Damage To Citrus Research Articles

Florida red scale, Chrysomphalus aonidum (Linnaeus, 1758) (Hemiptera: Diaspididae) in Morocco, infesting citrus orchards and an avocado tree

AbstractA study was conducted on citrus and avocado trees in north‐western Morocco between February 2023 and April 2024 to detect scale insects (Hemiptera: Coccomorpha) and their associated natural enemies. A total of 55 orchards in seven provinces were studied. The Florida red scale, Chrysomphalus aonidum (Linnaeus, 1758) (Diaspididae) was found on leaves at two sites: a moderate infestation in one citrus orchard and one specimen on an avocado tree. This work is the first record of the scale insect on avocado in Morocco, and the first morphological description of C. aonidum from the country, based on 100 adult females mounted on microscope slides. Chrysomphalus aonidum is not causing economic damage in citrus or avocado orchards in Morocco. Two ectoparasitoid wasps (Aphytis melinus DeBach and Aphytis sp.; Hymenoptera: Aphelinidae), and three predatory beetles (Rhyzobius lophanthae Blaisdell, Chilocorus bipustulatus Linnaeus, and Clitostethus arcuatus Rosso; Coleoptera: Coccinellidae), were found associated with C. aonidum on citrus leaves.

Transfer Learning-Based Lightweight SSD Model for Detection of Pests in Citrus

In citrus cultivation, it is a difficult task for farmers to classify different pests correctly and make proper decisions to prevent citrus damage. This work proposes an efficient modified lightweight transfer learning model which combines the effectiveness and accuracy of citrus pest characterization with mobile terminal counting. Firstly, we utilized typical transfer learning feature extraction networks such as ResNet50, InceptionV3, VGG16, and MobileNetV3, and pre-trained the single-shot multibox detector (SSD) network to compare and analyze the classification accuracy and efficiency of each model. Then, to further reduce the amount of calculations needed, we miniaturized the prediction convolution kernel at the end of the model and added a residual block of a 1 × 1 convolution kernel to predict category scores and frame offsets. Finally, we transplanted the preferred lightweight SSD model into the mobile terminals developed by us to verify its usability. Compared to other transfer learning models, the modified MobileNetV3+RPBM can enable the SSD network to achieve accurate detection of Panonychus Citri Mcgregor and Aphids, with a mean average precision (mAP) up to 86.10% and the counting accuracy reaching 91.0% and 89.0%, respectively. In terms of speed, the mean latency of MobileNetV3+RPBM is as low as 185 ms. It was concluded that this novel and efficient modified MobileNetV3+RPBM+SSD model is effective at classifying citrus pests, and can be integrated into devices that are embedded for mobile rapid detection as well as for counting pests in citrus orchards. The work presented herein can help encourage farm managers to judge the degree of pest damage and make correct decisions regarding pesticide application in orchard management.

Control of citrus molds using bioactive coatings incorporated with fungal chitosan/plant extracts composite.

The ongoing postharvest loss in citrus fruits, due to fungal infection, is a chronic economic and agricultural problem. Most of citrus damage is caused by Penicillium spp., e.g. green mold (P. digitatum) and blue mold (P. italicum). Fungal chitosan, from Mucor rouxii, and plant extracts from cress seeds, olive leaves, pomegranate peels and senna pods, were evaluated as antifungal agents against the phytopathogenic fungi, P. digitatum and P. italicum, using in vitro qualitative and quantitative assays. All natural agents tested exhibited potent antifungal activity; the most powerful agent was cress (Lepidium sativum) seed extract, followed by pomegranate (Punica granatum) peel extract. Fungal chitosan also had a remarkable fungicidal potentiality using both evaluation assays. Penicillium digitatum was generally more resistant than P. italicum toward all examined agents. The incorporation of each individual natural agent in coating material resulted in a great reduction in fungal growth and viability. The addition of chitosan combined with cress and pomegranate extracts, to the coating materials, prevented coated citrus fruit from decay by green and blue mold for a 2-week storage period. Natural derivatives could be recommended as powerful antifungal alternatives to protect citrus fruits from postharvest fungal decay.

First Report of the Dagger Nematode Xiphinema diversicaudatum in Citrus Orchards in Morocco

Xiphinema species are migratory ectoparasitic nematodes that feed on an extensive range of hosts, and several species are vectors of nepoviruses. In May 2012, during a survey of the citrus-growing areas in the Gharb region of Morocco, several Xiphinema nematodes were detected in three locations: Kénitra (INRA, plot P1), Sidi Kacem, and Sidi Slimane. Samples were taken 30 cm deep at 50 cm distance from the tree trunks, in 40-year-old orange groves planted with the variety Maroc Late, grafted on rootstocks of Sour Orange and Citrange Carrizo. The trees showed yellowing of leaves, reduced tree vigor, and swellings at the tips of the roots. There were no weeds or grasses in the sampled area. Nematodes were extracted from soil using an automated centrifuge for extracting free-living nematode stages (2) and identified morphologically and by sequencing. All specimens were identified as Xiphinema diversicaudatum based on key morphological features from females and males. The average measurements of six females were: body length 4.1 mm, body width 60.4 μm, odontostylet 133.5 μm, odontophore 64.0 μm, spear 197.5 μm, tail length 45 μm, body width at anus 31 μm, and vulval position 48%. The females had two genital branches of similar length and structure, which contained a pseudo-Z differentiation. The average measurements of four males were: body length 4.3 mm, body width 51 μm, odontostylet 139 μm, odontophore 70 μm, spear 209 μm, tail length 45 μm, body width at anus 35 μm. To confirm the morphological identification, molecular observations were made. DNA was extracted from one nematode of each location. The D3 expansion region of the 26S rRNA gene was amplified using the primers D3A (5'-GACCCGTCTTGAAACACGGA-3') and D3B (5'-TCGGAAGGAACCAGCTACTA-3') (1). The PCR products were purified and sequenced (Macrogen, Inc., Seoul, Korea). All sequences obtained (GenBank Accession Nos. KF057879, KF057880, and KF057881) were compared with sequences available from the GenBank database including several species of Xiphinema. This comparison revealed a sequence similarity of 99 to 100% with X. diversicaudatum. Morphological and molecular identification demonstrated that the isolates of dagger nematodes from three citrus growing areas in Gharb belonged to X. diversicaudatum. An average of six X. diversicaudatum per 100 cm3 soil were found. This is the first report of this species in Morocco. X. diversicaudatum can transmit Arabis mosaic and Strawberry latent ringspot viruses (3). Arabis mosaic virus is of great economic importance in viticulture as it is associated with grapevine fanleaf degeneration disease, together with Grapevine fan leaf virus transmitted by X. index (4). As vineyards are planted amid citrus orchards in the Gharb region, particular attention should be given to this nematode, especially to the risk of its spread by soil. Our finding of X. diversicaudatum in a citrus orchard does not necessarily imply that X. diversicaudatum causes damage in citrus. However, its presence indicates that this nematode species can survive in this environment from where it could spread to other, more susceptible, crops.

Rootstocks induce contrasting photosynthetic responses of orange plants to low night temperature without affecting the antioxidant metabolism

Low temperatures negatively impact the metabolism of orange trees, and the extent of damage can be influenced by the rootstock. We evaluated the effects of low nocturnal temperatures on Valencia orange scions grafted on Rangpur lime or Swingle citrumelo rootstocks. We exposed six-month-old plants to night temperatures of 20ºC and 8ºC under controlled conditions. After decreasing the temperature to 8ºC, there were decreases in leaf CO2 assimilation, stomatal conductance, mesophyll conductance and CO2 concentration in the chloroplasts, in plant hydraulic conductivity and in the maximum electron transport rate driven ribulose-1,5-bisphosphate (RuBP) regeneration in plants grafted on both rootstocks. However, the effects of low night temperature were more severe in plants grafted on Rangpur rootstock, which also presented reduction in the maximum rate of RuBP carboxylation and in the maximum quantum efficiency of the PSII. In general, irreversible damage due to night chilling was found in the photosynthetic apparatus of plants grafted on Rangpur lime. Low night temperatures induced similar changes in the antioxidant metabolism, preventing oxidative damage in citrus leaves on both rootstocks. As photosynthesis is linked to plant growth, our findings indicate that the rootstock may improve the performance of citrus trees in environments with low night temperatures, with Swingle rootstock improving the photosynthetic acclimation in leaves of orange plants.

Shock absorbing surfaces for collecting fruit during the mechanical harvesting of citrus

Damage to fresh citrus caused by impact of fruits onto collecting surfaces has restricted the adoption of mechanical harvesting. Two different experiments were carried out: investigating free-falling citrus and investigating the shock absorbing capacity of various surfaces. In free-falling experiment damage to mandarin, orange and lemon was studied. Three collecting surfaces were studied: a concrete floor, an elevated canvas provided with a frame and wheels, and a concrete floor covered with a shock absorbing canvases. Three dropping heights were used. In the shock absorbing experiment, an electronic sphere and a triaxial accelerometer were used to measure the shock capacity of seven receiving surfaces: earth, earth covered with a shock absorbing canvas, earth covered with weeds, earth covered with a mulch and an elevated canvas provided with a frame and wheels. The elevated canvases had a higher shock absorbing capacity compared to the other surfaces (260 m s−2 maximum acceleration compared with 1753 m s−2 to 2772 m s−2). Weeds, mulch and the shock absorbing canvases showed significantly higher shock absorbing capacity than the bare earth. Also, the shock absorbing canvas covering the concrete floor reduce impact and fruit damage (1866 m s−2 maximum acceleration compared to 2477 m s−2). Citrus damage susceptibility during harvest depended on variety. Weeds, mulch and shock absorbing canvases were shown to reduce impact when they cover earth during the mechanical harvesting of citrus. Elevated canvases could be used as collection systems for the mechanical harvesting of fresh citrus.

Mediterranean fruit fly suppression using chemosterilants for area-wide integrated pest management

The chemosterilisation technique has been demonstrated to reduce the population and fruit damage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in citrus orchards. Field trials showed efficacy by reducing the fruit fly population, which was progressively achieved by continuous application of lufenuron to several generations. Different authors have suggested that field trials should be carried out in isolated or wide areas in order to reduce fruit fly intrusion and obtain best results. To this end, a wide-area trial over 3600 hectares has been under investigation in Valencia (Spain) since 2002 to validate the chemosterilisation technique against the fruit fly. The whole area was treated with 24 traps ha(-1), using more than 86,000 traps in the field trial. A continuous decrease in fruit fly population was observed over the 4 years under trial. Moreover, results showed a significant reduction in persimmon damage in the chemosterilant treatment area compared with a malathion aerial treatment area. In the case of citrus damage, no significant differences were obtained between malathion and chemosterilant treatments. The chemosterilant method reduces Mediterranean fruit fly populations, and therefore it is a candidate treatment to replace aerial treatments with insecticides in order to suppress this pest. In addition, the efficacy of chemosterilant treatment is increasing year after year. The possibility of using this technique combined with other control methods is discussed.

Protective Treatments against Soilborne Pathogens in Citrus Orchards

The efficacy of applying biocontrol agents, chemical fungicide and nematicide as protective treatments against the soilborne parasites, Fusarium spp. (Fusaria) and citrus nematode Tylenchulus semipenetrans Cobb was evaluated. The experiment took place un- der field conditions in a citrus orchard cultivated with 16-year-old sweet orange (Citrus sinensis L.) osbech cv. Valencia trees grafted on sour orange (C. aurantium L.) rootstock during the growing season November 2006/ October 2007. This orchard is located at Bader district, Behera governorate, Egypt. The populations of soil fauna and flora under trees canopy were examined just before treatment, and 1, 3, 6, 9 and 12 months after the treatment application. A visual inspection for the appearance of symptoms related to Fusarium or nematode infection on treated and untreated citrus trees was carried out periodically every two weeks throughout the experimental period. The populations of Fusarium spp. were gradually decreased throughout the experimental period. However, the antagonistic bacterial isolates showed drastic effect for reducing the Fusaria population from 38.5% before treatments to a range of 1.2-4.0% after one month of such a bacterial application followed by the Kocide (fungicide) treatment which recorded 6.6%. Meanwhile, Fusaria populations of 18.4 and 16.3% were recorded as Fusaria population in treatments of the nematicide Carbofuran and entompathogenic nematode, respectively. Also, the population density of T. semipenetrans juveniles drastically decreased soon after all the treatment applications. Then after the nematode population build up during the growing season followed a natural distribution decline shape starting from the third month of application up to the ninth month, then it decreased. The citrus nematode increased steadily in the untreated check till September 2007 then its population level decreased. Treatments of Bacillus subtilis - B (20 ml) and Pseudomonas fluorescens (20 ml) gave the highest citrus yield followed by B. subtilis A (10 ml); B. subtilis B (10 ml) and Kocide (fungicide). Moreover, citrus trees treated with B. subtilis A (10 ml); P. fluorescens (10 ml) and Carbofuran (nematicide) had a higher yield production than trees treated with entomopathogenic nematodes Heterorhabditis egyptii (Abd-Elgawad and Ameen 2005). Yet, visual monitoring for disease incidence throughout the citrus orchard during the whole period of the study revealed no disease symptoms of any fusaria or nematode infection in treated trees. Untreated trees had a 1.9 and 3.1% fusaria and nematode infection, respectively. The importance of the present work, therefore, is based on the proposed bioagents as protective applications that are able to inhibit the citrus patho- gens and prevent them from causing citrus damage.

Girdling induces oxidative damage and triggers enzymatic and non-enzymatic antioxidative defences in Citrus leaves

The effects of girdling on oxidative damage, antioxidant enzyme activity, antioxidant metabolites and proline (Pro) were studied in leaves arising from different shoot types of potted 2-year-old ‘Loretina’ mandarin ( Citrus reticulata Blanco) trees during the spring flush period. Girdling increased malonyldialdehyde (MDA) and basal chlorophyll (Chl) a fluorescence ( F o) in young leaves 30 days after girdling but not in the mature leaves (ML) suggesting a disruption of photosynthetic apparatus and oxidative damage in young leaves. This phenomenon was accompanied by increasing levels of Pro. Paralleling these changes, an increase of all antioxidant enzyme activities occurred in leaves from vegetative (VG) and multiflowered leafy shoots (MLY) of girdled trees. Similarly, in ML of girdled trees, ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) activity also increased. However, dehydroascorbate reductase (DHAR) activity decreased and superoxide dismutase (SOD) activity remained unchanged. Total leaf carbohydrate content and starch also increased as a result of girdling in all shoot types. Whilst soluble sugars increased markedly in young leaves, they increased only slightly in ML. In conclusion, this study provides evidence that girdling gives rise to oxidative damage in Citrus during carbohydrate accumulation, triggering enzymatic and non-enzymatic defence mechanisms.

Hyperspectral detection of citrus damage with Mahalanobis kernel classifier

Presented is a full computer vision system for the identification of post-harvest damage in citrus packing houses. The method is based on the combined use of hyperspectral images and the Mahalanobis kernel classifier. More accurate and reliable results compared to other methods are obtained in several scenarios and acquired images.

2007 freeze: UV could cast new light on citrus damage

2007 freeze: UV could cast new light on citrus damage

Analysis of bitter limonoids in citrus juices by atmospheric pressure chemical ionization and electrospray ionization liquid chromatography-mass spectrometry.

Improved analytical techniques for bitter limonoids in citrus and citrus juices can expedite the evaluation of freeze-induced citrus damage for citrus growers and juice quality for citrus juice producers. Microbore normal-phase and reverse-phase chromatography coupled to a mass spectrometer operating in a positive ion atmospheric pressure chemical ionization and electrospray ionization modes were found to be rapid, selective, and sensitive methods for the analysis of the bitter limonoids limonin and nomilin in citrus juices. Analysis was performed on a chloroform extract of citrus juice to which an internal standard was added. The methods are capable of detecting citrus limonoids in citrus juice in the 60-200 picogram range and quantifying citrus juice limonoids in concentrations as low as 120 picograms. An accurate "total limonoid bitterness" in citrus juice, as represented by the combined occurrence of limonin and nomilin, is easily determined by these methods.

Florida Citrus Freezes and Polar Anticyclones in the Great Plains

Severe Florida citrus freezes since 1880 are identified and described in terms of the horticultural damage, overall frequency of occurrence, and association with polar anticyclone outbreaks in the plains of southern Canada and the United States. The most severe “advective” freezes are associated with strong cold anticyclones having tracks southward across the plains to Texas with subsequent northeastward movement. Other anticyclones move in a track somewhat east of this and ultimately pass over Florida or the eastern Gulf of Mexico. Over 80% of the worst Florida citrus freezes are associated with anticyclones with central pressures in excess of 1045 mb moving along these paths. However, anticyclones of similar intensity with more zonally oriented paths across higher latitudes are associated with minor citrus damage. The major freezes tend to be clustered in time in the 1890s and since 1977. On interdecadal time scales, the recent freezes are not linked to higher winter mean pressure in the northern plains, and there has not been an unusually high frequency of strong anticyclones in recent decades, compared to earlier this century. Compared to the freeze-free period of 1948–57, the winters of 1977–86 are characterized by a more amplified 500-mb mean standing wave pattern across North America. This is linked to changes in the Pacific/North American upper-air teleconnection pattern, the index for which had much lower values (characterized by zonal flow) prior to 1958.

Using GOES thermal infrared data to map freeze zones for citrus and consequences for water management

Geostationary Operational Environmental Satellite (GOES) thermal infrared data were used to study Florida citrus damage from four major freeze events during the period 1963–1982 and the impact on water management. The 1963 freeze predated satellite data, but extrapolations were made using the average low temperature obtained from recent satellite data. The results showed that satellite temperature patterns closely matched the citrus damage patterns. Consistent patterns of lower temperature for the west coast area and the interior portion of central Florida were found and were used to identify high‐risk freeze areas. Severe citrus damage for a large area in south central Florida north and west of Lake Okeechobee appears to be attributable to the drier surface resulting from severe drought.

In Polk & Hillsborough Counties, Florida

Air pollution in the citrus growing area in Polk and Hillsborough Counties, Florida, is described. This area has one of the world's largest and richest phosphate deposits, and therefore a large phosphate industry grew in the area. It supplies over 75% of the nation's phosphate rock. Expanded food and fiber production in the area caused removeal of most of the phosphorus in the soil used for agriculture. Therefore fertilizers such as triple superphosphate were applied in the area. This resulted in increased fertilizer production at the phosphate plants, and thus, increased air pollution due to fluorides. Cattle in the area were affected by fluorosis, and citrus showed chlorosis due to the gaseous fluorides in the air. The air pollution was worse in the winter and early spring; these months also had the greatest occurrence of cattle and citrus damage. Due to combined governmental and industrial efforts, fluoride emissions were reduced from 33,000 pounds/day (winter of 1961-1962) to 13,000 lbs/day (winter of 1963-1964). Since 1959, air pollution control equipment costing $16 million has been added. A new, pollution-free plant costing $20 million replaced an old one. A new proposal is being considered to limit fluoride emissions further.