Ommatissus Lybicus Research Articles

Isolation of Clonostachys rosea and Characterizing Its Entomopathogenic Activity against Dubas Bug (Ommatissus lybicus) Nymphs and Adults

The Dubas bug is a serious and widespread pest of date palms in several countries in the Middle East. Chemical pesticides are widely used for managing this pest; however, most pesticides fail due to the continuous development of pesticide resistance. The primary goal of this research was to isolate endophytic fungi and test their entomopathogenic activity against Dubas bug nymphs and adults. A total of 27 fungal isolates were obtained and identified using the nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) region. These strains represent 16 species, belonging to 10 genera of seven different families, Ascomycota with six families and Basidiomycota with a single family, Quambalariaceae. Due to its remarkable biological control ability against insect pests, Clonostachys rosea was further studied for its entomopathogenic activity against Ommatissus lybicus nymphs and adults in comparison to a commercial strain of Beauveria bassiana. The concentration of 1 × 108 conidia/mL of the selected endophytic isolate was used in lab experiments targeting Dubas bug healthy nymphs and adults. After 7 days of C. rosea treatment, the isolate caused significant mortality rates of 85% in the adult insects, while the mortality rates were moderate in the nymphs (33%). The commercial strain of B. bassiana resulted in 100% mortality levels in nymphs and adults of the Dubas bug. Scanning electron microscopy (SEM) of O. lybicus adults treated with C. rosea and B. bassiana showed mycelium growing on the eye, antenna, cuticle, and egg oviposition parts of O. lybicus. Mycelium growth of both fungi was also evident on the nymphs. This study reports for the first time the isolation of C. rosea from the Dubas bug, and its high entomopathogenic activity against an adult population of O. lybicus.

The role of sticky yellow traps in reducing the population of the Dubas Bug, Ommatissus lybicus.

The role of sticky yellow traps in reducing the population of the Dubas Bug, Ommatissus lybicus.

Isolation and identification of the microorganisms associated with some nymphs and adults of the dubas insect (Ommatissus lybicus) and evaluation of their effectiveness in the laboratory

The study aimed to isolate and diagnose the fungi associated with the Dubas insect and test their effectiveness in resisting this insect under laboratory conditions. The pest is feeding on leves of date plam tree. That couse dameg to dates. The results showed the presence of fungi associated with the samples of Dubas nymphs and adults in all samples included in the survey, as there was a difference in the percentage of frequency and presence of the fungi, as the Aspergillus fungus excelled with the highest percentage of appearance and frequency of 57.14 and 48.13%, respectively. The results of the pathogenicity test of the fungi isolated from Adults and nymphs of Dubas under laboratory conditions, the T2 (Penicillium sp.) fungus isolate in sample No. 1 was distinguished by giving it a high mortality rate of 6.58% , followed by the T1 (Aspergillus sp.) fungus isolate in the same sample, where its rate reached 4.49% compared to the control treatment in which only distilled water was used, as its rate reached 0.75%. The results of the identification of fungal isolates pathogenic to Dubas insects showed that 4 fungal isolates excelled in the pathogenicity test in the laboratory, and according to the taxonomic keys, they belonged to the species Aspergillus funigatus, A. versicolor, Penicillium janthinellum, and P. amrantiogriseum.

Laboratory Study to evaluate the efficiency of Nano-loaded tobacco aqueous extract on the different roles of Ommatissus lybicus De Berg

A laboratory study is conducted to evaluate the efficiency of the aqueous extract of nano- chitosan loaded tobacco plants and laboratory-made. When O. lybicus eggs were treated with an aqueous extract of nano- chitosan loaded tobacco plants at two concentrations (10-15) ppm, recorded the highest mortality rates reached (21.2-37) %, respectively. Furthermore, the highest egg mortality rates reached (47.8_66.6) % after (14_21) days. The same concentrations above also affected the mortality rates of first-instar nymphs, which amounted to (30.3_53.3%), respectively. The concentration (15) ppm had the highest significant differences at mortality rate reaching (58.3_70.0) % after (5_7) days. The mortality rates in third-instar nymphs reached (28.9-37.5%) at the concentration of (15) ppm, the highest mortality rates reached (39.9_44.6_40.3) % after (3_5_7) days. The mortality rates in the fifth instar nymphs amounted to (22.6_29.1) %, respectively, as they were the highest mortality rates at a concentration of (15) ppm after (5) days, reaching (39.1) %.

Relationship between Dubas Bug (Ommatissus lybicus) Infestation and the Development of Fungal-Induced Leaf Spots in Date Palms (Phoenix dactylifera)

The dubas bug (Ommatissus lybicus) (Hemiptera: Tropiduchidae) is a serious pest in date palms in several date-producing countries, including Oman. Infestation results in a severe reduction in yield and a weakening of date palm growth. In addition, egg laying, which causes injuries to date palm leaves, results in the development of necrotic lesions on the leaves. This study aimed at investigating the role of fungi in the development of necrotic leaf spots following dubas bug infestation. Leaf samples developing leaf spot symptoms were collected from dubas-bug-infested leaves, as the leaf spot symptoms were not observed on the non-infested leaves. Isolation from date palm leaves collected from 52 different farms yielded 74 fungal isolates. Molecular identification of the isolates revealed that they belonged to 31 fungal species, 16 genera, and 10 families. Among the isolated fungi, there were five Alternaria species, four species each of Penicillium and Fusarium, three species each of Cladosporium and Phaeoacremonium, and two species each of Quambalaria and Trichoderma. Out of the thirty-one fungal species, nine were pathogenic on date palm leaves and induced varying levels of leaf spot symptoms. The pathogenic species were Alternaria destruens, Fusarium fujikuroi species complex, F. humuli, F. microconidium, Cladosporium pseudochalastosporoides, C. endophyticum, Quambalaria cyanescens, Phaeoacremonium krajdenii, and P. venezuelense, which were reported for the first time as leaf spot causal agents in date palms. The study provided novel information on the effect of dubas bug infestation in date palms on the development of fungal infection and associated leaf spot symptoms.

Impact of Initial Population Density of the Dubas Bug, Ommatissus lybicus (Hemiptera: Tropiduchidae), on Oviposition Behaviour, Chlorophyll, Biomass and Nutritional Response of Date Palm (Phoenix dactylifera)

The Dubas bug (Ommatissus lybicus) is an economically significant pest of date palms. In this study, the effect of the population density of O. lybicus on chlorophyll, measured by the soil plant analysis development (SPAD) chlorophyll meter, palm biomass, and the nutritional composition of date palms, were investigated. A further objective was to determine significant relationships between the population density of O. lybicus, the number of honeydew droplets, and oviposited eggs. Reductions of up to 8-11% and 29-34% in chlorophyll content and plant biomass, respectively, were caused by infestations exceeding 300 nymphs per palm seedling. Increasing the population density of O. lybicus to 600 insects per palm decreased oviposition by females, suggesting intraspecific competition for resources. There was a significant relationship between honeydew droplets produced by the pest population and chlorophyll content in the rachis, suggesting that treatment can be triggered at 3-6 nymphs/leaflet. Egg oviposition was preferentially on the rachis. Ca, Mg, K, and P were the main nutrients affected by the activity of the pest. Mg content was associated with reduced chlorophyll content under increasing pest density, suggesting that supplemental nutrition can be potentially utilized to sustain chlorophyll and increase palm tolerance to pest infestation.

Geospatial detection of Ommatissus lybicus de Bergevin using spatial and machine learning techniques

Dubas bug (Ommatissus lybicus de Bergevin) infestations are frequent in several Middle Eastern and North African countries, causing havoc to date palms. The key objectives of this research were (1) to examine the prevalence of the Dubas bug geographically and (2) to identify hotspots and clusters at the local levels. Normalised difference vegetation indices, kernel density estimations, spatial autocorrelations, Getis-Ord G*, Anselin spatial indicators, ordinary regression and forest-based classification and regression algorithms were used to detect Dubas bug infestations in the Al Batinah North and Al Batinah South governorates in Oman from 2017 to 2021. Images of the region, including several sub-locations with diverse levels of infestation, were collected throughout the Dubas bug spring and autumn generations during the study period. The spring generation's kappa coefficient for identifying infestation levels was 0.97, whereas the autumn generation's kappa coefficient was 0.98. Varying infestation levels were observed over the study period, with some areas experiencing fewer or more cold spots or hotspots than others. The highest Moran's I value of 0.48, along with the highest z-score of 12.9, characterised the highly clustered pattern of infestation during the 2017 spring generation, while the lowest infestation clustering occurred during the 2019 spring generation, with the lowest Moran's I of 0.23 and the highest z-score of 7.2. Despite seasonal fluctuations, most Dubas bug hotspots were located in the southern parts of the study area. Thus, the infestations caused the greatest damage to palm tree farms in interior areas between mountains, away from the coastal plains. Dubas bugs were found in high-density clusters in the south of Sohar and Al Khaburah and in the southwest of Al Rustaq during the 2017 and 2018 spring generations. By observing statistically significant changes in infection clustering patterns, entomologists can assess the prevalence of infestation using spatial information techniques.

Management of Date Palm Pests: Lack of Commercial Input

According to Statista, the global date market was valued at about $13.4 billion in 2019 and is forecast to reach $16.25 billion by 2025. However, this valuable crop is threatened by numerous pests. In fact, the date palm is associated with 132 species of insect and mite pests, which feed on the leaves, roots, trunk, and fruits on the palm, as well as stored dates. The most economically important pests include the red palm weevil, (Rhynchophorus ferrugineus), old world date mite (Oligonychus afrasiaticus), lesser date moth (Batrachedra amydraula), Dubas date bug (Ommatissus lybicus), green pit scale (Palmaspis phoenicis), carob moth (Ectomyelois ceratoniae), date palm longhorn beetle (Jebusaea hammerschmidti) and almond moth (Cadra castellan). It has been estimated that effective curative approaches for red palm weevil infestations alone could result in savings as high as $104 million. Several research groups are working to find effective solutions to control these pests, but as yet no commercial biocontrol products are registered or available for curative control of the palm beetle and larvae. Therefore, a more robust Integrated Pest Management(IPM) system is needed to reduce the pest damage. Commercial formulations include root treatments, insecticide-based capsules that are injected into the trunk, or foliage/fruit sprays. However, chemical insecticides should not be the only solution to the management of date palm pests, especially those concealed inside the trunk or beneath palm tissues, making them difficult to target. This is primarily because chemical insecticides frequently just kill the target pest's natural enemies, while the pests themselves remain protected within the date palm. Several approaches are used but it has also been shown that resistance against a range of commonly used chemical insecticides (profenophos, imidacloprid, chlorpyrifos, cypermethrin, deltamethrin, spinosad, lambda-cyhalothrin, phosphine) develops after extensive use. Resistance ratios as high as 79-fold have been reported, compared with susceptible control pests. Researchers have reported significantly improved populations of natural enemies of target pests in date palm plantations when chemical insecticide use is reduced. Around 90 species of beneficial predators and parasitoids have so far been reported, suggesting that biological control with microbials could be incorporated into a synchronised IPM programme.

Resistance to deltamethrin and fenitrothion in dubas bug, Ommatissus lybicus de Bergevin (Homoptera: Tropiduchidae) and possible biochemical mechanisms

Environmental pollution, ill-effects on human health, insecticide resistance development and insect pest resurgence are some serious problems that may arise due to excessive chemical spraying for pest control. Despite of heavy aerial and surface insecticide spraying, incomplete control of Ommatissus lybicus de Bergevin 1930 (Homoptera: Tropiduchidae) is reported in Oman every year, which requires investigation of insecticides resistance in pest. Fifteen populations of O. lybicus, collected from diverse vicinities were exposed along with a deltamethrin-selected (DEL-SEL) and lab-susceptible (LAB-SUS) strain to deltamethrin and fenitrothion insecticides in bioassay tests for estimation of their resistance status. All the field populations of O. lybicus, exhibited minor (RR = 3–5-folds) to low (RR = 5–10-folds) levels of resistance to deltamethrin, however, two out fifteen populations collected from Al-Hajir and Sint were found susceptible against fenitrothion (RR < 3-folds). Enzyme assays were conducted to detect the activities of cytochrome p-450-reductase (CPR), glutathione s-transferase (GST) and acetylcholinesterase (AChE) in the field collected, DEL-SEL and LAB-SUS strains of O. lybicus. Results revealed significantly increased activities of all enzymes in the field collected as well as DEL-SEL strains of O. lybicus when compared with LAB-SUS strains.

Transcriptomic analysis of Dubas bug (Ommatissus lybicus Bergevin) infestation to Date Palm

Date palm (Phoenix dactylifera L.) and its fruit possess sociocultural, health and economic importance in Middle East. The date palm plantations are prone to Dubas bug (DB; Ommatissus lybicus DeBergevin; Homoptera: Tropiduchidae) attacks that severely damages the tree’s growth and reduces fruit production. However, the transcriptome related datasets are not known to understand how DB activates physiological and gene regulatory mechanisms during infestation. Hence, we performed RNA-Seq of leaf infected with or without DB to understand the molecular responses of date palm seedlings. Before doing that, we noticed that DB infestation significantly increase superoxide anion and malondialdehyde production to two-folds as compared to healthy control. Stress-responsive genes such as proline transporter 2, NADP-dependent glyceraldehyde and superoxide dismutase were found significantly upregulated in infected seedlings. The infection repercussions were also revealed by significantly higher contents of endogenous phytohormonal signaling of jasmonic acid (JA) and salicylic acid (SA) compared with control. These findings persuaded to dig out intrinsic mechanisms and gene regulatory networks behind DB infestation to date palm by RNA-Seq analysis. Transcriptome analysis revealed upregulation of 6,919 genes and down-regulation of 2,695 genes in leaf during the infection process. The differentially expressed genes were mostly belongs to cellular functions (calcium and MAPK), phytohormones (auxin, gibberellins, abscisic acid, JA and SA), and secondary metabolites (especially coumarinates and gossypol). The data showed that defense responses were aggravated by gene networks involved in hypersensitive responses (PAR1, RIN4, PBS1 etc.). In conclusion, the results revealed that date palm’s leaf up-regulates both cellular and phytohormonal determinants, followed by intrinsic hypersensitive responses to counter infestation process by Dubas bug.

Lethal and sublethal effects of Eforia on the reproduction, development and feeding behavior of Ommatissus lybicus (Hemiptera: Tropiduchidae)

Dubas bug, Ommatissus lybicus de Bergevin (Hemiptera: Tropiduchidae), is one of the most important pests of date palm (Phoenix dactylifera L.) in Iran. In the present study, the lethal and sublethal effects of commercial formulations of acetamiprid, clothianidin, diflubenzuron, Eforia® (thiamethoxam+lambda-cyhalothrin), and fenitrothion on O. lybicus were examined. The concentrations of tested insecticides were predetermined by concentration-setting experiments based on a logarithmic scale. Stock solutions of the compounds were prepared by diluting the stock solution in Triton X-100 (0.1%) in distilled water. Triton X-100 (0.1%) in distilled water was used as control. Among insecticides tested, Eforia and fenitrothion were the more toxic to O. lybicus adults with the LC50s of 7.2 and 9.4 mg/L. The sublethal effects of Eforia were assessed by treating O. lybicus adults with the LC10 (3.7 mg/L), LC30 (4.8 mg/L), and LC50 (7.2 mg/L). The significant differences were not found for nymphal development and fecundity in LC10 concentration (73.51 d and 86.24 eggs/female, respectively) compared to control (73.78 d and 84.52 eggs/female, respectively). However, a significant reduction in survival and growth rate was observed in this concentration. The longevity and fecundity of females exposed to LC30 and LC50 concentrations were reduced. At LC30 and LC50 concentrations, Eforia prolonged the developmental duration (80.91 and 84.08 d, respectively) and decreased the survival rate (54.3 and 33.7%, respectively) of immature stages of O. lybicus. Furthermore, the quantity of food assimilated by O. lybicus on the date palm was significantly reduced at the LC30 and LC50 concentrations (1.67 and 1.34 mg, respectively). Altogether, these results indicate that Eforia could be useful for the management of O. lybicus population in Iran.

First record of the red palm weevil Rhynchophorus ferrugineus (Olivier) on Socotra Island (Yemen), an exotic pest with high potential for adverse economic impacts

We report on the first finding of a widespread exotic pest species, the red palm weevil Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) on date palms Phoenix dactylifera L. (Arecaceae) on Socotra Island, Yemen. Our initial surveys reveal that the pest species is present in date palm plantations on the north-eastern coast of the island, within 5 km of the capital Hadiboh. More surveys are needed to determine the wider distribution of this palm pest on Socotra, and what impact current invasions are having on date production. This invasion, together with the impact of the dubas bug, Ommatissus lybicus de Bergevin (Hemiptera: Tropiduchidae), which seems well established on the island, is likely to have a significant negative impact on livelihoods, since dates are the most important locally produced food, after milk and meat. The invasion provides ample evidence of the risks associated with trade, and the need to strengthen biosecurity measures to protect traditional food production and biodiversity from further pest incursions in this UNESCO World Heritage Site.

Susceptibility survey of Ommatissus lybicus (de Bergevin) populations against deltamethrin and fenitrothion in Oman

Despite of extensive application of insecticides, severe infestation of date palms is reported with Ommatissus lybicus every year. The development of insecticide resistance in the field strains receiving heavy pesticide regimes can be a reason for unsuccessful control. Seventeen field strains of O. lybicus from Oman were appraised for resistance against deltamethrin and fenitrothion in years 2017 and 2018. Eleven field strains depicted susceptibility (RR < 3-fold) while six strains expressed minor (RR = 3–5-fold) to low level (RR = 5–10-fold) of resistance against deltamethrin when compared with lab-susceptible strain. In case of fenitrothion, fourteen field strains exhibited minor to low level of resistance and only two showed susceptibility. Intermediate resistance (RR = 10–40-fold) was also reported in one field strain against fenitrothion. A significant but low resistance (RR = 7.86-fold) was observed in a lab strain selected with deltamethrin for resistance development mechanism studies. The deltamethrin-selected strain exhibited minor resistance development (RR = 3.13-fold) against fenitrothion. Significant reduction in resistance was observed with higher toxicity values when the two pesticides were tested along with piperonyl butoxide (PBO) against all the field collected dubas bug strains. Higher susceptibility of field strains to deltamethrin suggest it a suitable alternate candidate to deter resistance development in O. lybicus.

Effect of Arsenophonus Endosymbiont Elimination on Fitness of the Date Palm Hopper, Ommatissus lybicus (Hemiptera: Tropiduchidae).

The date palm hopper, Ommatissus lybicus de Bergevin, is one of the most important pests of the date palm in the Middle East and North Africa. This insect uses its needle-like sucking mouthparts to feed on phloem, which is devoid of most essential amino acids and many vitamins. The absence of essential nutrient in its diet is suggested to be ameliorated by endosymbionts in O. lybicus. Arsenophonus is one of the main bacterial endosymbionts widely prevalent in O. lybicus. In this study, we used antibiotics to eliminate Arsenophonus from O. lybicus originating from three populations (Fin, Qale'e Qazi, and Roodan) and studied the effects on the fitness of the pest. Our results revealed that the removal of Arsenophonus increased the developmental time of the immature stages and reduced the values of different life-history parameters including nymphal survival rate and adult longevity in the host. Furthermore, elimination of Arsenophonus completely obliterated offspring production in all O. lybicus populations investigated. These results confirm the dependency of O. lybicus on Arsenophonus for fitness and give a new insight regarding the possibility of symbiotic control of O. lybicus.

Humid-thermal index for a new management approach of Ommatissus lybicus.

The Dubas bug, Ommatissus lybicus, is a serious insect pest for the date palm Phoenix dactylifera in Oman and other date palm growing countries throughout the Middle East and North Africa. Climate is a key factor affecting the insect population dynamics, including O. lybicus. There are limited studies of O. lybicus relating to microclimate. The aim of this study was to investigate the efficiency of the various humid thermal indices (HTIs) and daily accumulation of temperature and humidity to model the relationship with O. lybicus. The highly infested locations showed a strong relationship with cumulative daily mean relative humidity (RhCm ), followed by daily minimum temperature (Tmin ) for pooled data over two seasons. The next best regression models for the relationship between the infestation and climate was with the absolute factors, daily maximum humidity (Rhmx ) and daily minimum humidity (Rhmin ), compared with HTIm/m (ratio of mean humidity to mean temperature) for the autumn season. The best regression model for the spring season was daily mean humidity (Rhm ) and daily maximum temperature (Tmax ). Daily cumulative temperature was the best predictive model for O. lybicus infestation on date palms, considering the microclimate data at each location separately. The predication model points to the areas that are prone to infestation and need focus for monitoring and allocation of management resources. © 2019 Society of Chemical Industry.

Modelling the potential effects of climate factors on Dubas bug (Ommatissus lybicus) presence/absence and its infestation rate: A case study from Oman.

Ommatissus lybicus de Bergevin (Hemiptera: Tropiduchidae) (Dubas Bug, DB) is an insect pest attacking date palms. It occurs in Arab countries including Oman. In this paper, the logistic, ordinary least square, and geographical weighted regressions were applied to model the absence/presence and density of DB against climate factors. A method is proposed for modelling spatially correlated prorations annually over the study period, based on annual and seasonal outbreaks. The historical 2006-2015 climate data were obtained from weather stations located in nine governorates in northern Oman, while dataloggers collected the 2017 microclimate data in eight of these nine governorates. Logistic regression model showed the percentages of correctly predicted values using a cut-off point of 0.5 were 90%, 88% and 84%, indicating good classification accuracy. OLS and GWR models showed an overall trend of strong linear correlation between DB infestation levels and short- and long-term climate factors. The three models suggested that precipitation, elevation, temperature, humidity, wind direction and wind speed are important in influencing the spatial distribution and the presence/absence of dense DB populations. The results provide an improved understanding of climate factors that impact DB's spread and is considered useful for managing DB infestations in date palm plantations. © 2019 Society of Chemical Industry.

Ommatissus lybicus Infestation in Relation to Spatial Characteristics of Date Palm Plantations in Oman

The agricultural ecosystem and its interaction with the outside environment plays a major role in the population of herbivores. The infestation of the Dubas bug, Ommatissus lybicus, has shown a spatial and temporal variation among different date palm plantations in Oman. This study focused on the relationship of infestation with date palm cultivation environments. The infestation and some selected environmental factors were evaluated in 20 locations for four consecutive infestation seasons over two years. Ordinary least squares (OLS) regression was used to identify the significant factors and the global relationship. Geographically weighted regression (GWR) was used to determine the spatial relationship. The results showed that GWR had better prediction than OLS. The model explained 61% of the infestation variation in the studied locations. The most significant coefficient was the tree planting pattern, the trees planted in uneven rows and columns (irregular pattern) had a positive effect; the infestation increased as the irregularity increased due to an increase in tree density. This reduced the interaction of harsh outside weather with the date palm plantation microclimate. The proportion of side growing area had a negative effect on insect population; as the percentage of side growing area increased as the infestation decreased, assuming the side growing crops hosted natural enemies. The study concluded that the variation of spatial and temporal infestation was primarily due to the variation of the cultural practices and spatial environment of the date palm plantations.

Detecting Dubas bug infestations using high resolution multispectral satellite data in Oman

The Dubas bug, Ommatissus lybicus de Bergevin, is one of the major pests of the date palm, Phoenix dactylifera, in Oman, reducing its production by 28%. In addition to the important annual costs to control this pest nationwide, effort, cost and time are spent surveying and spotting O. lybicus infestations. Several studies have indicated the possibility of using remote sensing technology to identify plants stressed by pest infestation. The aim of the present study is to detect O. lybicus infestations by quantifying reflectance changes of different infestation levels and calculating different vegetation indices (VIs) using high-resolution multispectral (MS) images. An image of an area with different sub-locations that had varying levels of infestation was acquired in March 2017 using the WorldView-3 satellite.The reflectance of 8 bands, 32 spectral VIs and maximum likelihood classification (MLC) were derived from the image, and then the correlation was tested using ground-infestation data. The results revealed that the reflectance decreased in the red edge and near-infrared (NIR) bands as the infestation level increased. High levels of infestation showed a significant difference in three bands, red edge, NIR1 and NIR2, compared to no, low and medium levels of infestation. Nineteen out of 32 VIs showed a significant relation with the infestation levels. The relation ranged between r = −0.12, p < 0.05 using the Normalized Difference Mud Index (NDMI) and r = −0.39, p < 0.000 using the Transformed Difference Vegetation Index (TDVI)) and Tasselled Cap – Non - Such Index (TC-NSI). The location affected the relation between the infestation and VIs, where the correlation coefficients increased. The maximum correlation found was r = 0.64 using the Visible Atmospherically Resistant Index (VARI) in Al’Ayn Village. The overall accuracy of the supervised classification for detecting the infestation level was 68.3%, and the Kappa coefficient was 0.50.

Impacts of climate change on infestations of Dubas bug (Ommatissus lybicus Bergevin) on date palms in Oman.

Climate change has determined shifts in distributions of species and is likely to affect species in the future. Our study aimed to (i) demonstrate the linkage between spatial climatic variability and the current and historical Dubas bug (Ommatissus lybicus Bergevin) distribution in Oman and (ii) model areas becoming highly suitable for the pest in the future. The Dubas bug is a pest of date palm trees that can reduce the crop yield by 50% under future climate scenarios in Oman. Projections were made in three species distribution models; generalized linear model, maximum entropy, boosted regression tree using of four global circulation models (GCMs) (a) HadGEM2, (b) CCSM4, (c) MIROC5 and (d) HadGEM2-AO, under four representative concentration pathways (2.6, 4.5, 6.0 and 8.5) for the years 2050 and 2070. We utilized the most commonly used threshold of maximum sensitivity + specificity for classifying outputs. Results indicated that northern Oman is currently at great risk of Dubas bug infestations (highly suitable climatically) and the infestations level will remain high in 2050 and 2070. Other non-climatic integrated pest management methods may be greater value than climatic parameters for monitoring infestation levels, and may provide more effective strategies to manage Dubas bug infestations in Oman. This would ensure the continuing competitiveness of Oman in the global date fruit market and preserve national yields.

Predicting the potential geographical distribution of parasitic natural enemies of the Dubas bug (Ommatissus lybicus de Bergevin) using geographic information systems.

The Dubas bug (Ommatissus lybicus de Bergevin) is a pest species whose entire life cycle occurs on date palms, Phoenix dactylifera L, causing serious damage and reducing date palm growth and yield. Pseudoligosita babylonica Viggiani, Aprostocetus nr. Beatus, and Bocchus hyalinus Olmi are very important parasitic natural enemies of Ommatissus lybicus in northern Oman. In this study, random farms were selected to (a) model the link between occurrences of the Pseudoligosita babylonica, Aprostocetus nr beatus, and Bocchus hyalinus (dependent variables) with environmental, climatological, and Dubas bug infestation levels (the independent variables), and (b) produce distribution and predictive maps of these natural enemies in northern Oman. The multiple R 2 values showed the model explained 63%, 89%, and 94% of the presence of P. babylonica, A. nr beatus, and Bocchus hyalinus, respectively. However, the distribution of each species appears to be influenced by distinct and geographically associated climatological and environmental factors, as well as habitat characteristics. This study reveals that spatial analysis and modeling can be highly useful for studying the distribution, the presence or absence of Dubas bugs, and their natural enemies. It is anticipated to help contribute to the reduction in the extent and costs of aerial and ground insecticidal spraying needed in date palm plantations.