Orchard Conditions Research Articles

Vpliv različnih barv protitočnih mrež in geomorfoloških lastnosti na mikroklimatske in svetlobne razmere v nasadu jablan

Geomorphologic characteristics like altitude and terrain slope have an important but often neglected impact on light conditions in orchards. The study concentrated on the impact of altitude and terrain slope in combination with various colours of anti-hail nets (red, grey, blue, green and black) on the light and microclimate conditions in apple orchards. The results exhibit a large reduction of the photosynthetically active radiation (PAR) under the nets, most prominently under blue and red nets (reduction between 38.7 and 45.6%), while the impact of coloured nets on other microclimatic parameters (average air temperature, relative air humidity, temperature of dew point, wet-bulb temperature, heat index, minimum air temperature, maximum air temperature) remain irrelevant. The only consistent difference is an average of 2% increase of maximum air temperature under the blue net in comparison to other treatments. The use of the net also significantly reduce the wind speed (on average by 56.3%) and air flow (on average by 63.4%), and changes the distribution of precipitation in the orchard, most prominently in cases of heavy rain and drizzle. Regarding the orchard’s geomorphologic characteristics, a positive relationship exists between altitude and PAR.

Digital evaluation of leaf area of an individual tree canopy in the apple orchard using the LIDAR measurement system

This paper compares LIDAR and manual measurements of leaf area in orchards. The LIDAR measurements were performed in real orchard conditions. LIDAR data were used to count the number of points and to measure the canopy volume of individual volume elements. Manual measurements included defoliation, counting and leaf area measurements. Both types of measurements were performed in 8 volume elements for 20 apple trees of three different ages and varieties (‘Golden delicious’, ‘Jonagold’ and ‘Gala’). Using regression analysis, we estimated the relation between number of points in the cloud, canopy volume (both LIDAR measurements) and the leaf area (manual measurement). The maximum value of the correlation coefficient was 0.87816, when established from the relation between the number of points in the cloud and the canopy leaf area. The maximum value of the correlation coefficient was 0.80167, when established between the volume of tree canopy volume element and the leaf area.

Defining and Evaluating a Decision Support System (DSS) for the Precise Pest Management of the Mediterranean Fruit Fly, Ceratitis capitata, at the Farm Level

A Decision Support System (DSS) was developed and evaluated to control the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedermann), by incorporating a semi-automatic pest monitoring and a precision targeting approach in multi-varietal orchards. The DSS consists of three algorithms. DSS1, based on the degree days calculation, defines when the traps should be deployed in the field initiating the medfly population monitoring. DSS2 defines the areas to be treated and the type of treatment based on the number of adult medfly captures, harvesting time, and phenological stage of the host cultivar. DSS3 defines the spraying procedure considering the technical registration properties of the selected insecticide (e.g., withholding period and efficacy duration time) and weather conditions. The DSS was tested in commercial orchard conditions near Rome, central Italy, with a randomized complete blocks experimental design, comparing DSS-assisted and conventional management. In the DSS-assisted plots, a semi-automatic adult medfly monitoring system was deployed, composed of real-time, wireless electronic traps. The output of the functioning DSS is a map of spraying recommendation, reporting the areas to be treated and the treatment type (bait or cover insecticide spraying). The farmer was left free to follow, or not, the DSS indications. The first medfly captures were observed on June 30, whereas the DD threshold was reached on July 3 when the DSS started to operate. The field test produced 29 DSS decisions from July 3 to September 1 and confirmed that medfly management using the DSS substantially reduced the number of pesticide applications, the treated area, and the volumes of pesticide utilization. No significant differences in infested fruit were observed between DSS-assisted and conventional management. The level of acceptance of the DSS by the farmer was 78%. This evidence confirmed the requirement of fully involving farmers and pest managers during the evaluation process of DSS.

Effect of Time and Amount of Supplemental Irrigation at Different Distances from Tree Trunks on Quantity and Quality of Rain-fed Fig Production

Supplemental irrigation under prolonged drought conditions has a key role in providing water for transpiration of rain-fed fig trees. The effect of different times and amounts of supplemental irrigation at different distances from the tree trunk on quantity and quality of Estahban rain-fed fig production was evaluated during two years. A randomized complete block design with four replications on fig cultivars of Sabz was used to conduct the experiment. Treatments of supplemental irrigation included three different application positions including: close to tree trunks (NT); 1-1.1 m from tree trunk (UT) and outside of tree canopy (OT), using three different quantities of irrigation water as no supplemental irrigation (control), 1000 and 2000 liters irrigation water per tree, and with two different supplemental irrigation times in early spring and mid-summer. Results showed higher soil water content for irrigation during early spring, near tree trunk with 2000 liters irrigation water per tree. Despite the reduction in total soluble solids (TSS), supplemental irrigation improved the yield, size and skin color of fruits compared to the control. In both years, fig yield was higher in NT and OT treatments compared to UT. Irrigation out of canopy produced more fruits with higher quality. A non-significant difference between yields in irrigation water amount treatments during the second year indicated the adequacy of 1000 liters per tree. Application of 1000 liters, out of canopy in mid-summer would be recommended to fulfill marketing goals and sustainable use of regional water resource under drought conditions in rain-fed fig orchards.

Effect of Orchard Management Factors on Flesh Color of Two Red-Fleshed Apple Clones

Little is known about factors affecting anthocyanin biosynthesis in red-fleshed apples (Malus × domestica Borkh.). The objective was to establish the effects of orchard management factors on flesh anthocyanin content of dark-colored (DC) and light-colored (LC) apple clones. Flesh color was assessed by measuring color in the L, a, b mode using a spectrophotometer and predicting the anthocyanin content based on relationships between the absorption of a flesh extract at 530 nm and the L-value determined using a spectrophotometer (r2 = 0.99 ***). Fruit from the DC clone were red by 86 days after full bloom (DAFB), whereas the LC clone began to color at 136 DAFB. Color intensity in both clones decreased from the top of the tree to the base. Further, the intensity of the flesh color of the DC clone decreased with shading (94% absorption of incident photosynthetic active radiation). Covering a fruit with a UV absorbing film (100% UV absorption) had no effect on flesh color in the DC clone but decreased color in the LC clone. Fruit thinning increased color in DC and LC fruit. There was little change in flesh color during storage. However, the DC clone developed severe flesh browning as storage progressed beyond 30 days. The results demonstrated that light (visible and UV wavelength) stimulated, whereas shade inhibited, anthocyanin biosynthesis in the flesh under orchard conditions.

Orchard Conditions and Fruiting Body Characteristics Drive the Microbiome of the Black Truffle Tuber aestivum.

Truffle fungi are well known for their enticing aromas partially emitted by microbes colonizing truffle fruiting bodies. The identity and diversity of these microbes remain poorly investigated, because few studies have determined truffle-associated bacterial communities while considering only a small number of fruiting bodies. Hence, the factors driving the assembly of truffle microbiomes are yet to be elucidated. Here we investigated the bacterial community structure of more than 50 fruiting bodies of the black truffle Tuber aestivum in one French and one Swiss orchard using 16S rRNA gene amplicon high-throughput sequencing. Bacterial communities from truffles collected in both orchards shared their main dominant taxa: while 60% of fruiting bodies were dominated by α-Proteobacteria, in some cases the β-Proteobacteria or the Sphingobacteriia classes were the most abundant, suggesting that specific factors (i.e., truffle maturation and soil properties) shape differently truffle-associated microbiomes. We further attempted to assess the influence in truffle microbiome variation of factors related to collection season, truffle mating type, degree of maturation, and location within the truffle orchards. These factors had differential effects between the two truffle orchards, with season being the strongest predictor of community variation in the French orchard, and spatial location in the Swiss one. Surprisingly, genotype and fruiting body maturation did not have a significant effect on microbial community composition. In summary, our results show, regardless of the geographical location considered, the existence of heterogeneous bacterial communities within T. aestivum fruiting bodies that are dominated by three bacterial classes. They also indicate that factors shaping microbial communities within truffle fruiting bodies differ across local conditions.

UAV-Based Remote Sensing Technique to Detect Citrus Canker Disease Utilizing Hyperspectral Imaging and Machine Learning

A remote sensing technique was developed to detect citrus canker in laboratory conditions and was verified in the grove by utilizing an unmanned aerial vehicle (UAV). In the laboratory, a hyperspectral (400–1000 nm) imaging system was utilized for the detection of citrus canker in several disease development stages (i.e., asymptomatic, early, and late symptoms) on Sugar Belle leaves and immature (green) fruit by using two classification methods: (i) radial basis function (RBF) and (ii) K nearest neighbor (KNN). The same imaging system mounted on an UAV was used to detect citrus canker on tree canopies in the orchard. The overall classification accuracy of the RBF was higher (94%, 96%, and 100%) than the KNN method (94%, 95%, and 96%) for detecting canker in leaves. Among the 31 studied vegetation indices, the water index (WI) and the Modified Chlorophyll Absorption in Reflectance Index (ARI and TCARI 1) more accurately detected canker in laboratory and in orchard conditions, respectively. Immature fruit was not a reliable tissue for early detection of canker. However, the proposed technique successfully distinguished the late stage canker-infected fruit with 92% classification accuracy. The UAV-based technique achieved 100% classification accuracy for identifying healthy and canker-infected trees.

Monitoring fruit daily growth indicates the onset of mild drought stress in apple

This work tests the possibility to monitor fruit growth as a potential physiological indicator for tree water status and productive performance in apple, for potential implementation in decision support systems for irrigation scheduling. Starting from 10 weeks after full bloom (WAFB), a wide range of plant water statuses was induced in a “Gala” apple orchard by applying different shading (with red-50%, white-50%, and black-20% nets) and irrigation levels (severe-SS, moderate-MS and no-NS stress). For each net*irrigation treatment combination, midday stem water potential (mSWP) was assessed weekly, while fruit diameter variations were continuously monitored using automatic fruit gauges, from 10 WAFB until harvest. Leaf gas exchanges were also monitored at 14 and 16 WAFB. As expected, the different net*irrigation treatment combinations widely affected mSWP, leaf gas exchanges and fruit growth. On all dates of measurement, leaf gas exchanges were tightly correlated with mSWP, while daily fruit growth showed significant but weaker correlations with mSWP. In all cases, these relationships indicated the onset of drought stress below the threshold of about 1.2 g fruit−1 day−1, which corresponded to mSWP below -1 MPa. Almost no correlation was found between mSWP and the other parameters derived from the fruit daily growth pattern (midday, maximum and minimum absolute growth rates (AGR) and fruit shrinkage). Based on these results, we can conclude that, although fruit daily growth rate is not related to mSWP as tightly as leaf gas exchanges, it represents a promising physiological indicator to be implemented in a decision support system for irrigation scheduling. Specific fruit growth thresholds indicating the onset of drought should be defined, depending on the orchard conditions and productive target.

Limitations to photosynthesis of leaves of apple (Malus domestica) trees across the growing season prior to and after harvest

Photosynthetic responses to CO2 were followed on leaves of Malus domestica cv. Cox's Orange trees growing in orchard conditions, before and after harvest. Rates of photosynthesis, at ambient and CO2 saturated concentrations, were stable across the growing season, except for minor decreases at harvest although rates recovered and remained high thereafter. Stomatal conductance increased over the growing season but declined transiently just before harvest and recovered for most of the season. Rates of ribulose-1,5-bisphosphate (RuBP) carboxylation declined before harvest, however, rates of RuBP regeneration mirrored assimilation. After harvest, rates of RuBP regeneration increased whereas rates of carboxylation increased but remained low, limiting photosynthesis. Lack of change in photosynthesis after harvest was at odds with the literature where photosynthesis of high crop load trees declined soon after, suggesting crop load was not as demanding on the Cox's Orange trees as in other studies.

Actual Evapotranspiration and Tree Performance of Mature Micro-Irrigated Pistachio Orchards Grown on Saline-Sodic Soils in the San Joaquin Valley of California

In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and tree performance, and understanding the mechanisms regulating water-use reduction under saline and saline-sodic conditions. Pistachio ETa was measured with the residual of energy balance method using a combination of surface renewal and eddy covariance equipment. Saline and saline-sodic conditions in the soil adversely affected tree performance with different intensity. The analysis of field data showed that ETa, light interception by the tree canopy, and nut yield were highly and linearly related (r2 > 0.9). Moving from non-saline to saline and saline-sodic conditions, the canopy light interception decreased from 75% (non-saline) to around 50% (saline) and 30% (saline-sodic), and ETa decreased by 32% to 46% relative to the non-saline orchard. In saline-sodic soils, the nut yield resulted around 50% lower than that of non-saline orchard. A statistical analysis performed on the correlations between soil physical-chemical parameters and selected tree performance indicators (ETa, light interception, and nut yield) revealed that the sodium adsorption ratio (SAR) adversely affected tree performance more than the soil electrical conductivity (ECe). Results suggest that secondary effects of sodicity (i.e., degradation of soil structure, possibly leading to poor soil aeration and root hypoxia) might have had a stronger impact on pistachio performance than did salinity in the long term. The information presented in this paper can help pistachio growers and farm managers better tailor irrigation water allocation and management to site-specific orchard conditions (e.g., canopy features and soil-water salinity/sodicity), and potentially lead to water and energy savings through improved irrigation management practices.

DNA paternity testing indicates unexpectedly high levels of self-fertilisation in macadamia

The recently domesticated nut crop macadamia is partially self-incompatible. Variation in the capacity for self-fertilisation is likely to have significant consequences, both for commercial nut production and the conservation of native populations. Molecular paternity testing using 11 microsatellite markers was conducted on open-pollinated seedling progeny of cultivar ‘741’, and mature kernel from eight different cultivars, seven of which have been used in previous self- and cross-pollination studies. The study was based in a varietal trial plot containing 40 different cultivars. Paternity was assigned to 92% of seedlings and 87% of kernel assessed. For four cultivars, selfing rates of 20–40% were detected. Estimates of relatedness between cultivars indicate a first-degree relationship between the two most widely grown cultivars in Australia, ‘741’ and ‘344’, at the level of full-sib or parent-offspring. Insight into the breeding system of macadamia is likely to have major implications for landscape and orchard-scale management. Our results point to significant differences in the capacity for self-fertilisation between cultivars and provide new molecular evidence of pollen flow under orchard conditions.

Geostatistical analysis as essential information for efficient decision making in Anastrepha fraterculus (Diptera: Tephritidae) control in apple orchards

Anastrepha fraterculus Wiedemann (Diptera: Tephritidae) is a key pest in apple orchards (Malus domestica Borkh.). Decision making for fruit fly management relies on the mean number of flies captured per trap. The number of flies captured depends on trap distribution in the orchards and climatic conditions that explain population density patterns as a function of space and time. Knowledge of A. fraterculus spatial distribution patterns and climatic conditions in apple orchards may help to plan control measures, develop efficient monitoring plans and improve management by targeting specific sites and periods when A. fraterculus occurrence is highest. Therefore, our aim in this study was to determine the seasonal variation and spatial distribution patterns of A. fraterculus in commercial apple orchards using geostatistical analysis. Anastrepha fraterculus density was higher during the warmer periods of the year and when apple trees had fruit. The spatial distribution pattern for this pest varied over the years and between orchards. Pest outbreaks were initially small however, they subsequently spread throughout the entire orchard. The adults of A. fraterculus colonized the orchard during the reproductive phase of apple trees, initiating at the edge of the orchard. The different occurrence sites of the pest foci and their fast growth underline the importance of locating and controlling these foci at the initial stage. Still, basing decision making on mean pest density values when implementing control measures can lead to unnecessary applications. The information found in this study provides useful information to initiate methods for timely management, prevention and control during periods of high favorability in orchard sites with high A. fraterculus incidence, thereby reducing production costs and harmful effects of pesticide use.

Climate change projections for chilling and heat forcing conditions in European vineyards and olive orchards: a multi-model assessment

Air temperatures play a major role on temperate fruit development, and the projected future warming may thereby bring additional threats. The present study aims at analyzing the impacts of climate change on chilling and heat forcing on European vineyards and olive (V&O) orchards. Chilling portions (CP) and growing degree hours (GDH) were computed yearly for the recent past (1989–2005) and the RCP4.5 and RCP8.5 future scenarios (2021–2080), using several regional-global climate models, also considering model uncertainties and biases. Additionally, minimum CP and GDH values found in 90% of all years were also computed. These metrics were then extracted to the current location of V&O in Europe, and CP-GDH delimitations were assessed. For recent past, high CP values are found in north-central European regions, while lower values tend to exist on opposite sides of Europe. Regarding forcing, southern European regions currently show the highest GDH values. Future projections point to an increased warming, particularly under RCP8.5 and for 2041 onwards. A lower/higher CP is projected for south-western/eastern Europe, while most of Europe is projected to have higher GDH. Northern-central European V&O orchards should still have future CP-GDH similar to present values, while most of southern European orchards are expected to have much lower CP and higher GDH, especially under RCP8.5. These changes may bring limitations to some of the world most important V&O producers, such as Spain, Italy and Portugal. The planning of suitable adaptation measures against these threats is critical for the future sustainability of the European V&O sectors.

Canopy factors influencing sunburn and fruit quality of Japanese plum (Prunus salicinaLindl.)

High irradiance and high temperatures decrease Japanese plum (Prunus salicina Lindl.) quality by causing sunburn. We manipulated orchard conditions to determine how resultant light and temperature affected fruit quality and sunburn. In the 2013/14 season, early summer pruning, late pruning and a no pruning control were applied in an ‘African Delight’ plum orchard trained to a staggered V trellising system in the Western Cape Province of South Africa. In 2014/15, 20% shade net was incorporated during the hottest part of the season in a split plot design. Shade net and a no shade net control formed the main plots while pruning treatments were subplots. Photosynthetic photon flux (PPF), fruit surface temperature (FST) and sunburn were progressively assessed on two hourly intervals on typically hot days for upper, mid and lower canopy positions. PPF and FST generally decreased from top to bottom of the canopy. Upper canopy positions had bigger and softer fruit with higher sunburn incidence and higher total soluble solids (TSS). Fruit that developed sunburn received >50% PPF of full sun on average while average FST exceeded 35°C. Early summer pruning improved early light penetration but enabled vegetative regrowth for filtered light during the hottest part of the season resulting in bigger and redder fruit with higher TSS and low sunburn. Delayed pruning increased sunburn with no increase in fruit size, while the control delayed fruit maturity and reduced fruit size. The shade net reduced sunburn caused by delayed summer pruning. While it was apparent that proper timing of orchard light manipulation is essential, the use of shade net still has to be evaluated over the entire growing season to ascertain its full value.

Photosynthetic responses to CO2 at different leaf temperatures in leaves of apple trees (Malus domestica) grown in orchard conditions with different levels of soil nitrogen

The temperature-dependency of the photosynthetic response to CO2 was measured on apple (Malus domestica cv. Cox’s Orange) trees growing in orchard conditions with differing levels of nitrogen. Leaf nitrogen content varied from 1.7 to 2.2%. Nitrogen affected leaf attributes; larger areas but lower dry weights in high compared with low nitrogen trees. Across all leaf temperatures, higher rates of photosynthesis occurred in high nitrogen trees but rates differed mostly at 10 °C and progressively diminished to 35 °C. Rates of ribulose 1, 5-bisphosphate (RuBP) carboxylation, oxygenation and electron transport increased in a temperature-dependent pattern but nitrogen had no effect on rates at low (<25 °C) temperatures, whereas triose phosphate utilisation was higher and accounted for the increased photosynthesis. However, higher rates of RuBP carboxylation and regeneration in the high nitrogen trees accounted for the higher assimilation at temperatures above 30 °C. In addition, a stomatal limitation of assimilation at high temperatures was markedly increased by nitrogen but could not account for the increased photosynthesis, similarly, mesophyll conductance could not explain the effect. Basal (fruit subtending) leaves had lowest rates of assimilation and rates increased along the shoot. In addition, leaf nitrogen content also increased along the shoot and assimilation, carboxylation and regeneration all increased in concert, consistent with a causal relationship.

Metabolic mechanisms underpinning vegetative bud dormancy release and shoot development in sweet cherry

Few studies have focused on the metabolic characterization of bud dormancy and shoot growth in temperate fruit species, although this is an intresting framework to anticipate adaptation in global climate changes. To examine this issue, two experimental approaches were applied, using sweet cherry (Prunus avium L. cv ‘Grace Star’) bud and shoot tissues. Initially, annual shoots containing vegetative buds that collected at endodormancy and ecodormancy stages were used to compare changes in shoots- and buds-specific metabolic profiles under chamber-controlled conditions. Detailed analysis suggested that primary metabolites, such as arabitol, fucitol and tryptophan were modified in buds from endo- to eco-dormancy. Differences between buds and shoots metabolic fingerprints were also found in various secondary metabolites, including quercetin, glucosides and osmotic-associated metabolites. In order to investigate the mechanism underlying shoot developmental during bud dormancy break, metabolic analysis was also conducted in annual shoots, that were sampled at five distinct bud-related vegetative stages from ecodormancy to fully developed leaf stage under natural orchard conditions. Several amino acids (ornithine, alanine, isoleucine, GABA, asparagine and tryptophan) and classes of secondary metabolites, including anthocyanidins (peonidin-3-O-galactoside), flavonoids (apigenin, isorhamnetin, chrysin and trilobatin) and lignin-related compounds (sinapyl and coniferyl alcohols) were altered across developmental stages. Additionally, nutrient homeostasis was altered during shoot development, as N, P, Ca, Mg, B steady-state level as well as Ca/Mg + K and N/P stoichiometry were significantly changed. This study provides a bud- and shoot-based metabolic framework at different conditions and dormancy stages, thereby helps to understand dormancy release and bud-break in temperate fruit trees.

Influence of temperature and humidity on the survival of Monilinia fructicola conidia on stone fruits and inert surfaces

AbstractThe survival of the fungus Monilinia fructicola on fruit and inert surfaces at different temperatures (range: 0–30°C) and relative humidity (RH) (range: 60–100%) was investigated. M. fructicola conidia survived better on fruit than on inert surfaces. The viability reduction rate at 20°C and 60% RH was 1.2 and 5.8 days−1 on fruit and inert surfaces, respectively. Overall, on fruit surfaces, conidia viability was reduced at high temperatures and was longer at higher RH than at lower RH; in contrast, on inert surfaces, conidia viability was longer at only low temperatures. On fruit surfaces, at 0°C and 100% RH, conidia survived up to 35 days, and at 30°C and 60% RH, conidia survived up to 7 days. However, on inert surfaces at 20°C and 30°C, conidia lost their viability after 48 and 24 h, respectively. These results suggest that M. fructicola can remain viable in cold rooms for over 30 days on fruit surfaces or over 25 days on inert surfaces. Furthermore, under the orchard conditions during the growing season, conidia may remain viable for only 2–3 days on immature fruit surfaces before conidia will be unable to penetrate the host.

In Vitro Variation of Drought Tolerance in Five Actinidia Species

To select resistant germplasm resources and understand the growth and physiological responses of kiwifruit (Actinidia sp.) to drought stress, five species, Actinidia macrosperma (Acma), Actinidia longicarpa (Aclo), Actinidia deliciosa (Acde), Actinidia hemsleyana (Ache), and Actinidia valvata (Acva), were assessed under tissue culture conditions. Rootless seedlings of five species were cultured in a medium containing polyethylene glycol [PEG (formula weight 8000)] to induce drought stress (0%, 5%, 10%, 15%, and 20%). After a 30-day culture, three growth indices [fresh weight (FW), plant height (PLH), and leaf number (LN)] and six physiological indices were determined, and the drought damage index (DDI) was determined. The DDIs of five species increased, and three growth indices decreased with increasing PEG concentrations. The following changes were observed under 20% PEG treatment conditions: superoxide dismutase (SOD) activities increased significantly in Acma, Aclo, and Ache specimens; peroxidase (POX) activities remained stable in Acde, Ache, and Acva specimens; and catalase (CAT) activities increased sharply in Acma and Acva. Furthermore, the results indicated that soluble sugar (SS) content increased slightly in Acma, Aclo, Acde, and Ache but it decreased in Acva specimens. Proline (PRO) content increased significantly in Acma and Acva, and malondialdehyde (MDA) contents tended to increase under drought stress in all five species. Principal component analysis (PCA) results indicated that the order of drought tolerance in the five genotypes examined in this study under tissue culture conditions was as follows: Acma &gt; Acva &gt; Acde &gt; Aclo &gt; Ache. Therefore, we concluded that Acma and Acva are more resilient germplasm resources that represent promising kiwifruit-breeding materials. Furthermore, tolerance to drought stress in these species should be further investigated under orchard conditions.

Development of a Novel Dry, Sticky Trap Design Incorporating Visual Cues for Drosophila suzukii (Diptera: Drosophilidae).

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is currently one of the most serious invasive pests for berry crops and cherries worldwide. The development of an effective monitoring trap that is reliable at detecting small populations to guide management decisions is greatly needed. To develop a novel dry trapping system, D. suzukii were trapped under field conditions in cherry orchards and raspberry high tunnels using various baited dry trap designs that were compared with the currently available deli-cup style traps that utilize a liquid bait or drowning solution. In a test in cherry orchards, red panel and combination yellow panel plus red sphere traps captured significantly more flies than yellow panel traps when all were baited with a Scentry lure. In a separate test in cherry, red sphere traps with the Scentry lure captured significantly more flies than the deli-cup traps with the Scentry lure or with the yeast sugar bait, and red panel traps with the Scentry lure captured significantly more flies than deli-cup traps with the Scentry lure. In raspberry high tunnels, red sphere traps with the Scentry lure captured significantly more flies than deli-cup traps with the Scentry lure. Red traps baited with the same lure as clear deli-cup traps consistently captured more D. suzukii, demonstrating that traps integrating a visual cue in combination with an olfactory cue are superior tools for monitoring D. suzukii. A dry trap requires less labor and maintenance than cup traps containing a liquid, improving the ease of use of D. suzukii monitoring traps.

In vitro and in vivo activity of QoI fungicides against Colletotrichum gloeosporioides causing fruit anthracnose in Citrus sinensis

Abstract Anthracnose of sweet orange caused by Colletotrichum gloeosporioides was recently reported as a severe epidemic disease in pre-harvest conditions in several orchards of Sicily, one of the most important orange production areas for Europe. Nowadays, this emerging pathogen strongly reduce the amount of marketable fruits worldwide and fungicide applications are needed. In this study, sensitivity profile to QoI fungicides was preliminarily established for 37 C. gloeosporioides isolates collected from Sicilian orchards and fungal capacity to activate alternative respiration in presence of QoIs, a mechanism known for many phytopathogenic fungi when normal respiration is inhibited, was also determined. Tested isolates showed different fungicide sensitivity levels depending on salicylhydroxamic acid (SHAM) amendment of media. Medians of EC50 values ranged from 0.36 to 102 μg mL–1 for azoxystrobin and from 0.047 to 0.49 μg mL–1 for trifloxystrobin with or without SHAM amendment, respectively. Otherwise, EC50 medians of pyraclostrobin calculated within the same subset of fungal isolates were very similar in presence or in absence of SHAM (0.11 and 0.14 μg mL–1, respectively), thus indicating that only pyraclostrobin among the tested QoIs do not induce alternative respiration for this fungus. Subsequently, four field experiments were carried out in 2013–2014 in the same orange orchards, from which tested isolates were before collected, to determine QoIs performances against C. gloeosporioides. Although under low-medium disease pressure conditions, our data clearly showed that field applications of QoIs significantly managed both the incidence (reductions from 83.7 to 92%) of anthracnose infections on sweet orange in pre-harvest conditions and, approximately reduced up to 81 and 91.6% disease incidence and severity in postharvest stage. Pyraclostrobin, always applied at low rate (about 1/3 of label rate recommended for other targeted fungi of Citrus sinensis) showed good performances in reducing pre- and postharvest anthracnose infections on two cultivars, “Scire” and “Alcala”; of sweet orange. Based on our data, this latter molecule could be considered as a reliable chemical option to counteract this threatening disease on sweet orange, reducing environmental impact and the likelihood of fungicide resistance arising within Italian C. gloeosporioides population.