Journal of Phytopathology and Pest Management (Al-Azhar University)
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Management of coriander stem rot caused by Sclerotinia sclerotiorum using certain biocontrol agents and chemical inducers
Get PDFThe aim of the present study was to evaluate certain of bioagents (Trichoderma harzianum, T. hamatum, T. viride and ESRU bioformulation) and chemical inducers (salicylic acid and potassium silicate) on suppression of coriander stem rot disease caused by Sclerotinia sclerotiorum. The highest antagonistic bioagent was T. viride which reduced the mycelial growth to 3.9 cm in relation to control, being (9.0 cm). Moreover, five concentrations of each of salicylic acid and potassium silicate (0, 100, 250, 500 and 750 ppm) were evaluated against the growth and formation of sclerotia of the causal fungus in vitro and in a greenhouse. Salicylic acid completely inhibited both parameters at 250 and 500 ppm., respectively. Meanwhile, potassium silicates gave the same effect at 750 ppm. Under greenhouse conditions, spraying of coriander plants challenged with the causal fungus with any of the tested inducers and the bioagents lead to a critical reduction in the disease severity in relation to the control. Potassium silicate and salicylic acid as well as T. viride and ESRU formulation were the most efficient treatments, being 18.52, 22.22, 29.63 and 33.33%, respectively. Moreover, the effect of the tested inducers as a soil drench integrated with the bioagents as foliar spray was performed. Potassium silicate integrated with T. viride was the most effective treatment. Two season field experiments (2015-2016 and 2016-2017) showed that potassium silicate as soil drench integrated with T. viride as foliar spray was highly effective in reducing the percentage of dead plants and the area under the disease progress curve as well as increasing the weight of 100 seeds during the two seasons. An increase in the activity of polyphenoloxidase, peroxidase and phenylalanine ammonia lyase was recorded in the leaves sprayed with potassium silicate followed by those sprayed with salicylic acid then T. viride and the ESRU formulation.Â
In vitro antibacterial activity of some antibiotics against Xanthomonas campestris pv. musacearum: Ensete ventricosum (Welw.) Cheesman Pathogen
Get PDFEnset bacterial wilt caused by Xanthomonas campestris pv. musacearum (Xcm) is a destructive disease of Ensete ventricosum (Welw.) Cheesman) in south and southwestern Ethiopia. There is no known Bactericide against Xcm and the disease is systemic in nature, making the management very difficult. The objective of the study was to evaluate the antibacterial activity of amoxicillin, cephalexin, chloramphenicol, streptomycin sulphate and tetracycline in vitro against Xmc. The pathogen was isolated from infected Enset pseudostem and its identity was confirmed by pathogenicity test. The antibacterial activity of antibiotics was evaluated using disc diffusion method. Minimum inhibitory concentration (MIC) was determined using agar dilution method. Sub-culturing the contents of MIC onto growth medium was used to know the Minimum bactericidal concentration (MBC). All antibiotics showed antibacterial activity against Xcm, but with varied potency. Significant differences were recorded between test concentrations and antibiotics. Streptomycin sulphate was found to be the most effective antibiotic in inhibiting the growth of Xcm followed by amoxicillin and tetracycline. Moreover, the MIC and MBC values of antibiotics indicate the potential to use in Enset bacterial wilt control. Accordingly, tetracycline showed the lowest MIC (0.02 mg/mL) and MBC (0.049 mg/mL) values against Xcm as compared to others. Thus, it could be used in the management of Enset bacterial wilt. However, further studies need to be conducted on the effectiveness and method of application of tetracycline under field condition
Screening for tolerance of different citrus rootstocks against zoospores of Phytophthora nicotianae in infested soil
Get PDFCitrus gummosis, caused by Phytophthora nicotianae, becomes one of the most destructive diseases in citrus production in Tunisia. Thus, the selection of resistant rootstocks is needed to reduce the damage caused by this disease. In the present study, five citrus rootstocks (Citrange carrizo (Citrus sinensis x Poncirus trifoliata), Citrumelo Swingle-4475 (Citrus paradisi x Citrus trifoliata), Citrus volkameriana (Citrus limon x Citrus aurantium), Citrange C-35 (Citrus sinensis 'ruby blood' x Poncirus trifoliata) and Sour orange (Citrus aurantium)) were screened against P. nicotianae by inoculating young citrus seedlings with the freshly zoospores suspension. After three months of inoculation, the disease severity was evaluated based on root damaged, plant height, stem and root weights (fresh and dry) and density of P. nicotianae population in infested roots. The evaluation of the rootstocks response revealed different levels of susceptibility against P. nicotianae. Regarding to all the parameters studied, results showed that the rootstock Citrumelo Swingle-4475 and the rootstock Sour orange are tolerant to P. nicotianae. The rootstock Citrange C-35 was considered as a moderately tolerant, while the two rootstocks Citrange carrizo and Citrus volkameriana were very susceptible. The index severity was ranged from 1 for the tolerant rootstocks to 3.16 for the very susceptible one. The highest percent of the stem growth rate was 75.5 % recorded with the tolerant rootstocks, while it ranged between 18.25 % and 19 %, respectively, for the moderately tolerant and for the susceptible rootstocks. In the case of the other parameters like the fresh and the dry weight of stem and root, the tolerant rootstocks showed the minimum percent of reduction (17.8 %). However, the minimum percent of reduction of the moderately tolerant and of the very susceptible rootstocks was ranged between 38.5 and 30.8, respectively. The lowest number of propagules of P. nicotianae was found in the tolerant rootstocks (4.25), the highest number was found in the very susceptible rootstocks (24.5). However, the number was 12.25 in the case of the moderately tolerant one. It is believed that the rootstock Citrumelo Swingle-4475 should be involved with the resistance of citrus plants to P. nicotianae.Â
Feeding potential of the predatory ladybird beetle Coccinella septempunctata (Coleoptera; Coccinellidae) as affected by the hunger levels on natural host species
Get PDFLadybird beetles/Ladybugs, both adults and larvae, are well-known primarily as predators of aphids (plant lice); however, they also prey upon many other soft bodied insects and eggs of different borers. Laboratory rearing of predatory ladybirds often need a live host particularly aphids. Studies were conducted to check the suitability of live and frozen rose and mustard aphids to rear seven spotted ladybird beetle under two feeding conditions i.e., fed normally (unstarved beetles) or hungry (starved) for 16 hours. Results showed that hungriness may affect the food consumption efficiency. When the beetles were not starved, they showed preference for eating live mustard aphids as compared to frozen (Mean ± SE = 6.24 ± 0.37 live aphids, 4.43 ± 0.40frozen aphids). Similar trend was observed on rose aphids (6.51 ± 0.5 (live aphids) and 4.86 ± 0.49 (frozen aphids)). But the adults in starved condition consumed equal number of live and frozen aphids. During the 1st hour, starved beetles consumed more aphids of both species as compared to unstarved beetles. Also, more number of mealybugs was consumed in starved condition. This study highlights that feeding potential of predatory seven spotted ladybird is not only affected by the type of host but also the condition of host (live vs frozen). Moreover, starvation level of the predator can also be an important factor in determining its devouring capacity.Â
Effect of seed treatments with plant growth regulators on reducing damping-off and root rot diseases in common bean under greenhouse conditions
Get PDFThis study was carried out to evaluate the efficiency of some plant growth regulators (PGRs) to protect common bean plants against damping-off and root rot which caused by Rhizoctonia solani (Kuhn). Fourteen isolates of R. solani were isolated from common bean plants. Pathogenicity tests of these isolates were carried out on common bean (Giza 6 cv.) in greenhouse experiments during growing season in 2014. Results showed that all the tested isolates of R. solani were pathogenic to common bean plants with different degrees of infection. PGRs (indole 3-butric acid, gibberellic acid and N6-benzyladenine) have been evaluated as soaking seeds treatments before sowing at concentrations 50 and 100 ppm under greenhouse conditions. Treatments with the tested PGRs were effective in reducing disease severity (DS) percent at the tested parameters, i.e. damping-off and root rot. Also, data indicate that the highest significant reduction of diseases severity was observed in the case of N6-benzyladenine treatment (100 ppm), followed by indole 3-butyric acid (100 ppm). The concentration 50 ppm of PGRs was the most effective in reducing both diseases (damping-off and root rot). Application of the tested PGRs has significantly enhanced the height and the fresh weight of common bean plants compared to the control and fungicides (Moncut 25%). Gibberellic acid (100 ppm) was the most effective in increasing the height and the fresh weight of plants than the other treatments at seasons 2015 and 2016. Laboratory estimates, showed that treated plants with the tested PGRs content more phenolic compounds compared to untreated plants. The treatment with N6-benzyladenine was more content of phenolic compounds than the other treatments. There is an inverse relationship between the level of phenolic compounds in treated plants and the disease severity
Efficiency of certain insecticides against the black vine thrips, Retithrips syriacus (Mayet) (Thysanoptera: Thripidae) under laboratory and field conditions
Get PDFThe quantity and quality of grapevine fruit is very important to local and export productions. Black vine thrips (BVT), Retithrips syriacus (Mayet) (Thripidae: Thysanoptera) injured the leaves from seedling to the blooming fall. Insecticides are the main strategy to grapevine insect control. There is a little information about the susceptibility of BVT to insecticides. This study carried out to test the potency and residual activity of six insecticides with different mode of action under laboratory and field conditions. The LC50 values for leaf dip after 24 hours with the insecticides were different. The emamectin benzoate was the most toxic against nymphs, and teflubenzuron was the least one, LC50s value decreased significantly after 48, 72 hours post treatments. For teflubenzuron, the LC50 values recorded were 11900, 7.05, 2.58 µg a.i./ ml after 24, 48 and 72 hours from treatment respectively. Based on the laboratory potency ratios, emamectin benzoate , malathion, and mineral oil showed higher effect against nymphs than adults by 3.11, 1.79, 1.18 folds after 24 hours, being 1.63, 12.73 folds for emamectin benzoate and teflubenzuron after 48 hours, and 1.68 for teflubenzuron after 72 hours. King Roby grapevine variety showed the most significant susceptibility to thrips infestation, while the Flaim was the most tolerant one. Emamectin benzoate was the highest in reduction ratios of nymphs thrips, where 92.30, 93.19 and 93.83% reduction at Flaim, Banaty, and King Roby varieties respectively. These results could be used in integrated pest management (IPM) programs for thrips control in grapevine
Identification of Cylindrosporium padi associated with leaf spot disease of cherry in Kashmir Valley, India
Get PDFCherry an important stone fruit crop has been found to face a serious threat due to Blumeriella leaf spot disease. Survey of cherry orchards in Srinagar, Ganderbal and Baramulla districts revealed prevalence of the disease to varying extent. The disease incidence and intensity ranged from 13.00 to 52.50 per cent and 5.78 to 30.48 per cent, respectively. Maximum disease incidence of 41.02 per cent and intensity of 18.62 per cent was recorded in Ganderbal district, while minimum disease incidence of 18.10 per cent and intensity of 8.4 per cent was recorded in Baramulla district. The disease first appeared as small, circular to irregular, purple red speck on upper leaf surface. Periodical changes in colour, shape and size of the spots coupled with formation of irregular necrotic patches led to pre-mature defoliation. The fungus isolated on Potato Dextrose Agar medium produced compact and circular greyish white fungal colonies composed of hyaline, thick walled, septate and branched mycelium. Acervuli produced after 20 days of incubation at 20±1°C were dark brown to black, circular, discoid and measured 260.50 µm in diameter. Conidia (39.01 × 2.89 µm) were hyaline, bicelled, elongated, curved or flexous with tapered apex and rounded base. The pathogenic nature of the fungus was established on potted cherry saplings of cv. Bigarreau napoleon (Double). Based on morphological characters, pathogenicity test and comparision with the authentic description, the pathogen causing the disease was identified as Cylindrosporium padi (Lib.) P. Karst. Ex Sacc. the anamorph of Blumeriella jaapii (Rehm) Arx.Â
Morphological and molecular identification of root-knot nematodes infecting pomegranate in Assiut Governorate, Egypt
Get PDFRoot-knot nematodes are the most plant parasitic nematodes causing serious damage in pomegranate. Accurate identification of Meloidogyne species is of great importance for effective management of root-knot nematodes. Morphological identification of Meloidogyne spp. has been long and extensively used. However, molecular diagnostics was reported as a replacement or a complement method. Examination of the perineal patterns of the female was typically identified the nematode isolates as M. javanica which was dominant in all five pomegranate samples. For further confirmation of identification, a polymerase chain reaction (PCR)-based assay with two species-specific sequence characterized amplified regions (SCAR) primer sets was performed. The Fjav/Rjav and MJ-F/MJ-R primers efficiently amplified SCAR markers of 670 and 517 bp, respectively, which were previously reported for M. javanica. These results support that SCAR markers are a powerful tool for rapid and effective detection and could be used as a complementary tool together with the morphological identification of root-knot nematodes
Efficiency of fluazifop-p-butyl and Oxyfluorfen herbicides separately and in combinations with selected spray tank additives on weeds in onion field
Get PDFTwo field experiments were carried out at Faculty of Agriculture Farm, Al-Azhar University, Assiut governorate in 2014-2015 and 2015-2016 seasons to evaluate the efficiency of two post-emergence herbicides, i.e. Fusilade forte (fluazifop-p-butyl) and Goal (oxyfluorfen) on onion weed control at 30 and 60 days after treatment. Both herbicides were applied at their recommended and ¾ recommended rates with and without spray tank additives, i.e. sodium lauryl ether sulphate and organosilicone  adjuvants. The results showed that the tested adjuvants obviously increased the herbicidal efficiency of fusilade forte against grassy weeds and Goal against broad leave weeds. In most cases the maximum efficiency was achieved when both fusilade forte and Goal were applied at their recommended (187.5 and 180 g a.i/fed.) or ¾ recommended (140.625 and 135 g a.i/feddan) rates, + organosilicone adjuvant at 0.1% v/v concentration without significant adverse effects in onion crop
Evaluation of damage caused by some species of rodents on sugar cane and sugar beet
Get PDFThe damage caused by the nile grass rat, Arvicanthis niloticus  (Desmarest) and the white bellied rat, Rattus rattus frugivorous (Rafinesque) on sugar cane variety G.T. 54-9 was evaluated in three areas (Al-Hasany ; Al shek wefy and Ber El-Nos) at Qena Governorate during 2014 and 2015. The highest infestation was recorded in Ber Elnos area while Al-Hasany showed the lowest infestation during the two seasons. The percentage of infestation in sugar cane was higher in the first season than that in the second. The damage caused by A. niloticus, R. r. frugivorous and Rattus rattus alexandrines (Geoffray) on sugar beet was high in Assiut district during two cultivation seasons.. The losses in sugar beet weight was due to the damage caused by the three rodent species was (10.7, 10 and 6.7%) and (6.7, 6 and 4%) for the two seasons. The damage was concentrated at the upper part of the root