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

The control of rice striped stem borer in paddy fields requires the use of all components of integrated pest management. The implementation of these methods is effective if the rice field is in natural conditions in terms of water resources, but in case of drought stress, which one of the methods will be more effective for pest control? In order to answer this question, the present research was carried out in the Rice Research Institute of Iran (Rasht) in 2019 and 2020. In this research, different irrigation methods as the main factor include permanent flooding (every day) and irrigation with intervals of 5, 10 and 15 days and the secondary factor is different control methods including granule application with G10% diazinon insecticide, spraying with fipronil SC5% insecticide, biological control (release of Trichogramma wasp + use of commercial formulation of Bacillus thuringiensis subsp. kurstaki), a combination of methods (chemical control and biological control) and control (only water spraying) were used. The results of this research showed that the least damage by the rice striped stem pest in the vegetative and reproductive stages of rice plants was in the daily and five-day irrigation treatments with the combined use of methods as well as the granule spraying method in the experimental field. Also, the results of the investigations during the two years of the experiment showed that the highest yield was related to irrigation every day and five days, related to two methods, a combination of methods and a granulation method. In 10- and 15-days’ irrigation, the highest yield was observed in foliar spraying and biological control treatments. Therefore, according to the obtained results, it is recommended to use biological control and foliar spraying with one of the confirmed liquid insecticides to control the rice striped stem borer pest in water stress conditions

The increase in the earth temperature is one of the latest problems threatening the earth ecosystem. Insects as poikilothermic organisms have a high dependence on their environment's temperature so increasing global temperature makes impressions on their distributions, activity, and biological parameters. Trichogramma brassicae (Hymenoptera.: Trichogrammatidae) wasp is one of the most important biological control agents in Iran used to control many species of lepidopterans. In this study, the effect of temperature changes on biological parameters and the expression of two heat shock genes, HSP70 and HSP90, in T. brassicae was studied under laboratory conditions. At first, the main T. brassicae colony was divided into two groups, each of them was separately reared for 20 generations at 30 and 33° C. Then, biological parameters, such as the rate of parasitism, appearance rate, and sex ratio, beside two heat shock gene expressions were assessed. The results indicated that at 33°C, the HSP90 and HSP70 expressions were 2.45 and 1.9 times more than 30°C, respectively, suggesting significant differences at a 99% confidence level. Furthermore, the parasitism rate of T. brassicae at 30 and 33°C were 53.5±2.09 and 40.7±2.14 (from 200 initial eggs), respectively. The obtained results showed that rearing at higher temperature caused to affect the sex ratio, adult appearance rate, and preadult development time. The results of the current study show that increasing global temperature could be result in reducion of the natural enemies efficacy, which will lead to an increase in the probability of pest outbreaks.

In some Trichogramma species, parthenogenesis is mostly induced by intracellular symbiotic Wolbachia bacteria. Populations of this egg parasitoid wasp that produce more female progeny can potentially have higher fitness. After finding a thelytokous Wolbachia-infected native strain of Trichogramma brassicae, a study was conducted to evaluate its parasitism rate and foraging efficiency in the greenhouse and field conditions. Treatments included a Wolbachia-associated thelytokous T. brassicae strain (A), an uninfected natural bisexual population (B), and an antibiotic-cured bisexual population (CB). Results of the equal female wasps’ releases revealed no significant difference among the three populations regarding their dispersal ability, mean parasitized eggs (PE) and parasitized bait cards (PBC) per female on forage corn (SC704) in greenhouse condition. However, when equal wasp individuals were released (e.g. 100 individual wasps including males in the bisexual populations), the number of mean parasitized egg batches by asexual line (7.57 PBC) was significantly higher compared with that in B and CB bisexual populations (4.50 and 4.97 PBC, respectively). Similarly, in the corn field condition, the highest number of parasitized bait cards and parasitized egg numbers belonged to asexual wasp (A) (1.94±0.21 PBC and 7.26±1.2 PE/female) compared with those in B (1.56±0.39 PBC and 5.46±1.99 PE/female), and CB (1.6±0.3 PBC and 5.82 ± 1.96 PE/female) bisexual populations. In general, it can be concluded that the use of an asexual Wolbachia- associated line of T. brassicae can increase the efficiency of this biological control agent at the field level in addition to reducing mass production costs.

The egg parasitoid Trichogramma spp is biological control agents of a wide range of agricultural and forests pests. At least 12 species of Trichogramma are commercially used in biological control programs in different countries of the world. These wasps can be reared on secondary hosts more quickly and easily than other biological control agents. So far, 11 species of Trichogramma have been identified from different parts of Iran and some species have reached mass rearing in the country. During the last few decades, different species of Trichogramma have been used in biological control of many pests including carob moth in pomegranate, rice stem borer, codling moth, European corn stem borer and cotton bollworm in different parts of Iran. Chemical control is currently the most important tool in agricultural pest management, the use of hazardous chemical compounds has caused environmental pollution, secondary pest outbreaks, emergence of resistance, threats to human health and adverse effects on non–target organisms. Most conventional pesticides used to control pests are broad–spectrum compounds that kill natural enemy populations similar to the pests. Numerous studies have shown that pesticides used to control pests have many side effects on natural enemies, including changes in growth, development rate, and sex ratio. To evaluate the side effects of pesticides on various biological agents, some standards have been developed by the IOBC. The results of which, in addition to international acceptance, can provide valuable recommendations for use in IPM programs and help to find selected compounds compatible with biological control agents and reduces the use of pesticides. The present article is a review of studies on the side effects of pesticides on different species of Trichogramma wasps in Iran, which is being conducted for the first time and hoped to pave the way for the development of integrated pest control in the country..

Trichogramma wasp is one of the most successful parasitic species in the world, mainly used to control many pests. The effects of field (RC) and half recommended concentrations (half RC) of four insecticides: 1. Tetraniliprole, 2. Chlorantraniliprole 3. Lufenuron, and 4. Thiocyclam was studied in different preimaginal stages of 1. Trichogramma brassicae Bezdenko and 2. Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae). Parasitized eggs of the angoumois grain moth Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae) were treated by 1. The dipping method at the larval, 2. Prepupal, and 3. Pupal stages of the parasitoid. For persistence evaluation, the insecticides were applied at the recommended concentration on tomato plants in a pot by a hand sprayer till the Runoff point. Plants were maintained under a transparent polyethylene rain cover in the field. Leaves of the treated tomato plants were sampled and transferred to the laboratory at time intervals of 3, 5, 16, and 31 days after application. In this experiment were adults (< 24 hours old) of T. brassicae and T. evanescens. Based on our results, thiocyclam at both RC and half RC was the most harmful insecticide for immature stages of both parasitoids. This insecticide at the prepupal stage (at both RC and half RC) had more adverse effects than in pupal or larval stages. Tetraniliprole, with 23.33% and 21.11% mortality in less than five days, was classified as the short-lived insecticide for T. brassicae and T. evanescens, respectively. The same result was obtained in the chlorantraniliprole treatment. That caused 25% and 26.11% mortality to the parasitoids, T. brassicae, and T. evanescens. Lufenuron, with 30.55% and 30.00% mortality in less than five days, was short-lived. However, thiocyclam, with 14.44% and 16.67% mortality in less than 30 days and 65.55% and 69.44% mortality in less than five days, was classified as moderately persistent for those two species. Therefore, according to the results, 1. tetraniliprole, 2. chlorantraniliprole, and 3. lufenuron can control lepidopteran pests by observing the appropriate spraying distance to release Trichogramma wasps. Thiocyclam, on the other hand, should be employed with extreme caution.

The olfactory responses and biological attributes of Trichogramma evanescens (Te) and T. brassicae (Tb) were studied at laboratory conditions. Odor treatments included Carob moth eggs and healthy and infested pomegranate crown and seed and healthy and artificially damaged leaves. The olfactory apparatus consisted of a Y shape glass tube with 30° angle. Ninety mated females (0–24 hrs. old) of each species were exposed to the selected odor and clean air in 3 replications (each 30 wasps as one replication). In addition, biological characteristics of wasps were determined on Carob moth eggs using two sex age–staged life table approach. Olfactory results revealed that Te wasps significantly responded to the odors of Carob moth eggs and healthy and infested pomegranate crown and seed over clean air. In contrary, Tb wasps did not respond positively toward any tested odor. Considering biological trait investigations, Te male and female immature stage took 10.70 and 10.52 days being significantly shorter compared with that of Tb male (11.20 days) and female (10.95 days), respectively. Adult female Te had 3 days longevity which was one day longer than that of Tb wasps (2 days). The net reproductive rate and intrinsic rate of population increase of Te and Tb wasps were 16.56 offspring and 0.2337 day–1 and 15.20 offspring and 0.2220 day–1, respectively. Eventually, the transformation rate of host to parasitoid egg (Qp) was equal to 1 for both species. In order to select superior natural enemy candidates for biological control programs, the possibility of using fast olfactory tests instead of time consuming biological studies is discussed.

In this study, the immature stages of T. brassicae (Hym.: Trichogrammatidae) were exposed to the recommended field concentration and half of the recommended field concentration of four insecticides abamectin, emamectin benzoate, acetamipride, and flubendiamide.  The dipping method was carried out for the treatment of immature stages. The percentage decrease in emergence, rate of parasitism, longevity and sex ratio were determined. The results show that these concentrations of abamectin, emamectin benzoate, acetamipride and flubendiamide, especially the recommended field concentrations, affected the biological parameters of the wasp compared with the control. In the flubendiamide treatment with the recommended field concentration the percentage emergence of F0 and F1 larval, prepupal and pupal stages were (69.58±1.07, 81.67±2.15 and 78.75±2.20) (70.33±2.78, 80.25±3.57 and 88.45±3.60) and were classified in class 1 respectively and abamectin with percentage emergence of F0 and F1 (44.58±1.34, 49.58±1.19 and 40.00±3.02) (44.72±1.97, 42.35±7.28 and 48.76±2.87) were classified in class 2 in all the stages. Emamectin benzoate and acetamipride were also classified in some stages as class 1 and in the other stages as class 2. Furthermore, the most and the least side effects of other parameters of the pesticides were related to abamectin and flubendiamide, respectively. The results reveal that flubendiamide could be recommended for the control of butterfly pests in IPM programs due to lower toxicity to natural enemies.

     Most natural enemies have low maintenance capabilities so they are often cultivated shortly before release. In the case of parasitoids, their hosts can be stored instead of parasitoids. Since storage of host eggs can increase the efficiency of the mass production units of Trichogramma wasps, this approach has been suggested by various researchers as a suitable method for mass production of Trichogramma species. As regards that there are few studies on the effect of low temperatures on the growth population parameters of parasitoid, so in this study the effect of cold storage of Phthorimaea operculella (Zeller) eggs at 4°C for 0, 1, 4, 7, 15 and 30 days on biological and population parameters of Trichogramma brassicae Bezdenko were investigated. This experiment was conducted in a completely randomized design with 25 replications. Mean comparisons were performed using Duncan's test. The results showed that developmental time, longevity, parasitism rate, percentage of emergence, fecundity and oviposition period of T. brassicae were significantly different between treatments and the all parameters decreased when the storage period increased. It was also determined that all population growth parameters had a significant difference between the control and cold treatments. Due to the parasitism and adult emergency rate, longevity and fecundity of T. brassicae on stored host, eggs of P. operculella can be stored at 4°C for up to two weeks without significant negative effect on the efficiency of the T. brassicae. However, based on population growth parameters, maintenance of host eggs for up to one week are most recommended.

Parasitism rate of Trichogramma brassicae Bezdenko at laboratory conditions with six constant temperatures of 15, 20, 25, 30, 32 and 35 ± 1 °C, relative humidity of 65 ± 5% and a light period of 16 h. was evaluated on the eggs of gelechiid moth Sitotroga cerealella (Olivier). Parasitism rate of T. brassicae was significantly affected by different temperatures. The highest (40.257 hosts) and the lowest (3.731 hosts) values of net parasitism rate (C0) was obtained at 32 and 15 °C, respectively. The transformation rate of host population to parasitoid offspring (Qp) was equal to 1 at all temperatures. The values of stable parasitism rate (ψ) increased from 0.074 to 0.451 (host/parasitoid) with increasing temperature from 15 to 30 °C, but the values for this parameter at 32 and 35 °C significantly decreased. The highest recorded value for finite parasitism rate (ω) was obtained at 30 °C (0.654 day-1). The temperature thresholds for finite parasitism rate of T. brassicae were estimated by nonlinear models of Briere-1 and Lactin-2. The Lactin-2 better fitted the related data (SSE = 0.004833, R2adj = 0.977, AIC = -38.7438). The obtained values for the lower temperature threshold (Tmin), optimum temperature (Topt) and upper temperature threshold (Tmax) of parasitism activity of this parasitoid were 13.20, 31.20 and 35.40 °C, respectively.

The intracellular symbiont bacterium, Wolbachia is known as a reproductive parasite in different species of Trichogramma. Regard to importance of this symbiont in biological control programms, the present study addressed the efficiency of wsp gene to typing this symbiont from some populations of Trichogramma and also its prevalence. In this study which conducted through 2009 to 2010, 19 populations of Trichogramma were screened for Wolbachia infection. Among these, seven populations were determined as infected by Wolbachia. Eight strains of the bacterium were characterized which six strains belonged to subgroup Kue from A supergroup. The two remained strains were related to B supergroup and Sib subgroup. The double infection and superinfection were observed in Trichogramma populations. Among three species, T. embryophagum, T. brassicae and T. evanescens, the highest prevalence of Wolbachia was observed in T. brassicae with 57 % of samples populations. The most infection rate belonged to populations of Mazandaran province. Despite the separation of different strains of Wolbachia on the basis of wsp gene, recombination analysis indicated a doubt about the grouping results of this symbiont inferring from this gene. This analysis indicated existence of some geneticexchangesbetween different strains of Wolbachia in wsp gene. The new approach called Multilocus Sequence Typing (MLST system) could be effective solution in more accurate characterization of these endosymbionts.

Parasitoids of the genus, Trichogramma are the most widely used natural enemies for biological control of pests worldwide. The presence of flowering plants can improve efficiency of biological control agents by supplying sugar resource for parasitoids. In this study, two experiments were performed under laboratory condition (at 25±1ºC, 60±10% RH and a photoperiod 16L:8D), to evaluate the effect of buckwheat (Fagopyrum esculentum Moench) on biological characteristics of Trichogramma embryophagum (Hartig). The two conducted experiments were: 1) Study of biological characteristics of T. embryophagum in the first 24 hours after adult eclosion on floral plant buckwheat versus honey 10% and control (no feeding). 2) Study of the biological characteristics of T. embryophagum with continuous feeding on some nutritional resource as mentioned above during their adulthood. The angoumois grain moth, Sitotroga cereallela Olivier, eggs were used as a host in all experiments. In both experiments longevity was (3.26±0.22 and, 5.6±0.18 days, respectively) and number of host parasitized (36.8±2.78 and 63.36±1.6 eggs, respectively) of wasps in presence of buckwheat were significantly more than another treatment and control. In subsequent of laboratory experiments, a field survey was performed to evaluate T. embryophagum efficiency in presence of flowering buckwheat as an intercropping system with corn. Twenty sitocards were randomly placed in treatment and control field as an egg trap. The mean number of parasitized Sitotroga eggs in each card by T. embryophagum in the corn field with buckwheat and control field was 19.91±5.58 and 4.33±1.13 eggs, respectively that were significantly different. The results clearly showed the significant effect of flowering buckwheat on the efficiency of T. embryophagum that could be useful to develop an inundative biological control program using Trichogramma.

Learning host or prey-related olfactory cues may lead to increase efficiency and foraging capacity of biocontrol agents such as Trichogramma egg parasitoid wasps in nature. The egg parasitoids, Trichogramma species (Hym., Chalcidoidea, Trichogrammatidae), are most commonly and important biocontrol agents that have successfully been utilized against several lepidopteran pests, especially through inundative releases. Worldwide, over 32 million hectares of agriculture and forestry have been treated annually with Trichogramma for controlling various insect pests. Wolbachia is endosymbiotic bacterium induces parthenogenesis in Trichogramma wasps and producing female offspring. This research was conducted to study learning ability of Wolbachia infected T. brassicae to Lemon and Peppermint odors by wind tunnel under controlled conditions. According to obtained results, wasps showed significant difference in responses to conditioned and unconditioned odors. Memory duration of conditioned wasps lasted till 12 hours after conditioning. Odor learning ability recognition of biocontrol agents such as T.brassicae may result in increment of their efficiency in applied biological control programs.

This survey-based research was conducted to assess the challenges and bottlenecks of biological control development against rice striped stem borer, as a key pest of rice, in Mazandaran province during 2006. By using classified random sampling method, 200 rice farmers were asked to fill the questioners. One hundred farmers used biological control method in their pest management program against this key pest, and the other 100 farmers applied insecticides against the stem borer. Data analysis was done based on the questioners filled by the farmers. An economic evaluation model, named ‘logit’, was used to analyze the data. Results showed that the main factors affecting acceptance or rejection of biological control method are as follows: avoidance of risk by farmers, yield value per hectare, number of rice plots, frequency of Trichogramma release, adoption of technology by neighboring farmers, area under cultivation, the experience of applying biological control, farmer age, and participation of farmers in extension training courses. There were positive relations between all factors (except farmer age and number of rice plots) and acceptance of the biological control method. There were negative relations between farmer age and number of rice plots, and acceptance of the biological control method.