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G. W. Stutte and G. C. Martin

Abstract

Experiments were designed to alter the carbohydrate status of olive (Olea europaea L.) leaves during the presumed flower induction period. Bearing and nonbearing ‘Oblonga’ olive trees were exposed to either 850 μmol s-1n-2 PAR for 14 hr daily in a 1000 ppm CO2-enriched atmosphere, 150 μmol s-1m-2 PAR for 14 hr daily in 340 ppm CO2, or maintained in a lathhouse at ambient winter conditions of about 350 μmol s-1m-2 PAR and daily temperature fluctuations from 5° to 20°C. The trees exposed to 850 μmol s-1m-2 had 3 to 5 times the starch concentrations of either the 150 μmol s-1m-2 PAR or lathhouse treatments. There were few and inconsistent differences in sucrose, fructose or mannitol concentrations between treatments. The high levels of starch in the 850 μmol s-1m-2 PAR treatment had no effect on the flowering pattern of bearing or nonbearing trees. Gross levels of carbohydrates do not appear to limit flower induction of olive.

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Martin J. Bukovac, Paolo Sabbatini, and Philip G. Schwallier

The effect of ethephon on flowering and cropping of strongly alternate bearing spur-type `Delicious' apple (Malus domestica Borkh.) was evaluated in a 6-year study. Ethephon (200 mg·L–1), applied at 3, 3 + 6, and 3 + 6 + 9 weeks after full bloom in “on years,” increased flowering in “off years” by 33% and reduced flowering in “on years” by 17% compared with the control. The mean yield per tree for ethephon-treated trees over three “on years” and three “off years” was almost identical to that of the controls (82 vs. 80 kg/tree). However, the distribution of yield between “on” and “off” years was changed, 24% greater in “off years” and 10% less in “on years.” Ethephon reduced both the variation in yield, particularly in “off years,” and the magnitude of alternation. Ethephon had a direct effect on flower initiation because 1) it did not reduce shoot growth or yield in the “on years” (years of ethephon application) and 2) ethephon-treated trees initiated more flowers per kilogram of fruit produced than did the controls. The additional flowers initiated were functional because the amount of fruit produced per unit bloom density did not differ between control and ethephon-treated trees. Harvest maturity indices, namely internal ethylene concentration, firmness, starch index, soluble solids, and color, were not significantly affected, although internal ethylene concentration and starch index tended to be higher in fruit from treated trees.

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R.E. Byers, D.H. Carbaugh, and L.D. Combs

Technical grade prohexadione-calcium (93.2% a.i. P-Ca) applied to `Fuji'/M.9 trees in three applications in deionized water reduced shoot growth by 25%, but the addition of (NH4)2SO4 to P-Ca suppressed shoot growth by 47%. If P-Ca was mixed in well water (high in calcium salts), P-Ca did not suppress shoot growth at all. The commercially formulated prohexadione-calcium [Apogee: 27.5% P-Ca + 56.1% (NH4)2SO4 + 16.4% other proprietary additives] + Regulaid in well water (high calcium) was not as effective (reduced growth by 30%) as when additional (NH4)2SO4 was added (reduced growth by 53%), and if CaCl2 (used to control corking) was tank mixed with Apogee + Regulaid, the Ca++ interfered with the growth suppression of P-Ca. If (NH4)2SO4 was added at the same rate as CaCl2 (w/w), the Apogee growth suppression was completely restored (reduced growth by 50%). Choice (a commercial water conditioner that has (NH4)2SO4 in the formulation, among other ingredients) + Li-700, or (NH4)2SO4 + Silwet L-77, or (NH4)2SO4 + Silwet L-77 + Oil were among the most effective adjuvant combinations with Apogee. The addition of ethephon at 270 mg·L-1 improved the growth suppression of Apogee + (NH4)2SO4 + Regulaid. Solubor compromised the effectiveness of Apogee + Regulaid. Adjusting the pH of the Apogee + (NH4)2SO4+ Regulaid spray to either pH = 4 or pH = 9 did not affect efficacy. The combination of Apogee + (NH4)2SO4 + Regulaid caused increased fruit cracking of `Empire' fruit as compared to the control (7%), presumably due to increased absorption of P-Ca. Chemical names used: Prohexadione-calcium (P-Ca, 3-oxido-4-propionyl-5-oxo-3cyclohexenecarboxylate) formulated as BAS-125 (10% P-Ca); Apogee (27.5% P-Ca), or Technical 93.5% P-Ca); Regulaid (polyoxyethylenepolypropoxy-propanol, alkyl 2-ethoxethanol, and dihydroxy propane); Silwet L-77 (polyalkyleneoxide modified heptametyltrisiloxane, silicon surfactant), LI-700 (80%, phosphatidylcholine, methylacetic acid and alkyl polyoxyethylene ether); Superior Oil (Drexel Damoil 70-second delayed dormant spray oil); ethephon (2-chloroethyl phosphonic acid); Solubor (20.5%, Boron equivalent); captan (N-Trichloromethylthio-4-cyclohenene-1,2-dicarboximide).

Open access

Duane W. Greene and Wesley R. Autio

Abstract

Five chemical thinning trials, conducted over 4 years, indicated that BA is an effective thinner for ‘McIntosh’ apples (Malus domestica Borkh.). Although it can thin at concentrations as low as 25 mg·liter−1, in most years a higher concentration was required to thin adequately. It appeared that 14 to 18 days after full bloom, when fruit size was about 10 mm, may be the period when maximum thinning was achieved. Greater thinning occurred when BA and carbaryl were combined than when they were used individually. BA increased fruit weight, flesh firmness, and soluble solids content at harvest relative to no thinning. The storage life of fruit treated with BA was less than that of fruit from nonthinned trees, but this effect may have been an indirect response related to the larger fruit size rather than a direct response to the chemical. BA caused thinning and induced lateral branching simultaneously on young ‘Macspur McIntosh’ trees. Therefore, crop load on trees just coming into production may be significantly reduced when BA is used to induce lateral branching. Chemical names used: N-(phenylmethyl)-IH-purine-6-amine [benzyladenine (BA)], 1-napthaleneacetic acid [NAA], 1-naphthalenyl methylcarbamate [carbaryl].

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Thomas M. Kon, James R. Schupp, H. Edwin Winzeler, and Richard P. Marini

al., 1998 ; Damerow et al., 2007 ). Thinning with the Darwin (Fruit-Tec, Deggenhauserertal, Germany) string thinner reduced fruit set by 25%, enhanced return bloom when compared with the control, and did not significantly injure foliage ( Weibel et

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Duane W. Greene

thinners such as carbaryl on apples. Maas et al. (2010) reported that BA alone was a marginal thinner on ‘Conference’ pear but when combined with 1-naphthaleneacetic acid (NAA), significant thinning was achieved along with enhanced return bloom. The

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Michael W. Smith and Becky S. Cheary

, 2010 ). Low crop years are normally associated with a lack of return bloom rather than flower abortion ( Rohla et al., 2007 ). Alternate bearing trees show distinct differences in leaf K and P accumulation and depletion between large and small crops

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Matthew Arrington, Mateus S. Pasa, and Todd C. Einhorn

commercial maturity [i.e., fruit firmness (FF) between 8.6 and 7.6 kg]. Average fruit weight was determined by weighing individual fruit from a random 50-fruit sample per replication. Return bloom was determined the year after treatment applications from the

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Ockert P.J. Stander, Graham H. Barry, and Paul J.R. Cronjé

persistent fruit and new vegetative shoots that developed during the subsequent vegetative shoot flushes were recorded for each shoot, and return bloom and vegetative response were determined on the same shoots during the subsequent season. For the branch

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Linda M. Boyd and Andrew M. Barnett

inconsistent effects on concentrations of the inorganic nutrients in fruit. High croploads and partial defoliation reduced return bloom in ‘Hayward’ kiwifruit ( Buwalda and Smith, 1990 ; Cooper and Marshall, 1991 ). It is therefore not surprising that return