جستجوی مقالات مرتبط با کلیدواژه « mortality » در نشریات گروه « گیاهپزشکی »

The Pseudomonas bacteria include many species with different characteristics. Some species of the genus are considered as the plant growth stimulants. Recently, the potentials of the bacteria to insect pest control has been documented. In this study, the lethal effects of three strains, Pseudomonas protegens CHA0, P. soli VF16, and P. persica VKh13 to eggs and larvae of Anagasta keuhniella (Zeller) (Lep., Pyralidae) as an important stored product pest was studied. For this purpose, two concentrations of each strain, 0.2 and 0.5 OD at the wavelength of light of 600 nm, were provided and the 5th instar larvae and eggs of A. keuhniella were treated and the mortalities were recorded after 24h. Statistical investigations indicated that the strain P. protogens CHA has the highest mortality rate (79.16%) and after that, the strain P. soli VF16 (64.15%). Furthermore, it is demonstrated that the strain P. persica VKh13 has not the insecticidal property. The bacterial efficacy at suspension concentration 0.5 OD was significantly more than 0.2 OD. No significant difference was observed between susceptibility of the pest larva and eggs to different investigated strains in the study. The highest mortality was observed in application of the concentration 0.5 OD of P. protogens CHA on the pest larvae. Olfactory trials indicated that the female parasitoid wasps, Habrabracon hebetor, significantly avoided from treated larvae by all of the three strains. The results can be used for developing the microbial control of the pest.

Legumes are the second most significant plant source of human protein-rich diets after cereals. Additionally, these plants improve soil structure through biological nitrogen fixation. Plant pathogens are one of the most important global constraints on chickpea production. Plant-parasitic nematodes are key damaging agents to crop production. Broad beans, soybeans, lentils, beans, mung beans, and chickpeas are hosts for P. ritteri, and under greenhouse conditions, this nematode reduces the majority of plant growth indices. Various methods are employed to control plant-parasitic nematodes, most of which rely on chemical control. This study was conducted under laboratory and greenhouse conditions to examine the effects of refined wood vinegar, unrefined wood vinegar, chloro carboxylic acid, and sodium dioctyl sulfosuccinate on P. ritteri.

In this study, 66 soil and plant root samples were collected from chickpea fields in Lorestan province's counties. P. ritteri nematodes were identified after extraction using conventional techniques. The number of P. ritteri nematodes per kilogram of soil in an infected field soil was determined, and this soil was subsequently used in laboratory and greenhouse experiments. The effect of four compounds, including refined wood vinegar, unrefined wood vinegar, chloro carboxylic acid, and sodium dioctyl sulfosuccinate, on P. ritteri was investigated under laboratory and greenhouse conditions, as was the mortality of P. ritteri in chickpea. The data were analyzed using SPSS22 software, and tests were conducted using randomized complete block designs.

A comparison of the mean mortality of P. ritteri under laboratory conditions revealed that the highest mortality was associated with a 1% chloro carboxylic acid treatment for 24 h (100%), and the lowest mortality was attributed to a 0.5% refined wood vinegar treatment for 12 hours (25%). Under greenhouse conditions, the chloro carboxylic acid treatment resulted in the highest mortality, 1% (94%), while the unrefined wood vinegar treatment had the lowest mortality, 0.5% (49%). In addition, the mortality rate demonstrated a significant difference at P≤0.05 in two frames of 12 and 24 h for most compounds (except for sodium dioctyl sulfosuccinate 0.5%) and at P≤0.01 in two levels of 1% and 0. 5% for all compounds.

All investigated compounds induced nematode mortality, with chloro carboxylic acid proving to be the most effective for nematode mortality and unrefined wood vinegar the least effective. Consequently, these compounds can be used as pre-planting to control these nematodes.

Unrestricted use of chemical insecticides, especially at high concentrations, has reduced their efficacy. Plant-based pesticides, due to their relatively high safety levels to humans and environment as well as effective control on insects, have become a suitable alternative to conventional pesticides. The aim of this study was to investigate the biological and physiological effects of the formulated essential oil of Trachyspermum ammi (L.) on the larvae of Helicoverpa armigera Hüb. The obtained essential oil was formulated into an emulsion using Tween 20 as emulsifier. Chemical analysis of the extracted essential oil indicated that Terpinen (14.4%), Cymene (18.5%), and Thymol (61.6%) were the major compounds. The essential oil of T. ammi have a significant repellency rate on third and sixth instar larvae of cotton bollworm at different observed time intervals, with an average repellency rate of 61-76%. Regarding fumigant toxicity, the highest concentration of the essential oil (500 µL/L) resulted in 100% larval mortality. The LC50 value for fumigant toxicity measured as 82.73 µL/L. The duration of larval development significantly increased in treatments compared to control. In EO concentrations of 2.5-1.25 percent an increase was observed respectively in the duration of the larval stage by 9 and 7 days. The pupae and adult’s emergence affected in dose dependent manner. At concentration of 50 µl/l, 89% inhibition of protease enzyme recorded. With regards to the biological and physiological effects observed in the formulated T. ammi essential oil, with complimentary researches, it could be used in integrated management programs of cotton bollworm.

The Black bean aphid (BBA), Aphis fabae Scopoli (Hemiptera: Aphididae), is an important pest of agricultural and ornamental plants. Entomopathogenic fungi are important factors in the microbiological control of pests that are considered a good alternative for chemical insecticides. Isolation of novel potential IPF and evaluation of their efficacy against pests are primary steps for achieving a successful microbiological control program. In this study, the efficacies of three Iranian isolates of Akanthomyces lecanii (PAL6, PAL7, and PAL8) and an Iranian isolate of A. muscarius (GAM5) which had been isolated from two hemipteran pests, Pulvinaria aurantii Cock. and Aphis gossypii Glover, respectively, in citrus orchards of west Mazandaran (North of Iran), were evaluated against BBA.

Mortalities of the BBA nymphs and adults caused by different conidial concentrations (104, 105, 106, 107 108 conidia/ mL) of each fungal isolate during other days after treatment (DAT), 1–7 DAT, were determined under laboratory conditions.

All isolates were pathogenic to the aphid causing about 25% mortality. The efficiency of the isolates was not significantly different among the aphid life stages. When the isolate concentrations (up to 55%) and DAT (up to 53.13 times) increased, their effects increased significantly. The highest and lowest mortality rates were observed at concentrations 108 (12.83%) and 104 (5.86%) conidia/ mL, respectively. The highest effectiveness was recorded in seven DAT for all isolates, 15.14% mortality. At one DAT, the isolates caused about 1% mortality in the aphid population with the lowest effectiveness. The highest mortalities were observed for GAM and PAL7 isolates at six DAT, i.e., 16.83 and 16.67%, respectively. Furthermore, the lowest effectiveness was recorded for the isolates GAM and PAL7, at one DAT (<0.1% mortality), respectively.

The isolates had some potentials for microbiological control of the BBA. Time and conidial concentrations, are the critical factors determining the efficacies of the entomopathogenic fungi. The highest effectiveness can be achieved before six DATs. When the conidial concentrations increased, the obtained mortality by the isolates was enhanced. Due to the relatively low efficacies of the EPF and a lag time for getting sufficient mortality, integrated applications of the entomopathogenic fungi with other compatible control agents with faster effects such as biorational insecticides are recommended. However, the laboratory results should be supported with field or semi-field studies before recommending applications of the entomopathogenic fungi against the BBA aphids in greenhouse or field crops.

In the present study, the effect of hexytiazox, nano sulfur, alginate/sulfur (Al/S) and alginate/sulfur/hexytiazox (A/H/S) composites were examined on adult famale of two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). The diameters of sulfur nanoparticles and sodium/sulfur alginate and sodium/sulfur/hexithiazox alginate 300-60 nm were obtained using electron microscopy (SEM). Analysis of FT-IR spectra of sulfur alginate/sulfur (Al/S) and alginate/sulfur/hexytiazox (A/H/S) composites were performed, in the sulfur spectrum, only two peaks 870 and 3435, and in the alginate spectrum 1630, 1457 and 1341 peaks were observed. The highest mortality was obtained 24, 48 and 72 hours after application in the composite (Al/He/S) treatment with LC50 values of 3.48, 2.80 and 2.43 g/l, respectively. Also the lowest mortality was observed 24 hours after using nanosulfur treatment with LC50 value of 20.34 g/l and in 48 and 72 hours in nanosulfur and alginate/sulfur (Al/S) composite treatment with LC50 values of 12.37 and 9.87 g/l, respectively. Hexithiazox treatment with a concentration of 12.7 ml/l after 72 hour aplication showed the highest mortality (70%). Based on the results of this study, composite (Al/He/S) can be recommended in the preparation of commercial acaricide formulations and use in T. urticae integrated management program.

Sugarcane (interspecific hybrids of Saccharum) is a strategically important cash crop that has an economic and social impact in many countries. Sugarcane mite, Oligonychus sacchari is one of the most detrimental arthropod pests associated with sugarcane during summer. Control of this pest is mainly based on chemical pesticides and cultural practices as well as the application of silicon as a nutritional component of an integrated crop management. In this study, effects of silicon were evaluated on O. sacchari. Experiments were carried out during 2014–2015 and 2015– 2016 at Salman Farsi Agro Industry Farms, Ahwaz-Iran. The two varieties (CP57-614 and CP48-103) were treated by silicic acid fertilizer as foliar application. Five treatments including one spray (0.5 lit/ha), two sprays (0.5 and 1 lit/ha 3 weeks after spray 1), three sprays (0.5, 1 and 1 lit/ha 4 weeks after spray 2), four sprays (0.5, 1, 1 and 1 lit/ha 4 weeks after spray 3) and Control were applied. In each plot, 15 leaves were randomly selected from bottom, mid and top of plant and number of living mites and dry leaves were recorded. Samples were collected 7, 14, 21 and 28 days after the forth application of silicic acid. The results showed that all treatments had significant effects in mite population and leaf dryness versus Control. Among different treatments of silicic acid, four spray application of silicic acid was more efficient than other treatments on mite damage and leaf dryness. It seems that the silicic acid would be a promising product for management of mite damage and could be incorporated with other management strategies in sugarcane IPM.

In the present study, sublethal effects (LC10=21, LC20=52 and LC30=100 ppm) of Bifenazate (Floramite® 24% SC) on biological parameters of the most important phytophagous mite, Tetranychus urticae Koch, was evaluated under laboratory conditions. Data analysis was performed using Age-stage two sex life table theory. Our results revealed that immature development of treated deutonymphs of T. urticae was not significantly affected by sublethal treatments. Female longevity was affected by sublethal concentrations and the highest value for this period was recorded at control (23.36 day). Furthermore, total fecundity was also negatively affected in female mites developed from treated deutonymphs and the lowest value was obtained at LC30 (27.02 egg). We also present data supporting that the sublethal effects could carry over to the next generation. Accordingly, sublethal concentrations reduced the net reproductive rate (R0), and there were significant differences among the values of this parameter at all treatments tested when compared with control (control=57.93, LC10=49.17, LC20=41.50 and LC30=32.87 offspring/individual). The intrinsic (r) and finite (λ) rates of increase were also significantly lower in mites treated with sublethal concentrations. The highest estimated values for r and λ were recorded at control (0.208 and 1.232 day-1,respectively). Finally, with the reduce rate of development observed for individuals treated with sublethal concentrations, the mean generation time (T) was significantly higher in individuals exposed to any concentration tested (control=19.48, LC10=19.80, LC20=20.10and LC30=19.45 day). Our data underline the importance of considering the role of sublethal effects when attempting to evaluate the total impacts of specific pesticide on an insect pest population and its progeny.

The inclination of rice growers towards double cropping system has raised new concerns about changes in pest biological parameters and the excessive release of pesticides in the environment. In this study, some biological traits of the overwintering larvae of Chilo suppressalis (Walker) was compared between single and double cropping rice fields in the northern Iran during 2016 and 2017. Under the same geographical locality, a significantly higher density of the overwintering larvae was observed in double cropping fields during November-March of both years, while larval mortality was lower in double cropping fields. The larvae collected from double cropping fields had significantly wider head capsules and tended to be heavier than those from single cropping ones. Additionally, both male and female pupae collected from double cropping fields had significantly higher body mass than those from single cropping fields. A significant increase in the number of days required for pupation of the overwintering larvae was observed under double cropping system. However, the adult moths emerged from these pupae were significantly higher fecund than those reared from single cropping fields. Results of this study highlight significant changes in some biological traits of C. suppressalis under double cropping system. At least, some of these changes are expected to affect the level of crop damage in the next growing season and thereby, demand higher rates of pesticides for satisfactory management of the pest. Therefore, further studies are needed to explore the pest status and management of C. suppressalis under double cropping system.

In this study, the population density and survival of overwintering larvae of Chilo suppressalis (Walker) (Lep: Crambidae) was compared between single- and double cropped rice fields in north of Iran (Amol) during winter months (November-March) of 2016-2017. According to the results, a significantly higher frequency of overwintering larvae was observed in double cropped fields in both growing seasons and during all overwintering months. Additionally, larval mortality in double cropped fields was significantly lower than those in single cropped fields. The efficiency of three pesticides, diazinon (with two formulations G 10% and EC 60%), hexaflumuron (EC 10%) and fipronil (G 0.2%) as well as an integrated pest management approach (IPM) using mechanical, physical, and biological methods for control of Ch. suppressalis in double cropping fields of Amol was investigated during growing seasons of 2016 and 2017. According to fields experiments, a single application of hexaflumuron or diazinon EC at a concentration of 1.5 L/ha against the first instar larvae resulted in the most decrease in dead heart and white head damage and the highest crop yield in both growing seasons. The effect of IPM approaches on damage and crop yield was also considerable among treatments. Results of this study indicate that hexaflumuron, as an insect growth regulator (IGR) can be efficiently integrated in management programs of Ch. suppressalis. Besides environmental advantages, the integration of insecticides with novel modes of action in rotation with convenient pesticides can decrease the rate of resistance development by the pest in double cropping systems.

Nesidiocoris tenuis Reuter (Hemiptera: Miridae) is a zoophytophagous mirid known as a potential biological control agent of whiteflies and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). This predator is widely used in integrated pest management programs in greenhouses. In this study, side effects of four pesticides including pymetrozin, abamectin chlorantraniliprole, mancozeb and iprodion carbendazim on survival and number of offspring N. tenuis were evaluated. Adults of predators exposed to the pesticides through residual and oral routes simultaneously. None of the pesticides except abamectin chlorantraniliprole cause significant mortality on predator but all of them were affected the number of offspring. The highest reduction in fertility was related to abamectin chlorantraniliprole (92.5%). Iprodion carbendazim (43.22%), pymetrozin (37.44%) and mancozeb (17.14%) were next in rank, respectively. Toxicity of pesticides was calculated based on the reduction coefficient, Ex. According to IOBC classification abamectin chlorantraniliprole was moderately harmful, pymetrozin and iprodion carbendazim were slightly harmful and mancozeb was harmless.

The cowpea seed beetle (Callosobruchus maculatus F.) is one of the most injurious insects infesting a wide range of leguminous stored seeds such as Lens culinaris, Vigna radiata, Vicia faba and Vigna unguiculata (1). This insect also causes secondary infestation during pulse storage, and may cause total loss within three months. The bruchids can cause heavy losses in terms of both quantity and quality (4). Heavy infestations of bruchids can cause heating of commodity, which results in quality loss, and mould growth. Currently, the control strategies of stored product insect pests have exclusively relied upon application of fumigants and protectant synthetic insecticides. Chemical control of pests has led to insecticide residues in stored products and insecticide-resistant insect populations (3, 6). Therefore, there is a need for the ecologically benign methods to control cowpea weevil on chickpea. High temperature application has been used to satisfactorily disinfest stored commodities by various technologies. Microwave radiation is one of the most promising biorational pest management tools for farm stored grain and grain processing industries (29). Microwave is a type of electromagnetic energy that provides rapid heating. It appears that high temperatures in a short time period may be lethal to many stored product pests. The present study aimed to assess the lethal effects of microwave radiation on adults of cowpea seed beetle in stored pulses.
The population of C. maculatus was originally collected from Laboratory of Entomology at Ferdowsi University of Mashhad, Iran. The cowpea weevils were reared on chickpea, in a growth chamber at temperature of 28 ± 2 ºC, relative humidity of 60 ± 5 % in the dark. Male and female beetles were treated separately with 2450 MHz at power levels of 90-900 W over a range of irradiation periods from 20 to 960 seconds. Corrected mortality data were subjected to two-way factorial analysis of covariance (ANCOVA) in which the microwave power and insects’ sex were regarded as independent categorial factors and irradiation period as covariate using SPSS Version 16 software. Prior to the ANCOVA test, Levene's test for equality of variances was performed to examine the assumptions for ANCOVA. Moreover, at each radiation power, the values of median lethal time (LT50), i.e., microwave irradiation period needed for the death of 50% insect population, and 90% lethal time (LT90) with 95% confidence limits were estimated separately for male and female beetles by subjecting mortality data to the maximum likelihood program of probit regression analysis using POLO-PC software. This program has a provision for control mortality.
The results indicated that the mortality rates of both male and female adults increased as the exposure period and/or the power of radiation increased. When microwave power levels increased, the time elapsed to achieve maximum lethal effect decreased; this was implied by the results showing maximum mortality achievement in 960 and 80 seconds at 90 W and 900 W, respectively. Male beetles were more susceptible than females, but this difference was not significant based on the LT50 ratio. The LT50 values for the power levels between 90-900 W varied between 674.8 - 41.40 seconds for males and 741.5 - 47.2 seconds for females. The probit analysis showed that the slope values of mortality - exposure time regression lines were in the range of 3.23 - 5.51. According to the likelihood ratio test of parallelism, the slopes of probit mortality regressions differed significantly among various microwave power levels. However, further likelihood ratio test between the paired combinations concerned revealed that the slopes of probit mortality lines differed significantly only between those of 90 and 900W levels. The present results are in agreement with those of Singh et al. (2012) who worked on Callosobruchus chinensis (26). Also, Sadeghi Nasab et al (2004) working on the effect of microwave radiation on three stored product pests, found similar results (25).
The results from our study showed that microwave radiation has a potential to kill insects in stored beans. It was observed that at certain constant power levels, the mortality of beetles increased as the microwave exposure time elongated and vice-versa. Although this strategy can control insect population in stored beans in a short time whilst deserting no chemical residue on food products, the adverse effects of microwave radiation on nutritional quality of food products and seed germination should be investigated. Further research is also recommended to improve methodology for practical disinfection of stored pulses.

The effect of different concentrations of Metarhizium anisopliae strain EUT115 along with control was investigated on various life stages of green peach aphid Myzus persicae, and different canola cultivars, Brassica napus. Thirty aphids of each stage were treated with the fungus and then transferred onto Petri dishes containing leaf-discs placed on 2% water-agar medium. The aphid mortality was recorded daily for 14 days after the beginning of the test. According to the results, after 7 days, the highest mortality was obtained on the RGS003 (5.47 ± 0.44) and the lowest mortality was occurred on the Zarfam genotype (4.983 ± 0.45) and the significant difference was observed between the two genotypes. The highest mortality among the different life stages happened for the adults and was calculated 7.64 ± 0.65 and 8.82 ± 0.50 aphids after 7 and 14 days, respectively. Among the various fungal concentrations, 107 conidia/ml of the fungus caused the highest mortality after 7 (8.38 ± 0.24 aphids) and 14 days (9.60 ± 0.12 aphids), respectively. The results showed that there was interaction between the fungal concentration and the aphid life stage. It is suggested that to control enormous infestation of the green peach aphid in canola fields, the RGS003 genotype and 107 conidia/ml of the fungus can be used. The mean mortality of the aphid was increased by increasing the time from spraying the pathogenic fungus. It shows the importance of fungus-sporulating cadavers of the aphid as a reservoir in surrounding environment.

Cotton aphid, Aphis frangulae gossypii Glover, is a major pest of cucumber in Iran. One of the important parasitoids playing role in population control of this pest in the fields and greenhouses is Lysiphlebus fabarum Marshall. In this study, we investigated sensitivity of different instars of cotton aphids and pupal stage of L. fabarum to field recommended and half-recommended concentration of three pesticides, acetamiprid, dichlorvos and azadirachtin by leaf dipping method. The persistence toxicity test and bioassays were also carried out on adult of parasitoid. Results revealed a significant reduction in the toxicity by increasing the nymphal stages of the aphid. These results also demonstrated the highest mortality for dichlorvos on pupal stage ofparasitoid. According to obtained results, LC50 of acetamiprid was 28.18, for dichlorvos was 7.052 and for azadirachtin was 1780.338, µg/lit on adult of parasitoid respectively. Based on IOBC categories, azadirachtin with stability of less than 5days, dichlorvos with stability 5-15 days and acetamiprid with stability between 15-31 days were classified as short lived (class A), slightly persistent (class B) and moderately persistent (class C), respectively. These results approved a better integration potential of azadirachtin with the parasitoid, L. fabarum, for aphid control.

Ozone is a powerful oxidant potent agent for killing insects and microorganisms. In this study, ozone gas was used to evaluate the effect of ozone on the mill moth Ephestia kuehniella Zeller (Lep.: Pyralidae) in raisins. The samples of infested raisin (50gr each) with fifth-instar larvae of E. kuehniella were exposed to ozone at three concentrations (2, 3 and 5 ppm) in five different periods (15, 30, 45, 60 and 90 min).The mortality of the larvae was proportional to the exposure time. 100% mortality was observed at 5 ppm of ozone concentration within 90 minutes. There was no adverse effects on raisins in terms of changes of quality, organoleptic properties or color factors, fragility and stiffness during the ozone treatments. But ozone had negative impact on the aroma of raisins.