جستجوی مقالات مرتبط با کلیدواژه « پارازیتوئید » در نشریات گروه « گیاهپزشکی »

The cotton mealybug, Phenacoccus solenopsis Tinsley, is a potential pest that threatens green landscape in Ahvaz. In this study, the short-term and long-term effects of various insecticides (imidacloprid, diazinon, spinosad, Palizin®, and azadirachtin) on the populations of cotton mealybugs and predatory ladybird beetles, Nephus sp. and Hyperaspis sp., as well as on the parasitism rate of cotton mealybug by Aenasius bambawalei Hayat, were investigated under field conditions. The results of the bioassay at 24 h after treatment showed that imidacloprid (84.6%), diazinon (84.1%), and Palizin® (77.4%) significantly reduced the population of mealybugs compared to the control. The decrease effect of azadirachtin on the population density of cotton mealybugs 24 h after treatment was not significant (38.1% compared to the control). Furthermore, diazinin and azadirachtin had the greatest negative impacts (100% reduction compared to the control), and Palizin® had the least toxicity to ladybirds, with no significant difference compared to the control treatment. The long-term effects of the tested insecticides showed that, compared with the other treatments, imidacloprid and Palizin® had significant effects on reducing the pest population. Palizin® and azadirachtin had the least effect on the parasitism activity of Aenasius bambawalei. Both imidacloprid and insecticidal soap were more effective at reducing the P. solenopsis population than were the other treatments, but due to the greater negative effect of imidacloprid than of insecticidal soap on natural enemies and the limitation of using insecticides in green landspaces, insecticide soap is suggested for use in IPM programs for this pest.

Greenhouse whitefly Trialeurodes vaporariorum is a polyphagous and economically important pest throughout the world. In this study effect of the feeding of predatory bug Macrolophus pygmaeus and spraying of a free amino acid (Delphan Plus®) on biological parameters of the greenhouse whitefly on two cultivars of bean (Azna and Guli cultivars) and cucumber (Kish and Super Star cultivars) as well as the effect of the treatments on parasitation rate by Encarsia formosa were evaluated. Mean comparisons showed that the highest and lowest percentages of whitefly establishment were related to the treatments with predator and Delphan Plus in (Kish: predator 10.93 and Delphan 1.59) respectively, while the highest reduction in establishment was obtained on the Azena bean variety (with Delphan: 0.75) and Super Star variety on the cucumber (with Delphan: 0.81). Also, Delfan Plus has significantly reduced the percentage of herbivore eggs survival on both cucumber and bean varieties compared to the corresponding control as well as reduced the number of nymphs per female in the treatments. In addition, the number of adults that appeared per female decreased in treatments with Delphin Plus in the cultivars of both plants compared to the control. Regarding the parasitization percentage, the interaction effects bilateral interactions of plant-predator, plant-Delphan plus and predator- Delphan plus were also observed. In general, the effect of all the mentioned bilateral intractins caused an increase in the percentage of parasitization of third and fourth instar nymphs by E. formosa in the treatments compared to the control.

Habrobracon hebetor is an important ectoparasitoid of several lepidopteran pests. The efficiency of parasitoids would be affected by insecticides applications. Integrating the application of biological control agents and insecticides for pest management requires knowledge about impact and selectivity of the insecticides on biological control agents. In this study, the lethal and sublethal effects of indoxacarb, Voliam Targo and profenofos were evaluated on different life stages and some behavioral responses of the parasitoid. Field recommended rate of Voliam Targo and profenofos caused 100 % mortality on adult female wasps. Based on bioassay tests, the LC50 values of indoxacarb, Voliam Targo and profenofos on adult stage were 172.5, 4.4 and 2.9 mg a.i./L, respectively. The result of bioassay experiments on adult stage showed that profenofos had higher toxicity against adult stage compared to indoxacarb and Voliam Targo. Field recommended rate of indoxacarb and Voliam Targo had low toxicity on immature stages of the parasitoid. The effect of LC30 of the tested insecticides on functional response as an important behavioral factor of parasitoids was also studied. The functional response of the parasitoid revealed a type II functional response in control and all of insecticides treatments. This study showed that the control and profenofos treatment had the shortest and longest handling time, respectively. The highest and lowest maximum attack rate was observed in profenofos and control treatments with 0.992 and 0.507 h, respectively. Evaluation of sublethal effects of indoxacarb, Voliam Targo and profenofos on orientation behavior of the wasp by olfactometer showed that the parasitoid preferred untreated host larvae compared with treated host larvae by tested insecticides. Results showed that profenofos had more negative effects on the parasitoid. Due to the high toxicity effect of Voliam Targo on adults, it seems that Indoxacarb would be a more suitable insecticide for using in integrated pest management programs.

The wasp Habrobracon hebetor (Say) (Hym.: Braconidae) is an external and social larve stage parasitoid of a large number of pests, including the raisin moth Ephestia figulilella (Gregson) (Lep.: Pyralidae). Wasps of the Braconidae family are one of the most important pest parasitoids. The performance of parasitoids can be affected by use of insecticides. In order to simultaneously use of biological control agents and pesticides in pest management, it is necessary to know the effect of pesticides on biological control agents. In this study, the side effects of Lufenuron and Hexaflumuron on the biological parameters of the parasitoid wasp H. hebetor in laboratory conditions and the host flour moth Ephestia kuehniella (Zeller) (Lep.,: Pyralidae) in the form of a two-factor randomized complete design, the first factor is the type of insecticide (Lufenuron and Hexaflumuron each with a consumption concentration of 500ppm) and the second factor is the wasp life stage including three stages (larve, pupa and adult insect) were performed with three repetitions (5pairs of wasps per repetition). Hexaflumuron and Lufenuron insecticides are chitin synthesis inhibitors and belong to the group of insect growth regulators. Consumption of these two compounds disrupts the normal activity of the internal secretory systems and disrupts the growth and development of insects. The results of the present study showed that the insecticides Lufenuron and Hexaflumuron have an effect on the life span parameters, the average total egg, the number of daily eggs, the hatching rate and the sexual population ratio of the wasp H. hebetor. Both insecticides caused a decrease in the mentioned parameters, and this decrease was more observed in Hexaflumuron insecticide than in Lufenuron insecticide. Also, the life stages of the insect affected the above parameters and minimal effects and changes were obtained in the pupal stage.

The competition for limited resources is a common ecological interaction among animals. In most of insect parasitoid communities, different species compete for specific resources both in larval and adult stages. Intraspecific competition play a role in the size, structure, stability of insect communities and even it determines the fitness of species. Moreover, understanding how competition influences on different insect species is essential for basic ecological studies and pest control issues. The outcome of competition between adult parasitoid insects depends on host finding, ability to disperse, reproductive capacity, ability to fight, and physiological coordination with the host.While the outcome of competition in the larval stage can be influenced by differences in the growth rate of the parasitoid, the stage and physiological state of the attacked host, the order and the time interval between oviposition and the evolutionary history of the species. Competition between larvae can affect the development of adult parasitoids because the surviving individual or winners might to pay high costs for competency due to quantitative and qualitative changes in host resources.

The current study was carried on to determine the effect of intraspecific competition on searching efficiency and oviposition strategy of Habrobracon hebetor Say on 4th instar larvae of Heliothis viriplaca (Lep.: Noctuidae) at seven competition and four adult density levels (1, 2, 3 and 4) of parasitoid wasps per the spring chickpea plant (c.v. Bionij). All plants were grown under controlled climate conditions (25 ± 1 °C, and a light period of 16: 8 hours). Then, 10 fourth instar larvae of H. viriplaca per plant were released and allowed to feed and establish prior starting the experiments (about three hours). Then, fertile female wasps with different densities (2, 3 and 4) in separate treatments and a control treatment without the presence of a competitor (one fertile female wasp per plant) introduced to each microcosm unit and after 24 and 48 hours, the number of parasitized and oviposited larvae on each host plant counted, but the number of eggs oviposited on each host larvae recorded at the end of 48 hours. All eggs laid at each competitive level were kept separately until the emergence of adults to record sex ratio and mortality rate.

The results showed that, the searching efficiency of H. hebetor decreased with increasing the level of competition, so that, the highest searching efficiency was recorded after 48 hours, in non-competitive treatment (control) and at a density of four parasitoid individuals as 0.178 ± 0.002 /hour and the lowest value at the level of competition 12 and density of two parasitoid females as 0.023 ± 0.004/ hour. As the density levels of parasitoid increased, the searching efficiency was decreased to a density level of three, but then it increased at four individuals per chickpea plant. The interaction effect of density × competition was not significant, in other words, these two factors independently influenced on searching efficiency of H. hebetor. Time had a positive effect on searching efficiency so that, at all levels of competition and at different densities of parasitoid wasp, the difference was statistically significant. With increasing density of H. hebetor per plant, at all competition levels, the oviposition rate was increased, which means that the simultaneous presence of several parasitoid individuals does not have any negative effect on oviposition rate. Competition had a negative effect on the oviposition rate of female H. hebetor, as the highest oviposition rate recorded at one individual and lowest competition level as 14.7 ± 2.1 eggs and the lowest rate occurred at four individuals per host plant and competition level of 12 as 6.4 ± 0.05 eggs. According to linear regression line equation, the interference coefficient was calculated as -0.134. The negative slope of the regression line indicates the existence of mutual interference between the H. hebetor adult females. In other words, the interaction had a slight negative effect on parasitoid searching. At all competition levels, regardless of density, sex ratio was not affected by competition and other factors sounds influential in this regard, however, the difference between the ratio of female to male population at competition levels of one and two was greater than other levels. Moreover, the mortality rate has increased with the increase of the level of competition, so that the lowest mortality percentage occurred at the level of one and two and the highest at the level of competition 10 and 12.

The occurrence of interference between parasitoid wasps in laboratory environments could not be used as indicative of real conditions, because high pest densities in field conditions moderate the intraspecific competition intensity among parasitoid individuals. Given the significant differences in searching efficiency and other factors studied, it can be concluded that the number of competing larvae in a host can affect the suitability and vigor of adult parasitoid wasps. It should be noted, however, that in some cases competition does not directly affect searching capability, but instead, by reducing other factors, such as morphological characteristics (body size, ovary size, number and size of eggs, size of hind legs, wing size), number of embryonic eggs, oviposition days duration, and other biological characteristics will influence on the searching abilities of parasitoids indirectly.The study of H. hebetor parasitoid wasp foraging behavior showed that in high densities, it avoids competing with other conspecific individuals. Anyway, regarding the prevalency of competition among released natural enemies in greenhouses and fields, the study of this interaction from laboratory to fields is being recommended.

Adult insects of many parasitoids use carbohydrates to supply their energy. A high-carbohydrate diet increases the efficiency and other biological properties of parasitoids. Bracon hebetor Say (Hym: Braconidae) is one of the most important biological control factors on farms, orchards, and forests of the country, widely perceived to be found in nature, and can be effective in controlling larvae of leprose winged pests at an acceptable economic cost.

Materials and Methods:

 In this study, the effect of four sugar treatments [10% concentration of fructose, glucose, honey, and a mixture of fructose, glucose, and honey (1:1:1)] and distilled water (as a control for sugar treatments) was examined on the biological properties of B. hebetor male and female adults. B. hebetor was reared on fifth instars of Ephestia kuehniella Zeller (Lep: Pyralidae) in a growth chamber at 26±2 ºC‚ 60±5 %RH‚ and photoperiod of 16:8 (L: D) h. Daily observations and records were made for the development period and survival rate. The data were analyzed based on two-sex life table analysis using TWO SEX-MS Chart.

The present study showed a significant improvement in the biological reproductive and stable population parameters in sugar treatment groups compared with the distilled water treatment. The highest value of adult longevity and life expectancy (ex) of the B. hebetor occurred in fructose treatment. Moreover, the highest net reproduction rate(R0), finite rate of increase(λ), and lowest doubling time (DT) were observed in the mixed sugar treatment. On the other hand, the highest gross reproduction rate (GRR) and mean generation time (T) were found in glucose and fructose treatments. The results of study revealed that intrinsic rate of increase (rm) values for distilled water, fructose, glucose, honey, and mixed sugar were 0.257 ± 0.001, 0.272 ± .0011, 0.267 ± 0.033, 0.264 ± 0.007, and 0.291 ± 0.004 (day-1), respectively.

According to the results of the present study, B. hebetor was positively affected by the sugar treatments, and the suitability of sugar diets was ordered as mixed sugar > fructose > glucose and honey. In conclusion, sugar feeding is recommended for the mass rearing program of B. hebetor because suing them could increase the ability of this parasitoid in pest control. The highest rm value for the mixture of the three sugars indicated the importance of sugar-feeding quality in the mass-rearing program of natural enemies.

Braconid wasps (Braconidae) are one of the most important pest parasitoids. The function of parasitoids can be affected by the use of insecticides. In order to use biological control agents and pesticides simultaneously in pest management, it is necessary to know the effect of pesticides on biological control agents. In this study, the lethal and sub lethal effects of the flubendiamide, emamectin benzoate+lufenuron, thiocyclam and spinosad on the parasitoid Habrobracon hebetor</em> (Say) (Hymenoptera: Braconidae) were investigated. The LC50</sub> of spinosad on parasitoid wasps were 1.25 mg/L of active ingredient, which showed that this insecticide is the most toxic compound on this insect and LC50</sub> of thiocyclam, emamectin benzoate+lufenuron and flubendiamide were 19.99, 7.56 and 6.45 mg/L of active ingredient respectively, which were more toxic to this wasp, respectively. The results of bioassays on adult insects of parasitoid wasps showed that spinosad with LC30</sub> was 0.71 mg /L of active ingredient with high toxicity on adult insects compared to flubendiamide, emamectin benzoate+lufenuron and thiocyclam, which were LC30</sub>, 3.67, 4.26 and 14.44 respectively. According to the classification of the International Organization for Biological Control, spinosad was in the group of harmful insecticides and emamtectin benzoate + lufenuron and flubendiamide were in the group of moderately harmful insecticides. According to this classification, thiocyclam was classified as harmless insecticide on bracon wasp.

Cabbage white, Pieris brassicae (L.) (Lepidoptera: Pieridae) is an important pest of cruciferous in Iran and the world. In this study, the effect of four insecticides; hexaflumuron, spinosad, abamectin and indoxacarb on cabbage white and its parasitoid Cotesia glomerata L. was investigated The LC50 values obtained from the analysis of probit as a result of the effect of different concentrations of hexaflumuron, spinosad, abamectin and indoxacarb on the 3rd instar larvae of P. brassicae after 72 hours were (0.213, 0.298, 0.30 and 0.434) ml/L, respectively. The LC50 values obtained from the same insecticides on eggs of P. brassicae after 7 days were (0.831, 0.440, 0.267 and 0.489) ml/l, respectively. The results of the same compounds effects on parasitoid after 7 days showed that hexaflumuron and indoxacarb are the most harmful and abamectin is the least harmful for this natural enemy. The results showed that the most effective insecticides on 3rd instar larvae of P. brassicae during 72 hours was hexaflumuron. In the study of parasitization of third instar larvae of cabbage white under the influence of different concentrations of hexaflumuron, spinosad, abamectin and indoxacarb in compared with control, results showed at low concentrations of all four insecticides, there is no significant difference between control and insecticides, but there was a significant difference in higher concentrations and the mean number of third instar larvae in the control treatment increased. According to the results of this study, hexaflumuron can be suggested as a low-risk compound for parasitoid and effective against this pest.

Tomato leaf miner is one of the new and important pests of tomato in Iran and every year it reduces the yield and quality of the product in terms of marketability. Therefore, in order to use insecticides that are safer for the environment, consumers and natural enemies, in this study, the effect of spinosad, imidacloprid, indoxacarb and chlorantraniliprole insecticides on Tuta absoluta was evaluated under field conditions. This study was performed in a randomized complete block design with five treatments, one control and three replications. The results of this study showed that the efficacy of chlorantraniliprole and spinosad was higher than indoxacarb and imidacloprid on the third, seventh, tenth and fourteenth days after spraying. Also, the effect of LC25 of each of the mentioned insecticides on the parasitism rate of tomato leaf miner moth eggs by two species of parasitoid wasps T. brassicae and Trichogramma evanescens was evaluated under laboratory conditions. The rate of reduction of parasitism in spinsad, imidacloprid, indoxacarb and chlorantraniliprole treatments for T. brassicae was 23.73, 18.31, 14.58 and 9.37%, respectively, and for T. evanescens 24.02, 18.65, 13.78, 9.75% was determined. The results showed that chlorantraniliprole was less toxic compared to other compounds studied for parasitoid wasps and compared to other insecticides, the rate of parasitism of two species of Trichogramma was less affected. Hence, its use in integrated pest management programs of T. absoluta is recommended.

The greenhouse whitefly, Trialeurodes vaporarium (Westwood), is an invasive insect pest of agriculture and horticulture worldwide. Imidacloprid as chemical pesticide has been used as a key pesticide for controlling sap-sucking pests and play a major role in controlling this pest. The main purpose of this study was investigation of resistance status of T. vaporarium to imidacloprid SC 35% (Confidor®) and cross resistance to Eforia® and Proteus® and effect of imidacloprid resistance on Encarsia formosa Gahan. Thirteen greenhouse whitefly populations were collected from greenhouses and fields and used for tests. Collected populations reared on cucumber plants under laboratory conditions at 25±2˚C, 70±10 % relative humidity and a photoperiod of 16:8 h (L: D). The LC50 values were estimated on the second instar nymphs for all populations using leaf dipping bioassay method. The VGR population showed highest LC50 that was 856.2 mg/L. The development of resistance to imidacloprid was confirmed for all tested populations with resistance factors ranging from 2.54 to 44.3. The most resistant strain showed cross resistance to Eforia® and Proteus®. There was no significant difference between LC50 values of E. formosa populations that collected form field, reared on the most resistant population and sensitive population of T. vaporarium. The LC50s were 388.7, 324.7 and 317.7, respectively. We discuss our results in regard to the evolve of imidacloprid resistance in T. vaporariorum populations and its implications for whitefly control.

Cabbage aphid, Brevicoryne brassicae (L.), is one of the most important and harmful pests of crucifers, which is active in many parts of Iran and causes quantitative and qualitative damage in the cultivation of these plants during the winter. Some natural enemies such as the parasitoid wasp Diaeretiella rapae (McIntosh) are active on this pest. The indiscriminate use of insecticides for controlling pests caused evolution of pest resistance, environmental pollution and negative effects on natural enemies and beneficial insects. In recent years, environmentally compatible factors have received more attention due to less side effects in pest control. This study was carried out to determine the effects of the entomopathogenic fungus Beauveria bassiana (Bals.), and nanosilica separately and in combination on survival of the cabbage aphid and its parasitoid treated by different concentrations of fungus (103, 104, 105, 106 and 107spore/ml) and nanosilica (125, 250, 500, 1000 and 2000 ppm).

Cabbages (Brassica olearaceae var. capitata) were grown from seed in plastic flower pots. Aphids were collected from Brassicaceae plants in fields of Nazlo Campus of Urmia University near Urmia city. This colony was used as a source for all aphids used in all laboratory experiments. Also, a colony of D. rapae was reared on B. brassicae under greenhouse conditions. Wasps were fed a 10% honey solution and used to parasitize aphids, or for use in experiments, 24 hours later.Fungi was cultured on Sabouraud Dextrose Agar (SDA) in petri dishes (6 cm in diameter) and incubated for two weeks to induce sporulation. Spores were harvested from the surface of 14-day old culture and transferred to a test tube containing sterilized distilled water with 0.05% Tween®-80. The conidial concentration of final suspension was determined by direct count using a neubauer hemocytometer and serial dilutions were made to obtain different conidial concentrations. Sio2 nanoparticles of pashgamannano® company was used in bioassay tests. Bioassay test was carried out on aphid and its parasitoid. Aphids were treated by conidial concentrations using dipping method. Control adults were treated with distilled water containing 0.05% Tween®-80. In order to evaluate the effect of nanosilica on aphids, leaf discs were dipped in to different concentrations of nanosilica and after drying, adult cabbage aphids were transferred on treated leaf discs in Petri dishes. The mortality was counted 24, 48 and 72 hours after treatment. Experiments were carried out at 25±2 Co temperature, 65±5% RH and a photoperiod of 16: 8 h. (L: D) under laboratory conditions. LC25, LC50 and LT50 values of fungi and nanosilica were estimated. Also, combination effects of fungi and nanosilica were evaluated in laboratory. A preliminary test was evaluated to determine side effects of different concentrations of nanosilica on viability and germination of fungi spore. Germination rate for fungi was calculated after 24 hours. The LC25, LC50 and LT50 values (with 95% confidence limits) were calculated using the Probit analysis method. Bioassay data were subjected to one-way analysis of variance (ANOVA) after checking for normality and means were compared by Tukey’s test.

The LC50 values obtained from the analysis of probit as a result of the effect of different concentrations of B. bassiana 7 days after treatment and nanosilica 24, 48 and 72 hours after treatment on cabbage aphid were 2.2×105 spore/ml and 4356.14, 1164.42, 487.19 ppm, respectively. Furthermore the LC50 values of B. bassiana 4 days after treatment and nanosilica 24, 48 and 72 hours after treatment on D. rapae were 1.2×106 spore/ml and 3639.79, 619.51, 289.77 ppm, respectively. Results showed that the adults of the cabbage aphid were completely sensitive to the fungal isolate. The shortest time needed for the mortality of 50% of the population of cabbage aphid was 5.02 days at 107 conidia/ml concentration. The mortality rate of nanosilica at highest concentration, 72 hours after treatment was 90 and 96.6% respectively for cabbage aphid and parasitoid wasp. Also, combination of these factors against adults of cabbage aphid had significant difference with control.

According to the results of this study, it can be concluded that B. bassiana and nanosilica are effective on cabbage aphid and can be used as effective factors in the integrated pest management program of this pest.

 Bemisia tabaci (Genn.)(Hem: Aleyrodidae)is considered as one significant pest in the agricultural products in Iran. In this research, the effects of ZnO NPs, kaolin, B. bassiana (EUTP105 Isolate) were assessed alone or in combination to Neemarin® compared to thiacloprid insecticide under field conditions on eggs and nymphs of B. tabaci and pupae of its parasitoid Eretmocerus mundus.

This research was handled in the research field of the scientific staff of the Cotton Research Center of East Iran, Kashmar, in a randomized complete block design with three replications in August 2019. The experimental plots were separately 6 m2 and 1.5 m. The recommended concentration of Neemarin® (15 mg L-1 AZA), thiacloprid (0.3 mL L-1), Kaolin (30 g L-1), a concentration of 20 mg L-1 of ZnO NPs, a concentration of 1×1010 conidia mL-1 of B. bassiana, half- concentration of Neemarin® (7.5 mg L-1 AZA) + 10 mg L-1 of ZnO NPs, half- concentration of Neemarin® (7.5 mg L-1 AZA) + 15 g L-1 of Kaolin and half- concentration of Neemarin® (7.5 mg L-1 AZA) + a concentration of 1×105 conidia mL-1 of B. bassiana were prepared which sprayed on upper and lower surfaces of cotton plants using a knapsack sprayer, equivalent to an application volume of 500 l ha-1. The control treatment was sprayed by water. The mortality of B. tabaci eggs and nymphs and pupal stage of E. mundus were calculated using Henderson and Tilton equation . To this purpose, five plants were randomly selected in each plot and three leaves from each one (top, middle, and bottom section of plant canopy) were excised and transferred to a laboratory. Two pieces of 1 cm2 from each leaf were chosen so that the units included into main vein. Total live eggs and nymphs of pest as well pupae of parasitoid in each sample unit were counted using a binocular. Samplings were handled one day before and 3, 7 and 14 days after spraying.

In 3 DAT (days after treatment), the most effective treatments on eggs and nymphs of pest were Kaolin + Neemarin® and thiacloprid, respectively. While, the least effective treatments were B. bassiana. In 7 DAT, Kaolin + Neemarin® and ZnO NPs exerted the highest and lowest mortality, respectively, on the eggs of pest, Neemarin® and B. bassiana exerted the highest and lowest mortality, respectively to the nymph. In 14 DAT, the highest efficacy on eggs and nymphs was observed in Kaolin + Neemarin® and Neemarin®, respectively, while the lowest efficacy both on eggs and nymphs belonged to B. bassiana. The highest and lowest mortality of the pupae of parasitoid in 3 DAT belonged to thiacloprid and B. bassiana, respectively. In 7 DAT, Neemarin® and ZnO exerted the highest and lowest mortality on the parasitoid pupae, respectively.  In 14 DAT, Kaolin exerted the highest mortality on the pupae of parasitoid that was followed by Kaolin + Neemarin®, Neemarin®, and thiacloprid. The maximum yield and benefit/cost ratio were observed in Kaolin + Neemarin®, followed by Kaolin treatments. 

Considering the results, ZnO NPs and Kaolin alone, or in combination to Neemarin® can be the suitable candidates as an alternative in the IPM programs of B. tabaci on the cotton field.

Chemical control is the most commonly practice in controlling pests. The application of chemical control is recommended in combination with other reduced risks control techniques such as biological control under Integrated Pest Management programs. Therefore, finding the appropriate chemical insecticide and the right time of spraying seems essential. In this study,three different growth stages of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) including larvae, pre-pupae, and pupae were exposed to the field recommended concentration of deltamethrin, Spirotetramat and flupyradifurone insecticides using insect dipping method. After which, the reproductive, biological characteristics and life table parameters of T. evanescens female adults were estimated. The eggs treated with deltamethrin in all three developmental stage of T. evanescens significantly reduced fecundity rate and oviposition period of the female adult parasitoids. Thegross reproductive rate (GRR), finite rate of increase (λ), intrinsic rates of increase (r), and net reproductive rate (R0) were not affected when larval and pre-pupal stages of T. evanescens were exposed to field recommended concentration of spirotetramat and flupyradifurone in comparison with control. However, the pupal stage showed to be the most susceptible stage and all of the life table parameters were affected upon exposure to three insecticides. Results of this research suggest a relative compatibility of spirotetramat and flupyradifurone with T. evanescens parasitoid. However, experiments under field conditions to evaluate the impact of tested insecticides on T. evanescens are required to confirm the results.

Aphids are small insects which are famous as pests in agriculture, horticulture and forestry. They cause economic damages directly by feeding plants’ sap and indirectly by transmitting plant viruses. Sitobion avenae (F.) is one the important pests in the United States, Europe and Asia. In Iran, it has been reported on wheat, barley, and the other cereals from the different provinces including Kermanshah. Investigating on the population dynamics of pests is a major factor in evaluation of the pest management. The aim of the present study was to determine the most appropriate life stage of S. avenae for sampling to investigate its population dynamics and identify natural enemies of S. avenae in Sar-Pole Zahab region in Kermanshah province.

This study was conducted in a wheat field in Sar-Pole Zahab region in Kermanshah province during years 2015 and 2016. None of pesticides were used to control the insect pests during experiments.  Population survey and sampling were began each year in the middle of February and continued weekly until the end of wheat growth season in the middle of June. Sampling pattern was X-shaped and totally 30 samples were collected from the field. The selected plants were separately put in plastic bags and transferred to the laboratory for counting the number of nymphs, winged and wingless adults. To examine probable emergence of parasitoids, the aphids were kept in Petri-dishes in laboratory for two weeks and the results were recorded. A standard insect collecting net was used for sampling of the predators. The collected predators were transferred to the laboratory in glass jars for identification. The aphids and collected natural enemies were sent to Plant Protection Research institution in Tehran for confirmation.

At the first sampling date in 2015, there were a few adult aphids in the field. However, the population of adults and nymphs were gradually increased and the highest population of aphids was observed between March 12th 2015 and April 30th 2015.The peak density of adult aphids was on April 9th 2015 (9.5 aphids per spike) and for nymphs, it occurred a week earlier, on April 2nd 2015. In the second year, however, the population fluctuation pattern was very different. Although some aphid colonies were seen in the field from 25th of February, 2016, the number of aphids was decreased due to severe cold happened in March, thus no aphids was found in the samples in the next two weeks. The peak population of adult aphids was observed on 14th of April 2016 (36.9 aphids in spike) and then gradually decreased during the next weeks. Coccinella septempunctata L. (Coleoptera: Coccinellidae), Eupeodes corolla (Fabricius) (Diptera: Syrphidae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) were reported as aphid’s predators in the field. All predators were present at the field from the first sampling date. In the first year, E. corolla showed two distinct peak in its population during sampling including 19th of March 2015 and 16th of April 2015. In the second year, there were 17 adult flies per net in the first day of sampling, but the number of flies was increased gradually and reached to a maximum of 35.5 flies per net on 14th April 2016. C. septempunctata and C. carnea populations’ dynamics also followed the same patterns and showed two peaks in the first year and one peak in the second year of studies. No parasitoid was emerged from the aphids in Petri dishes

Due to presence of active predators in the wheat fields of Sar-Pole Zahab region and their high population, using of chemical pesticide should be restricted. Thus, if spray of pesticides is essential, the most appropriate time is when it has the least detrimental effects on natural enemies.