جستجوی مقالات مرتبط با کلیدواژه "essential oils" در نشریات گروه "گیاهپزشکی"

The ever increasing population and global issue for food security have led us to use multiple approaches to overcome the weed problems that can reduce the crop productivity up to 70%. Chemical herbicides and mechanical and other biological approaches have overcome weed problem on one hand but also destroy the environment and caused some human health impacts on the other hand. Bioherbicides are biological control agents applied in similar ways to chemical herbicides to control weeds. Of the array of bioherbicides currently available, the most successful products appear to be sourced from fungi (mycoherbicides), with at least 16 products being developed for commercial use globally. Over the last few decades, bioherbicides sourced from bacteria and plant extracts (such as allelochemicals and essential oils), together with viruses, have also shown marked success in controlling various weeds. Despite this encouraging trend, ongoing research is still required for these compounds to be economically viable and successful in the long term. This review will explain the importance and impacts of the bioherbicides by elaborating the constraints which this approach is facing in its production and application.

Varroa destructor Anderson & Trueman is one of the most perilous pests of honey bee colonies around the world. So, natural products such as plant essential oils are considered as a suitable replacement for chemical compounds in pest control. This study was planned to check the respiratory killing effect of essential oils of four perennial Satureja species on Varroa destructor and Apis mellifera meda in an apiary. The sensitivity of the mite to four essential oils was according to the following, S. khuzestanica Jamzad, S. rechingeri Jamzad, S. mutica and, S. bachtiarica Bunge. The calculated LC50 values for S. khuzestanica Jamzad and S. rechingeri Jamzad were 151.6 and 161.77 ppm for Varroa mite and 328.22 and 337.7 for honey bee, respectively. Qualitative analysis of essential oils showed that the major component of the oils for all species was carvacrol. Satureja khuzestanica Jamzad and S. rechingeri Jamzad had the highest amount of carvacrol with 93.5% and 88.8%, respectively. In general, the essential oil of S. khuzestanica Jamzad and S. rechingeri Jamzad had a high ability to control Varroa mites.

The lesser grain borer, Rhyzopertha dominica F. is an important pest of the stored products, which causes severe economic damage on grain. Regarding necesity of using alternative methods to chemical insecticides, in the present study the lethal and sublethal effects of the essential oils of Ajwain (Carum copticum L.) and fennel (Foeniculum vulgare Mill) along with diatomaceous earth were evaluated against R. dominica. The chemical compositions of the essential oils were determined by gas chromatography-mass spectrometry. The major components of Ajwain were phenol, benzene, and γ-terpinene and those of the fennel were propanal, trans-anethole, γ-terpinene, benzene, and cyclohexene. The toxicity of fennel essential oil (LC50 = 103.83 µl/l air) against the adults of R. dominica was higher than Ajwain essential oil (LC50 = 167.46 µl/l air). The LC50 for the diatomaceous earth was obtained 0.052 g/kg. Results of the experiment of sublethal effects (LC30) showed that males and females’ longevity and the fecundity of females were significantly lowest in the combination of Ajwain essential oil along with diatomaceous earth. Furthermore, the net reproductive rate (R0), intrinsic rate of natural increase (rm), and finite rate of increase (λ) of the pest, in both the combination of Ajwain essential oil along with diatomaceous earth and fennel essential oil along with diatomaceous earth were significantly lower (P < 0.05) than other treatments. The results of this study indicated that the essential oils of each of these plants in combination with diatomaceous earth can be used in the management programs of R. dominica.

Sitotroga cerealella Olivier, is a species with worldwide distribution, which causes substantial damage to the grain kernels. In the present study, fumigant toxicity (LC50 and LC90) and sublethal effects (LC25) of the essential oils of three medicinal plants including black cumin, cinnamon, and peppermint were evaluated against the eggs and adults of this pest. The chemical constituents of the essential oils were detected by gas chromatography-mass spectrometry. Monoterpenes were the main chemical compounds of the tested essential oils. Fumigant toxicity of peppermint (LC50: 0.5 µl/l air) essential oil against the adults was higher than cinnamon (LC50: 0.94 µl/l air) and black cumin (LC50: 2.42 µl/l air) essential oils. The same trend was also observed against the eggs. The speed of mortality for peppermint (LT50: 8.05 h) and cinnamon (LT50: 9.68 h) essential oils were higher than black cumin (LT50: 14.78 h) essential oil. Results of the experiment of sublethal effects showed that the developmental time of the pest on the essential oils treatments were significantly longer than on control. The lowest fecundity of the pest was observed on peppermint treatment. Furthermore, the tested essential oils significantly reduced the net reproductive rate (R0), intrinsic rate of natural increase (rm), and finite rate of increase (λ) of the pest. The results of this study showed that the tested essential oils, especially the essential oil of peppermint have a suitable potential for decreasing the population of S. cerealella and they can be used in the IPM programs of the pest.

 In this research after formulating essential oils of Mentha longifolia, Mentha piperita and Oliveria decumbens, quality of the prepared formulations was studied according to the FAO standards. Then insecticidal efficacy of these compounds was investigated in comparison with Dayabon (Dayabon®) and acetamiprid (Mospilan®) against first instar nymphs and adults of Phenacoccus solenopsis in lab and field conditions. The LC50 values of formulated essential oils of M. longifolia, M. piperita, O. decumbens, Dayabon, Dayabon+ sesame oil and  acetamiprid on the adults and the nymphs of P. solenopsis were 164.55, 171.41, 195.92, 6177.85, 3316.58, 69.28 and 49.77, 55.13, 65.32, 4256.10, 2159.89 and 16.45 mg/l, 48h after treatment respectively. Field experiments were also conducted with four replications in a randomized complete block design. The numbers of P. solenopsis (nymph and adult) on branch samples were counted before treatment and 1, 3, 7 and 14 days after treatment. The field bioassay results showed that formulated essential oils had acceptable effects on developmental stages of P. solenopsis. Acetamiprid toxicity was higher than the other treatments but gradually reduced. The total results revealed that formulated essential oils were known as promising compounds in integrated management of this pest.

In recent decades, one of the most important methods of replacing synthetic pesticides is the use of new formulations based on plant essential oils (EOs) that can increase the quality and effectiveness of them. Due to application restrictions of EOs in their pure form, preparation of commercial formulations of these compounds is essential. In this research, At first, the contact toxicity of fifteen different plant EOs was evaluated on reared Phenacoccus solenopsis 1st instar nymphs at 25±1°C and 65±5% RH, with a 16:8-h L:D photoperiod. Three EOs of Mentha longifolia (L.), Mentha piperita (L.), and Oliveria decumbens (Vent.), had the highest contact toxicity and were selected for the rest of the experiments. According to GC and GC/MS analysis, pulegone (51.49%), menthone (22.75%), and 1,8-cineole (11.69%) were the principal components of M. longifolia, menthone (36.51%), menthene (28.51%), menthol (8.12%), and 1, 8-cineole (7.66%) were the principal components of M. piperita and the main components of O. decumbens EO were thymol (43.99%), γ-terpinene (13.96%), and p-cymene (12.62%). After making formulation, contact toxicity of the EOs before and after formulation, was evaluated on P. solenopsis 1st instar nymphs under laboratory conditions. Based on lethal concentration trials, LC50 values of pure and formulated EOs of M. longifolia, M. piperita, and O. decumbens on 1st instar nymphs after 48 hours were 113.49, 129.74, 149.93, and 48.22, 55.55, 61.68 ppm, respectively. Therefore, the contact toxicity of formulated EOs of M. longifolia, M. piperita, and O. decumbens were 2.34, 2.36, and 2.43-fold higher than the pure EOs.

In order to find a suitable alternative to conventional pesticides, fumigant toxicity of essential oils from Mentha longifolia, Tagetes minuta and Salvia macrosiphon were tested against adult of Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) on laboratory condition. The experiment was conducted using a completely randomized design of factorial experiment with five concentrations and three replications at 25±10C, 60±5% R.H in darkness. The results showed that the percentage of mortality was increased with increase in concentration and exposure of time. The results also showed the effect of fumigant toxicity of Mentha longifolia was weaker than Salvia macrosiphon on the studied insects. The LC50 values were evaluated by M. longifoli, T. minuta and S. macrosiphon were 9.595, 12.434 and16.649 μl/l after 12h as well as 7.422, 9.128 and 13.071 μl/l after 24h for T. castaneum, respectively. Mean adult mortalities of Tribolium castaneum, at the highest concentration of essential oils (25μl/l), by M. longifolia, T. minuta and S. macrosiphon as 76.6%, 73.3% and 63.3% after 12h as well as 90%, 76.6%, and 70% after 24h, were recorded, respectively. It was found that plant essential oils could be used as a safe pesticide or model for new synthetic pesticides to control of insect pests

Using medicinal plants essential oils to control or suppress plant diseases causing reduce of undesirable chemical pesticides. In order to study the effect of essential oils on control of two plant pathogens, an experiment was conducted as a three factorial experiment based on randomized complete block design with four replications carried out In-Vitro condition. The factors were including four essential oils of medicinal plants (Lavender, Rosemary, Cinnamon and Eucalyptus) in five concentration (0, 500, 1000, 1500 and 2000 µL/ L) on control of Fusarium oxysporum and Fusarium solani fungi. The results showed that essential oil of Cinnamon can wholly control (100 %) mycelium growth of F. solani fungi in all concentrations, but in F. oxysporum fungi, only in 1500 and 2000 µL/ L of essential oil can control growth of fungus.The least and most of essential oil of lavender (88/5 and 100 %) observed in F. oxysporum and F. solani respectively. The highest of control in F. solani and F. oxysporum by Rosemary was 100 and 46/6 % respectively. The eucalyptus essential oil was the lowest effect on control of fungi. The highest of eucalyptus concentration can with 48 and 49 % inhibitor growth mycelium of F. solani and F. oxysporum respectively. On average, the maximum and minimum control of F. solani fungus observed respectively in cinnamon and eucalyptus essential oils, and in F. oxysporum was in cinnamon and rosemary essential oils. Cinnamaldehyde in cinnamon essential oil is a very strong inhibitor and can be used to control plant fungi.

Tomato Fusarium wilt caused by Fusarium oxysporum fsp lycopersici is an important disease to tropical regions and sandy soils of Iran. In this study, the effect of essential oils of thyme, zynan, fennel and antagonist fungus of Tricoderma harzianum (Th-va-104) evaluated on the colony growth rate and growth inhibition in seven concentrations of 100-1000 ppm on PDA medium in vitro. The minimum percentage of inhibitory growth (Ec50) determined in essences of thyme, zynan and fennel with 83.95, 62/685, and 59.97% respectively. Tricoderma showed the maximum inhibition of fungal mycelial growth of F. oxysporum fsp lycopersici as 78.53% followed by thyme. The effect of thyme, Fennel and zynan essential oils at the concentration of 0.5 and 1, Fungicide (Iprodione+Carbendazim 52.5% WP) by concentrations of 1.5 and Tricoderma were evaluated in a completely randomized block design in greenhouse experiments. The essential oils were incorporated with potting soil with planting seedlings and Trichoderma fungus simultaneously in three days before transplanting. The percentage of disease severity index was assessed four weeks after inoculation. The results demonstrated that the disease index severity of thyme and Trichoderma by 2.6 and 2.06 respectively were placed in the closest disease index to check. The root area fresh and dry of thyme treatment (1.53, 2 gr), shoot area weight mean (13.19, 1.82) and the root area fresh and dry of Trichoderma (1.79, 0.27 gr) and shoot area weight mean (12.77, 1.63 gr), respectively were classified in the similar statistical groups with check.