JOURNAL OF CROP PROTECTION
Year:2020 | Volume:9 | Issue:4|Papers Count:14

The cotton bollworm, Helicoverpa armigera (Hü bner), is a destructive pest on a wide range of economic crops in many parts of the world. In this research, demographic parameters of H. armigera were determined on five host plant species including cowpea (cv. Mashhad), navy bean (cv. Dehghan), chickpea (cv. Hashem), soybean (cv. 033) and corn (cv. Single cross 704). All experiments were carried out under laboratory conditions at 25 ± 1 C, 65 ± 5% RH and a photoperiod of 16: 8 (L: D) h. The results revealed that females and males had the shortest development time on chickpea (36. 16 and 34. 98 d, respectively) and the longest development time on corn (42. 00 and 42. 95 d, respectively). The highest daily and total fecundity of H. armigera were observed on cowpea and the lowest ones were on corn. The values of the intrinsic rate of increase (rm) on the abovementioned host plants were 0. 180, 0. 144, 0. 161, 0. 161 and 0. 126 day-1, respectively. Also, the values of the net reproductive rate (R0) were 365. 66, 294. 28, 365. 67, 239. 69 and 147. 40 female offspring, respectively. The longest mean generation time (T) (37. 90 ± 0. 26 d) and doubling time (DT) (5. 62 ± 0. 17 d) were observed on corn. Our findings revealed that cowpea and corn were the most susceptible and resistant host plants to H. armigera, respectively.

In the present study, the cuticle-degrading enzymes production potential of five native Beauveria bassiana (TV, OZ, UN, DV and DE) isolates was investigated in the presence of cuticles from Eurygaster integriceps, Ephestia kuehniella and Zophobas morio. Furthermore, histopathology of infected insects by B. bassiana was studied. The level of cuticle degrading enzymes was the highest and lowest for TV (as the most virulent isolate) and DE (as the weakest isolate), respectively. E. integriceps nymphs as the most sensitive host produced the highest level of cuticle degrading enzymes (Pr2, exochitinase, and lipase) while Z. morio as the most resistant host, produced the lowest level of hydrolytic enzymes. According to histopathological study, the fungal isolate could not penetrate into Z. morio cuticle, as no mycelia or hyphae were observed in its tissues after inoculation, while fungal bodies were detected in microscopic slides of the other two insects. Overall, the chemical and topographical structure of insect cuticle had a substantial effect on the virulence of entomopathogenic fungus. Production of enzymes including proteases (especially Pr2), chitinase (N-acetyl-glucosaminidase), and lipases was positively related to virulence of fungus isolates. It can be concluded that not only the hydrolytic activity of B. bassiana isolates, but also host cuticle composition determine the pathogenesis and virulence cascade in fungusinsect interactions.

Three Trichoderma harzianum isolates, were evaluated for their antagonistic effect on Rosellinia necatrix causal agent of white root rot (WRT). According to in vitro evaluations, T. harzianum T20A isolate showed the most pathogen growth inhibition. The inoculum of T20A isolate was applied to control WRT disease on four commercial apple rootstocks: Malling (M7, M25) and Malling Merton (MM111, MM106) in greenhouse experiments. Root rot and leaf fall indices were measured 70 days after pathogen inoculation. The biocontrol agent had a significant effect (p < 0. 01) on the reduction of pathogen indices but the effect of rootstocks was not significant. Root rot reduction on MM111, MM106, M25 and M7 rootstocks were 63. 84%, 61. 13%, 28. 63% and 17. 47%, respectively. The antagonist also caused reduction of leaf drop symptom on MM106, M7, MM111 and M25 infected apple rootstocks by 57. 4%, 56. 06%, 44. 09% and 40. 24%, respectively. Disease indices were also measured for fungicide treatment and the results were compared with disease indices in antagonist treatments. The most biological control was observed on MM111 (63. 84%) and MM106 (57. 4%) according to the reduction in root rot and leaf drop, respectively. The reactions of apple rootstocks to WRT were also evaluated. The results showed that all the rootstocks were susceptible to WRT in the greenhouse condition. The MM106 rootstock which showed 100% root rot and 78% leaf drop was the most susceptible and M7with 43. 5% root rot and 84. 56 leaf drop was the least susceptible in our experiment. This was the first study of reaction and biocontrol of white root rot disease on apple commercial rootstocks in Iran and the results suggest a better insight to disease management either by integrating resistance and biocontrol measures or replacing chemical control by antagonist application to soil.

For effective integrated pest management (IPM) programs, it is essential to determine the thermal requirements and apply an accurate forecasting method based on daily degree units of pests. The present study investigated the physiological time (Degree-Days) and the number of generations of tomato leaf miner (TLM), Tuta absoluta (Meyrick) in Varamin region (Tehran, Iran) on two tomato cultivars (Cal JN3 and Early Urbana Y) under field-cage and open-field conditions during tomato growing seasons in 2015 and 2016. The environmental temperature was recorded hourly using an electronic data logger. The results indicated that TLM completed three generations during tomato growing seasons on the two tomato cultivars in both years. Degree-days for each generation and the thermal requirements of immature stages were a little different under field-cage and open-field conditions in 2015 and 2016. Furthermore, the pest completed each generation, one to three days earlier in the open-field conditions depending on tomato cultivars. On the whole, findings of this study can improve monitoring and forecasting phenological events of T. absoluta and thereby assist in timely adoption of management practices in IPM programs.

Wheat is one of the strategic products and has rich nutritional value. Plant diseases are major limiting factors that reduce the yield and quality of wheat, and yellow rust Puccinia striiformis f. sp. tritici causes considerable damage to wheat production. The most reliable way to control this disease is the use of resistant varieties. Plants have different mechanisms to defend against pathogens, one of which being proteomics employed to examine defense mechanisms in both sensitive and resistant plants. In this research, in order to identify the expression pathways and proteins involved in the mechanisms, resistant (Gaspart) and sensitive (Morvarid) wheat varieties were inoculated with P. striiformis, followed by the examination of peroxidase, catalase enzymes, intracellular osmoprotectants. The results showed that the amount of protein, carbohydrates, proline concentration, and peroxidase and catalase activity significantly increased by rust in the resistant variety. Also, results of the electrophoresis of two-dimensional proteins with stripes of IPG = 17 cm and pH = 4-7 showed that expression changes of proteins could be divided into two groups in response to P. striiformis. The first group included the proteins that directly reacted to pathogens such as peroxidase and PR10 proteins. The second group consists of the resistance proteins as transcription factors or proteins involved in signaling pathways or chaperons in determining proteins' partial structure such as molecular chaperone protein Hsp90.

Mediterranean flour moth, Ephestia kuehniella Zeller, is important for mass rearing of parasitoid insects such as Bracon wasps and it's feeding on cereals leads to economic losses in flour mills. In current research, the effects of four different diets: wheat, barley, oat, and maize flours, on protein content of larval and pupal whole-body, gut and fat bodies of the last instars and the digestive α-amylase activity were evaluated. In addition, their protein patterns were compared using polyacrylamide gel electrophoresis (SDS-PAGE). The protein contents of fifth instars whole-body, fat bodies, gut, and also pupa varied in different diets. On the whole, the lowest protein levels were found in all experiments in oat and the highest in barley and wheat. Other biological parameters such as insect weight and digestive α-amylase activity were also significantly affected by the decrease in protein content. The results obtained from the estimation of protein content by a colorimetric method and SDS-PAGE were consistent with each other; the low or high protein contents were also clearly visible in the gels. According to the results of enzyme activity and protein contents of insects reared on different diets, barley and wheat are reported to be appropriate diets for this pest, while oat and maize are not suitable diets.

Sheath blight disease of rice caused by Rhizoctonia solani AG-1 IA, has become one of the major diseases in some rice-growing areas in recent years. Primary inoculum density seems to be a major factor in disease outbreak. The aim of the current study was to determine the relationship between the primary inoculum density and type and the disease intensity, grain yield and yield loss. Field experiments were conducted in both years of 2017 and 2018 in Guilan province, Iran. Disease incidence and severity were significantly higher when the highest inoculum densities (mycelial and sclerotial) were tested. When sclerotia were applied as the primary inoculum, disease developed more quickly. Based on the results of the current study, in a temperate lowland rice system in Guilan province, sclerotia floating on the water surface after puddling can be the primary source of inoculum and play a major role in sheath blight epidemics whereas mycelia in plant debris probably lose their viability in winter. These results suggested that control of sheath blight disease in order to prevent sclerotia production and reduce the main disease inoculum can be a promising strategy for suppressing this disease in the rice fields of Guilan province.

The life table parameters of the parasitoid wasp, Aenasius bambawalei Hayat (Hym.: Encyrtidae) were studied at 25, 30, and 35  C, 65 ± 5% R. H. and 14L: 10D h. Third instar nymphs of Pseudococcus solenopsis Tinesly (Hem.: Pseudococcidae) were used as host for the wasp. Adult longevity and preoviposition period of female wasps were assessed and the raw data were analyzed using the age-stage, two-sex life table. According to the results, the total preovipostion period of females was 17 days at 25  C and decreased to 13. 07 days at 35  C. The highest and lowest longevity was recorded for females at 25  C (40. 12 days) and males at 35  C (3. 71 days), respectively. The intrinsic rates of increase (r) of A. bambawalei were 0. 1192, 0. 1599, 0. 2142 d-1 at 25, 30 and 35  C, respectively. The net reproductive rate (R0) was calculated to be 38. 04, 55. 30, and 81. 22 eggs/individual at 25, 30 and 35  C, respectively. The mean generation time (T) of A. bambawalei ranged from 20. 52 days at 35  C to 30. 52 days at 25  C. Our results suggested that A. bambawalei may be a more efficient biological control agent for P. solenopsis at 35  C than at 25 and 30  C.

Cellular energy allocation (CEA) test was performed in order to investigate the effects and costs of bare carbon nanotubes (CNTs) and CNTs in combination with titanium dioxide nanoparticles (CNTs/TiO2-NPs) on Glyphodes pyloalis Walker after 24, 48 and 72 hours of exposure to 100, 200, 300, 400 and 500 ppm of the treatments. Results showed the negative correlation between total lipid amounts and concentrations of treatments (i. e. CNTs and CNTs/TiO2-NPs) as well as exposure time. Contrary to CNTs treatments, carbohydrate contents were affected by both of CNTs/TiO2-NPs concentration and time of exposure. Results showed that the effect of bare CNTs in the enhancement of glycogen content appeared significantly faster than that of CNTs/TiO2-NPs. Increasing time of exposure to all concentrations of CNTs, except for 100 ppm, prevented enhancement of protein content. The effect of bare CNTs on the reduction of protein contents was faster and greater than that of CNTs/TiO2-NPs. The results indicated that G. pyloalis cannot regulate internal CNTs and CNTs/TiO2-NPs concentrations efficiently without considerable impact on the energy reserves (Ea). The comparison of energy consumed (Ec) in treated larvae showed that CNTs/TiO2-NPs reflected the higher energy demand of the stress response than CNTs. Generally, CEA was significantly decreased as the concentration of CNTs treatments increased. More reduction in CEA amount of all treatments by CNTs/TiO2-NPs than that of the control is also probably considered as a cost to deal with detoxification when the concentration increased and at all the tested time points. Therefore, CEA test might be considered as an early biochemical biomarker for assessing immediate response of organisms after acute exposure to stressors and thus could be applied to risk assessment of nanomaterials.

Apples are the main horticultural crops grown in West Azarbaijan province of Iran. In recent surveys of apple orchards in Urmia and Miyandoab, West Azarbaijan Province, symptoms including branch and twig bark cracks, cankers, dieback and tree decline were commonly seen. Isolation of the fungi from cracked and cankered branches yielded fungal isolates with typical characteristics of the genera Paecilomyces and Paramyrothecium. Based on combination of morphological characteristics and sequence data obtained from ITS-rDNA and β-tubulin gene sequences for Paecilomyces isolates and ITS-rDNA region for Paramyrothecium isolates, they were identified as Paecilomyces formosus and Paramyrothecium foliicola. Results of the pathogenicity tests on detached shoots of ‘ Golden Delicious’ and ‘ Red Delicious’ cultivars showed that isolates of P. formosus were pathogenic only on ‘ Red Delicious’ cultivar, but Pa. foliicola isolates were pathogenic on both cultivars and showed symptoms of infection. Reisolation of the fungi from inoculated shoots confirmed Koch’ s postulates. To the best of our knowledge, the involvement of P. formosus and Pa. foliicola in the development of canker disease of apple trees is reported for the first time. Also, Pa. foliicola is a new record to Iran mycobiota.

The purpose of this study was to determine the distribution of Tobacco streak virus (TSV) in the vegetable fields of the Markazi, Qom, Lorestan and Hamadan provinces. This study was performed in 2017, and a total of 475 samples of parsley plants were collected. Using the specific antibody of the virus, the TSV infection of these samples was investigated by the immunosorbent assay through the double antibody sandwich ELISA (DAS-ELISA) method. The results of this study indicated that the TSV infection of parsley samples in Qom, Markazi, Hamedan and Lorestan provinces were 14, 18. 8, 15. 4 and 20. 1%, respectively. Also, the phylogenetic analysis of nucleotide and amino acid sequences of the coat protein of these isolates showed that Iranian and Indian isolates could be clustered along with each other. The phylogenetic tree obtained based on nucleotide and amino acid sequences of the coat protein gene, showed that the isolates were divided into two and three clusters, respectively. Iranian isolates were clustered along with global TSV isolates and other Ilarviruses formed a separate cluster. This is the first report of TSV genetic diversity in Iran, and also the first report of TSV infection in the vegetable fields of Qom, Markazi, Hamedan and Lorestan provinces.

The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is one of the most damaging tomato pests in the world and in Iran. The toxicity of acetamiprid, eforia (thiamethoxam + lambda-cyhalothrin) and hexaflumuron alone and in mixture with emamectin benzoate was studied against 4th-instars of Tuta absoluta (Meyrick) at 25 ± 2 ° C, 65 ± 5% RH and 16: 8 (L: D) h. Moreover, the mixtures of examined insecticides with emamectin benzoate at LC15: LC15 ratio were assessed on the general esterase enzyme activity and total protein content of 4th-instars. The highest toxicity was found for emamectin benzoate after 72 h (LC50 = 0. 48 mg a. i. /l), followed by acetamiprid (LC50 = 46. 94 mg a. i. /l), eforia (LC50 = 156. 24 mg a. i/l) and hexaflumuron (LC50 = 670. 32 mg a. i/l). Mixing emamectin benzoate with acetamiprid at the ratio of LC50: LC50 and LC25: LC25 resulted in synergistic impacts while mix of two other ratios of the same pesticides represented additive influences. The mixture of emamectin benzoate with either hexaflumuron or eforia at all ratios created antagonistic and additive effects, respectively. Mixing emamectin benzoate with either acetamiprid or eforia increased larval esterase activity, however, there was no significant difference between emamectin benzoate in mixture with hexaflumuron and using it alone. Mixing emamectin benzoate with the examined insecticides considerably decreased the larval total protein content. Based on the findings of this work, the mixtures of eforia and acetamiprid with emamectin benzoate represented greater negative effects against 4th-instars compared to emamectin benzoate alone and the control.

It is possible to increase the efficacy of herbicides by adding vegetable oils to the spray tank. In order to evaluate and study this fact a greenhouse study was conducted. Three vegetable oils: coconut, sesame and almond oils at 0. 3% (v/v) were applied to compare their influence on enhancing the efficacy of pinoxaden and haloxyfop-R-methyl on littleseed canarygrass Phalaris minor Retz. (Poaceae) control, in 2012. The experimental design was completely randomized design with six replications in a factorial arrangement for each herbicide. The factors for each herbicide included vegetable oils in three levels and herbicide dose at six levels (0, 6, 12. 5, 25, 50 and 100 percent of recommended doses). The results of experiment revealed that by adding each vegetable oils haloxyfop-R-methyl ester weed suppressing influence was further increased compared to pinoxaden which was attributed to a positive relationship between oil receptivity and the high octanol– water partition coefficient of haloxyfop-R-methyl ester herbicide. Among the evaluated vegetable oils, coconut oil had the highest ability to enhance the efficacy of the two herbicides.

Although, weed control in saffron farms is critical, no herbicide is registered for saffron fields. This experiment was carried out in a randomized complete block design with three replicates during 2016-2017. Treatments included application of trifluralin, pendimethalin, metribuzin, bentazon, ioxynil, oxadiazon, oxyfluorfen, haloxyfop-r-methyl, sethoxydim, clethodim, cycloxydim, nicosulfuron, rimsulfuron, tribenuron methyl, foramsulfuron, paraquat, dicamba + triasulfuron, and dicamba + tritosulfuron herbicides at recommended and reduced doses. Mother corms were planted on 10th of September 2016 at 5 × 10 cm corms distance and planting depth of 15 cm. Measured indices included: number of flowers, fresh and dry weights of flower and stigma, number of replacement corms and total corms weight. Results showed that visual phytotoxic symptoms were not observed in pre emergence herbicides. Post emergence herbicides showed different levels of phytotoxicity from slight to severe. The application of paraquat, oxyfluorfen and oxadiazon, caused higher levels of phytotoxicity compared to other herbicides. Acetyl CoA carboxylase inhibitor herbicides caused the least injury to saffron, while acetolactate synthase inhibitor herbicides damaged saffron severely. The highest and the lowest dried stigma yield was obtained from control treatment (0. 54 g. m-2) and post application of tribenuron methyl (0. 003 g. m-2) respectively. Among pre emergence herbicides, the highest dried stigma yield was recorded for pendimethalin herbicide. The post application of metribuzin, oxadiazone and oxyfluorfen resulted in greater dried stigma yield than other broadleaf herbicides. By reducing herbicide dose saffron yield increased and phytotoxic levels were reduced significantly. Among the studied herbicides, trifluralin, oxyfluorfen, pendimethalin and metribuzin can be used as selected herbicides in saffron.