DETECTION OF THE RED PALM WEEVIL RHYNCHOPHORUS FERRUGINEUS USING ITS BIOACOUSTICS FEATURES

ABSTRACT

The Red Palm Weevil (RPW) is the most destructive pest of the date palm in the world and a serious pest of coconuts. The insect has caused up to 20% loss of these plantations in Asia and the Middle East. The economic damage to palm crops due to RPW could be mitigated significantly by bioacoustics recognition in an earlier phase of infestation and by applying the appropriate treatment. This study is conducted under the hypothesis that distinctive spectral and temporal features in RPW larval sounds can be combined to construct improved indicators for automated detection of infestations. In this paper, a signal processing system is developed with available acoustic technology to detect the existence of RPW in a tree through its feeding sounds. A large set of features are extracted, including unconventional features such as temporal roll-off, temporal slope and temporal spread. Additionally, an analysis is provided of the criteria for the choice of the optimum frame length, as well as the selection of the suitable window function. The results confirm the efficiency of the developed system with the selected representative features, window functions and frame length to detect the existence of the RPW.     

Production of a biopesticide on host and Non-Host serine protease inhibitors for red palm weevil in palm trees

Serine proteases are essential metabolic enzymes in the midgut of many pests, including the red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, which has a significant impact economically, environmentally and socially worldwide especially in the middle east. Some methods have been used to manage this pest such as trapping of RPW with pheromones, chemicals, and X-rays. However, these methods are costly, not effective and negatively impact the human. The main objective of this study is to contribute to the discovery of an eco-friendly pesticide to eradicate this infection by using serine protease inhibitors (SPIs) extracted from different parts of plant resources. In this research, both in vitro and in vivo effects of SPIs activity against RPW were examined. The protease inhibitors (PIs) activity was recorded in the crude extract that was isolated from the date’s kernel (DKE), host and Calotropis latex (CLE), non-host. These PIs were partially purified by ammonium sulfate precipitation. The midgut tissue of RPW was extracted and analyzed for protases activity assay. PIs assays were consistent with the increased in the inhibitory activity against the midgut proteases after treatment with a DKE and CLE. The reduction of gut proteases by DKE solution and CLE was 39%, 18%, respectively. Partially purified DKE showed the most prominent inhibition pattern of protease activity of the gut extract. While, latex exhibited acute toxicity, imparting the least LC₅₀ (5.132 mg/mL) against RPW larvae. Taken together, these findings provide evidence for the hypothesis that SPIs activity may play an important role in enhancing the mortality of RPW and relieving the toxicity of insecticide in palm trees.     

Hemocytes of Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) and their response to Saccharomyces cerevisiae and Bacillus thuringiensis

Originally from tropical Asia, the Red Palm Weevil (RPW Rhynchophorus ferrugineus (Olivier)) is the most dangerous and deadly pest of many palm trees, and there have been reports of its recent detection in France, Greece and Italy. At present, emphasis is on the development of integrated pest management based on biological control rather than on chemical insecticides, however the success of both systems is often insufficient. In this regard, RPW appears to be one pest that is very difficult to control. Thus investigations into the natural defences of this curculionid are advisable. RPW hemocytes, the main immunocompetent cells in the insect, are described for the first time. We identified five hemocyte cell types from the hemolymph of R. ferrugineus: plasmatocytes (∼50%), granulocytes (∼35%), prohemocytes (∼8%), oenocytes (∼4%) and spherulocytes (∼3%). SEM observations were also carried out. Some aspects of RPW interaction with non-self organisms, such as Saccharomyces cerevisiae and the entomopathogen bacterium, Bacillus thuringiensis (Bt), are discussed. Plasmatocytes and granulocytes were involved in nodules and capsule formation as well as in the phagocytosis of yeast. The hemocyte response of RPW larvae to sub-lethal doses of commercial products containing Bt was examined. In vivo assays were carried out and Bt in vegetative form was found in the hemolymph. After a diet containing Bt, the number of total hemocytes, mainly plasmatocytes, in the RPW larva hemolymph declined sharply (∼12%) and then remained at a low level, while the number of other circulating cells was almost unchanged.     

Sampling Rhodnius neglectus in Mauritia flexuosa palm trees: a field study in the Brazilian savanna

Two sampling methods (manual capture and live-baited adhesive traps) were compared for collecting the bug Rhodnius neglectus Lent (Hemiptera: Reduviidae: Triatominae) from palm trees, Mauritia flexuosa L. (Arecaceae), in the savanna of Brasília DF. R. neglectus was found in 19/50 (38%) of palm trees sampled. The detection rate was much higher by visual inspection and manual capture (18/50=36%) than by our trapping method (5/50=10%), although one tree was found to be positive by trapping but not by manual capture. Bugs collected manually were mostly (146/154=95%) found among the dead organic material in palm crowns. In combination, these sampling techniques are useful for quick detection of triatomine bug infestation in palm trees, especially in areas of high ecological value where the palms should not be cut and dissected, but arboreal Rhodnius are suspected to transmit enzootic Trypanosoma cruzi that might represent a risk of causing human cases of Chagas disease.     

Attraction of entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora to the red palm weevil (Rhynchophorus ferrugineus)

The red palm weevil (RPW), Rhynchophorus ferrugineus, is a serious pest of date palms. Its larvae bore deep into the trunk disrupt the vascular tissues and kill the infested trees. Behavioral features of entomopathogenic nematodes (EPNs), reflected by attraction and distribution patterns, are fundamental aspect in determining their parasitic ability and potential management of RPW. We studied the attraction behavior of the EPNs Steinernema carpocapsae and Heterorhabditis bacteriophora to the RPW under simulated natural conditions in tubes to evaluate their infective potential. In all experiments, a certain proportion of infective juveniles (IJs) (16–20%) stayed near the inoculated site and a major proportion (38–48%) was attracted to the host end. Both H. bacteriophora and S. carpocapsae were efficient crawlers, climbing up and descending when locating their insect host. They were efficiently attracted to the various larval sizes and stages of the RPW life cycle. Host localization by ascending movement was more prominent in S. carpocapsae than in H. bacteriophora. In general, H. bacteriophora is classified as a cruiser forager and S. carpocapsae as an ambusher. However, in this study, we discovered a higher percentage of cruiser foragers among S. carpocapsae IJs. They dispersed much faster and their cruising behavior was prominent characteristic in controlling the cryptic RPW concealed in organic habitats.     

Entomopathogenic fungi-mediated biological control of the red palm weevil Rhynchophorus ferrugineus

The red palm weevil (RPW), Rhynchophorus ferrugineus, is an important pest of palms, and difficult to control by conventional methods. Therefore, microbial control is an alternative strategy for controlling RPW. Herein, a total of 15 entomopathogenic fungi (EPFs) were subjected to primary pathogenicity screening against last stage of RPW larvae. The preliminary data showed that four Beauveria bassiana isolates (JEF-484, 158, 462 and 507) and one Isaria fumosorosea isolate (JEF-014) resulted in 100 % mortality within 5–10 days post inoculation (d.p.i.), respectively. According to the time required for RPW mortality, JEF-484, 158, 462 and 014 were further subjected to bioassays using 10⁷ conidia/ml suspensions by spraying method. Based on the results, JEF-484 showed the highest mortality and shortest LT₅₀ on the last stage of RPW larvae, followed by JEF-158. The two isolates also showed good conidial production and high thermal stability compared to the other isolates. Therefore, JEF-484 and JEF-158 were selected for bioassays against RPW egg and the last larval stage with different concentrations of 10⁵, 10⁶ and 10⁷ conidia/ml conidial suspensions by spraying method. For the bioassay at the egg stage, JEF-158 showed a significantly higher ovicidal effect than JEF-484. In the larval bioassay, both EPF isolates showed a dosage-dependent effect on the RPW larvae. JEF-484 caused higher mortality in RPW larvae than JEF-158. In summary, the combination of the 2 promising EPF isolates might provide an opportunity for the practical microbial control of RPW at different life stages in palm tree fields.     

Genetic variance between some Egyptian Date Palm cultivars using PCR-based markers with emphasis on the prevalence of Al wijam disease

Date Palm is one of the most important crops in Egypt. At present, Egypt ranked second in world date production. The objectives of this study are the identification the genetic variance between some local varieties of Date Palm, in line with the establishment of a molecular diagnostic method to study the aetiology and the prevalence of Al Wijam disease. Date palm plantations have been suffering from number of pests and diseases infestation, mainly due to Dubas Bug, Red Palm Weevil, Lesser Date moth, and Al Wijam disease. Genomic DNAs were extracted from 18 Date Palm cultivars collected from Date Palm Research Institute, ARC using three different extraction methods. Nine common cultivars (Zaghlool, Hayani, Oraibi, Samani, Sultan, Bent-Aisha, Amrey, Aglani, and Barhee) and nine Siwi cultivars (Siwi, Fryhee, Taktakt, Quaipe, Karama Ghazally, Helw Ghanem, Gorm Agazal, and Oshbeigel,) were used in this study. In order to determine the genetic polymorphism and discriminate between each of these cultivars, RAPD and ISSR analysis were conducted on the isolated DNA samples from each cultivar. DNA fingerprints of the studied cultivars were conducted using 10 RAPD and eight ISSR primers. Dendrograms representing genetic relationships as well as genetic similarity matrices were performed for the studied cultivars using the UPGMA (Unweighted Pair Group Method with Arithmetic Average). Furthermore, 40 date palm trees representing the studied cultivars were collected from El-Marazik, El-Badrasheen, El-Wahat, and Demiate Governorates to study the prevalence of Al-Wijam disease using the DNA hybridisation technique. Symptoms including retardation in terminal bud growth, whole crown of leaves (rosetting symptoms), and yellow longitudinal lines on the midribs were observed. Non-radioactive Dig-labeled probes specific for 16s rDNA region of virus like agents were used to detect the infected trees.     

Modeling Disease Vector Occurrence when Detection Is Imperfect: Infestation of Amazonian Palm Trees by Triatomine Bugs at Three Spatial Scales

Background

Failure to detect a disease agent or vector where it actually occurs constitutes a serious drawback in epidemiology. In the pervasive situation where no sampling technique is perfect, the explicit analytical treatment of detection failure becomes a key step in the estimation of epidemiological parameters. We illustrate this approach with a study of Attalea palm tree infestation by Rhodnius spp. (Triatominae), the most important vectors of Chagas disease (CD) in northern South America.

Methodology/Principal Findings

The probability of detecting triatomines in infested palms is estimated by repeatedly sampling each palm. This knowledge is used to derive an unbiased estimate of the biologically relevant probability of palm infestation. We combine maximum-likelihood analysis and information-theoretic model selection to test the relationships between environmental covariates and infestation of 298 Amazonian palm trees over three spatial scales: region within Amazonia, landscape, and individual palm. Palm infestation estimates are high (40–60%) across regions, and well above the observed infestation rate (24%). Detection probability is higher (∼0.55 on average) in the richest-soil region than elsewhere (∼0.08). Infestation estimates are similar in forest and rural areas, but lower in urban landscapes. Finally, individual palm covariates (accumulated organic matter and stem height) explain most of infestation rate variation.

Conclusions/Significance

Individual palm attributes appear as key drivers of infestation, suggesting that CD surveillance must incorporate local-scale knowledge and that peridomestic palm tree management might help lower transmission risk. Vector populations are probably denser in rich-soil sub-regions, where CD prevalence tends to be higher; this suggests a target for research on broad-scale risk mapping. Landscape-scale effects indicate that palm triatomine populations can endure deforestation in rural areas, but become rarer in heavily disturbed urban settings. Our methodological approach has wide application in infectious disease research; by improving eco-epidemiological parameter estimation, it can also significantly strengthen vector surveillance-control strategies.     

Studies on host preference and its biological effects on the red palm weevil,Rhynchophorus ferrugineus Olivier in Egypt The fruit trees

A comparative bioassay (choice or non-choice) was developed to evaluate the efficacy of different species of fruit trees as alternative host plants on the morphological and biological aspects of the red palm weevil, Rhynchophorus ferrugineus and also the latent effect of feeding the larvae on pupal and adult stages. Highly significant differences exist between averages of larval body weight of R. ferrugineus larvae fed on fruit trees. The lowest average of larval weight occurred in the larvae fed on the pieces of sour orange, mandarin followed by olive and lime trees. A small increase in body weight appeared in larvae fed on mango, fig and guava in comparison with those fed on date palm trees (control). The larval mortality reached the highest percentages (100%) by obligatory feeding of R. ferrugineus insects on olive, lime, sour orange and mandarin followed by mango (97%) and guava (96%) compared with control (0%), respectively. The latent effect of obligatory feeding on the larvae of R. ferrugineus was highly decreased during pupation (4%, 4% and 8%) when the insect fed on mango, guava and fig, compared with 100% pupation in the case of larvae fed on ornamental palm or date palm, respectively. Most pupae resulting from the treated larvae by R. ferrugineus failed in adult emergence especially those insects fed on olive, lime, sour orange and mandarin trees compared to untreated insects (95.6–96.2%), respectively. Data also proved that if an insect is forced to feed on a non-preferred host plant, this results in death of the insect often during the larval stage, a decrease of pupation or failure of adult emergence. These results led to the conclusion that mango, fig, and guava trees are believed to be vulnerable hosts for red weevil attack. The lowest percentage of food consumption appeared in those larvae fed on mandarin, sour orange, lime and olive trees compared with those fed on palm. The present results emphasise the need to test the efficiency of the compounds extracted from these host plants if it is considered as an insecticide or an alternative host protectant for management of the red palm weevil R. ferrugineus.     

Molecular characterization and phylogenetic analysis of Rhynchophorus ferrugineus (Olivier) in Eastern Province,Saudi Arabia

Red palm weevil (RPW) is the most aggressive date palm parasite in the Middle East, and especially in the Gulf region. Originated in Southeast Asia, this pest has been detected in the entire Arabian Peninsula, North Africa, Italy, Latin America, and other territories. It is important to local from obtrusive species, which help augmenting the pest control strategies. In the present study we collected 21 RPW samples from 21 different locations in the Eastern Province, Saudi Arabia to genetically characterize them using RAPD- and ISSR-based clustering. Unweighted pair group method with arithmetic mean (UPGMA) for RAPD data categorized the 21 accessions into seven distinct groups, with Al-Oyonn and Juaymah each categorized in solitary group, meanwhile, UPGMA for ISSR indicated six different groups, with Battaliyah, Al-Oyoon, and Juaymah each assigned to a separate group. Combining RAPD and ISSR data revealed two accession; Al-Oyoon and Juaymah that might be considered obtrusive species. Based on distance calculations, we proposed that the potential origins of RPW collected from these locations are Iran and the United Arab Emirates. However, this assumption needs further studies for confirmation.     

Characterization of ten date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia using AFLP and ISSR markers

Date palm is the most economically important plant in the Middle East due to its nutritionally valuable fruit. The development of accurate DNA fingerprints to characterize cultivars and the detection of genetic diversity are of great value for breeding programs. The present study explores the usefulness of ISSR and AFLP molecular markers to detect relationships among 10 date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia. Thirteen ISSR primers and six AFLP primer combinations were examined. The level of polymorphism among cultivars for ISSRs ranged from 20% to 100% with an average of 85%. Polymorphism levels for AFLPs ranged from 63% to 84% with an average of 76%. The total number of cultivar-specific markers was 241, 208 of which were generated from AFLP analysis. AJWA cultivar had the highest number of cultivar-specific ISSR markers, whereas DEK, PER, SUK-Q, SHA and MOS-H cultivars had the lowest. RAB and SHA cultivars had the most and least AFLP cultivar-specific markers, respectively. The highest pairwise similarity indices for ISSRs, AFLPs and combined markers were 84% between DEK (female) and PER (female), 81% between SUK-Q (male) and RAB (male), and 80% between SUK-Q (male) and RAB (male), respectively. The lowest similarity indices were 65% between TAB (female) and SUK-Q (male), 67% between SUK-A (female) and SUK-Q (male), and 67% between SUK-A (female) and SUK-Q (male). Cultivars of the same sex had higher pairwise similarities than those between cultivars of different sex. The Neighbor-Joining (NJ) tree generated from the ISSR dataset was not well resolved and bootstrap support for resolved nodes in the tree was low. AFLP and combined data generated completely resolved trees with high levels of bootstrap support. In conclusion, AFLP and ISSR approaches enabled discrimination among 10 date palm cultivars of from Saudi Arabia, which will provide valuable information for future improvement of this important crop.     

Date Palm DNA Mini-Preparation without Liquid Nitrogen

We have developed a new mini-procedure for isolation of total cellular DNA from date palm (Phoenix dactylifera L.). The procedure, which does not use liquid nitrogen, has proved useful due to temporary disruptions in supplies of liquid nitrogen that occur in countries where date palm trees are cultivated. DNA suitable for RFLP and PCR analyses is obtained.     

The culturable bacterial community of frass produced by larvae of Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) in the Canary island date palm

Aims: Larvae of the red palm weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) feed inside palm stem tissues, making galleries and producing a wet fermenting frass. We characterized the culturable bacteria associated with frass produced by tunnelling larvae inside the Canary island date palms and investigated the role of frass and gut bacteria in plant polymers breakdown. Methods and Results: A culture‐dependent method was used to isolate bacteria from frass and noninfested palm tissues. Bacterial isolates were grouped into operational taxonomic units based on polymorphisms in the ITS‐PCR profiles, and representative isolates were identified by partial sequencing of the 16S rRNA gene. Frass bacteria were dominated by 2,3‐butanediol fermenter Enterobacteriaceae. None of the bacterial isolates was able to degrade cellulose; however, cellulolytic and hemicellulolytic bacteria were isolated from the larval gut enrichment cultures. Conclusions: Frass bacteria are specifically associated with the RPW larvae and might play beneficial roles for RPW, other than nutritional, that deserve further investigations. Breakdown of plant polymers probably occurs inside the larvae digestive system. Significance and Impact of the Study: Frass and gut micro‐organisms of R. ferrugineus should be included in studies of the interactions between RPW, its plant hosts, and its enemies.     

Molecular study of two distinct phytoplasma species associated with streak yellows of date palm in Iran

A disease with symptoms similar to palm lethal yellowing was noticed in the early 2013 in Khuzestan Province (Iran) in date palm (Phoenix dactylifera). Infected trees displaying symptoms of streak yellows and varied in the incidence and severity of yellowing. A study was initiated to determine whether phytoplasma was the causal agent. Polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) methods using universal phytoplasma primers pairs R16mF1/mR1 and M1/M2 were employed to detect putative phytoplasma(s) associated with date palm trees. Nested PCR using universal primers revealed that 40 out of 53 trees were positive for phytoplasma while asymptomatic date palms from another location (controls) tested negative. RFLP analyses and DNA sequencing of 16S rDNA indicated that the presence of two different phytoplasmas most closely related to clover proliferation (CP) phytoplasma (group 16SrVI) and ash yellows (AY) phytoplasma (group 16SrVII). Sequence analysis confirmed that palm streak yellows phytoplasmas in each group were uniform and to be phylogenetically closest to “CandidatusP. fraxini” (MF374755) and “Ca. P. trifolii” isolate Rus‐CP361Fc1 (KX773529). Result of RFLP analysis of secA gene of positive samples using TruI and TaqI endonuclease is in agreement with rDNA analysis. On this basis, both strains were classified as members of subgroups 16SrVI‐A and 16SrVII‐A. This is the first report of a phytoplasma related to CP and AY phytoplasma causing date palm yellows disease symptoms.     

A randomized controlled trial of interventions to impede date palm sap contamination by bats to prevent nipah virus transmission in bangladesh

Background

Drinking raw date palm sap is a risk factor for human Nipah virus (NiV) infection. Fruit bats, the natural reservoir of NiV, commonly contaminate raw sap with saliva by licking date palm’s sap producing surface. We evaluated four types of physical barriers that may prevent bats from contacting sap.

Methods

During 2009, we used a crossover design and randomly selected 20 date palm sap producing trees and observed each tree for 2 nights: one night with a bamboo skirt intervention applied and one night without the intervention. During 2010, we selected 120 trees and randomly assigned four types of interventions to 15 trees each: bamboo, dhoincha (local plant), jute stick and polythene skirts covering the shaved part, sap stream, tap and collection pot. We enrolled the remaining 60 trees as controls. We used motion sensor activated infrared cameras to examine bat contact with sap.

Results

During 2009 bats contacted date palm sap in 85% of observation nights when no intervention was used compared with 35% of nights when the intervention was used [p<0.001]. Bats were able to contact the sap when the skirt did not entirely cover the sap producing surface. Therefore, in 2010 we requested the sap harvesters to use larger skirts. During 2010 bats contacted date palm sap [2% vs. 83%, p<0.001] less frequently in trees protected with skirts compared to control trees. No bats contacted sap in trees with bamboo (p<0.001 compared to control), dhoincha skirt (p<0.001) or polythene covering (p<0.001), but bats did contact sap during one night (7%) with the jute stick skirt (p<0.001).

Conclusion

Bamboo, dhoincha, jute stick and polythene skirts covering the sap producing areas of a tree effectively prevented bat-sap contact. Community interventions should promote applying these skirts to prevent occasional Nipah spillovers to human.     

Characterization of Growth-Retardant Effects on Vegetative Growth of Date Palm Seedlings

The leaves, inflorescences, and fruit bunches of date palm trees develop at the crown, which is the apex of a single trunk that can be up to 25 m tall. Because palm trees are monocots, the leaves and inflorescences are generated deep within the trunk from a single meristem—the palm heart—and are inaccessible for direct bioregulator treatments. We followed the effects of two growth regulators, paclobutrazol and uniconazole-P, on the vegetative growth of young date palm seedlings. Both growth regulators constrained the elongation rate of the leaves and reduced the leaf length. Microscopic analysis of dissected palm hearts revealed that the growth retardants did not affect the generation of new leaves. However, the treatments did change the dimensions of the developing embryonic leaves as well as the shape of the apical meristem. The results suggest the possible future use of growth retardants to reduce trunk height, enabling cheaper, safer, and more efficient management of date palm trees.     

Strong population genetic structure of an invasive species,Rhynchophorus ferrugineus (Olivier), in southern China

The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), was initially reported in China in the 1990s and is now considered one of the most successful invasive pests of palm plants in the country. A total of 14 microsatellite loci and one mitochondrial cytochrome oxidase subunit Ι (cox I) gene fragment were used to investigate the genetic characteristics and structure of R. ferrugineus in southern China. High levels of genetic differentiation among populations and significant correlations between genetic and geographical distances indicated an important role of geographical distance in the distribution of the RPW in southern China. High gene flow between Fujian and Taiwan province populations illustrated the increased effects of frequent anthropogenic activities on gene flow between them. Genetic similarity (i.e., haplotype similarity) indicated that RPW individuals from Taiwan and Fujian invaded from a different source than those from Hainan. To some extent, the genetic structure of the RPW in southern China correlated well with the geographic origins of this pest. We propose that geographical distance, anthropogenic activities, and the biological attributes of this pest are responsible for the distribution pattern of the RPW in southern China. The phylogenetic analysis suggests that the most likely native sources of the RPW in southern China are India, the Philippines, and Vietnam.     

Use of Infrared Camera to Understand Bats’ Access to Date Palm Sap: Implications for Preventing Nipah Virus Transmission

Pteropus bats are commonly infected with Nipah virus, but show no signs of illness. Human Nipah outbreaks in Bangladesh coincide with the date palm sap harvesting season. In epidemiologic studies, drinking raw date palm sap is a risk factor for human Nipah infection. We conducted a study to evaluate bats’ access to date palm sap. We mounted infrared cameras that silently captured images upon detection of motion on date palm trees from 5:00 pm to 6:00 am. Additionally, we placed two locally used preventative techniques, bamboo skirts and lime (CaCO₃) smeared on date palm trees to assess their effectiveness in preventing bats access to sap. Out of 20 camera-nights of observations, 14 identified 132 visits of bats around the tree, 91 to the shaved surface of the tree where the sap flow originates, 4 at the stream of sap moving toward the collection pot, and no bats at the tap or on the collection pots; the remaining 6 camera-nights recorded no visits. Of the preventative techniques, the bamboo skirt placed for four camera-nights prevented bats access to sap. This study confirmed that bats commonly visited date palm trees and physically contacted the sap collected for human consumption. This is further evidence that date palm sap is an important link between Nipah virus in bats and Nipah virus in humans. Efforts that prevent bat access to the shaved surface and the sap stream of the tree could reduce Nipah spillovers to the human population.     

Phenology and abundance of date palm mite Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) in Riyadh,Saudi Arabia

In the present study, we evaluated the effect of management practices, fruit season, host habitats (young and old fronds, date fruits and grasses), and temperature on the phenology and abundance of the date palm mite (DPM). The study was conducted in two date palm orchards (two plots each): a managed and an unmanaged plot. The phenology of DPM was assessed based on adult cumulative mite days (ACMDs), while mean mite density was used to assess the mite abundance on different host habitats. The ACMDs and mean mite density were significantly different between managed and unmanaged plots on different host habitats in both fruiting and off-seasons. The date fruits had highest ACMDs during fruiting season. While young fronds had significantly higher ACMDs than on old fronds an grasses during both seasons in both plots.. The temperature and season type significantly affected the mean density of DPM eggs and adults. There was a significant effect of host habitats mean density of DPM eggs and immatures. Based on the adult phenology and abundance of DPM, the mite overwinters in young fronds and aerial offshoots of infested date palm trees. These overwintering DPM caused the seasonal date fruit infestation, each year. Additionally, different phytophagous and predatory mites, which co-occur with DPM, and were found on different host habitats affected the phenology and abundance of DPM. Moreover, the change in DPM body color was related to the host habitat that they fed in. Exceptionally, the brown color of females collected during the winter season could be due to physiological changes due to low temperature. In DPM males collected from different host habitats throughout the study, some morphological variations in the width of the knob, height of the hook, and the angle between the knob axis and dorsal margin of the shaft were also recorded. The results of this study suggest that young fronds and grasses are the suitable sites for DPM survival and overwintering. Hence, the management practices, early in the fruit season and/or during off fruit winter months, should be directed towards these habitats. These could provide efficient reduction in seasonal infestation of DPM.