Iranian Journal of Plant Protection Science
Year:2020 | Volume:50 | Issue:2|Papers Count:9

Some essential oils and plant extracts have shown suitable insecticidal properties against the sweet potato whitefly, Bemisia tabaci. In this study, essential oils of rosemary, peppermint and eucalyptus and extract of thyme were formulated separately in Tween 80 as well as formulated in the form of nanoemulsion and bioassyed against 2nd instar nymphs of B. tabaci. The bioassay tests were done by leaf dip method on the leaves containing 2nd instar nymphs and LC50s were determined. The LC50 of rosemary, peppermint, eucalyptus essential oils and thyme extract prepared in Tween 80 were estimated as 4198, 3925, 4312 and 9626 mL/L and LC50 of nanoemulsion of above items were estimated as 2759, 2987, 3189 and 5659 mL/L, respectively. The results showed that nanoemulsion of rosemary and peppermint essential oils have the highest toxicity on the 2nd instar nymphs of B. tabaci. Also, effects of combination of essential oils and extract formulation on biochemical and enzymatic changes were investigated with LC50 of T1 (emulsified from essential oils and the extract), T2 (extract emulsion) and T3 (emulsification of essential oils). The amount of activities of esterases and glutathione s-transferases were increased in T1, T2 and T3 treatments; while, the cholinesterase activity was not affected. The amount of energy reserves (total lipid, carbohydrate and protein) decreased significantly in T1 and T3 treatments; although the amount of total glycogen was not affected significantly by treatments. Therefore, T1 and T3 treatments showed a greater effect on the biochemical parameters, by induction of detoxification of some enzymes and reducing some of the energy reserves, in 2nd instar nymphs of sweet potato whitefly.

Bacillus velezensis is one of the plant probiotic bacteria that has been recently considered as one of the most powerful biocontrol agents. The purpose of this study is to introduce and investigate some of the characteristics of B. velezensis bacterium, which has been isolated from tomato rhizosphere in Kermanshah Province. In this study, B. velezensis increased shoot length, root length and dry weight of tomato plants by 78. 86%, 56. 68%, and 45. 83%, respectively in comparison to uninoculated control; it also promoted seed germination percentage and seed vigor index under in vitro condition. Furthermore, some of the biocontrol properties of this strain such as the production of siderophore, HCN, and indole-3-acetic acid and solubilization of phosphate were evaluated. Biocontrol bioassay of this strain against Fusarium oxysporum f. sp. lycopersici under in vitro condition revealed that this strain can inhibit the mycelial growth in both dual culture and volatile compounds methods about 83% and 58%, respectively. The pot experiment results showed that B. velezensis caused a reduction in disease symptoms up to 87%. Finally, the whole genome sequence of this strain was identified using Illumina HiSeq2500 technology. Then genomic locations and coding sequences were identified in RAST database. In addition, the sequencing data were compared with existing sequences in the NCBI database. Results showed that this isolate has high similarity to (%100) B. velezensis. The genome of this isolate contains 4132868bp and 4329 CDs. The results suggest that B. velezensis has a good potential to be introduced as a plant probiotic bacterium.

Water is an important carrier for pesticide spraying. Physical and chemical properties of water can affect the quality control indexes and the efficiency of diluted pesticides. So, the study of the water characteristics in different regions of the country is very important. For this purpose, water samples from Mazandaran, Fars, Isfahan, Markazi, Guilan, Qazvin, Kerman (two regions), Khorasan Razavi, Yazd and Tehran provinces were collected. The effects of water hardness, pH and electrical conductivity (ec) on the quality control of two insecticides chlorpyrifos (EC 40. 8%) and imidacloprid (SC 35%) as prevalent and highly-consumption formulations in the country were studied. The results of water hardness test showed that water sample from Kerman with 2255 ppm and then the water of Fars with 744 ppm had the highest hardness and sample of water in Guilan region with 60 ppm had the lowest degree of hardness in water tested areas. The emulsion stability of chlorpyrifos in water samples from Qazvin, Guilan and Khorasan Razavi (with low water hardness), showed no creaming, while in provinces which hardness was high, including Kerman, Fars and Yazd, creaming at diluted insecticides were high. The suspensibility of imidacloprid in water samples showed that suspension in water from Kerman, Fars and Yazd samples was unacceptable and suspensions from the other areas were acceptable.

Honey bee is one of the most important pollinator and producer insects that have a high economic and environmental value. Different hybrids and subtypes for this insect have been introduced around the world with respect to the climate. One of the races is Apis mellifera meda with some characters. Unfortunately, in the recent years with importing honey bees from foreign countries, this race became impure. In this study we compare some characters of native honey bee races with Carniolan hybrid in Hamedan province that is the famous area for queen rearing. For this purpose 3 angels in forewing including A4, D7 and G18, length and width of fore and hind wings and proboscis length were evaluated in 50 individuals from each population (n= 50 for native and n= 50 for hybrid honey bees). Dinocapture and Digimizer software data were used to calculate. The results of the research showed that two angles and widths of fore and hind wing and proboscis length have significant differences but other characters didn't have any difference. These differences in two races may be due to methods of evaluating, differences in gene pools and problems importing queen.

The effect of Glomus intraradices and G. mosseae (Gm+Gi) as Arbuscular mycorrhizal fungi (AMF) was investigated on Phytophthora root rot of pistachio seedlings caused by Phytophthora drechsleri (Pd) in salinity level of 1400 and 3200 mg NaCl per gram of soil. Two month old pistachio seedlings cultivar Badami-Zarand were inoculated by 200 propagules gr-1 of Gm+Gi mycorrhizae and after 50 days, salinity treatments with different concentration of NaCl were added to seedling pots through irrigation during 15 days. After two weeks, seedling roots were inoculated by P. drechsleri. The results showed that seedlings inoculation by mycorrhizae, significantly increased the shoot and root dry weight, leaf area, seedling height, chlorophyll and soluble sugars concentration in all salinity levels as well as non-saline treatments. But proline concentration as well as Na and Cl ions were reduced in shoot and root of mycorrhizal seedlings. P. drechsleri inoculation could have no significant effects on root colonization by AMF whereas in myorrhizal seedlings, the colonization of pathogen was significantly decreased in all salinity treatments. The results of the interaction treatment of AM fungi and P. drechsleri showed that the shoot and root dry weight, leaf area, seedling height, chlorophyll and soluble sugars concentration were significantly increased in all salinity levels compared to P. drechsleri inoculated seedlings whereas the concentration of Na and Cl ions in shoot and root was significantly lower. In conclusion, the presence of AM fungi could reduce the destructive effects of salinity and Phytophthora root rot of pistachio.

Charcoal rot is one of the most important and destructive disease of sesame in Iran and worldwide. In order to evaluate reactions of different genotypes of sesame, infected plant tissues of sesame with charcoal rot symptoms collected and different isolates of the pathogen obtained, purified by hyphal tip method and finally using morphological criteria, 10 isolates identified as Macrophomina phaseolina. In order to determine virulence of the isolates, pathogenicity test was performed on 1% water agar plates at 30 C using pre-germinated seeds of Darab-1 cultivar. The result showed the variability of virulence of the isolates. Then reaction of the 26 cultivars and genotypes using the most virulent isolate (MP-3-13) was performed by the standard method of Cut-Stem in greenhouse condition. Mean of necrosis length of different genotypes were measured five days after inoculation. Statistical analyses indicated the significant difference among the necrosis length of sesame genotypes. The results showed that AT6, Dashtestan 2, Darab 1, AT1 and AT2 were the most tolerant ones, respectively. Yellow white had the most susceptible reaction to the charcoal rot disease in this experiment. The rest of genotypes showed a range of necrosis length in response to the pathogen.

To investigate the effects of mycorrhizal fungus on competitive relations between wheat (Triticum aestivum) and weeds, two separated factorial experiments based on a completely randomized design were carried out at greenhouse conditions in Karaj, during 2017-2018. The factors of the 1st experiment were wheat and six weed species and two levels of mycorrhiza inoculation (with and without fungus) and that of the 2ndexperiment were pure stand of wheat, wild oat and rye and mixed cropping of wheat with wild oat and wheat with rye, and two levels of mycorrhiza inoculation (with and without fungus). In the 1stexperiment, mycorrhizal growth response of shepherd's purse (Capsella bursa-pastoris), bunchgrass (Phalaris minor), Londonrocket (Sisymbrium irio), perennial ryegrass (Lolium rigidum) and wheat were 18, 19. 5, 23, 38 and 41 percentage, respectively and that of Rey (Secale cereale) and wild oat (Avena ludoviciana) were-29. 28 and-22. 40 percentage, respectively. In the 2nd experiment Rye and wild oat competition in non-fungus inoculated treatment reduced wheat dry weight by 41. 58% and 51. 4%, respectively. In the presence of fungus, wheat dry weight in competition with rye and wild oat, increased by 43. 10% and 47. 11%, respectively. In pure stand of wheat in the presence of fungus, wheat yield was 5. 51 g/plant, which increased by 51. 79% in comparison with non-application of fungus. The results of this research indicate that if the dominant weeds in the wheat fields, are non-mycorrhizal, or their mycorrhizal growth response is negative, the application of mycorrhizal fungi can reduce the damage of those weeds.

Compatibility of Beauveria bassiana (Balsamo) with hexaflumuron, chromafenozide, chlorfluazuron, phosalone, garlic extract and pepper extract was studied at the laboratory condition. In details, 75, 150, 300 and 500 μ l of the insecticides and extracts were incorporated into 100 ml of liquefied potato dextrose agar (PDA) culture medium. Seven, 15, 17 and 19 days after treatment, diameter of the colonies was measured and compared in the treatments and control. In the second part of the study, the effects of B. bassiana, chromafenozide, chlorfluazuron, phosalone, garlic extract, pepper extract, hexaflumuron, azadirachtin and B. bassiana + garlic extract, were determined on alfalfa leaf weevil Hypera postica (Gyllenhal), pea aphid Acyrthosiphon pisum Harris and the two species of coccinellids including Hyppodamia variegata (Goeze) and Coccinella undecimpunctata L. under field conditions. Experiments were conducted using randomized complete block design with four replicates. A sampling was conducted a day before treatments and three samplings were conducted 1, 3 and 7 days after treatments. The Efficacy of treatments was calculated using Henderson-Tilton's formula. The results indicated that garlic and pepper extracts were compatible with B. bassiana and those can be used simultaneously in pest management programs. Three days after treatment, efficiency of garlic and pepper extracts, hexaflumuron and B. bassiana + garlic extract was significantly higher on young larvae of H. postica than other treatments and those can be considered in this pest management programs. Chromafenozide, azadirachtin and hexaflumuron had > 50% efficiency on pea aphid population. Among these insecticides, hexaflumuron may be recommended for pea aphid control due to its relatively low effects on the lady beetles.

Bacillus subtilis has a good potential for plant pathogens control due to the formation of endospores, tolerance to variable pH conditions, wide thermal range and because of antibiotics production. In this study, the biocontrol potential of native Bacillus against Rhizoctonia solani AG2-2 was evaluated. Fengycin many antibiotic extracted and the relationship between antibiotic-producing isolates with sugar beet root and crown rot control, investigated in the greenhouse. In laboratory and greenhouse tests, 82 selected Bacillus subtilis isolates with 2 standard antagonist isolates were used. Of the 84 isolates, in double culture test in petri dish, isolate UTB1 with 55. 3% had the most inhibitory effect. In greenhouse tests, bacterial isolates UTB27, UTB65 and UTB71, reduced disease by 60. 09% (the most inhibitory on disease). Of the 84 bacterial isolates, 52 isolates had a significant effect on wet and dry weight of plant. Of the 84 bacterial isolates in the HPTLC assay, for antibiotic extraction, 19 isolates produced fengycin and 65 isolates were unable to produce. In the greenhouse test, 75 bacterial isolates reduced disease, which was significant at 5% level, and 19 isolates of them were producing fengycin. The native bacterial isolate UTB1 is a good candidate for a successful biocontrol agent.