s. a. a. fathi

Strip cultivation is one of the effective methods to reduce the population of pests and increase the abundance and diversity of natural enemies in any habitat. Onion thrips, Thrips tabaci Lind., is a pest of onion (Allium cepa L.) worldwide. Larvae and adults of thrips feed on cell sap and cause silver spots on the surface of leaves of onion plants that consequently result in a significant reduction in onion yield. Control of onion thrips is difficult due to the short generation time, high fecundity, and the emergence of insecticide-resistant genotypes. Predators in each region, such as hemipterans, ladybugs, syrphid flies, carabid beetles, mites, and spiders, are effective in the biological control of the onion thrips population in fields. Intercropping systems can affect the biological control of pests by providing food and habitat resources for natural enemies. Therefore, designing effective and appropriate methods to reduce the population of onion thrips and increase the diversity and abundance of natural enemies can effectively manage T. tabaci in fields.

In this study, the effect of intercropping four rows of onion (Allium cepa L.) with two rows of fenugreek (Trigonella foenum-graecum L.) (4O:2F) and four rows of onion with two rows of safflower (Carthamus tinctorius L.) (4O:4S) was investigated on densities of the onion thrips, biodiversity of predators, and crop yields in 2022 and 2023. The experiments were accomplished in a randomized complete block design with two intercrops of 4O:2F and 4O:4S along with the sole crops. The density of onion thrips and predators per plant was counted and recorded on weakly sampling dates by direct counting using a magnifying glass. The predatory species that we suspected in their identification were transferred to the laboratory and carefully identified through morphological characteristics under a stereomicroscope. The average annual abundance of each predator species and the abundance of predators per plant in each plot were calculated during the onion growing season. In addition, Shannon's diversity index (H') and Pielou's evenness index (J') were calculated for the complexity of predators in each plot and in each tested year to compare the cropping systems. The onion, fenugreek, and safflower yield per square meter were estimated in strip intercropping systems and single crops. Then, the land equality ratio (LER) was calculated for both intercrops to estimate the yield advantage regarding the monoculture of each crop.

Three intercrops led to a significant reduction in the densities of larvae and adults of onion thrips compared with sole onion. Further, the leaf damage index was lower in intercrops than in single onion in two seasons. A significant coefficient of determination (R2) was calculated between the leaf damage index and the dry weight of onion per plant in two intercrop and sole onions. The total abundance of predators was higher in intercrops, especially 4O:2F than in the sole crop. More values of the Shannon diversity index and the Pielou's evenness index for predators were recorded in intercrops compared with the sole crop in two seasons. The dry yield of onions per square meter was more significant in both strip intercropping systems compared to single onions in 2022 and 2023. On the contrary, the dry yield of fenugreek and safflower per square meter was insignificant among intercrops and single crops in two years. The highest land equivalent ratio (LER) was calculated for 4O:2F.

Overall, the intercropping of onion and fenugreek (4O:2F) and onion and safflower (4O:2S) demonstrated a reduction in the population of onion thrips. Both intercrops, particularly 4O:2F, contributed to an increase in the abundance and diversity of predators and the values of LER when compared with sole crops. As a result, farmers could consider implementing both intercrops, particularly 4O:2F, as an environmentally conscious approach to managing T. tabaci in the field.

Sowing cover crops is one of the agricultural practices in habitat management for enhancing the diversity of beneficial arthropods. In this study, the impact of sowing cover crops between the lines of pear trees, Pyrus communis L., was assessed on the densities and damage of the pear psylla, Cacopsylla pyricola (Förster), and natural enemies on the pear orchards over two growing seasons (2022 and 2023). Experimental cover crops were (1) red clover, Trifolium pratense L., (2) rosemary, Rosmarinus officinalis L., (3) canola, Brassica napus L., (4) mix cultivation clover-rosemary-canola, and (5) absence of cover crops (as control). The results indicated that the lowest densities of the eggs, nymphs, and adults, and the percent of infested leaves and fruits of the pear psylla per 30-cm branch were observed in the plots with mixed cultivation of clover-rosemary-canola. Moreover, the highest total abundance of predators was recorded in the mix of clover-rosemary-canola plots. Among the collected natural enemies, Anthocoris nemoralis (Fabricius), Orius niger (Wolff), Hippodamia variegata (Goeze), Chrysoperla carnea (Stephens), and Episyrphus balteatus De Geer, respectively indicated the higher abundance. The greatest values of the Shannon diversity index (H΄ = 2.22 in 2022 and 2.20 in 2023) and the Pielou's evenness index (J' = 0.96 in two years) for the combination of predators were calculated in the mix clover-rosemary-canola plots. Therefore, it could be concluded that cultivating of the mix clover-rosemary-canola between pear trees results in the rise of diversity and abundance of predators and the reduction of pear psylla.

Trogoderma granarium (Everts) is an economic insect pest of stored grains in Iran and many tropical and subtropical regions. If stored products contaminated with this insect are consumed by humans, it would cause serious digestive diseases. To control T. granarium in storage, chemical insecticides and fumigants are often used, but due to their extreme toxicity to humans and other dangerous side-effects, their application has been limited. Therefore, in order to develop alternative control methods with minimal harmful effects to humans and other non-target organisms, there is a need to understand feeding performances of the pest on different cultivars. The use of insect-resistant plants is one of the effective methods in integrated pest management programs. Study of nutritional indices of stored product insects is one of the important methods of measuring the resistance in plant cultivars.

Nutritional indices of T. granarium larvae were investigated using the gravimetric method provided by Wadbauer (1968). The grains of wheat genotypes including N-91-9, Heidari, Aftab, Tirgan, N-92-19, Gaskojen and Kouhdasht were crushed using a grinder. Then, first instar larvae were reared on the grains of these genotypes under 33 ± 1°C, 65 ± 5% R.H., and 14:10 (L:D) h. After emergence of fifth instar, the weight of larvae, before and after feeding, and the amount of grain eaten by the larvae were measured. The data were analyzed using one-way ANOVA using SPSS ver.16. Then, Tukey's HSD test, with a probability level of 5%, was used to investigate the statistical differences among the means.

There were significant differences in the nutritional indices of T. granarium fifth instar larvae on grain of different wheat genotypes. The larvae raised on line N-91-9 had the lowest weight of food consumption (24.33 ± 3.38 mg/10 larvae) compared to other genotypes tested. Larvae fed with line N-91-9 (5.33 ± 0.33 mg/10 larvae) and cultivars Aftab (3.00 ± 0.57 mg/10 larvae) and Heidari (3.00 ± 0.57 mg/10 larvae) showed lower weight gain than those fed with other genotypes. The highest efficiency of conversion of ingested food (ECI) was on cultivars Gascojen (36.56 ± 1.46 %) and Tirgan (33.42 ± 0.60 %), and the lowest was observed on cultivars Aftab (7.32 ± 1.51 %) and Heidari (7.86 ± 1.38 %). The highest relative consumption rate (RCR) was found on cultivar Gascojen (1.08 ± 0.05 mg/mg/day) and line N-92-19 (0.95 ± 0.02 mg/mg/day), and the lowest was seen on line N-91-9 (0.16 ± 0.03 mg/mg/day), and cultivars Heidari (0.19 ± 0.02 mg/mg/day) and Aftab (0.24 ± 0.02 mg/mg/day). As compared with the other examined genotypes, the relative growth rate (RGR) was the highest on cultivar Gascojen (0.394 ± 0.022 mg/mg/day). Larvae feeding from cultivar Gascojen (5.61 ± 0.17 mg/day) had the highest growth rate (GR), and larvae feeding from line N-91-9 (0.76 ± 0.04 mg/day) and cultivars Heidari (0.42 ± 0.08 mg/day) and Aftab (0.42 ± 0.08 mg/day) had the lowest GR value. The change in the nutritional indices of T. granarium larvae can be due to the differences in physical and chemical characteristics of the grains of tested wheat genotypes. The ECI index represents the ability of an insect to use eaten food to increase its body size and weight. In other words, the increase in ECI value on cultivars Gaskojen and Tirgan indicates the high ability of fifth instar larvae to convert the eaten grain into body biomass. This finding may be due to the high protein content and low grain hardness of these cultivars. The low weight of food eaten and body weight in larvae fed with cultivar Heidari and line N-91-9 may be due to the high grain hardness of these genotypes.

Our results showed that line N-91-9 and cultivars Heidari and Aftab had lower nutritional value than the other tested genotypes for T. granarium larvae, because the amount of food eaten, larval weight gain and nutritional indices of larvae fed with these genotypes were lower than other genotypes tested. So, these two genotypes can be used in genetic engineering programs to minimize the damage of T. granarium. The presence of defensive chemical compounds, grain hardness or the lack of essential nutrients for the development of the pest may be the reason why some of the tested cultivars are unsuitable for T. granarium feeding.

Potato tuber moth, Phthorimaea operculella (Zeller), is the most important pest in potato fields in the world and Iran. The use of appropriate agricultural and protection strategies to prevent oviosition of Ph. operculella on newly formed potato tubers at the end of the cropping season can be effective in reducing its damage. The effects of cover crops on damage reduction on newly formed potato tubers were investigated in a randomized complete block design with three replications during two years 2020 and 2021. After the senescence of potato foliage, the cover crops including of vetch (Vicia sativa), grass pea (Lathyrus sativus), rye (Secale montanu), and strengthening of the natural field vegetation were used as cover crops in the field. Tuber infestation (%) during two years in vetch, grass pea, reinforcement of field vegetation and rye was 8.00, 12.33, 26.33 and 26.17%, respectively and all treatments significantly reduced the damage on potato tubers when compared with control (39.17%). The number of larvae in the infested tubers showed a significant difference between treatments, and the treatments of vetch, grass pea, reinforcement of field vegetation and rye showed a lower larval density, respectively. Based on results, vetch is the most effective plant to cover the soil and prevent Ph. operculella oviposition on the potato tubers. Moreover, maintaining and strengthening of weeds in the field at the end of the growing season and after the drying of potato foliage could be a low-cost method to prevent damage by Ph. operculella on tubers in the soil.

Due to environmental pollution caused by chemical pesticide application, the use of eco-friendly methods such as induced resistance to manage insect pests is necessary. In this study, the induced resistance potential of gibberellic acid, with a concentration of 0.125 g/L, in cabbage was investigated against cabbage aphid Brevicoryne brassicae L. Population growth parameters of cabbage aphid, including intrinsic population growth rate (r), net reproduction rate (R0), finite population growth rate (λ), gross reproduction rate (GRR), and population doubling time (DT) affected by gibberellic acid were significantly reduced compared to the control group (P < 0.05). However, there was not any significant difference between gibberellic acid treatment and the control for mean generation time (T) and the mean fecundity per adult female. The mortality rate of nymphs and adult females, age-specific survival rate (lx), and age-specific fertility (mx) in gibberellic acid treatment were significantly decreased compared to the control (P < 0.05). The mortality rate of first-stage nymphs was higher than the control and other stages. The dispersal percentage of first-stage nymphs and adult females treated with gibberellic acid was increased compared to the control (P < 0.05). Based on the results of this study, gibberellic acid was effective for decreasing the population growth parameters of cabbage aphid, and it can be considered in the integrated management of the pest.

In Iran, potato Solanum tuberosum L. is an important crop, and its cultivation extends over more than 186,000 ha annually. The onion thrips, Thrips tabaci Lindeman, is a highly polyphagous species and a serious pest of a wide range of economically important crops. In Iran, T. tabaci causes damage on different agricultural crops including: potato, onion, cucumber and tobacco. Onion thrips feeds by piercing the surface of the tissues (leaves and leaf buds) and sucking up the exuded cellular contents. On infested leaves, the empty cells create silvery-white spots, silver damage, which cause yield loss. Use of insecticides for controlling T. tabaci has low efficacy because females lay eggs within leaf tissues, larvae hide in leaf domatia and between the inner leaves of plants, and pupae rest in the soil. Therefore, it is necessary to use alternative management approaches for control of T. tabaci such as resistant cultivars integrated with natural enemies. The interactions between natural enemies and resistant cultivars have a direct effect on the pest by effecting its developmental rate, fecundity and survival rate. They may also have an indirect effect on natural enemies by increasing generation time of the pest and, as a result, increasing exposure time of the pest to its natural enemies. In this study, we assumed that the different potato cultivars affect population density of T. tabaci and diversity of its natural enemies. Therefore, the present research was designed to evaluate the onion thrips density and species diversity of its natural enemies on four potato cultivars under field condition.

Tubers of four potato cultivars including Agria, Savalan, Arensa and Fantasia (commonly cultivated in Ardabil region) were selected for evaluation of population density of T. tabaci and diversity of its natural enemies under field condition during 2011-2012. The tubers were obtained from the Seed and Plant Improvement Institute of Karaj, Iran. Tubers of four tested cultivars of potato were planted in four experimental fields, each of 500 m2,at four different locations in the Ardabil plain. The fields were managed according to the local practice with flood irrigation and hand weeding once every ten days. No insecticides were applied in these fields. The onion thrips populations were monitored on the four cultivars of potato from late stem elongation to petal fall stages by examining four plants from each cultivar chosen randomly from each of four fields (16 plants per cultivar). The numbers of thripslarvae and adults and each of natural enemies per plant were counted using a 20X hand lens. Moreover, onion thrips and its natural enemies were collected from each of potato cultivars, transferred to the laboratory, and identified to species by morphological characteristics under a stereomicroscope or a microscope according to the valid identification keys. The Shannon diversity index (H), Shannon evanesces index (E), and Morisita-Horn index (CMH) were then calculated for each of four potato cultivars by use of EstimateS Win 8.20 software (6). Data on population densities of onion thrips and its dominant natural enemies were analyzed using one-way ANOVA and significant differences among cultivars were compared using Tukey's HSD test. 

In two years, the lowest densities of onion thrips larvae and adults were observed on Agria. In this study, 21 species of onion thrips predator were collected and identified. Amongst the predator species, Aeolothrips intermedius Bagnall and Orius niger (Wolff) had the highest relative abundance on each of four potato cultivar. The predator A. intermedius with small size and ability to penetrate into leaf domatia, faster development rate and higher fecundity is effective in control of herbivore thrips on host plants (19). Moreover, previous researches have reported that the species of Orius are efficient in control of onion thrips. The Shannon diversity index for the complex of predators was greatest on Agria. Species richness and their relative abundance are two main factors for measuring Shannon diversity index in each ecosystem. Moreover, the values of Morisita–Horn index for the complex of predators between the four cultivars of potato ranged from 0.948 to 0.989. The value of this index varies between 0 and 1. When the value of this index increases from 0 to 1, the species complex of predators between two cultivars becomes more identical. In two years, densities of two predator species A. intermedius and O. niger on Agria and Savalan were significantly higher than on Arensa and Fantasia. Furthermore, the greatest percentage of females of two predator species was observed on the thrips-infested plants of Agria. These results indicated that the preference and performance of two mentioned predators were higher on Agria and Savalan among the tested cultivars.

Based on the results of our study, it can be concluded that the cultivation of Agria could be useful in reduction of T. tabaci population and conservation of its predators in potato fields.

Background and Objectives:

 The melon aphid, Aphis gossypii Glover, is one of the most important pests of tomato in Iran. This aphid causes severe damage on tomato crop in northern Iran. 

Materials and Methods:

 Present study was conducted in an experimental field, 0.3 h, in Behshahr region in Mazandaran province based on a randomized completely block design. In this study, the effectiveness of intercropping tomato (T) with clover (C) in the three combinations: (1) one row of tomato with two rows of clover (1T:2C), (2) two rows of tomato with two rows of clover (2T:2C), and (3) three rows of tomato with two rows of clover (3T:2C) along with sole tomato were assessed on the densities of melon aphid, Aphis gossypii Glover, diversity of its natural enemies and yield of both crops in 2016 and 2017.

 Results:

 The density of nymphs and adults of A. gossypii were significantly higher in sole tomato compared with intercrops. Among intercrops, the lowest density of nymphs and adults of A. gossypii were observed in 1T:2C intercrop. In present study, 13 predator species were collected and identified on aphid-infested plants of tomato in the experimental field. Among the predators, Coccinella septempunctata L., Chrysoperla carnea (Stephens) and Episyrphus balteatus DeGeer had more abundance in the two studied years.  The Shannon diversity index (H´) and the Pielou’s evenness index (J´) for composition of predator species were significantly higher in intercrops compared with sole tomato crop. Moreover, more nymphs and adults of A. gossypii were parasitized in all intercrops compared with sole tomato crop in 2016 and 2017. The highest value of land equivalent ratio was found in 1T: 2C (LER = 1.28 in 2016 and 1.30 in 2017) among intercrops in the two cropping seasons.   

Discussion:

 All the three intercropping patterns of tomato with clover including 1T:2C, 2T:2C and 3T:2C, especially 1T:2C could be recommended in management programs of the melon aphid in tomato fields.

The pistachio fruit hull borer moth, Arimania komaroffi Ragonot (Lepidoptera: Pyralidae) has become a major pest of pistachio in recent years. The purpose of this study was to determine the lower threshold temperature and thermal constant of this pest under laboratory condition which can be used in predicting the time of pest control. Immature stages of this pest were reared at four constant temperatures 25, 27.5, 30, 32.5 and 35°C (±1), 65±5% RH, and 16:8 L:D photoperiod on fruit of Ohadi pistachio cultivar in growth chamber. Lower threshold temperature (T0) and thermal constant (K) of various stages of this pest were calculated with ordinary linear regression method and Ikemoto & Takai method. Moreover, thermal requirements for different generations of pest were determined under the field conditions during two years, 2013-2014. According to the results the lower threshold temperature for total immature stage (from egg to adult emergence) of this pest with ordinary linear regression and Ikemoto & Takai were 10.29 and 10.42°C, respectively. Thermal constant for completing immature period (egg to adult emergence) was calculated as 826.05 and 820.11 degree-days with ordinary linear regression and Ikemoto & Takai equations, respectively. Thermal requirements were measured as 763.7, 750.9 and 811.7 DD for first, second and third generations under field conditions which is consistent with laboratory results. Results of this study could be used in forecasting and pest management of this pest.

The sugar beet weevil, Lixus incanescens Boheman, is one of the important insect pests of sugar beet, Beta vulgaris L., in Khorasan Razavi province. In this research, the effect of three types of vegetation in the sugar beet field margin on the population density of L. incanescens and its larval parasitism by parasitoid wasps were studied in the experimental fields of Juvein, Khorasan Razavi province from year 2013 to 2014. In this study a sugar beet plant was selected as sampling unit. In two years, the lowest density of eggs (6 and 6.3 eggs per plant, respectively) and larvae (3.1 and 3.3 larvae per plant, respectively) was recorded in the sugar beet field located nearby forage with trees. Also, four larval parasitoid species of L. incanescens including Bracon intercessor Nees, B. kozak Telenga, Eurytoma aciculata Ratzeburg and E. ghilarovi Zerova were collected and identified from the experimental fields. Among identified four parasitoid species, B. intercessor had the highest percentage of larval parasitism in two years (69 and 76%), respectively. In addition, the highest percentage of larval parasitism by each of four parasitoid species and the highest percentage of females of each of them were observed in the sugar beet field located nearby forage with trees. Therefore, it can be concluded that the presence of forage with trees on the margin of the sugar beet fields can increase larval parasitism and reduce population density of L. incanescens. These results could be useful in integrated management of L. incanescens in the sugar beet fields.

The potato tuberworm، Phthorimaea operculella (Zeller)، is a major pest of potato in both store and field. In this research، host preference، biology and life table parameters of this pest were studied on leaves of 12 potato germplasm including seven commercial cultivars (Agria، Ausonia، Sprit، Satina، Savalan، Kondor، Morene) and five Iranian clones (PI396156-5، PI397045-15، PI397097-2، PI397082-2، PI396124) in a greenhouse at 25 ± 2ºC، 60 ± 5% RH and photoperiod 14:10 (L: D). In choice experiments، one potted plant from each of 12 tested germplasm were placed in a circle inside the cage (1×1×1. 5 meter)، then 12 pairs adults (one-day-old) were released inside the cage. After one week، numbers of mines per plant and number of live larvae per plant were counted. The results indicated that the lowest percentage of injured leaflets and the lowest live larvae (5. 1، 4. 8) were observed on PI397097-2 among the tested germplasm. In no-choice experiments، development time of larvae and pupa، survival rate of larvae and pupa، weight of pupa and life table parameters of the potato tuberworm reared on the leaves of each of 12 tested germplasm were determined. The development time of larvae، pupa and generation time on PI397097-2 were significantly higher than those on the other studied germplasm. The lowest weight of pupa، the lowest survival rate of larvae and the lowest intrinsic rate of increase (0. 076) and innate rate of increase (1. 079) were observed on PI397097-2. Therefore، it can be concluded that clone PI397097-2 is the least suitable for the potato tuberworm among the tested germplasm.

Potato tuberworm، Phthorimaea operculella (Zeller)، is an important pest of potatoes in the storage. In this study، the life history parameters of P. operculella were studied on eight potato germplasms including five potato cultivars (Agria، Savalan، Morene، Sprit، Kondor) and three potato clones (PI 397097-2، PI 396124 and PI 397082-2) in the laboratory at 25 ± 1°C، 65 ± 5% RH and 0:24 (L: D) h. Feeding on the tubers of different potato germplasms had significant effect on development of immature stages، adult longevity and life span of P. operculella. The highest immature stage development time، the lowest survival rate of immature stages and the lowest fecundity were observed on PI 397097-2، and in contrast، the shortest immature stage development time، the highest survival rate of immature stages and the highest fecundity were observed on Savalan. The lowest intrinsic rate of natural increase (rm = 0. 135)، the lowest finit rate of increase (λ = 1. 149)، the lowest net reproductive rate (R0 = 15. 4)، the highest mean generation time (T = 20. 1 days) and the highest doubling time (DT = 5. 1 days) were observed on PI 397097-2. Because of longer immature development time and lower intrinsic rate of natural increase، finit rate of increase and net reproductive rate of the potato tuberworm on PI 397097-2، it was concluded that this clone is less suitable host for the potato tuberworm compared to other potato germplasms studied in this research. Therfore، it can be used in potato tuberworm IPM programs.