فصلنامه گیاه پزشکی
سال چهل و چهارم شماره 1 (بهار 1400)

Background and Objectives Tetranychus urticae, as the two-spotted spider mite, is considered as one of the most important and destructive herbivorous mites in farms and greenhouses, which is very important to control due to its wide host range. The damage caused by agricultural pests combined with the harmful effects of synthetic chemicals used in their control can be mitigated or eliminated by using botanicals, which are derived from renewable resources including a mixture of various bioactive ingredients. Therefore, finding a suitable alternative way for controlling this pest is necessary by considering the resistance to acaricides, as well as undesirable effects of chemical compounds. The present work aims to evaluate microcapsule essential oil of Mentha piperita and its lethal and sublethal toxicity to T. urticae. Materials and Methods Laboratory bioassays were used for evaluating the sublethal effects of peppermint essential oil microcapsules on biological and population parameters of T. urticae. The life table parameters of T. urticae were conducted on leaf discs under laboratory conditions at 25 ± 2°C, 60 ± 5% relative humidity, and a photoperiod of 16:8 (L: D) hours. Then, the duration of each stage, developmental time, and survival were observed and recorded daily. In addition, the raw data were analyzed based on age stage two-sex life table theory with MS-Chart. Results Based on the results, microcapsules of Menthe piperita caused a significant reduction in fecundity and longevity. Those treated with LC20 and LC30 had a significant reduction at net reproductive rate, compared to those treated with LC10 and untreated ones. The intrinsic and finite rate of increase reduced significantly in higher concentration compared to the control. In addition, the mean generation time decreased significantly at the upper dose, compared with LC10. Discussion Botanic acaricides can be used for controlling Tetranychus urticae, and the microencapsulated formulation of these products makes them more stable. Familiarity with the chemical nature of the bio-active pesticide/acaricidal compound can be considered in future research which can play a role in developing an effective and environmentally friendly treatment against spider mites, leading to a decrease in reliance on synthetic pesticides/acaricides. The results of this study can be used in designing the mentioned pest management programs by considering the detrimental effects of M. piperita essential oil microcapsule on some biological parameters of T. urticae.

Background and Objective Root-knot nematodes (Meloidogyne spp.) are among the most important pathogens which cause great damage to the agricultural products. However, only a few methods such as crop rotation, resistant cultivars, and chemical compounds were approved for their control so far. Considering their environmental hazards and the relatively high price of chemical compounds, using non-chemical methods such as the application of plants and plant extracts for the nematode management increased. This study aimed to investigate the inhibitory effects of seaweed (Ascophyllum nodosum), and pagoda tree (Sophora alopecuroides) extracts on the activity of root-knot nematode (Meloidogyne incognita), including eggs hatching inhibition and second-stage juveniles (J2) mortality through the laboratory and greenhouse conditions. Materials and Methods After the sampling, the morphological properties of isolated nematodes were characterized and the species determined. Three different concentrations of each extract were used in three replications in laboratory tests. Egg hatching and second juvenile mortality (M. incognita) were evaluated after 24, 48, and 72 hours. In the greenhouse tests, two months after the inoculation, some plant growth traits (fresh shoot weight, fresh root weight, stem length) and nematode-related characteristics (number of galls, egg mass, and reproduction factor) were measured. The experiments were repeated twice, and the mean of two-step data was used for the statistical analysis. The analysis was performed using SAS software, and the comparison of means was achieved by the Tukey test. Results The laboratory results showed that the rate of egg hatching inhibition and mortality of J2 were directly related to the concentrations of applied extracts. Moreover, the results indicated that there was a significant difference among the treatments. The highest assessed percentage of larval mortality and hatching inhibition was observed in the seaweed extract application with 4/1000 concentration and pagoda tree extract with 1.5/1000 concentration, respectively. According to greenhouse results, the mean mortality of nematodes (J2) in seaweed, pagoda tree, and cadusafos nematicide was 66.80%, 35.81%, and 85.31%, respectively. Furthermore, the addition of plant extracts reduced the reproduction of root-knot nematodes in the infected tomato plants. The highest growth factors were observed on the nematode-free plant when seaweed extract was inoculated to the plant. In the nematode-infected tomato plants, all treatments which were applied to potting soil caused a significant increase in fresh shoot weight. Discussion The results indicated the positive effects of the studied treatments of Seaweed and Pagoda tree extracts and are promising for using plant extracts to control tomato root-knot nematode in greenhouses, the point that can be considered in the management of this nematode in greenhouse crops and combination with other control methods.

Background and Objectives The melon or cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is hazardous to many agricultural crops. Melon aphid is a highly polyphagous pest, feeding on more than 320 plant species including cucumber. Melon aphids physically damage plants by directly sucking their phloem sap, resulting in premature leaf drop, wilting, and desiccation of host plants. Application of insecticides is usually considered as the most common method to control this pest. As a result of the widespread use of these chemical compounds, this pest has become resistant against several classes of synthetic insecticides. Therefore, in this study, sub-lethal concentrations of pirimicarb, and a parasitoid wasp, Lysiphlebus fabarum (Marshall) (Braconidae: Aphidiinae) were simultaneously used to control melon aphid on cucumber, as part of a comprehensive study for the integrated pest management. Materials and Methods In this research, first, bioassay of pirimicarb was performed with third instar of A. gossypii to calculate lethal concentrations of pirimicarb and then, another experiment was conducted to determine stability of pirimicarb, and also its effects on survival of a parasitoid wasp adult, L. fabarum. In the following, the effects of simultaneous releasing of L. fabarum with applying sub-lethal concentration (LC50) of pirimicarb on cucumber were investigated by determining population dynamics A. gossypii, every 5 days. In the first treatment, as a control treatment; the plants were sprayed with the recommended field concentration, at the beginning of the experiment, without releasing of the parasitoid wasp. In the second and third treatments, 40 male and female parasitoid wasps were released every 3 days on each plant. In the fourth and fifth treatments, 60 male and female parasitoid wasps were released. In all the last four treatments, at the beginning of the experiment, and in the third and fifth treatments on the 15th day, the plants were sprayed with LC50 of pirimicarb. After 30 days, the experiment was ended and the total number of alive aphids and total number of the mummified aphids were counted on each plant.   Results Mean lethal concentration (LC50) of pirimicarb was equal to 212.6 µg/L for the third nymphal instar and due to low stability of this concentration of pirimicarb; it was possible to release the wasps 3 days after spraying. The results of releasing different densities of wasp showed that higher density of wasps (60 wasps per release) did not have a highly significant effect, and low density of wasps (40 wasps) was able to control aphids. After a significant reduction in aphid population due to pesticide use, the parasitoid wasp was able to prevent growth of aphid population, but if necessary, spraying can be repeated by sub-lethal concentration (LC50)of the pirimicarb, after 15 days. Discussion Findings of the present study suggested that lethal concentration (LC50) of pirimicarb can be applied as a suitable insecticide, simultaneously with L. fabarum, for the integrated pest management of melon aphids.

Background and Objectives The lacewings are predatory insects which are widely used in biological control programs. Meanwhile, the green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae), has attracted considerable attention as a promising biological control agent for greenhouse and field pests. Green lacewing is considered as an important bio-control agent due to its geographical distribution, broad host range, potency of suitable compatibility in agro-ecosystems, high searching ability, easy mass rearing in laboratory, high reproductive potential and broad resistance to numerous insecticides especially in larval and pupa stages. In this regard, it is highly important to reduce the consumption of the conventional pesticides which are compatible with predators and have low negative effects on beneficial organisms. In addition, life tables should be highlighted as the most reliable and effective technique for assessing the fitness of a population. Among the methods for selecting suitable pesticides in integrated pest management (IPM) programs, evaluating all of its effects on the different biological parameters of both sexes is the prime tool for population ecology studies. Materials and Methods Laboratory bioassays were investigated to evaluate the sub-lethal effects (LC30) of thiamtoxam, imidacloprid, and acetamiprid on biological characters and population parameters of C. carnea. The sub-lethal effects of thiamtoxam, imidacloprid, and acetamiprid on the demographic parameters of green lacewing were evaluated in vitro at 25±2° C, relative humidity of 65±5%, and light period of 8:16 h (light: dark). The raw data were analyzed based on two-sex life table analysis. Results All sub-lethal concentrations caused a significant decrease in oviposition period, total fecundity, longevity, and total life span in comparison to the control. Maximum and minimum mean lifespans of C. carnea individuals were observed in the untreated group and LC30 concentration of thiamtoxam. Total fecundity varied from 208.7 (offspring/individual) in treatment with LC30 thiamtoxam to 302.3 (offspring/individual) in the control treatment. The intrinsic and finite rates of increase (r, λ) were not affected by the imidacloprid concentration. The net reproduction rate (R0) reached its lowest level (141.1 offspring /individual) in acetamiprid treatment. Discussion The adaptability of pesticides with biological agents is one of the major concerns of IPM practitioners. Hence, it is essential to have necessary information about the action mode of pesticides on non-target insects. Furthermore, finding efficient biological control agents is considered as the first step in developing biological control programs. Therefore, the effects of sublethal concentrations of thiamtoxam, imidacloprid, and acetamiprid in combination with C. carnea were discussed in order to design integrated management programs.

Okra is considered as one of the most important fruit vegetables of tropical regions, one of the main cultivation areas of which in Iran is Khuzestan province. Due to the lack of a comprehensive research on identifying the plant-parasitic nematodes related to okra in Iran, the present study tried to identify the nematode species in Khuzestan province. In this regard, several root and soil samples were collected from okra fields in the different areas of the province. In addition, centrifugal-floatation and tray methods were applied to extract the nematodes from soil samples. Further, the adult females of Meloidogyne javanica were separated from root galls by using a sterilized needle and scalpel, fixed, and transferred to pure glycerin through using modified De Grisse method. After preparing permanent microscopic slides, the species were identified on a light microscope equipped with a drawing tube based on the morphological and morphometric characteristics, and valid keys. Based on the results, M. javanica was isolated from the roots and rhizosphere of okra. Furthermore, the other recovered species included Geocenamus brevidens, G. microdorus, G. rugosus, Pratylenchus thornei, Psilenchus hilarulus, P. vinciguerrae and Tylenchorhynchus elegans. In the study, the morphometric data and photomicrographs of the species under study were provided and their differences with other populations were discussed. To the best of our knowledge, the study is the first report of all the latter seven species associated with okra.The morphological and morphometric data related to the Iranian populations of P. vinciguerrae and T. elegans were presented forthe first time.

Background and objectives Cucumber crown and root rot, caused by Fusarium oxysporum f. sp. radicis cucumerinum, is one of its major destructive agents in the glasshouse planting in Iran. This disease is also known as the Fusarium damping-off. Several methods, such as chemical control and agronomic methods have been recommended so far to control this disease, but none of them has established effective control over this disease. One of the newly established strategies for the management of this disease is the biological control using endophytic bacteria, which live inside plants and can enhance plant growth by improving nutrient uptake and producing phytohormones. These bacteria can compete and control the population of other bacteria and plant pathogens within plants. This study evaluated the biocontrol capability of some selected cucumber endophytic bacteria over Fusarium crown and root disease. Materials and methods Endophytic bacteria were isolated from roots, stems, leaves, flowers, fruits, and seeds of different healthy cucumber cultivars including, Negin, Danje 98, Danje 195, Nagin and, Native Basmang. Bacterial strains were isolated from plant tissues using different culture media. In-vitro biological control assays, such as cross-culture and agar permeable metabolite assays, were performed to determine the biocontrol efficiency of endophytic bacteria against F. oxysporum f.sp. radicis cucumerinum. The bacterial strains with better results were chosen for glasshouse assay. Two isolates with significant biocontrol efficiency were selected for molecular indentification. The 16srDNA barcoding was performed using universal primers for bacterial identification. Then, the sequencing results were analyzed using MEGA-X software, and phylogenic trees were drawn using the neighbor-joining method. The selected biochemical tests confirmed the molecular results. Results and discussion A total of 140 endophytic bacterial isolates were isolated and purified from roots, stems, leaves, flowers, fruits, and seeds of some common healthy cucumber cultivars. Based on initial cross-culture, 14 isolates out of 140 isolates showed significant antagonism properties in the cross-culture and agar permeable metabolite assays, which were selected for further studies. After evaluation of the effective mechanisms, their antagonistic properties, such as the production capability of antibiotics, volatile compounds, siderophore, auxins, hydrogen cyanide, and protease enzyme, eight isolates were selected as the most potential bacterial isolates for biocontrol activity in the greenhouse. Finally, two bacterial isolates were selected for molecular identification using 16srDNA barcoding. The sequencing results indicated that the two selected isolates with 98% similarity could belong to Lysinibacillus mangiferihumi and Lyisinibaillus fusiformis species. The biochemical results confirmed the molecular results.

Background and Objectives Flea beetles are the main pests of oilseed rape which the adult beetles cause damage via feeding on cotyledons and early leaves of crop. They gnaw small round holes into leaves, decreasing assimilation surface and slowing down plant's growth. Heavy damage at the early stage of cotyledons may destroy the plant. The critical period of damage on the crop is from germination and cotyledon stage until the appearance of 4–6 true leaves, later the damage is less harmful. Control of this pest mostly depends on using chemical pesticides via seed dressing and/or foliar application. This study aimed to estimate the effects of new chemical insecticides to control this pest in Iran. Materials and Methods To chemical control flea beetles, the project was carried out in a Randomized Complete Blocks Design with six treatments and three replications in the provinces of Mazandaran and Golestan in 2018. The treatments were alpha-cypermethrin 15% WDG, with two doses (300 g/ha and 150 g/ha), lambda-cyhalothrin CS10% (75 ml/ha), malathion EC 57% (600 ml/ha), thiacloprid OD24% (300 ml/ha) and control. Sampling and counting of the flea beetles were done 1 day before and 3, 7, and 14 days after treatment via counting the cached beetles on yellow sticky traps (one trap in the center of each plot) as well as the active beetles in a 0.5×0.5m quadrate in each plot center. Fourteen days after treatment, the percentage of infested plants and leaf surface damage were measured. The beetle's mortality was calculated by the Henderson-Tilton formula. Data were analyzed with SAS ver. 9 software, and the means were compared using Duncan.  Results All insecticides showed a significant difference at 1% probability level comparing with control. Alpha-cypermethrin with 300 and 150g/ha and lambda-cyhalothrin in Mazandaran and Golestan provinces with 87.17,84.19, 81.66; 76.66, 86.12, and 76 percentage efficacies had the highest effectiveness in control the pest, respectively. Malathion in Mazandaran and Golestan with 24.59% and 22.66% and thiaclopride 14.01% and 19%, respectively, were less effective in controlling and reducing flea beetles damage on the crop. Moreover, the percentage of infested plants was significantly different among insecticides 14 days after treatment at a probability level of 1%. Discussion Pest management of canola flea beetles faces ecological challenges and severe dependence on synthetic chemical pesticides. Insufficient soil moisture, late planting, unsuitable planting beds, and hot and sunny days with dry winds in the early growing stages of canola in autumn increase the damage and reduce the green area of the field in a short time. Due to the unsatisfactory effect of biological substances and plant compounds on canola flea beetles, chemical insecticides are one of the main options to reduce the population of this distractive pest in rapeseed fields. In various studies, in addition to chemical insecticides, biological compounds and botanical insecticides were tested to manage the control of pest. But in most cases, chemical insecticides were more effective. Therefore, determining the appropriate time for application and using effective insecticides are integral parts of the pest control strategy. This study's result showed that alpha-cypermethrin 15% WDG (150 and 300 g/ha) and lambda-cyhalothrin CS10% (75 ml/ha) could be used as new insecticides to control canola flea beetles.