Bacteria from four phylogroups of the Pseudomonas syringae complex can cause bacterial canker of apricot

Pseudomonas syringae is described as a species complex, containing P. syringae-related species classified into 13 phylogroups and 23 clades. Pseudomonas syringae is one of the main pathogens of fruit trees, affecting nut trees, hazelnut and kiwi, pome and stone fruits. Bacterial canker of apricots is an important disease in regions of production with cold winters and conducive soils. This work characterizes the bacteria able to induce canker in apricots isolated in different French orchards. Bacteria from four phylogroups were able to induce canker. The pathogenicity to apricot was not linked to the pathogenicity to the three herbaceous species and cherry fruits tested, and was not always related to hypersensitive reaction on tobacco and ice nucleation activity. Bacteria pathogenic to apricot belong to phylogroups 01, 02, 03 and 07. The bacteria of phylogroups 01a and 07a (Pseudomonas viridiflava) characterized in this work have not previously been described as pathogenic to apricot.     

Frequency of brown rot fungi on blossoms and fruit in stone fruit orchards in Greece

Brown rot is a devastating disease of stone fruits caused by Monilinia spp. This study was conducted to investigate the disease aetiology on blossoms and fruit in peach, apricot, sweet cherry and plum orchards, in Greece. In total, 1433 isolates obtained from orchards located in the main stone fruit production regions of Greece were identified to species based on the presence/size of a cyt b intron. Monilinia laxa and M. fructicola were detected at frequencies of 59 and 41%, respectively, while M. fructigena was absent. Monilinia fructicola was more common on fruit whereas M. laxa occurred in similar frequency on blossoms and fruit. Monilinia laxa was replaced by M. fructicola in fruit infections of peach in both regions investigated and in fruit infections of plum in the Imathia region. Assessments of aggressiveness of 30 isolates of both species on the petals and fruits of the hosts showed that M. fructicola isolates were more aggressive. This suggests that the predominance of M. laxa on the blossoms cannot be explained by higher aggressiveness. Measurements of the effect of temperature on mycelial growth showed that M. laxa isolates had a higher growth rate than M. fructicola at the lowest temperature tested of 5°C, whereas M. fructicola isolates showed higher growth rates at higher temperatures. The observed high frequency of M. fructicola in Greece represents a major threat for stone fruit production. Furthermore, the information obtained about delineation of species and plant organ preference could be useful for the implementation of disease management strategies.     

An important new apricot disease in Spain is associated with <Emphasis Type="Italic">Hop stunt viroid</Emphasis> infection

The province of Murcia (Murcia Region) is the one of the most important apricot growing regions in Europe. In recent years a fruit disorder named by growers as “degeneración” has been detected in apricot commercial orchards of this region, mainly in the variety Velázquez Fino. Affected fruits are characterized by changes in their external appearance involving rugosity and a loss of organoleptic characteristics, which leads to an unmarketable product. In order to identify the causal agent of this disorder, the presence of the most important viruses affecting stone fruit trees and Hop stunt viroid (HSVd) was tested. While negative results were obtained for all viruses analysed, the viroid was detected in all the symptomatic trees. Within a single tree, the viroid was restricted to branches bearing fruits with the characteristic symptoms but was usually absent from the rest of the tree. Sequence analysis of several isolates of HSVd obtained from these affected trees revealed the presence of two variants previously detected in other apricot cultivars. Taken together, these results suggest that degeneration is associated with HSVd.     

Management implications of earwigs' overwintering sites in a Mediterranean citrus grove

To promote earwigs as natural enemies of pests, or to control their populations if they damage crops, earwigs can be managed during their overwintering period on the ground. Here, we obtained more than a ton of soil to study earwigs' overwintering sites in a citrus grove. We found four species of earwigs: Forficula pubescens, Euborellia annulipes, Euborellia moesta, and Nala lividipes. Surprisingly, and although the European earwig Forficula auricularia is abundant in the citrus canopies the rest of the year, we did not find any F. auricularia, indicating that this species spends the winter outside the citrus grove. Therefore, farmers willing to manage European earwig populations in citrus orchards need to consider the possibility that earwigs may spend the winter outside the field. Earwigs that were overwintering in the citrus grove were more abundant at the south side beneath the canopies than at the north side or between rows, indicating that management practices such as soil tillage can impact overwintering earwigs only beneath the canopies, but not between citrus rows. Overall, our results provide insights into how earwig populations can be successfully managed during winter in citrus orchards.     

Determination and management of weaver ant,Oecophylla smaragdina (Fabricius) (Hymenoptera: Formicidae), marks on mango fruit in the Northern Territory of Australia

Weaver ants, Oecophylla smaragdina (Fabricius), can be used to manage insect pests in mango orchards in the Northern Territory of Australia, but previously unidentified black marks on fruit can reduce fruit marketability. To determine the cause of the marks, and to reduce the number of fruits by such marks, field experiments were conducted in three mango orchards in the Darwin area of Australia in 2001 and 2002. The results from netting bag-rearing showed that the black marks on fruit were due to the deposition of weaver ant formic acid, and fighting between weaver ant colonies was the major cause of the deposition. In treatments without isolation of weaver ant colonies, an average of 4.8% of fruits with the ant marks were downgraded, and this damage level was reduced to 2.1% in treatments with isolation of weaver ant colonies. Because of weaver ant foraging behaviour, this small proportion of downgraded fruits was unavoidable, but the benefits of the ants as biocontrol agents against a range of pests outweighs the cost of the damage the ants cause.     

First report of Myzus mumecola (Matsumura, 1917) in Europe

During the spring of 2016, the aphid Myzus mumecola (Matsumura) (Hemiptera: Aphididae) was detected on its preferential host plant, Prunus armeniaca L. (Rosaceae), in Italy. This was the first record of the species in Europe. Several populations of the aphid have been collected in various apricot orchards in Emilia‐Romagna, in the localities of Imola, Campiano, Cesena and Castiglione di Cervia. The species is considered to be an apricot pest in India and East Asia. Details on the morphology, biology and distribution of this aphid species and the damage it causes are given.     

Distribution and damage caused by Halyomorpha halys in Italy

Since the first occurrence of Halyomorpha halys (Heteroptera: Pentatomidae) in Italy in 2012, the pest has spread in the Po Valley causing severe damage in summer 2015, particularly in pear orchards. At present, populations of H. halys have been reported in the regions of Emilia‐Romagna (Modena, Reggio Emilia and Bologna provinces), Piedmont, Lombardy, Veneto and Friuli. The damage caused by H. halys is typical of pentatomids and is aggravated by the pest's polyphagy and by the behaviour of adults which move continuously from plant to plant, from hedges or herbaceous crops to fruit orchards. The unpredictability of H. halys’ movements, along with the effect of the aggregating pheromone that concentrates the pest in certain areas of the orchards, therefore making chemical spraying complicated.     

Phenology and damage of Anarsia lineatella Zell. (Lepidoptera: Gelechiidae) in peach,apricot and nectarine orchards under semi-arid conditions

This study was conducted under semi-arid conditions in ?anl?urfa province (Turkey) in 2010–2011. One orchard each of peach, apricot and nectarine was selected for the study. There was less than one mile distance separating the orchards, and therefore climate, soil and topography were similar. Adult emergence, population peaks, number of generations per year and damage of the peach twig borer [PTB] [Anarsia lineatella Zell. (Lepidoptera: Gelechiidae)] on twigs and fruits were determined. Sex pheromone traps were used to determine moth population dynamics. Fruits and twigs were checked to determine damage rate and host preference of the PTB among peach, apricot and nectarine. This study showed that the first adults of the PTB were detected in early May and pest populations peaked four times during both years. The highest numbers of adults captured by the pheromone traps in peach, apricot and nectarine orchards were 115, 86 and 70 adults/trap, respectively. The PTB damage rates on twigs were 38, 18 and 16% (2010) (P < 0.05) and 30, 22 and 14% (2011) (P < 0.05), while damage rates on fruits were 29, 6 and 6% (2010) (P < 0.05) and 14, 8 and 5% (2011) (P < 0.05) in peach, nectarine and apricot, respectively. The results showed that A. lineatella caused greater damage on peaches than on apricots and nectarines.     

Stammapplikationen im Obstbau mit nanostrukturierten Silikaten gegen die Blutlaus Eriosoma lanigerum (Hausm.) und den Gemeinen Ohrwurm Forficula auricularia L.

The present work deals with a new strategy to control Eriosoma lanigerum (Hausm.) in apple and Forficula auricularia?(L.) in apricots. With common insecticides, both pests are difficult to control. Although F.?auricularia is regarded as a beneficial insect, in ecological agriculture it has the potential to cause severe economical damage in apricots. In apple and apricot orchards we tested treatments on the bark with diatomaceous earth (DE) products to prevent insects from reaching the tree crown. DE has been applied as liquid (“Fossil Shield^®” translucend) by a backpack sprayer or electrostatically as powder (“Fossil Shield^®” 90.0?s). In some trials we covered the treated area with a plastic funnel (fruitcap) in order to protect the silica-product from wind and rain. Experiments were evaluated weekly and number of insects in the tree crown was counted. During the first two months after treatment E.?lanigerum population in the crown was reduced by 98.2%. However, over the whole period of six month the barriers turned out to be ineffective (p?=?0.617). Winged adults have been capable to pass the barriere. In contrast to this fruitcap barriers were able to keep F. auricularia away from the crown (p?=?0.000). They have been as effective as standard treatment using glue. In such treatments apricot yield increased 6-fold for the cultivar “Goldrich” and 5.5-fold for the cultivar “Hargrand”.     

The dimpling bug,Campylomma austrina Malipatil (Hemiptera: Miridae): the damage and its relationship with ants in mango orchards in the Northern Territory of Australia

The dimpling bug, Campylomma austrina Malipatil, has been recognised since 2002 as a serious mango pest in the Northern Territory, Australia. To fully understand the damage the bug causes and its relationship with ants, field experiments were conducted in five mango orchards in the Darwin area from 2001 to 2003 along with laboratory rearing trials. The latter revealed that the dimpling bug sucked sap mainly from the ovary of the flowers. As the ovary ripened, each puncture resulted in a black pimple on the skin of the marble-sized fruit (<5 mm in diameter). All of the most heavily damaged marble-sized fruits (>10 pimples/fruitlet) dropped from the trees. A field survey and field experiments showed that marble-sized fruit damage levels on trees bearing abundant weaver ants, Oecophylla smaragdina Fabricius, were similar to those protected by chemical insecticides, however both suffered less damage than trees bearing fewer or no weaver ants or black ants, Iridomyrmex sp. We propose that the weaver ant is an efficient bio-control agent of the dimpling bug, and to limit the bug damage, high levels of weaver ant populations are required in mango orchards.     

Alternaria Brown Spot of Minneola in Greece; Evaluation of Citrus Species Susceptibility

During the last three years, a new disease was observed in northwestern Greece on Minneola trees, hybrid of mandarin and grapefruit. On May small brown necrotic leaf spots surrounded by yellow halo areas of various sizes appeared and covered a major portion of the leaves with extension of necrosis into the veins. On young fruits small, slightly depressed black spots were the first symptoms, which later became 2–7 mm in diameter. Brown spots were observed on the leaves and fruits in several orchards in the same area, causing leaves and fruits to drop. In some orchards over 50% of the fruits were affected. From the fruit and leaf spots the typical small-spore species Alternaria alternata was isolated. Pathogenicity tests were performed by artificially inoculating fruits of Minneola, common mandarin and Clementine. The symptoms of the disease were reproduced only on fruits of Minneola hybrids by the specific strain of the fungus Alternaria alternata pv. citri. Different citrus susceptibility tests indicated that mandarins Minneola, Nova and Page were very susceptible to tested isolates while Clementine SRA and Poros Clementine were not. All lemons and lime Seedless were not susceptible. Grapefruit New Hall was not susceptible, while the Star Ruby was. Orange Lane Late, Navel Late, Oval Poros, Olinda, Navel Athos were not susceptible and only Moro showed reaction being slightly susceptible only to one isolate.     

Studies on the diagnosis of hop stunt viroid in fruit trees: Identification of new hosts and application of a nucleic acid extraction procedure based on non-organic solvents

A non-radioactive digoxigenin-labelled RNA probe specific for hop stunt viroid (HSVd) diagnosis has been developed. The high sensitivity and specificity of this RNA probe in dot blot hybridizations to nucleic acids from field samples, allowed the confirmation of the presence of HSVd in apricot (Prunus armeniaca L.) and its detection in two fruit tree species not previously described as hosts of this pathogen, almond (Prunus dulcis Miller) and pomegranate (Punica granatum L.). This result supports and extends the notion of the world wide distribution of HSVd, infecting cultivated fruit trees. HSVd was also found to accumulate to much higher levels in mature apricot fruits than in leaves. Additionally, a sample processing procedure which does not involve the use of organic solvents was demonstrated to render faithful results when used for viroid detection. The combined reliability and facility of use of both this extraction procedure and the non-radioactive probe will benefit agronomic investigations addressing the detection and eradication of HSVd. Other applications of the work described here, as the study of possible causal relations between specific disorders and HSVd infection, are also discussed.     

Mapping the spread of apricot chlorotic leaf roll (ACLR) in southern France and implication of Cacopsylla pruni as a vector of European stone fruit yellows (ESFY) phytoplasmas

An epidemiological study on European stone fruit yellows (ESFY) phytoplasmas infecting Prunus fruit trees was carried out from 1994 to 2000 in Languedoc-Roussillon (southern France). The spread of the disease was monitored for 7 years by visual observation of symptoms and by PCR detection of the phytoplasma in an experimental orchard planted with apricot hybrid seedlings. This indicated that aerial vectors were responsible for disease spread, and that transmission rates were low at the beginning of the spread. Seventy thousand homopteran insects were captured within and in the surroundings of highly ESFY-infected apricot orchards, of which about 10 000 were used in PCR and nested-PCR assays with universal ribosomal and ESFY-specific nonribosomal primers to detect ESFY phytoplasmas. The other insects were confined in cages for trials of transmission to test plants. ESFY phytoplasmas could not be detected by PCR in any of the leafhopper species captured but could be detected in the psyllid Cacopsylla pruni caught on Prunus domestica and Prunus cerasifera rootstock suckers of apricot trees and on Prunus spinosa . Nested PCR revealed ESFY phytoplasmas in one individual of the deltocephalid Synophropsis lauri captured on an apricot tree. Transmission trials confirmed the role of Cacopsylla pruni as the ESFY phytoplasma vector in France. When apricot seedlings were used as bait plants from April to November during two consecutive years, no natural transmission could be demonstrated. However, one out of 50 apricot seedlings left for the whole year in the orchard became infected. An early spring ESFY infection is in agreement with both the natural transmission results and the life cycle of Cacopsylla pruni .     

Host specialization of <Emphasis Type="Italic">Tranzschelia discolor</Emphasis> on stone fruits at the uredinial infection stage

The host range specialization of Tranzschelia discolor (Fckl.) Tranz. & Litv. on stone fruits at the uredinial infection stage was investigated. Aeciospore inocula were collected from the alternate host, Anemone coronaria, at ten different locations of Aydın Province in early spring and were separately inoculated to 1–2-year-old nursery stocks of plum, peach, apricot, almond and sweet cherry under growth chamber conditions. Rust pustules developed only on plums, 15–21 days after inoculations, but no infections occurred on the other stone fruits. Urediniospore inocula were collected from naturally infected plums, apricots, peaches and almonds and were inoculated to four host species as well as sweet cherry in a series of cross-inoculations. Rust pustules developed on plants of the respective original host species from which the urediniospore inoculum was collected. No morphological differences were found among teliospores and urediniospores of T. discolor sampled from the different stone fruit species. Results of this study indicate that there is host specialization of T. discolor on stone fruits at the uredinial infection stage. Aecial inoculum from anemones in Aydin Province was infectious only on plums. The alternate host for the other stone fruits in this province was not found.     

Investigations on avian pests of oil palm,Elaeis guineensis Jacq. in India†

Abstract

The common myna Acridotheres tristis Linn., the jungle crow Corvus macrorhynchus Wagner and the house crow Corvus splendens Viellot are the major pests of oil palm in India. Other birds like crow pheasant Centropus sinensis Stresmann, parrot Loriculus sp. and pariah kite Milvus migrans Sykes also feed on oil palm fruits. These birds feed on the fleshy mesocarp of the ripe fruits resulting in heavy fruit loss, significantly reducing oil yield. Gizzard and intestinal content analysis indicated that oil palm fruits are the major source of food for these birds. Observations on 1657 oil palm fruit bunches during 1985–86 revealed that 76% of the ripe bunches and 5.6% of the unripe bunches were damaged by birds. The damage by birds was either ‘partial’ or ‘complete’, where 40–50% and 80–100% respectively, of the individual fruit weight was lost. The partial fruit damage was more common in 130–160 day‐old bunches and the complete fruit damage increased after 150 days of fruit set. Fruit loss due to bird damage was higher in palms in the border area of the plantation (2.3 kg/bunch) than in the interior (1.3 kg/bunch). It is estimated that around 2.8 tonnes of fresh fruits/ha/yr, equivalent to 420 kg of palm oil, are lost due to bird damage.     

Untersuchungen zur Europäischen Steinobstvergilbung (ESFY) in Deutschland

From 2003 to 2007 surveys have been conducted in different stone fruit growing regions in southwest Germany to detect European stone fruit yellows (ESFY) disease in Germany. Samplings have been done regularly in selected reference orchards in the regions Neuwieder Becken, Rheinhessen, Vorderpfalz and Südpfalz in summer on trees showing ESFY typical symptoms as well as on branches of trees with unspecific symptoms. All samples have been analysed by PCR for infection with Candidatus Phytoplasma prunorum. The phytoplasma could be detected in all investigated regions on the cultivated Prunus species P. armeniaca, P. persica and P. domestica. No infection was found in wild Prunus species. The main spread of the disease appeared on apricot while peach and European plum were less affected. A good correlation between symptoms and molecular detection of the pathogen could be shown for the typical symptoms in summer and winter for apricot as well as for peach. During regular psyllid captures in the reference orchards the population dynamics of Cacopsylla pruni could be described in southwest Germany for several years. By PCR-testing all collected insects individually a yearly natural infection rate of about 1–2% of all individuals of C. pruni could be calculated.     

Pesticide use,arthropod fauna and fruit damage in apple orchards in a Nordic climate

BACKGROUND

Integrated pest management (IPM) has a long history in fruit production and has become even more important with the implementation of the EU directive 2009/128/EC making IPM mandatory. In this study, we surveyed 30 apple orchards in Norway for 3 years (2016–2018) monitoring pest- and beneficial arthropods as well as evaluating fruit damage. We obtained growers’ diaries of pest management and used these data to study positive and negative correlations of pesticides with the different arthropod groups and damage due to pests.

RESULTS

IPM level had no significant effects on damage of harvested apples by arthropod pests. Furthermore, damage by arthropods was mainly caused by lepidopteran larvae, tortricids being especially important. The number of insecticide applications varied between 0 and 3 per year (mean 0.8), while acaricide applications varied between 0 and 1 per year (mean 0.06). Applications were often based on forecasts of important pest species such as the apple fruit moth (Argyresthia conjugella). Narrow-spectrum insecticides were commonly used against aphids and lepidopteran larvae, although broad-spectrum neonicotinoid (thiacloprid) insecticides were also applied. Anthocorid bugs and phytoseiid mites were the most abundant natural enemies in the studied orchards. However, we found large differences in abundance of various “beneficials” (e.g., lacewings, anthocorids, parasitic wasps) between eastern and western Norway. A low level of IPM negatively affected the abundance of spiders.

CONCLUSION

Lepidoptera was found to be the most important pest group in apple orchards. Insecticide use was overall low, but number of spray applications and use of broad-spectrum insecticides varied between growers and regions. IPM level did not predict the level of fruit damage by insects nor the abundance of important pests or most beneficial groups in an apple orchard. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Effect of pest management systems on foliage- and grass-dwelling spider communities in an apple orchard in Hungary

Spider communities (Araneae) inhabiting the canopy, the herbaceous layer and the borders, as well as the populations overwintering on the tree trunks of different aged IPM and conventional apple orchards were investigated in Hungary. Abundance and species richness of entire spider communities in IPM plots were significantly higher than in conventional plots, probably owing to the lower toxicity of pesticides used and higher prey densities. In the case of abundance, similar tendencies were observed in web-building and hunting spider guilds. Age of plantations can significantly influence spider density in the canopy, acting through the prey density. In young plantations, where size of the canopy was smaller and density of the pear lace bug (Stephanitis pyri L.) higher, significantly higher numbers of hunting spider communities were present than in old plantations which had been similarly treated. This relationship was not observed for web-building spiders. Diversity of canopy-inhabiting spider communities was higher in old plots, regardless of the treatments. The effect of the border of the orchard on spider communities was investigated and it was found that when selective insecticides were used, migration of spiders into orchards was increased significantly. When broad-spectrum insecticides were applied, spider densities in the canopy did not differ between outer and inner rows of the orchards. The effect of the treatments and orchard age, both on abundance and species richness of overwintering spider communities on the trunk, showed the same result as for canopy spiders, namely significantly larger spider communities were found in IPM plots and in the young plantation than in conventionally-treated plots and in the old plantation. Broad-spectrum insecticides reduced abundance and species richness of spider communities in the herbaceous layer of the conventionally-treated plot. At the same time, the spider communities of the herbaceous layer of the IPM plot did not differ significantly from adjacent herbaceous plants. A significant overlap exists between spider communities of the canopy and herbaceous layer. Despite chemical treatments, migration from the herbaceous layer into the canopy occurs. The effects of chemical treatments on the dominant species are discussed. There were no significant differences between the differently treated plots in abundance of one of the dominant species Oxyopes heterophthalmus Latreille. However, the other dominant species, Cheiracanthium mildei L. Koch, was more abundant in the IPM plots.     

Pheromone-based communication disruption ofAdoxophyes orana on peach using the new RAK 3+4 dispensers and their effect on development of fruit rot diseases

The effectiveness of the pheromone-based communication disruption method was examined against the summerfruit tortrix,Adoxophyes orana F.v.R. (Lepidoptera: Tortricidae), a pest of peach trees, using the new RAK 3+4 dispenser (BASF). NoA. orana males were captured in pheromone traps inside the experimental orchards, which were saturated with the RAK 3+4 dispensers. The percent of damaged leaves was practically zero, while the level of damaged fruits was 0–6% in pheromone-treated orchards. The percentage of fruit rot caused byMonilinia laxa was lower in pheromone-based communication disruption orchards than in the control. It was concluded that the RAK 3+4 dispenser could be used againstA. orana as an economical and environmentally friendly method.     

Epidemiology,histopathology and aetiology of olive anthracnose caused by Colletotrichum acutatum and C. gloeosporioides in Portugal

Anthracnose is an important disease affecting mature olive fruits, causing significant yield losses, and poor fruit and oil quality. In Portugal, high anthracnose incidence was recorded during 2003–2007 with 41% of 908 orchards surveyed displaying disease symptoms. In another 14% of the orchards, the pathogen was recorded in symptomless plants. Disease severity was on average 36%, frequently reaching 100%. In Portugal, anthracnose is endemic to neglected orchards of susceptible cultivars, but under favourable conditions it can also severely affect less susceptible cultivars. Pathogens were genetically heterogeneous, with Colletotrichum acutatum genetic group A2 as the most frequent (80%), followed by group A4 (12%) and group A5 along with C. gloeosporioides (3–4%), while groups A3 and A6 of C. acutatum were sporadic. Important geographic variations were observed in the frequencies of these populations, accompanied by year‐to‐year populational shifts. Epidemiology and histopathology studies showed the presence of the pathogens on vegetative organs year‐round, particularly on olive leaves and branches, and on weeds. These represent inoculum reservoirs where secondary conidiation occurs, and conidia are then dispersed by spring rains reaching flowers and young fruits or by autumn rains reaching pre‐mature fruits. Unripe fruits were colonized without showing symptoms up to penetration of the cuticle, but further colonization and symptom production was completed only as fruits matured. These findings challenge current control practices, particularly the timing of fungicide treatment, and contribute to improved disease management.