Peach Tree Orchard Research Articles

Chemical thinning of peach trees

Peach tree thinning is essential to harvest quality fruits and to keep balanced production for several years. Manual thinning of peach trees demands much work force and increases production costs. Chemical thinning may be an alternative solution, but efficiency depends on doses and species. This study aimed at evaluating the effect of metamitron – applied at different concentrations – on chemical thinning of peach trees in the south of Brazil. The experiment was carried out in a commercial peach tree orchard where ‘Sensação’ cultivars, in Morro Redondo, Rio Grande do Sul (RS) state, Brazil. The following metamitron concentrations were applied at concentrations of 100 mg L-1, 200 mg L-1, 300 mg L-1, 400 mg L-1, manual thinning was carried out 40 days after full bloom (DAFB) and to the treatment where the plants have no thinning. Fruit abscission, effective fructification, total number of plants per plant, production per plant, mean mass and fruit diameter were evaluated. Concentrations of 300 and 400 mg L-1 metamitron 40 DAFB provides promoted high fruit abscission, besides decreasing the number of fruits and production. Therefore, concentrations of 100 and 200 mg L-1 of metamitron 40 DAFB provides results in an efficient thinning practice similar to manual thinning for production, mass and fruit diameter.

Two years old peach trees intercropped with a grass mixture can grow through a lithic discontinuity to access water the grass cannot

The hypothesis of niche complementarity for the use of soil resources is crucial for the performance of agroforestry systems. Our aim was to test the hypothesis that roots of 2 years old peach trees intercropped with grass can extract deep soil water below a shallow lithic discontinuity, composed of a layer of pebbles in a powdery calcareous matrix and that hardens in dry conditions. A peach tree orchard was planted on a soil with an average 0.5 m deep lithic discontinuity. Soil water content was measured every fortnight on the row and the inter-row with a neutron probe every 0.2 m up to 3 m depth. The contribution of each soil layer to trees and grass transpiration was simulated with a dynamic water balance model. Results show that tree roots grew through the lithic discontinuity and accessed a water refilled soil layer beneath it only 2 years after plantation, whereas grass roots did not grow below 0.5 m. Soil water content decrease up to 2 m depth after the cessation of irrigation was analysed as the result of tree water uptake. Tree water uptake simulations showed that soil layers below 1 m can contribute up to 17% of the total water uptake of the 2 years old trees. Our results suggest that a lithic discontinuity such as the one in our study may not be an impediment to the perennial trees root growth allowing them to access deep soil water. This suggests that soils with such a lithic discontinuity may be suitable for dryland agroforestry in which deep soil water available to the trees may help in reducing competition for water.

A spraying path planning algorithm based on colour-depth fusion segmentation in peach orchards

Automatic and precise spraying in orchards is currently an active area in precision agriculture research. Research on this topic mainly focuses on the recognition of fruit trees and the planning of driving paths. The dense canopy and complex background of peach tree orchards present great challenges in fruit tree recognition. In this study, an algorithm based on colour-depth vision was developed to solve the path planning problem for precise spraying in peach orchards. First, a colour-depth binocular sensor was used to acquire video images in peach orchards. Then, a colour-depth fusion segmentation method (CDFS) based on the leaf wall area (LWA) of the colour-depth images was proposed. This method combines the result of Otsu segmentation for the green layer of the colour image and the K-means layering result of the depth image to accurately detect the LWA of peach trees. Then, image erosion was used to delimit the two largest LWAs as the region of interest (ROI). Finally, the spraying path was planned by detecting the midpoint of ROI spacing as the end of the spraying path. A comparative analysis of five image segmentation algorithms showed that the proposed CDFS algorithm produced the closest LWA to that obtained by manual segmentation and thus achieved the best segmentation effect. Comparing this automatic path plan method with the drivable areas showed that the overall accuracy rate of the path planning was 97.5%. Therefore, the proposed algorithm planned paths within the drivable area and can thus be used to accurately and automatically plan spraying paths in peach orchards, except when there were gaps between rows in the fruit orchard.

Influence of the Period of Peach Tree Chemical Thinning on Fruit Quality

The need to decrease production costs along with the lack of man power in the countryside has asked for cultural practices which lead to these factors, such as thinning. Thus, chemical thinning has been studied as an alternative to fruit manual thinning. Therefore, this study aimed at evaluating the quality of peach tree fruits after chemical thinning with metamitron at different time periods in the south of Brazil. The experiment was carried out in a commercial peach tree orchard with cultivars ‘Maciel’ in Morro Redondo, Rio Grande do Sul state, Brazil, from 2015 to 2016. Treatments consisted in the application of metamitron (doses of 200 mg L-1) on the 20th, 30th, 40th, 50th and 60th day after full bloom (DAFB) and manual thinning on the 40th DAFB. Epidermis color, pulp firmness, ripeness index, soluble solids, titratable acidity, juice pH, total phenolic compounds and antioxidant activity were evaluated. The application of metamitron in peach tree thinning did not affect peach color. Changes in the other variables related to the quality of fruits depended on the application period of metamitron in the thinning process and between crops.

Assessing ranked set sampling and ancillary data to improve fruit load estimates in peach orchards

Fruit load estimation at plot level before harvest is a key issue in fruit growing. To face this challenge, two sampling methods to estimate fruit load in a peach tree orchard were compared: simple random sampling (SRS) and ranked set sampling (RSS). The study was carried out in a peach orchard (Prunus persica cv. ‘Platycarpa’) covering a total area of 2.24 ha. Having previously sampled the plot systematically to cover the entire area (104 individual trees or sampling points), both sampling methods (SRS and RSS) were tested by taking samples from this population with varying sample sizes from N = 4 to N = 12. Since RSS requires ancillary information to obtain the samples (ranking mechanism), several proximal and remote sensors already used or recently introduced in agriculture were assessed as data sources. A total of 14 variables provided by 5 different sensors and platforms were considered as potential ancillary variables. Among them, RGB images captured by an unmanned aerial vehicle (UAV), and used to estimate the canopy projected area of individual trees, proved to be the best of the options. This was shown by the high correlation (R = 0.85) between this area and the fruit load, providing RSS with the UAV-based canopy projected area the lowest Coefficient of Error (CE) for a given tree sample size. Then, comparing relative efficiency between random sampling (SRS) and RSS, the latter enables more precise fruit load estimates for any of the considered sample sizes. Interest and opportunity of RSS can be raised from two points of view. In terms of confidence, RSS managed to reduce the variance of fruit load estimates by about half compared to SRS. Sampling errors above the 10% threshold were always produced significantly fewer times using RSS, regardless of the sample size. In terms of operation within the plot, sample size could be reduced by 50%, from N = 10 for SRS to N = 5 for RSS, and this being expected sampling errors less than 10% in practically 70% of the samplings performed in both cases. In summary, fruit growers can take advantage of the combined use of appropriate data (RGB images from UAV) and RSS to optimize sample sizes and operational sampling costs in fruit growing.

Effect of combined deficit irrigation and grass competition at plantation on peach tree root distribution

Agroforestry systems success is predicated on the assumption of root spatial separation between the tree and the crop species. Such a feature, where tree roots prospect subsoil horizons whereas intercrop roots prospect top soil horizon is thought to eventually happen as the system ages and trees get older. However, since roots are very plastic, we can hypothesise that it is possible to shape the tree root system when trees are young, i.e. after plantation. In this experiment, we tested the hypothesis that combining a moderate water deficit to change the carbon allocation pattern in favour of root over shoot growth combined with the top soil competition brought about by the intercrop will force tree roots to grow deeper, thus leading to the vertical separation of the trees and the intercrop root systems. To test this hypothesis, a peach tree orchard was established in 2014 with three water regime treatments: (i) a fully irrigated control without intercrop (C), (ii) a moderate water deficit treatment without intercrop (RDI) and (iii) a moderate water deficit treatment intercropped with a grass + legume mixture (RDI + G). Roots were manually excavated at the end of the first and the second growing seasons and root length and biomass per soil horizon and distance to the tree trunk were measured. The juvenile tree root system in all treatments was mainly plagiotropic, reaching 1.5 m from the tree trunk (middle of the inter row) horizontally as opposed to 0.7 m vertically, without difference between treatments. The combination of water deficit and intercrop competition reduced tree root biomass fourfold in 2014 and by 3 in 2015. Tree roots in RDI + G were also excluded from the topsoil horizon (0–10 cm) due to grass + legume competition, but because of the strong reduction in their total biomass, they did not grow in deeper soil horizons than the control tree roots (C). Secondary vertical tap roots were only starting to grow by the end of the second year, suggesting that root growth at depth could not take place the year after plantation especially in grafted scions.

Root and aerial growth in early-maturing peach trees under two crop load treatments

The objectives of the paper were to study the pattern of root growth (measured by minirhizotrons) in relation to trunk, fruit and shoot growth and the effects of crop load on tree growth and yield in peach trees. Two crop load (commercial and low) treatments were applied in a mature early-maturing peach tree orchard growing in Mediterranean conditions. Root growth dynamics were measured using minirhizotrons during one growing season. Shoot, trunk and fruit growth were also measured. At harvest, all fruits were weighed, counted and sized. Roots grew throughout the year but at lower rates during the active fruit growth phase. Root growth was asynchronous with shoot growth, while root and trunk growth rates were highest after harvest, when the canopy was big enough to allocate the photo-assimilates to organs that would ensure the following season’s yield. Shoot and fruit growth was greater in the low crop load treatment and was accompanied by a non-significant increase in root growth. High level of fruit thinning decreased the current yield but the fruits were more marketable because of their greater size.

Influence of Irrigation Scheduling Using Thermometry on Peach Tree Water Status and Yield under Different Irrigation Systems

Remotely-sensed canopy temperature from infrared thermometer (IRT) sensors has long been shown to be effective for detecting plant water stress. A field study was conducted to investigate peach tree responses to deficit irrigation which was controlled using canopy to air temperature difference (ΔT) during the postharvest period at the USDA-ARS (U.S. Department of Agriculture, Agricultural Research Service) San Joaquin Valley Agricultural Sciences Center in Parlier, California, USA. The experimental site consisted of a 1.6 ha early maturing peach tree orchard. A total of 18 IRT sensors were used to control six irrigation treatments including furrow, micro-spray, and surface drip irrigation systems with and without postharvest deficit irrigation. During the postharvest period in the 2012–2013 and 2013–2014 growing seasons, ΔT threshold values at mid-day was tested to trigger irrigation in three irrigation systems. The results showed that mid-day stem water potentials (ψ) for well irrigated trees were maintained at a range of −0.5 to −1.2 MPa while ψ of deficit irrigated trees dropped to lower values. Soil water content in deficit surface drip irrigation treatment was higher compared to deficit furrow and micro-spray irrigation treatments in 2012. The number of fruits and fruit weight from peach trees under postharvest deficit irrigation treatment were less than those well-watered trees; however, no statistically significant (at the p < 0.05 level) reduction in fruit size or quality was found for trees irrigated by surface drip and micro-spray irrigation systems by deficit irrigation. Beside doubles, we found an increased number of fruits with deep sutures and dimples which may be a long-term (seven-year postharvest regulated deficit irrigation) impact of deficit irrigation on this peach tree variety. Overall, deployment of IRT sensors provided real-time measurement of canopy water status and the information is valuable for making irrigation management decisions.

Assessment of the Dominance Level of the R81T Target Resistance to Two Neonicotinoid Insecticides inMyzus persicae(Hemiptera: Aphididae)

Myzus persicae (Sulzer, 1776), a major crop pest worldwide, displays insecticide resistance to most molecules. The R81T substitution on the β1 subunit of nicotinic receptors of acetylcholine (nAChR) confers target site resistance to neonicotinoids and is widespread in aphid populations colonizing peach tree orchards in Southern Europe. But the impact of this resistance in the field, as well as ways to optimize its management, depends largely on the dominance level of the R81T mutation. In this study, we measured by in vitro assays the response of R81T mutation to two neonicotinoids (imidacloprid and thiacloprid) in 23 M. persicae clones with different resistance genotypes in order to assess the dominance status of this allele. In this study, all homozygous clones for the R81T mutation (genotype 81(TT)) showed a much higher level of resistance to both active substances than other clones. The heterozygous clones 81(RT) displayed a slightly higher level of resistance than wild homozygous, though resistance phenotypes against both neonicotinoids in these two genotypes were overlapping. A great variation of resistance level was found within these two latter clones' categories. The dominance level of insecticide resistance (DLC) strongly suggested that the mutant allele 81T is semirecessive (the wild 81R allele being rather dominant) for both insecticide molecules under test. Mean DLC values were 0.316 for imidacloprid and 0.351 for thiacloprid. Cross-resistance was shown between imidacloprid and thiacloprid. This partial recessivity is valuable information to broaden the knowledge on neonicotinoid resistance, a prerequisite for devising adapted management strategies against insecticide-resistant populations of M. persicae.

Development of a Selective Automated Blossom Thinning System for Peaches

The objective of this investigation was to develop and test an automated selective fruit-thinning system for blossom removal in peach tree orchards. The proposed system needed to visualize the tree fruit canopy, discriminate targets (blossoms), mechanically reach the canopy from a stable platform, and remove unwanted targets. The system consisted of kinematic targeting and heuristic programming, a robotic arm, and a pomologically designed end-effector. A quarter-scale robotic arm based on a Fanuc M-16iL manipulator model and rotating brush end-effector were designed and constructed for this study. The normal and tangential force requirements to remove a peach blossom from a shoot were also evaluated. The resultant blossom force tests yielded a range of 0.44 to 0.57 N for the normal force and 0.49 to 0.71 N for the tangential force. The precision and accuracy of the robotic arm and end-effector placement were then examined. A kinematic positioning test for the robotic arm consisting of 120 repetitions fell within the first standard deviation of a proposed ±2.54 cm precision standard. With a confidence level of 95% and a margin of error of ±8.96%, the robotic arm had a consistent range of -1.26 cm to +1.57 cm vector magnitude per target location. For the end-effector positioning test, the brushes reached the proposed ±2.54 cm target area 100% of the time. The deviation from the target to the center of the brushes was within the first standard deviation with a confidence level of 95% and a margin of error of ±10.33%, and the end-effector brushes had a consistent range of -2.97 cm to +3.04 cm per target location. The selective spatial thinning heuristic algorithm was also tested. The heuristic test consisted of a series of branches that varied in length from 10, 15, and 20 cm spanwise across the branch, with three artificial blossoms placed every 5 cm. The end-effector successfully removed the unwanted blossom in each case.

Desenvolvimento de plântulas de pessegueiro 'Okinawa' inoculadas com micorrizas arbusculares isoladas de pomares de pessegueiros e de vinhedos

O objetivo deste trabalho foi avaliar a influência das espécies de micorrizas arbusculares (MA) Glomus clarum e Glomus etunicatum isoladas de pomares de pessegueiros e de vinhedos sobre o crescimento vegetativo, conteúdo de macronutrientes e substâncias de reserva em plantas do porta-enxerto de pessegueiro cv. Okinawa. O experimento foi conduzido em telado, com delineamento experimental de blocos casualizados, em parcelas subdivididas, com 15 plantas por parcela e quatro repetições. A inoculação dos isolados de MA favoreceu a absorção de nitrogênio, fósforo e potássio, contribuindo para que as plantas inoculadas apresentassem as maiores respostas em altura, diâmetro, área foliar, biomassa fresca e seca da parte aérea, e conteúdo de reservas, superiores às plantas não inoculadas. A eficiência da simbiose foi maior com os isolados oriundos de pomares de pessegueiros, quando comparados aos isolados oriundos de vinhedos.

Soil water content criteria for peach trees water stress detection during the postharvest period

Abstract Irrigation scheduling based on soil water moisture sensors requires that the soil water status be maintained within a range that is optimal for plant growth. The objective of this work was to evaluate whether soil water content dynamics, measured by multi-sensor capacitance probes, could be used to determine indices of a drying soil to detect the commencement of water stress in a peach tree orchard. For this, an experiment was carried out in a drip irrigated mature peach tree orchard in Murcia (Spain). During the postharvest period well irrigated trees (control treatment) were compared with two water stress treatments consisting of a drying cycle applied for one month in two ways: withholding irrigation (Rapid Stress) and progressively reducing irrigation (Gradual Stress). The soil water content (SWC) was measured continuously using multi-sensor capacitance probes. The beginning of plant water stress was identified by the first significant difference in midday stem water potential (Ψstem) between stressed and control trees. The ‘breaking point’ (the transition between a relatively rapid reduction of SWC in the drying soil to a slower rate) as well as the stabilization of the SWC-derived indices coincided with appearance of a water stress level as severe as to reduce plant water uptake, as judged from the Ψstem reduction. The results suggested that a lower SWC limit could be established for irrigation management in early maturing peach trees using capacitance probes at 90% of the field capacity value during the postharvest period.

Soil fungal communities as indicators for replanting new peach orchards in intensively cultivated areas

Italy and Spain are Europe's main peach-producing countries. Since the mid-90s, however, peach-growing areas have decreased in Italy thus causing its loss of European leadership. One of the reasons for the decline is the presence of replant disorders in peach orchards. As soil-borne pathogens are one of the biotic components of aetiology, a study was performed in an intensively cultivated area of southern Italy, to investigate the use of soil fungi as indicators of soil health when planting new peach orchards. Soil sampling was carried out in five replanted peach orchards and five horticultural sites in the “Piana del Sele”, a peach and vegetable-growing valley in the Campania region. Three different soil fungi communities were recorded: soil-inhabiting filamentous fungi; endophytic root fungi, based on cultural methods; and uncultured soil fungi, based on nucleotide sequences of internal transcribed spacers (ITS1 and ITS2) and rDNA gene fragments. Soil health was evaluated with a greenhouse bioassay, using young plants of peach rootstock GF677. Diversity and composition of fungal communities were compared using PAST, a software which includes several functions commonly used in paleoecology. Each peach tree orchard was characterized by a significantly higher diversity score than horticultural crops. The two cultivation systems differed widely for species composition suggesting that vegetative cover and cultivation practices strongly affected fungal community composition. The bioassay to evaluate soil health showed a significant growth reduction in horticultural sites compared to peach sites. This finding was supported by the high abundance of Cylindrocarpon destructans and Thielviopsis basicola, two aggressive root rot agents, within endophytic fungal communities in horticultural sites. In this survey, greatest fungal diversity corresponds to best plant growth. From a practical point of view, when deciding to replant a new fruit tree orchards in intensively cultivated areas, a greenhouse bioassay with the target crop, combined with a quantitative analysis of endophytic root fungal communities, may help in deciding the best soil use.

Qualidade de pêssegos em pomares conduzidos de forma convencional e integrada

O objetivo do trabalho foi avaliar as características de qualidade de frutas nos sistemas de produção integrada (PIF) e produção convencional (PC) em pomar de pessegueiro, cultivar Eldorado, no município de Candiota, RS. Os sistemas de produção foram caracterizados da seguinte forma: PC, PIF e PIF-ráfia. No PC, prevaleceu o manejo e práticas convencionais utilizadas pelo produtor. No PIF, foram utilizadas as práticas de manejo definidas nas Normas para Produção Integrada de Pêssego, já no PIF-ráfia, o diferencial foi à implantação de uma manta plástica de ráfia sob a copa das plantas. O delineamento experimental adotado foi o de blocos casualizados, com quatro repetições e as médias foram submetidas ao teste de Duncan a 5% de significância. As variáveis avaliadas foram: coloração da epiderme, sólidos solúveis totais (SST), acidez total titulável (ATT), relação SST/ATT e firmeza de polpa. Os resultados mostraram que a utilização de plástico de ráfia sob a copa das plantas na cultivar Eldorado, intensificou a coloração vermelha na epiderme e não interferiu nas qualidades químicas das frutas.

Effets d'un extrait de neem (Azadirachta indica A. Juss) sur le développement de Forficula auricularia L (Dermaptera)

Abstract: Effects of a neem seed extract (Azadirachta indica A. Juss) on the development of the Dermaptera, Forficula auricularia L.: Young nymphs and adults of the European earwig, Forficula auricularia L., were exposed in the laboratory and in the field to an extract from seed kernels of the neem tree, Azadirachta indica A. Juss. No effect was observed on mortality, weight, food intake or fecundity of adults when treated directly in the laboratory with 50 ppm of azadirachtin. None of the second instar nymphs treated by contact with the fresh residue or fed on medium treated with 25, 50, or 250 ppm of the product could achieve their development. The nymphs exhibited a decrease of food intake and of ponderal growth a few days after the treatment, as well as an increase of the intermoulting delay. Behavioural tests revealed no repellent or antifeedant effect of the product. Applications in peach tree orchards resulted in a 70% reduction of nymphal population of earwigs. Neem products could be used to reduce earwig populations if applied when young instars are present. They should therefore be avoided during this period on crops where these insects need to be preserved because of their predation on aphids.

The consequences of cultural practices on growth and cropping of peach trees subjected to localized irrigation: Effects of soil management, nitrogen fertilization and tree density

SUMMARYCultural practices were studied in peach tree orchards irrigated with microsprinklers, herbicide strips being maintained along the tree rows. Differences in fruit cropping between treatments varied in the same way as tree vigour, the most vigorous trees having the highest production capacities. Concerning soil management, ground cover vegetation (permanent or temporary) improved fruit production compared with soil cultivation. According to leaf analysis, ground cover vegetation appeared to ameliorate the conditions of trees nutrition. This effect was probably mainly due to increasing soil resistance to compaction; applying organic matter was not effective in improving the performance of trees grown with soil cultivation compared with those grown with ground cover vegetation. Increasing fruit tree density also contributed to increased fruit production. Nevertheless, more than 600 trees per hectare did not allow further increase in fruit yield for the experimental cultivar. Lastly, nitrogen fertilization seemed particularly important for improving the fruiting of peach trees.