Thinning ‘Red Fuji’ apples with ethephon or NAA

Summary

A series of trials in Tasmania examined the thinning effects of ethephon and NAA on ‘Red Fuji’ apple. In the ethephon trials, concentrations from 25 to 600 ppm were applied at full bloom (FB) or 14 days after full bloom (AFB) to trees on either seedling or M.M.106 rootstocks. The NAA trial involved spraying concentrations of 5, 10 or 15 ppm at FB or 14 days AFB to trees on seedling rootstocks. Ethephon thinning of ‘Red Fuji’ was similar at FB and 14 days AFB. The dependence of fruit thinning on ethephon concentration was described by fitting non-linear response curves. These relationships were stronger and less variable for M.M.106 than seedling trees. Ethephon proved a satisfactory thinner for trees on both rootstocks. At the high spray volume used, the preferred concentrations at both FB and 14 days AFB would be 25 or 50 ppm for seedling and 100 or 200 ppm for M.M.106 rootstocks. NAA under-thinned at 5 ppm and over-thinned at 10 and 15 ppm at both FB and 14 days AFB. No firm recommendation can be given for NAA as a thinner of ‘Fuji’ at this stage.     

Flower thinning method affects mineral composition of `Braeburn' and `Fiesta' apple fruit

Summary

Fruit mineral concentrations measured at harvest can have major effects on apple fruit quality on the tree or during storage. Orchard practices must therefore seek to optimize fruit mineral composition. The purpose of this study was to describe and elucidate the effects of hand thinning on whole trees and individual spurs on apple fruit mineral composition. Two methods of flower and fruitlet thinning were compared with no thinning on `Braeburn' and `Fiesta' apple trees. Alternate whole flower/fruitlet clusters or all but one flower/fruitlet within every cluster were removed at full bloom or 14±21 d after full bloom. Alternate-cluster thinning reduced final fruit numbers per tree and fruit Ca concentrations by up to 22%, while increasing final fruit size by up to 21%, compared with no thinning. These effects on fruit Ca concentrations were also measured across a range of fruit size classes. Within-cluster thinning at full bloom or up to 21 d after full bloom also reduced fruit numbers per tree but increased fruit size substantially, by up to 65% compared with no thinning, this effect being less for later thinning. However, fruit mineral concentrations were not influenced by this treatment. Some fruiting spurs were singled to one fruit 14 d after full bloom on alternately flower cluster thinned trees and on trees that had not been thinned at bloom, and compared with unthinned spurs on the same trees. Fruit Ca concentrations, primary spur leaf areas and primary spur leaf areas per fruit were greater for spurs bearing a single fruit (achieved by thinning manually or through natural abscission) than for multi-fruited spurs on the same trees. Spurs bearing one fruit on unthinned trees had greater fruit Ca concentrations, primary spur leaf areas and primary spur leaf areas per fruit, but lower fruit weight than the same spurs on alternate-cluster thinned trees. However, spurs on unthinned and alternate-cluster thinned trees with the same primary leaf areas per fruit had similar final Ca concentrations. Fruit size and crop loads were found not to be important in explaining fruit Ca concentration differences between thinning methods. However our results suggest that thinning method may affect Ca accumulation in apple fruit by altering the relationship between fruit numbers and leaf areas on individual spurs.     

敌百虫对国光、金冠苹果疏除幼果的效应

敌百虫对国光、金冠苹果疏果效应的研究结果表明,国光盛花后10d 喷布1125mg·1~(-1)敌百虫或加20mg·1~(-1)NAA;金冠盛花后12d 喷布900mg·1~(-1)敌百虫或加10mg·1~(-1)NAA,疏除幼果效应显著.果实单果重、翌年花量增加;果实品质、经济效益提高;大小年幅度降低.     

The interaction of Cytolin and NAA on cropping red ‘Delicious’ apple

A trial, at Spreyton in north-western Tasmania, studied the effects of Cytolin and NAA sprays on the thinning and shape of ‘Delicious’ apples. Untreated control and hand thinned trees were compared with trees treated with Cytolin or NAA alone, or in combination. Cytolin was applied at 25 mg 1~‘ at the king petal (KP) stage. NAA was applied at 8 mg I“1 at full bloom (FB) and 7,10, or 15 days after full bloom (AFB). Cytolin alone had no effect on thinning, fruit weight or on pip numbers but it did improve fruit shape. The combination of cytolin and NAA at FB overthinned. Cytolin and NAA combinations applied at all times after FB significantly decreased both mean fruit weight and pip numbers and reduced the percentage of fruit > 70 mm. All Cytolin-NAA combinations and the NAA treatments applied at 10 and 15 days AFB resulted in unacceptably high percentages of apples < 45 mm in diameter (pygmy fruit). It is recommended that Cytolin and NAA should not be used in the same spray programme. NAA alone is a most effective thinner at FB or seven days AFB.     

Biology of the Fruit Tree Red Spider Mite Metatetranychus Ulmi (Koch) in South-East England

Measurements of the rate of fruit drop and the hormone content of the seeds, made at weekly intervals on three varieties of apple, have shown that periods of very active hormone production are invariably associated with periods of low fruit drop. On the basis of these and other observations, an hypothesis is proposed to account for the periodicity of fruit drop. It is suggested that, throughout its development, the fruit possesses an inherent tendency to separate from the spur but that, at certain periods, it is prevented from doing so by hormonal stimuli emanating from the developing seeds. Two such stimuli have been demonstrated, at 3–4 weeks and 7–10 weeks after petal-fall respectively, both of which are associated with particular developmental stages of the endosperm. In addition the existence of a third, as yet undetected stimulus at the time of fertilization, is postulated.     

Thinning ‘McIntosh’ apple in British Columbia

Trials were conducted on 11-year-old trees of ‘McIntosh’ apple (Malus domestica, Borkh.) in Creston, British Columbia, to analyse the thinning effects of the blossom spray sodium 4,6-dinitro-ortho-cresylate (DNOC), and single and combination treatments of the post-bloom sprays naphthalene acetic acid (NAA), naphthaleneacetamide (NAD), and 1-naphthyl-(N-)methyl carbamate (carbaryl). DNOC was ineffective as a thinning agent when used alone. NAA did not significantly affect numbers of remaining fruit when used alone or with NAD or carbaryl. NAD showed significant thinning effects when applied alone or with carbaryl. Carbaryl was an effective thinning agent when used alone. The effects of carbaryl alone and carbaryl with NAD were found to persist after spacing the fruit on the branches by hand.     

Identifying the optimum thinning time for red ‘Fuji’ apples

Two trials assessed the relationship between time of spray application and the effectiveness of naphthalene acetic acid (NAA) or ethephon on thinning of red ‘Fuji’ apples. In particular the effectiveness of sprays at, before, or just after full bloom (FB) were assessed. Both NAA and ethephon were effective thinners at FB. The thinners differed in efficacy with time; NAA was less effective before and after FB, ethephon was efficient before FB but this thinning power declined over time linearly, becoming ineffective 5-6 d after full bloom (DAFB) Thinning effectiveness was reflected in improved mean fruit weight and size. With NAA, increasing the concentration from 10 to 20 mg P1 did not improve fruit thinning. Whereas NAA sprays 5-10 DAFB reduced pip numbers to fewer than the controls, ethephon sprays did not result in such large reductions. It was concluded that the most effective time to thin red ‘Fuji’ was at or near FB. This recommendation is firm for ethephon but further clarification is needed for NAA. This conclusion supports some work for other cultivars. However, the problem of the preoccupation with fruit set by many orchardists in countries with climates cooler than Australia is recognized as a continuing problem for the recommendation for such general early use of thinners.     

The Hormone Content of the Seed in Relation to Endosperm Development and Fruit Drop in the Apple

Apple seeds at certain stages of development have been shown to contain a hormone which can be extracted with boiling water and which is active in stimulating the development of unpollinated tomato ovaries. Use has been made of this latter fact to detect and measure the amount of hormone present in the seeds at various stages of development, using the methods described in the previous paper (see pp. 19 to 31).

In the variety Beauty of Bath the appearance of the hormone in the seed at 25-30 days after petal-fall corresponded with the cessation of the post-blossom drop, and the disappearance of hormone from the seeds of nearly ripe apples was correlated with the occurrence of the pre-harvest drop. The seeds from “ June drop ” fruitlets of two other varieties contained much less hormone than those from fruitlets remaining attached to the tree, and from this and other evidence it is concluded that this hormone is concerned with the control of fruit drop. It appears to be produced in the endosperm tissue of the seed but not in the embryo. Although it will stimulate the development of tomato ovaries it apparently plays no direct part in initiating fruit growth in the apple. The presence of a second, as yet undetected, hormone with this function is postulated.     

The thinning effect of benzyladenine on red ‘Fuji’ apple trees

A trial, at the Grove Research Station in southern Tasmania, studied the thinning effect of benzyladenine (BA) on five year old red ‘Fuji’ apple trees. Untreated control trees were compared with trees treated at four timings, from full bloom (FB) to 30 d after full bloom (AFB), with four concentrations of BA (50, 100, 200 or 400 mg I-1). The most effective time of thinning was 20 d AFB, when increasing concentration also increased thinning. Further advantages of this successful thinning were reflected in better fruit size and weight. At 30 d AFB high concentrations of BA depressed fruit weight. Return bloom was improved significantly by both 20 and 30 d. AFB sprays with a concentration effect at 20 d AFB. Timing of sprays had no effect on the incidence of russet which was increased only by applications of 400 mg l-1. Both the higher concentrations and later timings resulted in an increase in shoot numbers and total growth. Reduction in mean shoot length was related more to the concentration of BA used than to differences in the timing of sprays. BA has shown potential as a thinner for red ‘Fuji’ apple at 20 d AFB.     

Effects of 1-aminocyclopropane carboxylic acid on the rate of ethylene release from detached fruiting spurs and on fruit abscission in apple

Summary

1-Aminocyclopropane carboxylic acid (ACC) was applied to apple (Malus × domestica Borkh.) trees or to individual fruiting spurs between full bloom (FB) and 31 d after full bloom (DAFB; mean fruit diameter of 20 mm) to determine the effects of ACC on the ethylene released from detached spurs and on fruit abscission. The rate of ethylene release from detached fruiting spurs increased 1 d after applying 50 mg l^–1 ACC at full bloom or 16 DAFB (mean fruit diameter of 10 mm), but ACC had a reduced effect on the rate of ethylene release when it was applied 31 DAFB (mean fruit diameter of 20 mm). ACC reduced fruit set in ‘GoldRush’ apple in a concentration-dependent manner in 2009 and in 2010, but had no thinning activity on ‘Pink Lady’ in 2010. ACC at 200 mg l^–1 resulted in the yellowing and abscission of ‘GoldRush’ spur leaves in 2009, but not in 2010. The effects of combining ACC and 5 mg l^–1 naphthaleneacetic acid on fruit set in ‘GoldRush’ apple were additive. The application of 200 mg l^–1 ACC when fruit are ca. 10 mm in diameter may therefore be a useful chemical thinning treatment for apple fruit.     

不同中间砧对苹果果实苹果酸代谢关键酶活性及其相关基因表达的影响

为深入探究中间砧影响苹果果实苹果酸代谢的机理,以SH40实生后代（代号53、111和236）为中间砧嫁接的‘天红2号’苹果树为试材,测定果实发育过程中苹果酸含量、相关代谢酶活性及基因相对表达量。结果表明：果实成熟时,以53号为中间砧嫁接的‘天红2号’果实苹果酸含量显著高于以111号为中间砧的。盛花后30、40、100 ~ 160 d,以53号为中间砧的果实中苹果酸脱氢酶（NAD-MDH）活性显著高于以111号为中间砧的;盛花后30、40和130 d,53号处理的磷酸烯醇式丙酮酸羧化酶（PEPC）活性显著高于111号处理的;盛花后100 d,以111号为中间砧的果实中苹果酸酶（NADP-ME）活性显著高于以53号为中间砧的。基因表达结果显示,盛花后100和160 d,以53号为中间砧的NAD-MDH基因相对表达量显著高于以111号为中间砧的,同时NADP-ME基因表达量也显著高于以111号为中间砧的;盛花后30 和160 d,以53号为中间砧的PEPC基因相对表达量显著高于以111号为中间砧的。     

A comparison of high- and low-volume spray techniques in the thinning of ‘Golden Delicious’ apples

A trial at the Grove Research Station, southern Tasmania in 1989-90 examined the thinning of mature ‘Golden Delicious’ apple trees. High-volume sprays were applied at 6,0001 ha^-1 as air blast or vertical boom using NAA at 10mg l^-1 4d after full bloom (AFB) and 18 d AFB. Carbaryl at 1,000 mg l^-1 and thiram at 1200 mg l^-1 were also applied as combined sprays, 30 and 38 d AFB. These high-volume sprays were compared with unsprayed controls and Micron and Micronair low volume sprayers at 200 and 1,1000 l ha^-1. The dosages of the low volume applications were equilibrated to apply the same rates of chemical per hectare as the high-volume sprays, and the timing was the same. All spray treatments reduced crop load to acceptable levels when compared with the overcropped controls. There were no consistent differences between treatments for number of fruit per cm² limb area except that the lowest volume Micron spray thinned significantly less than most other treatments. Considering the number of fruit per 100 blossom clusters the airblast spray was the only treatment to be significantly better than the Micron at 2001 ha^-1. These numbers were reflected in mean fruit weight with the control fruit being significantly lighter than any sprayed fruit. The air blast treatment produced significantly heavier fruit than all other treatments, apart from the other high volume treatment. Fruit size distribution (FSD) showed significant differences between the control and all the spray treatments. The airblast treatment produced significantly more fruit in the 80 mm or larger category than all treatments, apart from the vertical boom application. These preliminary results suggest that although low-volume sprays can thin apple trees, the use of ultra low volumes (ULV) should be explored using machines capable of controlled droplet application (CDA). This may ultimately lead to less chemical being applied per hectare.     

苹果化学疏花疏果研究进展

根据文献报道对苹果的化学疏花疏果研究及其应用情况进行了综述和分析。苹果化学疏花疏果从1930年开始研究以来,发现20余种化学药剂有疏花疏果作用,其中实际应用最广泛的有西维因、NAA、石硫合剂,西维因和NAA用于疏果,石硫合剂用于疏花。但由于这些疏花疏果剂及其应用效果都存在一定缺点,近年来各国研究工作者致力于研究和寻找无公害的疏花疏果剂。影响化学疏花疏果的因子基本明确,有关研究报道比较一致。对化学疏花疏果剂的作用机理研究结果不一,尚存在分歧。     

Prohexadione–Ca inhibits vegetative growth of ‘Smoothee Golden Delicious’ apple trees

Experiments to test the effectiveness of prohexadione–Ca as a growth inhibitor in apple trees have been carried out for 3 years in the Middle Ebro Valley (Spain). Also, effects on fruit quality and flower initiation were evaluated. The application of 100–400 mg l⁻¹ of prohexadione–Ca between 12 and 30 days after full bloom (DAFB) to ‘Smoothee Golden Delicious’/M9 apple trees resulted in the inhibition of shoot growth, the effect increasing with concentration, and a greater inhibition was obtained when the trees were first sprayed 12–20 DAFB. A second spray was usually needed to avoid a regrowth of the shoots. The effectiveness of the second application was related to the concentration applied and the date of the first spray. The relative increase in trunk-cross-sectional area was not affected by the growth inhibitor. No negative effects on yield and fruit quality were found except for a reduction of soluble solid content. Flower initiation in the following year was not affected. Concentrations of 100–200 mg l⁻¹ applied shortly after full bloom should be recommended, bearing in mind that a second application might be necessary 6–8 weeks later.     

Individual and combined effects of shading and thinning chemicals on abscission and dry-matter accumulation of ‘Royal Gala’ apple fruit

Summary

Shade and chemical thinning treatments were applied to mature ‘Royal Gala’/M.26 apple trees either alone or in combination to study their effects on the pattern of abscission and growth of spur fruit. Natural fruit drop occurred in two distinct waves in both years; the first wave peaked 20 d after bloom (DAB) at a weekly abscission rate of c 15% in both years. The second wave of fruit drop in 2001 occurred earlier and was more intense than in the previous season. Application of NAA as a bloom thinner increased the maximum weekly abscission rate during the first wave of fruit drop in both years. Chemical fruit thinning treatments (Carbaryl in 2000, BA or delayed lime sulphur in 2001) had no effect on abscission or growth of spur fruit. Covering trees with 80% shade cloth for 3 d (2000) or 5 d (2001) stimulated a wave of fruit abscission that peaked c 10–15 d after removal of the cloth. Shade during the period from 20–25 DAB stimulated more fruit drop than earlier shade treatments, resulting in weekly abscission rates as high as 70%.There were no additive effects of combining thinning chemicals and shade treatments on abscission of fruit from spurs. However, additive effects of shade and thinning treatments were observed when measured as whole-tree crop density values, indicating that abscission of fruit from one-year wood was stimulated when low light conditions preceded application of (fruit) thinning chemicals. Shading trees from 34–39 DAB in 2000 resulted in a transient reduction and subsequent increase in the rate of dry-matter accumulation in fruit that were retained. Considerable challenges lie ahead in developing models of fruit growth that can account for the inter-dependent effects of light and crop load on fruit abscission and development that exist within an orchard environment.     

Preliminary studies on the use of (2RS, 3RS)-paclobutrazol for fruitlet thinning and growth control of ‘Conference’ pear

Summary

Single foliar sprays of paclobutrazol (PP333) at 300, 1000 or 3000 mg H applied at three different stages from full bloom to petal-fall in a year of average initial sets . and fruit size were equally effective in thinning ‘Conference’ pear, increasing the proportion of large fruits at harvest, but decreasing their absolute numbers. Sprays applied nine days after petal-fall reduced initial sets less effectively and, applied 21 days after petal-fall, were ineffective. Thinning was completed within 25 days after petal-fall. Shoot extension was initially retarded at all three concentrations, but later increased, so that the total growth made during the season was not reduced. Single foliar sprays at 300 or 1000 mg l^?1 applied at 70% full bloom in a year of heavy set and small fruit size increased the numbers of large fruits in the >55 mm size category by 66% and decreased those of fruits <55 mm by a similar amount. The increase in the yield of fruits >55 mm and decrease of unsaleable <45 mm fruits was equivalent to about 3 and 2 t ha^?1 respectively from a total average yield of about 17.5 t ha^?1. In the same experiment, similar sprays counteracted the stimulation in the production of small fruits by sprays of gibberellic acid (GA) applied on the same day, but did not increase the harvest of large fruits. Sprays of paclobutrazol at 30 or 100 mg l^?1 applied two weeks after petal-fall and then on three successive occasions at two-week intervals inhibited total extension growth per shoot during the season without affecting initial or final sets, fruit size or flower bud production. Single sprays applied at 100 mg l?1 in July reduced total extension per shoot almost as effectively as the repeated sprays. For more effective control of ‘Conference’ shoot growth, paclobutrazol may have to be sprayed later in the season than commercially recommended. Applied as a blossom thinner, paclobutrazol may increase the yield of large fruits only in years of heavy set and small fruit size, requiring that applications be delayed until set can be judged.     

Chemical thinning of ‘satsuma’ mandarin (citrus unshiu marc.) fruit by 1-naphthaleneacetic acid: Role of ethylene and cellulase

Experiments were conducted to find the effects of 1-naphthaleneacetic acid (NAA) on fruit thinning of ‘Satsuma’ mandarins, and to see whether it affected ethylene production and cellulase activity at the abscission zone.NAA at 300 p.p.m. sprayed 25 days after full bloom was found to thin fruit causing a 30% increase in fruit drop in 1973. The following year, however, the effect of spraying was not significant because the overall percentage of fruit set was low. Cellulase activity of abscission zones of NAA-treated fruit showed considerably increased values in 1973, whereas in 1974 cellulase activity of control and NAA-treated fruit showed similar high values reflecting a higher fruit drop from control trees. Yellow, ready-to-abscise fruit from NAA-treated and from control trees produced higher amounts of ethylene than did apparently healthy green fruit from both treated and control trees. Essentially NAA caused no leaf abscission nor any increase in cellulase activity in abscission zones. Ethylene production from the leaves also remained low. Spraying 500 p.p.m. ethephon (2-chloroethylphosphonic acid) caused severe leaf fall, markedly increased cellulase activity in abscission zones and ethylene production.The mechanism of fruit thinning by NAA is discussed in relation to the role of ethylene and cellulase.     

Effects of Thinning Blossom and Fruitlets on Growth and Cropping of Sunset Apple

The results of a fruit-thinning trial, by hand, on the apple variety Sunset on M.IX are reported. Thinning flowers at the pink bud stage, and fruitlets at one, two and three weeks after full bloom, increased fruit size and trunk-girth increment. The two earliest treatments increased the number of shoots but mean shoot length was unaffected by any of the treatments.

The increase in fruit size was due to an increase in cell number per fruit rather than to an increase in cell volume. The concept of competition between meristematic regions of the aerial parts of the tree is discussed. No residual effect of thinning on yield, fruit size or shoot growth occurred in the season following the three-year experimental period, when the trees were left untreated.     

Thinning golden delicious apples using ethephon sprays

In southern Tasmania ethephon sprays were applied at two stages of bloom and after bloom at concentrations from 350 to 1 400 ppm. At both the balloon blossom stage and 42 days after full bloom (AFB) 350 ppm ethephon caused satisfactory thinning of fruit by decreasing fruit set and increasing the number of fruits 70 mm or more in diameter. Higher concentrations of ethephon at these stages overthinned. At full bloom concentrations below 1 050 ppm ethephon did not remove significant numbers of fruit but both 1 050 and 1 400 ppm spray concentrations satisfactorily thinned the fruit. The spray of 1 400 ppm ethephon 42 days AFB significantly restricted fruit growth. Shoot length was reduced by all ethephon treatments and return bloom in the following spring was heavy in all thinned treatments. A mathematical model describing numbers of fruit set was developed and used to demonstrate a three-dimensional response surface to ethephon thinning sprays.     

Timing of fruit removal affects concurrent vegetative growth and subsequent return bloom and yield in olive (Olea europaea L.)

Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.