Unsprayed Control Trees Research Articles

Calcium Sprays and Crop Load Reduction Increase Fruit Quality and Postharvest Storage in Sweet Cherry (Prunus avium L.)

In many fruit trees, the thinning of buds, flowers, or fruits is used to increase the leaf area-to-fruit ratio (LA:F) and reduce competition for carbohydrates. Meanwhile, calcium (Ca) sprays during fruit development are also used to increase fruit quality and postharvest storage. Such practices have been recommended to increase fruit firmness and reduce fruit cracking in sweet cherries. To understand the effects of foliar Ca sprays and crop load reductions in the combination ‘Lapins’/‘Colt’, trained as the Kym Green Bush, a factorial experiment to determine the interactions between both managements was established in the Central Valley of Chile during the 2018/2019 growing season. Two levels of crop load (CL) were established—thinned (50% crop load) and unthinned (100% crop load) during Stage I of fruit development (31 days after full bloom, DAFB). Three timings of foliar applications of CaCl2 (TFA; 0.8%) were evaluated: early 26 DAFB, later 39 DAFB, or late 62 DAFB. Natural fruit contents and concentrations of Ca were determined on unsprayed control trees. Fruit from the thinned trees were significantly larger and heavier and had a higher titratable acidity than unthinned trees did. Significant interactions between TFA and CL were observed for SSC, without a clear trend. Thinned trees were less affected by pedicel detachment, browning, and fruit decay after 45 d of storage (0 °C). In unthinned trees, a foliar CaCl2 spray at Stage I allowed a higher fruit firmness than CaCl2 sprays at Stage II and III of fruit development. The CaCl2 applications at 39 or 62 DAFB reduced the incidence of cracking in thinned trees. Natural Ca concentrations decreased during fruit development, indicating a cessation of Ca import and a dilution by subsequent growth. Our results suggest that the early reduction of crop load has positive effects on fruit quality and condition during storage, and early Ca sprays (Stage I) improve fruit textural properties, even under high crop loads.

Selenium enrichment, fruit quality and yield of winter jujube as affected by addition of sodium selenite

Winter jujube (Zizyphus jujuba Mill.) is a kind of high quality, fresh jujube fruit originated from China. Selenium (Se) affects the chemical composition and antioxidative properties in plants. At appropriate concentrations, Se acts as an antioxidant or activates mechanisms that can alleviate oxidative stress in the chloroplast, and enhances plant growth. Although the addition of Se is known to increase Se uptake in crops, it is unclear whether exogenous Se affects nutritional and functional components in winter jujube. Winter jujube trees were sprayed with selenium (as sodium selenite) at five concentrations (0, 25, 50, 100, or 200mg/L of Se) three times at the fruitlet stage between July and August. The Se content, ratio of organic Se to total Se in leaves and fruits, fruit quality, and yield were measured. At Se concentrations of 50mg/L or higher, total Se content increased rapidly whereas the ratio increased initially and decreased later. Different Se concentrations affected the quality of fruits differently: at 50mg/L, compared to their values in the unsprayed control trees, vitamin C content was greater by 20.94%; soluble sugars, 29.48%; total flavonoids, 43.48%; and the sugar: acid ratio, 41.81%. Along with the increase of Se addition, average fruit weight and yield of winter jujube presented a trend of increasing up to 50mgL−1 and decreasing thereafter. Thus, the foliar spray of sodium selenite at Se concentration of 50mg/L is recommended during the fruitlet stage of Zhanhua winter jujube.

Evaluation of the field impacts of simulatedBacillus thuringiensis-transgenicPinus radiataon nontarget native Lepidoptera and their natural enemies in a New Zealand plantation forest

Future options for the control of biosecurity risk pests in New Zealand's plantation Pinus radiata forests include Bacillus thuringiensis (Bt) sprays and transgenic trees expressing Bt. Potential impacts on nontarget native Lepidoptera and their natural enemies were assessed via monthly samples of larvae from P. radiata trees sprayed fortnightly for 18 months with Bt at a rate that mimicked the insecticidal effects of transgenic Bt-pines. Bt-treated trees supported fewer larvae of Pseudocoremia leucelaea, Pseudocoremia fenerata, Declana floccosa, Planotortrix notophaea and Ctenopseustis obliquana than unsprayed control trees during both summer seasons. Populations of the most abundant species Pseudocoremia suavis were reduced on Bt trees in the second summer only. Proportions of lepidopteran larvae on Bt and control trees infected with an unidentified microsporidium were not significantly different. Pseudocoremia suavis and D. floccosa were less likely to be parasitized by Meteorus pulchricornis when collected from Bt rather than control trees, although parasitism rates in other species did not differ. Transgenic Bt-pines could cause nontarget lepidopteran mortality in New Zealand plantations but population effects are likely to vary with species, weather and availability of refugia; natural enemies are unlikely to be at significant risk.

Sensitivity of Populations of Botrytis cinerea from Pear-Related Sources to Benzimidazole and Dicarboximide Fungicides.

Botrytis cinerea is responsible for a major portion of postharvest decay in winter pears in the Pacific Northwest. The baseline sensitivity levels (mean EC50 values) of a wild-type B. cinerea population to thiabendazole and iprodione were 6.66 and 0.56 mg/liter, respectively. B. cinerea from commercial orchards not treated with a benzimidazole had significantly lower incidence of resistance (0.59%) to a discriminatory concentration of thiabendazole at 10 mg/liter than did isolates from orchards in which benomyl had been applied for experimental purposes (16.0%), unsprayed control trees in benomyl-sprayed orchards (5.34%), and isolates from packinghouses where thiabendazole was applied as a prestorage drench or packingline spray (3.23%). The mean EC50 value of isolates in the wild-type population was lower than those of resistant isolates from all other sources. High-level thiabendazole resistance (EC50 > 100 mg/liter) was found in 0.20% of isolates from unsprayed commercial orchards, 9.33% of isolates from benomyl-sprayed orchards, and 2.67% of isolates from unsprayed control trees in these benomyl-sprayed orchards. In isolates from packinghouses where a thiabendazole line spray was applied, 1.52% had high-level thiabendazole resistance. All isolates from all pear-related sources tested were sensitive to iprodione at 10 mg/liter. This study provides evidence supporting current recommendations of a single postharvest application of a benzimidazole to control decay caused by B. cinerea, and no application of benzimidazole fungicides in the orchard.

Ethylene Evolution from Detached Apple Spurs in Response to Chemical Thinners

Ethylene evolution from detached fruiting apple spurs was measured after application of various bloom and post-bloom thinning agents. Ethylene evolution from fresh detached spurs of `Splendor' apple trees increased one day after application of a bloom thinning spray of ethephon or NAA, and remained higher than rates of ethylene evolution by detached spurs from unsprayed control trees for 6 (NAA) or 10 (ethephon) days. Both ethylene evolution and fruit abscission during the initial drop period were higher on trees treated with ethephon compared to NAA, however final fruit set was similar for these two treatments. Ethylene evolution was significantly higher following NAA application onto `Fuji' trees compared with NAAm, but final fruit set was reduced by a similar amount (≈20%) for both of these materials. Application of BA to `Pacific Rose™' apple trees when the average diameter of spur fruit was either 4 mm (6 days after full bloom) or 7 mm (12 days after full bloom) resulted in a significant increase in the rate of ethylene evolution and also reduced final fruit set. When application of BA was delayed until the average diameter of spur fruit was 14 mm (24 days after full bloom) neither the rate of ethylene evolution or final fruit set was affected. Although an increase in the rate of ethylene evolution was a prerequisite for thinning in the present experiments, the magnitude of this increase was not related to the final thinning efficacy. Chemical names used: benzyladenine (BA); 2-chloroethyl phosphonic acid (ethephon); naphthaleneacetic acid (NAA); naphthalene acetamide (NAAm).

Influence of different calcium materials and spray timing on mineral composition, yield, fruit quality, and control of fruit disorders of ‘anjou’ pears

Abstract During a six‐year period (1980, 1985–1989), 20 different calcium (Ca) materials were sprayed at an early (3X; June to July), late (3X; July to August), and an early plus late (5X; June to August) timing on 25‐year‐old ‘Anjou’ pear (Pyrus communis L.) trees. Calcium chloride (CaCl2) sprays increased fruit Ca in the cortex by an average of 10.5% greater than in unsprayed controls and cork spot was reduced by an average of six‐fold. Yield from trees sprayed with Ca materials averaged greater than 13% more crop load than the unsprayed control trees. Leaf and fruit injury from CaCl2 sprays in 1980 were near borderline acceptability, but injury was reduced slightly by halving the spray concentration rate to 681 g CaCl2 per 379 liters of water in 1985 to 1989. Due to temperatures above 26°C, leaf and fruit injury from Ca sprays, particularly calcium nitrate [Ca(NO3)2], were more severe for the late or early plus late sprays than for the early sprays. Fruit size was slightly larger on trees sprayed only ...

Effects of preharvest calcium sprays on apple and pear quality

Abstract Fruit from apple (Malus domestica Borkh.) and pear (Pyrus communis L.) trees sprayed with calcium chloride (CaCl2) had higher fruit calcium (Ca) concentrations by 10% or more than the unsprayed control trees. In ‘Delicious’ and ‘Golden Delicious’ apples, the incidences of bitter pit, scald, and internal breakdown were substantially reduced with CaCl2 sprays. In most instances, firmness, total acidity, and juiciness ratings of apples were improved with CaCl2 sprays. In ‘Anjou’ pears, the incidence of cork spot was reduced with CaCl2 sprays. Only sprays of NutriCal and CaCl2 + Regulaid showed substantial increases in fruit firmness of ‘Anjou’ pear. In 1991, yield of ‘Anjou’ pear trees was increased by 36% with CaCl2 sprays compared with the control trees.

Effect of cobalt ions on floral malformation, yield and fruit quality of ‘Dusheri’ mango(Mangifera indicaL.)

four year study of malformation in mango (Mangifera indica L.) revealed that a single foliar spray application of 1000 ppm cobalt sulphate prior to flower bud differentiation in the first week of October successfully reduced floral malformation by 93,94,87 and 84% in each year respectively, as compared with the earlier recommended treatment of naphthalene acetic acid (100 ppm) and with unsprayed control trees. The single foliar spray of cobalt sulphate was more effective in reducing floral malformation than a double spray. This treatment also increased fruit yield in all four years. The foliar application of cobalt improved fruit weight, size, TSS/acid ratio and the total sugars in the fruit. Experimental findings based upon three years’ data clearly demonstrated that the deficiency or toxicity of cobalt is not related to the cause of mango malformation because the concentrations of cobalt did not vary between healthy and malformed organs.

Autumn Foliage Applications of ZnSO4 Reduced Leaf Nitrogen Remobilization in Peach and Nectarine

Premature defoliation of peach and nectarine (Prunus persica L. Batsch) trees resulting from foliar applications of ZnSO4 reduced N remobilization that typically occurs during leaf senescence. Leaf N remobilization in unsprayed control trees ranged from 45% to 50%, irrespective of tree N status. Leaf N remobilization in trees receiving foliar applications of ZnSO4 ranged from a positive influx of N into the leaf to ≈30% of the N remobilized, depending on ZnSO4 application timing and method of expressing leaf N levels. Early ZnSO4 applications resulted in less N remobilization. Measuring leaf N on an area basis was a more precise indicator of N remobilization than N per unit dry weight, because leaf weight per unit area changes during leaf senescence.

EFFECTS OF PHOSPHATE SPRAYS ON McINTOSH APPLE FRUIT AND LEAF COMPOSITION, FLESH FIRMNESS AND SUSCEPTIBILITY TO LOW-TEMPERATURE DISORDERS

Phosphate compounds (NH4H2PO4, KH2PO4 and CaH4(PO4)2 in 1982; NH4H2PO4 in 1983) applied to McIntosh apple trees as six foliar sprays at weekly intervals starting 4 wk after bloom, increased leaf and fruit P, decreased loss of firmness under some storage conditions and decreased incidence of low-temperature storage disorders. Phosphate sprays improved firmness retention of apples stored in either 5% CO2 plus 3% O2 or 0.7% CO2 plus 1% O2 in 1982 and maintained fruit firmness during a simulated shelf life at 20 °C for apples stored at 0 °C. Firmness retention at 20 °C of the 1983 crop was improved by monobasic ammonium phosphate regardless of storage temperature. Apple samples from unsprayed control trees had mean phosphorus concentrations of 85.4 and 94.4 ppm fresh weight in 1982 and 1983, respectively (whole fruit less seeds and stems).Key words: Apple, fruit phosphorus, low temperature breakdown, core flush

The influence of paclobutrazol on the growth and cropping of sweet cherry cultivars. I. The effect of annual soil treatments on the growth and cropping of cv Early Rivers

SummaryAnnual treatments with paclobutrazol to the soil beneath cv Early Rivers sweet cherry trees significantly inhibited the growth of new extension shoots. An application of 1.6 g a.i. per tree in March 1981, followed by 0.8 g a.i. per tree in March 1982,1983 and 1984 sustained almost complete inhibition of extension growth on young trees on either Colt or FB 22 (a sibling of Colt) rootstocks. On treated trees, crown volume at the end of 1984 was only one-third that of unsprayed control trees. The density of floral bud production was doubled in 1982 and 1983 and trebled in 1984 on the treated trees, and the treatment also increased the number of floral buds per cluster and the number of flowers per floral bud. Frost damage to floral buds was reduced by more than 20% in the winter of 1981/82, as was the damage to blossoms by spring frosts in 1983. The time of blossoming was slightly advanced by the treatment. The percentage final fruit set was not influenced by the treatments in 1982 and 1983, but was halved on treated trees in 1984. Yields per tree were increased by the treatment in 1982 but reduced in 1983 and 1984; however, yields m−3 of tree crown were increased on treated trees by 92% and 69% in 1983 and 1984 respectively. Larger fruits were harvested from treated trees in all three years of the experiment.

Impact of etaconazole and benomyl on powdery mildew, leaf characteristics, growth and yield of Rome Beauty apple trees

SummaryTwo fungicides, etaconazole and benomyl, used to control powdery mildew (Podosphaera leucotricha [Ell. et. ev.] Salm) on apples were tested for their effects on the growth and leaf characteristics of cv Rome Beauty apple trees and seedlings (Malus sylvestris, Mill*). Etaconazole is a sterol-inhibiting fungicide and benomyl a non-sterol-inhibiting fungicide. Compared to the controls, etaconazole treatment caused shorter internodes and a smaller leaf area in both greenhouse-grown seedlings and orchard trees. The etaconazole-treated trees, however, produced greater fruit yields than the unsprayed control trees that had high mildew infection. Benomyl did not control the mildew as well as etaconazole and also did not produce as pronounced an effect on growth.*Commonly designated M. pumila