نشریه گیاه پزشکی کاربردی
سال نهم شماره 2 (پیاپی 28، اسفند 1399)

Root and stem rot of cucumber with Fusarium oxysporum f. sp. radicis-cucumerinum is one of the most harmful diseases in cucumber greenhouses in Iran. Chemical fungicides do not have the acceptable ability to control this pathogen. Also, due to their economic costs and adverse effects on the environment, the use of biocontrol agents in the control plant diseases has been considered in recent years. Trichoderma antagonist isolates has been shown to be an effective biocontrol agent against a wide range of fungal pathogens. In this study, the effect of Trichoderma isolates on root rot and cucumber rot fungi was investigated. Three Trichoderma isolates were obtained from the mycology collection of the Department of Plant Protection, University of Tehran. Mean peroxidase activity (POX) as a marker of induced resistance was measured using a spectrophotometer. Also, the effect of Trichoderma isolates on disease control in greenhouse conditions was determined by soaking the soil with spore suspension of antagonist and fungal pathogen. All three Trichoderma isolates T11, T6 and T9 have an acceptable effect on growth inhibition of F. oxysporum f. sp. radicis-cucumerinum. T11 and T9 isolates showed 85.51% and 81.03% inhibition of mycelial growth of F42 strain, respectively. Peroxidase activity was assessed within seven days after inoculation. The highest peroxidase activity was observed on the fourth day in T11 isolate. Based on the results obtained in this study, it can be concluded that T11 isolate (T. harizianum T11) had the greatest effect among Trichoderma isolates in inducing resistance.

Tobacco aphid (Myzus nicotianae) is one of the most important pests of tobacco and reduces the quality and quantity the tobacco product, directly and indirectly. Today, chemical insecticides are used to control pests. Due to the fact that plant extracts have a short shelf life in the environment and have low toxicity to humans, mammals and other living organisms, they are a good alternative to the side effects of chemical insecticides. In this study, the insecticidal properties of nettle Urtica dioica leaf and stem extracts on tobacco aphids were investigated. The experiments were performed at a temperature of 25 ±5° C, a relative humidity of 60±5% and a photoperiod of 16L: 8D. After extracting the aqueous extract of nettle by soaking method, for bioassay experiments, the 15 number of adults tobacco aphids were placed on filter paper and the lethal effect of mortality concentrations up to one percent in four replications on tobacco aphids were investigated. The lethal effect of these two extracts at 5 different concentrations (0.5, 1, 5, 10 and 15 mL/L) in four replications on the percentage of tobacco aphid mortality was investigated. The 50% lethal concentration (LC50) was calculated using the Probit program. The results showed that nettle leaf extract with (LC50 = 3.08 mL / L) showed more toxicity than nettle stem extract with (LC50 = 5.11 mL /L). The application of nettle leaf extract with a concentration of 15 mL / L after 48 hours caused 100% mortality on tobacco aphids, which is significantly higher than nettle stem extract (with 90% mortality). Overall, the results of this study showed that the extracts of both plant organs, especially nettle leaf extract, have good power to control tobacco aphids.

The black willow aphid, Chaitophorus niger Mordvilko, is a pest of willow trees in the green space, whose activity weakens the trees as well as secreting honeydew during the spring and summer. The predatory ladybug, Oenopia conglobata L. (Col.:Coccinellidae), is one of the most common predators of aphids. In this study, the pupal stage of the ladybug was collected from the municipal parks (Sabzeh, Salamat) and was reared in the Plant protection laboratory of the Green Space Education and Consulting Research Center of Tehran Municipality, District 17. Homogenization of second instar and adults of aphid was performed in vitro conditions (15-30 °C, relative humidity 65 ± 5%, photoperiod 16: 8 L: D). Then, the micro-emulsion contact toxicity effect of aqueous extract of Caesalpinia gilliesii (fruit; seed) prepared from the pesticide research department of the Iranian Plant Protection Research Institute, was determined on the nymphs and adults of willow black aphid and Oenopia adult by foliar application with LC50 determination in vitro. Bioassay was carried out in 24, 48 and 72 hours in a completely randomized full factorial design with four replications of C. gilliesii (1000, 2000, 3000, 4000 and 5000 ppm) and diazinon (1000-2000 ppm).The results were statistically analyzed using Design Expert 12 software. The lowest mortality was observed in nymphs and adult aphids after 24 hours at a concentration of 1000ppm with an average of 33.3% and 16.6% respectively in Egyptian silk. However, the highest mortality was observed at the concentration of 5oooppm of Egyptian silk, which was not significantly different with 2000 ppm diazinon. The average mortality of ladybugs in 72 hours after the experiment was 1.6% in 1000ppm of Egyptian silk extract, while the highest mortality was observed at 5000 ppm of this extract in 72 hours after the experiment (21.6%). According to the results, the highest aphid mortality in the plant formulation was related to the concentration of 5000 ppm. Therefore, the formulated composition of Egyptian silk can be improved by slightly changing the formulation process to reduce the consumption concentration, and this new combination can be used for sustainable urban management in pest control and maintaining environmental health.

Barley brown spot disease by the infecting agent of Pyrenophora graminea is one of the most important and common barley diseases in most parts of the world and Iran. The aim of this study was to investigate the field yield of several fungicides and non-chemical composition in the control of spotting disease on several barley genotypes with different levels of resistance during the crop year 2018-2019 in two Agriculture and Natural Resources Research Centers in Neishabour and Torogh (Mashhad). Factorial experiment in the form of a randomized complete block design with experimental factors including barley genotype in 5 levels (Yousef, Goharan, Sahra, Jolgeh and one line ABY-C95-12) and fungicide in 4 levels (control, oral TS one per thousand, half azalea one and a half per thousand, vinegar (1.5 /1000) + mustard (35 g / kg) were combined. Percentage of infected plants at harvest time was calculated and analyzed by Duncan test at 0.05% probability level. In combined analysis, the percentage of infection was affected by region, genotype, fungicide and genotype interaction in fungicide .ABY - C95-12 line with 3.86% contamination were in the first place and Yousef and Gohran genotype were in the second place. The study of mean comparisons showed that the percentage of infection in control plants and free-ranging treatment was at the highest rate and was equal to 2.95 and 3.10%. The use of vinegar and mustard reduced this trait to 2.59%. Among all genotypes, the percentage of infection decreased to a significant level when oral TS was used.

Using plant resistance inducers leads to the reduction of disease incidence and severity. The effect of several resistance inducer compounds on onion downy mildew disease was tested in a factorial experiment with a randomized complete block design comprising of 10 treatments in 3 replications at Behbahan Agricultural Research Station. Treatments consisted of chemical indicers in five levels of 50mμ dipotassium phosphate, 80mμ nicotinic acid and 3mμ salicylic acid, and ridomil mancozeb fungicide (3g/L) and control that treated with water. Treatments were applied 5 times from mid-February when the plants were in 3 to 4 leaf stage until late April every two weeks. Genotypes were in two levels including modified onion of Behbahan and Early White Texas. Disease severity was calculated by evaluating 40 plants in each treatment when the disease index in the control treatment was more than 75% in two middle rows of each plot in each treatment. The highest percentage of disease severity (75.50%) was observed in the control treatment with no spraying and the lowest rate of disease severity was observed in the application of Ridomil with 14.17%. The severity of the disease was 28.33%, 33.33% and 23.33% in dipotassium phosphate, salicylic acid and nicotinic acid treatments, respectively. Therefore, the use of resistance inducers can be a substitute of fungicides.

Wheat leaf rust, caused by Puccinia triticina Eriks, is one of the most important wheat diseases due to the extent of dispersion and damage in the world. This research project was conducted in order to evaluate reaction of 111 wheat genotypes of Elite Regional Wheat Yield Trials (ERWYT-97) to wheat rust disease under field conditions in Gorgan, Sari and Ahvaz. At the planting seasons, each genotype was planted in two meter rows in three replications for two years. In Karaj, resistance of genotypes was evaluated at seedling stage and under greenhouse conditions. In greenhouse, data were recorded 12 days after inoculation by McIntosh et al. method. The results showed that out of 111 advanced wheat lines, four climates had 25 acceptable resistance lines at three locations in two years. 86 lines were susceptible in one area or over two years. Also 7, 25, 7, 3, 7 line of 26 promising lines of South Zone wheat, the 25 promising lines of North Zone wheat, 20 promising lines of Cold Zone wheat 20 promising lines of Moderate Zone wheat, 20 promising line of salinity wheat respectively showed only one resistance line.