نشریه نامه انجمن حشره شناسی ایران
سال چهل و سوم شماره 3 (پیاپی 95، تابستان 1402)

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.

Storage insect pests cause considerable damage to grains every year, and reduce quantitative and qualitative value of stored products. One of the most important problems of controlling storage pests with chemical pesticides is occurrence of resistant to these pesticides, residues remaining on food products and endangering the health of the environment and other living beings. Diatomaceous earth has been introduced as a suitable alternative to chemical insecticides and can be used as one of the parts of integrated pest control programs. In this study, the insecticidal effect of different formulations of diatomaceous earth was evaluated against the lesser grain borer, Rhyzoperta dominica F. (Coleptera: Bostrychidae) adults in different grains including wheat, barley, rice, paddy and corn. Cereal grains were treated with a concentration of 400 ppm of a commercial formulation, Silicosec®, Iranian DE formulation Dryasil alone, Dryasil + 0.05% plant extract (Mentha longifolia L.), talcum powder + 0.05% M. longifolia extract. The insects’ mortality was counted 1, 5, 7, 10 and 14 days after treatment. The Dryasil formulation and Silicosec® were significantly controlled the populations of tested insects in the grain mass. The mean mortality percentage of R. dominica in wheat, barley, rice, paddy and corn treated with Silicosec® were 53.3, 98.8, 44.4, 60.0 and 68.8%, respectively, 14 days after treatment. While the Iranian formulation of diatomaceous earth was able to control 50.0, 91.1, 60.0, 58.8 and 67.2 % of R. dominica adults, respectively. The insecticidal effect of diatomaceous earth increased over time. The lowest LT50 value was reported in barley, which indicated greater protection of this product than other cereals. In barley, Silicosec®, Dryasil, and Dryasil + M. longifolia extract caused 50% mortality on R. dominica adults after 3.06, 5.39, and 9.01 days, respectively.

The tomato leafminer moth, Tuta absoluta (Meyrick), is a key pest in greenhouses and tomato-growing regions in the world. In the present study, the lethal and sublethal (LC25) effects of two insecticides, thiocyclam hydrogen oxalate, and flubendiamide were evaluated on the life table parameters of T. absoluta under laboratory conditions. The leaf dipping was used for the bioassays. The life table data were analyzed based on the age-stage, two-sex life table theory. The results showed that thiocyclam hydrogen oxalate (LC50: 175.327 ppm) was more toxic than flubendiamide (LC50: 219.759 ppm) on the T. absoluta eggs. However, the sublethal concentrations of mentioned insecticides affected the life table parameters of T.absoluta significantly compared with the control, but flubendiamide prolonged the developmental time (embryonic, pre-adult, and pupal period) of T. absoluta, significantly more than thiocyclam hydrogen oxalate. Also, the population growth parameters such as intrinsic rate of increase, finite rate of increase, and net reproductive rate of insects treated by insecticides were lower than the control, significantly. The total results revealed that either thiocyclam hydrogen oxalate or flubendiamide have admissible lethal and sublethal effects on tomato leafminer eggs and can be considered in the integrated pest management program (IPM) of this pest.

The wooly apple aphid, Eriosoma lanigerum Hausmann (Hem.: Aphididae), is one of the main pests of apples all over the world. The purpose of this research was to investigate the host preference of wooly apple aphids toward 10 selected genotypes among the promising offspring obtained from hybridization and free pollination of indigenous apple genotypes (Azaish Isfahan and Marbai Mashhad) as maternal parent, and commercial apple cultivars (M9, M27, B9) as a paternal parent. This project was carried out during 2020 to 2022. The colonies of wooly apple aphids were monitored every 2 weeks from the beginning of April to November. Relative establishment rate and aphid preference index were calculated. Vegetative traits including percentage of rooting, number of roots produced, length of the rooting zone on stems, length of roots and number of stems produced were measured. In order to differentiate the hybrids, the cluster analysis method and the degree of effect of different traits on the indices were investigated through correlation analysis. The average establishment rate and preference index were 2.42±0.14 and 0.96±0.06, respectively. The most insensitive and the most sensitive hybrid base were Azop3(1386) and M9op3, respectively. Some of the vegetative characteristics of the hybrid rootstocks, including the average length of the productive root of the line have been effective in the occurrence of differences in the studied apple hybrid rootstocks in terms of establishment rate and host preference of wooly apple aphid. The results of this research are used in the future improvement programs of apple cultivars.

Wheat is the most important strategic crop in Iran and the world. Sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) causes a lot of damage annually. Currently, two groups of IRAC insecticides including pyrethroids and organic phosphorus compounds are recommended against this pest in Iran and other countries infested with the Sunn pest. In this research, different insecticides were selected from the eight insecticide groups of IRAC, and contact bioassay was carried out on two life stages of the Sunn pest. The results showed that among the tested insecticides, Deltamethrin (LC50=2.93 mg a.i./L) as a pyrethroid group, had the most contact toxicity among chemical compounds against overwintered adults of the Sunn pest, and Fenitrothion as an organic phosphorus compound  (LC50=19.4 mg a.i./L) was ranked in the second group. But on the new generation of the Sunn pest, both insecticides were ranked in the same group at 72 hours after exposure (LC50=4-4.6 mg a.i./L). Further investigations revealed that among neonicotinoid insecticides, Thiamethoxam had more contact toxicity and ranked in the next group. Mortality comparison of different insecticides in high concentration (60-20000mg/L) based on commercial formulations showed that Deltamethrin and Fenitrothion insecticides caused 90-100% mortality in both life stages of the Sunn pest. The new insecticides, Spirotetramat, Flonicamid, and Chlorantraniliprole did not show acceptable effectiveness 72 hours after exposure on overwintered and new-generation adults (3.3-43%). Therefore, most of the new insecticides tested for the chemical control of the overwintered and the new generation adults did not have acceptable mortality, and only thiamethoxam insecticide can be studied on Sunn pests in field conditions.

Azolla (Azolla spp.: Salviniaceae) is an aquatic fern that was introduced to the northern region of Iran with the aim of increasing the fertility of paddy fields, but due to suitable climatic conditions and the absence of natural enemies it became a problem in rice production and a destructive factor in aquatic ecosystems. In recent years, the biological control agent of this weed, Azolla weevil Stenopelmus rufinasus Gyllenhal (Curculionidae), was introduced in northern region of Iran. In this study, geographical distribution and seasonal population density of S. rufinasus in northern Iran were investigated through regular monthly sampling. The results showed that the time required to complete one generation in semi-field conditions is about two weeks. Both larvae and adults feed on Azolla. Azolla weevil is well distributed and established in the north regions of Iran and by feeding on Azolla, it has reduced its population in wetlands, permanent ponds and paddy fields. Comparing the population density of the weevil in three regions of Guilan province, indicated that the highest number of total density (667 insect in 1 kg Azolla) and adult (363 adults in 1 kg Azolla) belong to the central region of the province, while the density of larvae (397 larvae in 1 kg Azolla) in the eastern region of the province was higher than other regions. In the survey of the density in different cities, the highest density of total (2690 adults and larvae in 1 kg Azolla) and adult insects (2022 adults in 1 kg Azolla) was observed in Shaft city and the highest density of larvae (1920 larvae in 1 kg Azolla) was observed in the Rudbane of Lahijan. Based on the obtained results, the population density of the weevil is higher in spring and winter, which is not far from the mind considering the climatic conditions of the region and the sensitivity of Azolla to heat and low humidity. Based on the findings of this survey, the weevil has spread and settled well in the northern regions

The tomato leaf miner, Tuta absoluta (Meyrick) is one of the most destructive pests of tomato in field and greenhouses. Llife history and population growth of this pest were investigated on three solanaceous plants including four varieties of tomato (Western Red, Matin, Serin, and Rio-Grand), three varieties of eggplant (White-Casper, Ravia, and Pearl-Ground) and three varieties of sweet pepper (Bachata, Lorca, and Nirvin). The developmental time, survival, longevity, and fecundity of the pest on the leaves of tested varieties were investigated. The experiments were conducted at 25 ± 2°C, relative humidity of 65 ± 5% and a photoperiod of 16:8 (L: D) h. The results of the statistical comparison of the varieties within each host plant showed that life table parameters of the insect were not significantly different on tomato varieties and on eggplant varieties. However, among pepper varieties, the net reproductive rate, intrinsic rate of increase, and finite rate of increase rate on variey Lorca were higher than on Nervin and Bachata. The results of comparison among varieties of different hosts showed that the highest immature survival was observed on tomato, varieties Serin and Matin, and the lowest survival was seen on pepper, varieties Lorca and Nirvin. The longest developmental time was obtained on pepper, varieties Bachata and Nirvin. The lowest fecundity and the shortest oviposition period were found on pepper, varieties Bachata and Nirvin. The net reproductive rate, intrinsic rate of increase, and finite rate of increase were lowest on pepper, varieties Bachata and Nirvin, and other varieties showed no significant differences. In general, tomato varieties were susceptible,, and eggplant variety White-Casper and pepper varieties Bachata and Nirvin were partially resistant against T. absoluta. This information provides the possibility of using these varieties in order to manage T. absoluta populations during its outbreak.

The The effects of individual predatory include predatory capacity, cannibalism, starvation, and different interactions of predatory on each other which causes effects on the population of the prey and the population of the predatory. Intraguild predation is a combination of competition and predatory. This study investigates the predatory capacity, intraguild predation, and cannibalism of Gaeolaelaps aculeifer and Protogamasellopsis predatory mites. All the tests were studied at 25 ± 1 ºC, with a relative humidity of 60 ± 10%, and at darkness conditions and in transparent plastic bottles (4 cm diameter and 4 cm height) filled with a mixture of Paris plaster and charcoal (7: 1) and a lid covered by a nylon mesh with 0.05 mm pore size and with 30 repetitions. A sufficient amount of C. lactis or R. echinopus including nymph and egg stages was provided as food. The results showed that in predatory capacity, the highest amount of daily egg feeding is related to Gaeolaelaps aculeifer mite feeding on Carpoglyphus lactis eggs and the lowest feeding amount is related to protonymph of Protogamasellopsis rhizoglyphusi mite feeding on Rhizoglyphus echinopus (onion mite). Also, the highest number of prey nymphs used in adults is related to dry fruit mites with 24 prey nymphs per day, which is used by G. aculeifer, and the lowest number of nymphs used is related to P. rhizoglyphusi, which feeds on 10 nymphs of onion mite. The results of cannibalism showed that the survival rate of egg cohorts for predators in predators of 20 eggs was 19.8 days for P. rhizoglyphusi mites and 24.1 days for predators of 30 eggs for G. aculeifer mites. Mites of the same age never fed each other except from the corpses or during molting, when mite locomotory activity and resistance decreased. The results of intraguild predation showed that the predation is asymmetrical IGP. Predatory mite G. aculeifer feed on all the protonymph and deutonymph of P. rhizoglyphusi mites when there is no food. Only 6.7% of the adult female mites of P. rhizoglyphusi survived. Because they are much smaller. When the immature stage of both types of mites is present along with prey mites, the survival rate of P. rhizoglyphusi reaches more than 60%. In the adults of both predators, this rate reaches 100% survival for both species of adult female mites.

Due to the long-term use of some chemical insecticides to control rice striped stem borer, Chilo suppressalis in rice fields in the north of Iran and in order to prevent the development of stem borer resistance to them, it is necessary to use new insecticides such as thiocyclam hydrogen oxalate granules 4% (Vibrant®) to control this pest. Experimental treatments in this research include, 1- (VibrantR) granule insecticide 4% at the rate of 10 kg/ha. 2- (VibrantR) granule insecticide at the rate of 12.5 kg/ha. 3- (VibrantR) granule insecticide 4% at the rate of 15 Kg/ha. 4- Diazinon granule insecticide 10% at the rate of 15 kg/ha. 5- Fipronil granule insecticide 0.2% at the rate of 20 kg/ha. 6- Control (only watering). The present study was conducted in the form of randomized complete block design with 3 replications. The following characteristics including: the percentage of dead hearts in the first generation, the percentage of white heads in the second generation, the percentage of insecticide efficiency, the population of larvae and the yield of rice were evaluated. The results of this research showed that among the tested insecticides, (Vibrant®) insecticide in amounts of 12.5 and 15 kg per hectare has significant advantage in controlling the rice stem bore for the first and second generations of the pest, respectively. Also, the results of this study showed that the least contamination of dead hearts (5.22%), white heads (2.33%), the highest larval mortality (86.01%) and the highest yield (4020.83 kg/ha.) was observed in the treatment Vibrant 4% in the amount of 15 kg/ha. Therefore, the findings of the present study indicate that the new thiocyclam hydrogen oxalate insecticide has a good potential in controlling rice striped stem borer and can be used for integrated management of stem borer in paddy field ecosystems.

The sugarcane stem borers, Sesamia spp. are the main pests of sugarcane in Khuzestan province of Iran. In order to evaluate the stem borers infestation in plant and ratoon crops, two field experiments were carried out in Amir-Kabir Agro-industry in south of Khuzestan province. In the first experiment, at plant cane fields during three consecutive years, and in the second experiment at different crop ages (plant, first ratoon and second ratoon) at the same time stalk and internode infestation by sugarcane borers were determined. Results in both experiments indicate percent of stalk and internode infestation by stem borers in plant crops significantly increased than ratoon crops. The findings of this research can be used in management of sugarcane stem borers.