Chemical names used: N -(phenylmethyl)-1 H -purine-6-amine [benzyladenine (BA)]; BA plus gibberellins A, and A, [Promalin (PR)]; 1-naphthaleneacetic acid (NAA); 1-naphthalenyl methylcarbamate [carbaryl (CB)].
In three trials, 2004 crop loads were adjusted at the balloon stage of blossom development on heavily cropped whole apple trees by clipping all flower pedicels within a cluster while leaving the spur intact. Trees were adjusted to 0% crop (all flowers removed), 50% crop (half of all clusters removed), or left as 100% crop (no flowers removed). On `Cameo'/Bud.9, 400 ppm GA4+7 were applied to trees of each crop level at petal fall, 10 mm, 20 mm, or left unsprayed. At each crop load, GA4+7 marginally diminished the 2005 return bloom regardless of application timing, but the 2004 crop level was far more influential in 2005 flowering. In a second `Cameo'/Bud.9 trial, 0, 300, 600, or 900 ppm ethephon were applied to whole trees of each crop level at 45 DAFB. Ethephon generally demonstrated a rate response in improving the 2005 return bloom, but the 2005 flowering was more dramatically influenced by 2004 crop levels. On `Honeycrisp'/M.9, 300 ppm GA4+7 were applied to whole trees of each crop level at 10 mm. GA4+7 diminished 2005 return bloom at the 50% crop load, but spray effects were not as clear at the extreme 2004 crop levels. These results suggest that commercial floral inhibitors and promoters have difficulty overcoming endogenous effects of heavy or light bloom and crop in severely alternating apple trees. In a fourth trial, lightly cropped organic `Fuji'/MM.106 trees were sprayed with 0, 150, 300, or 450 ppm GA4 at petal fall, 10 mm, or 20 mm timings in 2004. The 2005 return bloom was inversely correlated with spray rates, with 10 mm showing more floral inhibition than other timings. Overall, `Cameo' was less sensitive to GA and ethephon than `Honeycrisp' or `Fuji'.
In 2001 and 2002, we imposed a wide range of croploads (0-15 fruits/cm2 of TCA) on 4- and 5-year-old Honeycrisp/M.9 trees by manual hand thinning soon after bloom to define appropriate croploads that give adequate repeat bloom and also the best fruit quality. At harvest each year we evaluated fruit ripening and quality. Samples were stored for 5 months in air at 38 °F and 33 °F and evaluated for fruit firmness and storage disorders. Cropload was negatively correlated with tree growth, return bloom, fruit size, fruit red color, fruit sugar content, fruit starch content, fruit firmness, fruit acidity, fruit bitter pit, fruit senescent breakdown, fruit rot and fruit superficial scald, but was positively correlated with leaf blotch symptoms, fruit internal ethylene concentration at harvest, and fruit soggy breakdown. There was a strong effect of cropload on fruit size up to a cropload 7, beyond which there was only a small additional effect. Although there was considerable variation in return bloom, a relatively low cropload was required to obtain adequate return bloom. Fruit red color was reduced only slightly up to a cropload of 8 beyond which it was reduced dramatically. The reduced fruit color and sugar content at high croploads could indicate a delay in maturity of but, fruits from high croploads were also softer, had less starch and greater internal ethylene. It that excessive croploads advance maturity. Overall, croploads greater than 10 resulted in no bloom the next year, and poor fruit size, color and flavor, but these fruits tended to have the least storage disorders. Moderate croploads (7-8) resulted in disappointing return bloom and mediocre fruit quality. For optimum quality and annual cropping, relatively low croploads of 4-5 were necessary.
Alternate-bearing trees produce a heavy on-crop followed by a light off-crop. Whereas climatic events initiate alternate bearing, it is perpetuated by endogenous tree factors. For citrus, the mechanism and underlying physiology by which fruit influence floral intensity the next spring was unresolved. To determine whether reduced return bloom of on-crop trees was due to inhibition of vegetative shoot production and, thus, a lack of “wood” on which to bear next spring's inflorescences or, alternatively, to inhibition of phase transition and inflorescence development on an adequate number of vegetative shoots, fruit were removed from individual shoots monthly or from entire on-crop `Pixie' mandarin trees during periods critical to shoot initiation (summer) and phase transition (winter). Fruit removal provided clear evidence that the on-crop exerted a significant effect on return bloom during the summer by reducing summer–fall shoot growth and, hence, the number of flowers borne on these shoots as well as on old wood of fruit-bearing shoots. The on-crop had less effect in winter on phase transition and return bloom. Buds collected during the summer from on-crop `Pixie' mandarin trees were characterized by high indoleacetic acid and low isopentenyladenosine concentrations compared to buds from off-crop trees. The starch level of the buds was not affected. No differences in hormone concentrations were detected for buds collected during winter from on- and off-crop trees, but buds of on-crop trees had less starch. The results demonstrate that the on-crop reduces return bloom predominantly by inhibiting summer-fall vegetative shoot growth by a mechanism similar to apical dominance, not a lack of available carbohydrate.
Biennial bearing has long been thought to occur in cranberry (Vaccinium macrocarpon Ait). Researchers have shown that percent return bloom on fruiting uprights can range from 12% to 65% depending on year, bed vigor and cultivar. Resource limitation and/or hormonal factors in a fruiting upright may be related to flower bud initiation and, thus, percent return bloom the following year. This research was undertaken to determine the extent of biennial bearing by cranberry cultivar and growing region. Seven cultivars were studied; three found in all states (MA, NJ, WI, OR), two common to MA and NJ, and two different cultivars in WI and OR representing cultivars commercially grown in these areas. In the fall or winter of 1989/1990 six 2-m transects were randomly selected within a cranberry bed for each cultivar. Along the transect, 60 uprights that fruited in 1989 were tagged. In the summer of 1990, fifty of the uprights will be sampled to determine percent return bloom and percent set.
Biennial bearing has long been thought to occur in cranberry (Vaccinium macrocarpon Ait). Researchers have shown that percent return bloom on fruiting uprights can range from 12% to 65% depending on year, bed vigor and cultivar. Resource limitation and/or hormonal factors in a fruiting upright may be related to flower bud initiation and, thus, percent return bloom the following year. This research was undertaken to determine the extent of biennial bearing by cranberry cultivar and growing region. Seven cultivars were studied; three found in all states (MA, NJ, WI, OR), two common to MA and NJ, and two different cultivars in WI and OR representing cultivars commercially grown in these areas. In the fall or winter of 1989/1990 six 2-m transects were randomly selected within a cranberry bed for each cultivar. Along the transect, 60 uprights that fruited in 1989 were tagged. In the summer of 1990, fifty of the uprights will be sampled to determine percent return bloom and percent set.
Abstract
‘Schley’ pecan [Carya illinoensis (Wang.) K. Koch] fruit were selectively thinned within one week after treatment with (2-chloroethyl)phosphonic acid (ethephon) without causing leaf abscission. A concentration range of 25, 50, 75, 100, 150, and 200 ppm caused progressive and selective fruit thinning ranging from 25 to 75%, depending upon concentration and fruit age. Fruit treated when at 4-mm diameter (June 15) were more heavily thinned at the same rate than fruit at 12-mm diameter (July 15). Leaf abscission occurred at rates of 300 ppm or greater on each treatment date. Ethephon levels had no effect on return bloom or fruit set.
Abstract
‘Richared Delicious’ trees received 10 μW·cm−2 of red light, peaking at 660 nm for 1.5 or 15 min nightly at midnight from full bloom until the end of “June drop” in early July. Both light treatments reduced abscission during the June drop period. ‘McIntosh’ apple trees received 10 or 200 μW·cm−2 of red light for 15 min at midnight, beginning in mid-August and continuing nightly until mid-October. Preharvest drop of fruit was delayed considerably one year and slightly reduced the 2nd year. With either cultivar, light treatment had no effect on fruit size, fruit quality, or return bloom in either year.