فصلنامه تحقیقات آفات گیاهی
سال چهاردهم شماره 4 (زمستان 1403)

Due to several side-effects of chemical pesticides' utilization and necessity of the introduction of efficient and eco-friendly alternatives, the insecticidal effects of ajwain, cumin, and fennel essential oils, separately and in combination, were investigated against the saw-toothed grain beetle in the present study. Chemical analyses of the essential oils revealed that thymol (43.07%) and cymol (26.16%) in ajwain, g-terpinene (39.89%) and cymol (31.96%) in cumin, and anethole (70.98%) and limonene (18.95%) in fennel essential oils were dominant. The 50% lethal concentration ​​(LC50) values of cumin, ajwain, and fennel essential oils were decreased from 0.701, 1.492, and 1.805 μl/g in 24 h to 0.394, 0.603, and 0.613 μl/g after 72 h, respectively. The combined use of the studied essential oils increased their toxicity and the mortality of pest; so the mixing of 30% lethal concentrations (LC30) of ajwain and cumin essential oils had a synergistic effect on the mortality of insect pest. In other combinations, an additive effect was observed in the toxicity of essential oils. Nutritional indices of the pest including consumption index, relative consumption rate, and relative growth rate, influenced by separate and combined application of ​​ essential oils, were significantly decreased compared to the control group. The relative growth rate of the pest showed the greatest reduction by ajwain+cumin+fennel essential oils' treatment compared to others. The results of the present research showed that it is possible to use ajwain, cumin, and fennel essential oils, separately and in combination, to manage saw-toothed grain beetle.

The lesser grain borer, Rhyzopertha dominica (F.), with a worldwide distribution, is among the important pests of stored products, which causes significant economic damage to cereal grains such as wheat and rice. The lethal and sub-lethal effects of essential oils extracted from two species of the Mentha, including Mentha piperita L. and Mentha spicata L., on biological and life-table parameters and nutritional indices of R. dominica at 28±1°C, 60±5% relative humidity, and 14:10 h (light:darkness) photoperiod were evaluated in the current study. Results indicated that both essential oils were toxic to the adults of R. dominica, in which M. piperita essential oil with lower LC50 (16.72 and 12.55 μl/l, respectively) had more fumigant toxicity compared toM. spicata essential oil (41.11 and 35.73 μl/l, respectively) after 24 and 48 h. The egg incubation period and development time of immature stages were increased by essential oils' treatments. Female fecundity and adults longevity along with population parameters of the pest, including r (intrinsic rate of population increase), R0 (net reproductive rate), GRR (gross reproductive rate), and λ (finite rate of population increase), exposed to the essential oils were decreased. Nutritional indices, including consumption index, relative consumption rate, and relative growth rate, of pest treated with essential oils were also significantly reduced compared to the control group. Results revealed that M. piperita and M. spicata essential oils, as available and eco-friendly botanical agents, possess significant potential for the management of R. dominica.

The present study was designed to evaluate the effect of different heights and times of UV-C radiation on the egg and 3rd nymphal stage of Trialeurodes vaporariorum (Westwood) and the oviposition and emergence rate of Encarsia formosa Gahan. In this study, four different times and three heights were selected for irradiation. The analysis of variance showed that there is no interaction between different times and heights of radiation on eggs and nymphs’ mortality, but their effects were found to be significant separately. The mortality rates of eggs and the third nymphal stage rose with longer exposure times and lower irradiation heights. Conversely, the emergence of parasitoids from the parasitized-irradiated third nymphal stage decreased as the duration of exposure increased and the height of irradiation diminished. In assessing the oviposition preferences of E. formosa through both choice and non-choice methods, the results showed that there is no significant difference between the irradiated nymphs and the control treatment, but the emergence of E. formosa was significantly affected, and the highest emergence was observed in the non-irradiation treatment. In addition, an analysis of the impact of varying irradiation heights for 72-hour period on the chlorophyll index of pinto bean leaves revealed no significant differences between the chlorophyll index of the treatments and the control. Therefore, the concurrent application of the parasitoid E. formosa and UV-C radiation for the integrated management of this pest is not advisable.

Plant growth-promoting rhizobacteria (PGPR) may influence plant defense against soil-borne and aerial pathogens as well as herbivores. The present study was conducted to assess the effect of using some PGPR strains of Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense on biological and reproductive parameters of Tetranychus urticae Koch in cucumber plants. Cucumber plants were treated with the above-mentioned bacterial suspension (concentration of 107 CFU/g-1) during the two to four-leaf growth stage. Two generations of two-spotted spider mites were reared on the treated cucumber plants prior to the experimental assessments. The obtained results indicated that the application of rhizobacteria negatively influenced the biological parameters of T. urticae. The duration of the immature development period was significantly affected by the rhizobacteria, so the longest duration was related to B. subtilis (10.06 days). While the pre-oviposition period and adult male longevity remained unaffected by the rhizobacteria, the oviposition period (2.64 to 4.58 days), adult female longevity (1.81 to 3.35 days), and fecundity (9.22 to 12.07 eggs/female) were significantly reduced in treated groups compared to the control (without bacteria). The lowest values and the greatest reduction of these parameters were found in individuals fed on cucumber plants treated with B. subtilis. Results showed that the rhizobacteria used in this experiment, especially B. subtilis, strengthen and induce the anti-herbivore defense mechanisms in the cucumber plant against T. urticae.

Biodiversity indices of rhodacaroid mites were studied at the Saravan dumpsite during the spring to autumn of 2021. Biodiversity indices were studied and compared across three distinct locations: near the garbage dump (adjacent), in the middle (400 meters away), and far (600 meters away) from the waste collection site. In this study, a total of six species from five genera belonging to three families of the superfamily Rhodadroidea were collected and identified. Among the collected species, Gamasiphis pulchellus was identified as the dominant species with a relative abundance of 48.45%. The highest value of the Shannon Weiner index corresponds to the far part in summer and autumn (1.154 and 1.141, respectively). The lowest value of the Shannon Weiner index corresponds to the near part in spring (0). The highest value of the species richness index was calculated in the part far from the polluted section in summer and autumn seasons (0.954 and 0.944, respectively). The lowest value of richness index was related to the part close to the polluted section in the spring season (0).  The results of this study indicated that, in addition to the possible impact of soil contamination levels in the area due to leachates from waste, different seasons also influence the biodiversity indices of mites of the superfamily Rhodacaroidea.

In the present study, integrated application of essential oil extracted from Mentha longifolia and entomopathogenic spores of Beauveria bassiana (Bals.) Vuill. Strain OZ1 to decrease the population of red flour beetle Tribolium castaneum (Herbst), was investigated. The highest mortality of adult insects of red flour beetle (82.5%) was observed at the highest concentration of M. longifolia (26.67 μL/L air). The estimated lethal concentration required to eliminate 50% of the tested insects was determined to be LC50: 15.26 μL/L air. The M. longifolia successfully preserved its toxic properties in a suitable form for a duration of 20 days. The application of various concentrations of M. longifolia essential oil (LC10, LC20, LC30, and LC40) to adult insects significantly altered the patterns of population growth and feeding behavior over a three-month duration. The pathogenicity of B. bassiana in adult beetles indicated that those subjected to the highest concentration tested (108 conidia/ml) experienced a mortality rate of merely 6%. The study examined the impacts of integrated treatments, which included: 1. The concurrent use of various sublethal concentrations of M. longifolia essential oil (LC5, LC10, LC15, LC20, and LC25) alongside B. bassiana at a concentration of 106 conidia/ml, 2. The prioritized application of M. longifolia essential oil, and 3. The precedence of the pathogenic fungus B. bassiana in inducing mortality among the adult population of T. castaneum. The obtained results revealed that the mortality rate of adult stage of red flour beetle was higher in the treatments involving simultaneous application of essential oil and pathogenic fungus and the priority for application of essential oil. The findings of the present study confirm the synergistic effects of integrated treatments.

Citrus trees are attacked by many aphid species in northern Iran. Utilizing entomopathogenic fungi presents a valuable approachin the integrated management of this group of pests, significantly decreasing dependence on chemical insecticides. The first step in implementing these microbial control agents involves the identification of native species and strains. In this study, entomopathogenic fungi were extracted from citrus aphids in Ramsar district of Mazandaran province, north of Iran, during two years. In total of five fungal species were isolated. Among them, Aspergillus versicolor (Vuill.) and Cladosporium oxysporum Berk. & Curtis are reported for the first time as enthomopathogens of citrus aphids. Additionally Microascus sp. and C. cladosporiodes (Fresenius) are newly documented as the first entomopathogenic fungi associated with aphids globally. Furthermore, Epicoccum nigrum Link was isolated from an arthropod pest for the first time in the world. This initial study highlights the necessity for further research to thoroughly assess the pathogenicity of these fungi.