pest management

Canola, Brassica napus L. is a significant oilseed crop, containing 35 to 45% oil in its seeds, and can be cultivated in various climatic regions. Cabbage aphid, Brevicoryne brassicae L. is the most important pest of the canola fields in Iran. Chemical insecticide application using ground sprayers is the primary method for controlling B. brassicae in canola fields. However, the dense and tall growth of canola plants poses challenges for maneuvering ground sprayers, which can potentially cause damage to the plants. Therefore, in this study, we evaluated the feasibility and efficacy of aerial spraying of canola fields against cabbage aphid using drone, and compared it with ground spraying. During two growing seasons, this study was conducted in canola fields of Miandoab and Ilakhchi in northwest Iran. Aphid populations were sampled 24 hours before sprayings and 48 hours, 72 hours, and two weeks after sprayings. A six-rotor drone equipped with micronair rotary atomizers was employed for aerial spraying, while a tractor-mounted sprayer was used for ground applications. Results demonstrated that aerial spraying with drone was significantly more efficient, achieving two to six times higher efficacy against cabbage aphids than ground spraying, as measured by the reduction in aphid populations. Image analysis of water-sensitive cards indicated that drones produced finer droplets with smaller volume median diameters. Economic analysis revealed that aerial spraying was more cost-effective despite higher initial costs due to lower operational expenses and reduced water usage. These findings underscore the potential of using drones for precision pesticide application in canola farming

The alfalfa weevil (AW), Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), is a major pest of alfalfa Medicago sativa L. (Fabaceae). Both adults and larvae feed on alfalfa foliage, damage and reduce hay yield and quality, especially in spring. Larval feeding rate was estimated based on alfalfa leaflet consumption under laboratory conditions (18 ± 2 °C, 60–70% RH). Adults did not consume after emergence, apparently due to diapause. The first instar larvae of AW (n=150) were removed immediately after hatching in the laboratory and were confined with alfalfa leaves. The leaf weights (g) were measured prior to and each 24h after larval feeding. The larvae fed for 33-35 days in the laboratory and underwent four instars. The results revealed that average larval consumption is 8.178±0.153 g leaf tissue during the whole larval stages. Our estimates show that insecticide treatment will cost 6,700,000-14,700,000 IRR/ha depending on market values. One kg alfalfa feed appreciates 40000 IRR. Hence, 167.5-367.5 kg of feed corresponds to control costs. If all larvae survive to pupate (whole lifetime consumption), 2.0-4.5 larvae m-2 are tolerable and need no action. However, if a total mortality of 25, 50, or 75% occurs with a constant rate, tolerable densities will increase to (2.5-5.4), (3.2-7.0), and (4.8-10.6) m-2, respectively. Assuming that an insecticide kills 90- 99% of the pest, 7.9-17.4 to 21.1-46.3 larvae m-2 will cause no loss if farmers intervene on time.

Pistachio psylla Agonoscena pistaciae Burckhardt & Lauterer is Iran's most important pest of pistachio trees. Due to the negative effects of excessive use of chemical insecticides, alternative strategies are necessary to control this pest. In this research, some resistance-inducing compounds, including chitosan, gamma-aminobutyric acid (GABA), and potassium silicate in pistachio trees, were studied on the percentage of population growth and detoxifying enzymes of this psyllid. Based on the results obtained, 7 days after spraying, the lowest and highest population growth of pistachio psyllid nymphs were observed in chitosan treatment and control, respectively. Also, the average growth percentage of the nymph population after 14 days did not show a significant difference among GABA, chitosan and potassium silicate, but it significantly decreased on these treatments compared to the control. In this study, the highest and lowest activity levels of esterase enzyme in psyllid nymphs were achieved in the control and chitosan treatments, respectively.On the other hand, the highest level of glutathione S-transferase activity was obtained in chitosan and potassium silicate treatments, and the lowest one was found in the control. The study results revealed that the different inducers could reduce the A. pistaciae population growth by generating physiological changes in the host plant and, subsequently the pest insect. Therefore, these compounds could be considered in the integrated management of this pest.

Application of insecticides against overwintered adults of Sunn pest has limitations. To find the new measurement against the insect, two insecticides imidacloprid, and thiamethoxam, were tested as seed treatments against overwintered adults of Sunn pest in semi-field and field conditions in Alborz province. This project was carried out in a split-plot design with planting dates at 3 levels (at the beginning of wheat cultivation in 2016, Nov. 7, mid- and late-dates in 2016, Nov. 20, and Dec. 4) as the main plots and seed treatments at 5 levels, including imidacloprid 700WS with two concentrations of 1 and 0.5 g/kg of wheat seed and thiamethoxam 350FS with two concentrations of 0.8 and 0.4 g/kg and control (without seed treatment) as the sub-plots. The comparison of the mean efficiency of treatments at different cultivation dates in the semi-field conditions showed that the lowest (9.1%) and the highest (71.66%) efficiencies were observed at the beginning and late cultivation dates, respectively. In seed treatments, thiamethoxam at high concentration had the maximum efficacy (84.4%) 48 days after the last planting date, and the minimum efficacy (5.55%) was related to thiamethoxam at low concentration 116 days after. The results of field conditions showed that the highest (15%) and lowest (1.25%) efficacies of seed treatments were 97 days after the last cultivation date. Thiamethoxam seed treatment at high concentration had the highest efficiency (21.6%) among the treatments at the first sampling date. On other sampling dates, the efficiency of all treatments was less than 10%. The seed treatment with imidacloprid and thiamethoxam did not have acceptable effectiveness against overwintered adults and nymphs of Sunn pest. Also, the change in the cultivation date of seed-treated wheat cannot be effective in reducing the overwintered adult population of Sunn pest.

Grafting is a technique greatly used in fruit trees and vegetable crops by joining the rootstock of one plant with the scion of another plant. The rootstock is chosen for its ability to provide the scion with a healthy root system that provides not only higher tolerance to abiotic stress conditions but also a stronger resistance against pests and pathogens. Therefore, this study aimed to evaluate the effects of two commonly used rootstocks, sour orange and volkamer lemon, in lemon grafting on population densities and life table parameters of Eutetranychus orientalis (Klein). The results were then related to the chemical identification of polyphenol compounds using HPLC. Significant changes in population density and life table parameters of E. orientalis were observed between the two rootstocks used in lemon grafting. The rootstock sour orange had a high influence on population growth of E. orientalis. Balady limes and adalia lemons grafted onto sour orange showed lower density of E. orientalis movable stages than balady limes grafted onto volkamer lemon. Balady limes and adalia lemons grafted onto sour orange significantly increased the total developmental periods of E. orientalis and decreased the adult longevity period, oviposition period, and the total fecundity of females. The total developmental period was 9.64 and 10.14 days, the adult longevity period was 3.58 and 3.59 days, and the total fecundity of females was 4.59 and 5.50 eggs/female, respectively. Additionally, the use of sour orange in grafting lemon resulted in a decrease in the net (R0) and gross (GRR) reproductive rates, which in turn reduced the intrinsic (r) and finite (λ) rates of increase. The rootstock's high performance may be attributed to the presence of high concentrations of polyphenol compounds that deter feeding and reproduction by E. orientalis. The study suggests that this rootstock can be utilized as a tool in integrated pest management strategies against the citrus brown mite, E. orientalis. When incorporated into an integrated pest control program for E. orientalis in citrus orchards, this technique enhances plant tolerance to infestation, while also ensuring that the output is effective and sustainable.

For IPM programs, it is crucial to use plant cultivars that are less sensitive to pests or resistant to them. In this research, the susceptibility and resistance of 20 canola cultivars to the diamondback moth, one of the most destructive pests of canola worldwide, were evaluated under laboratory conditions based on the biological performance of the moth and the response of the secondary metabolites and protein of canola plants leaves. The biological performance of the pest was evaluated using larval development and pupal weight, oviposition preference, and the age-stage, two-sex life table. The highest intrinsic rate of increase (r), the net reproductive rate (R0), developmental time, and lowest pupal weight were observed on the 1009 cultivar, while the lowest r, R0, and highest pupal period were obtained on the RGS003 cultivar. Also, fecundity in RGS003 and Zarfam cultivars was lower than the other cultivars. Overall, study findings suggested that the Hyula50, Zarfam, and RGS003 cultivars would be suitable candidates for inclusion in integrated pest management programs against diamondback moth.

Spodoptera exigua (Hübner), a highly destructive pest of agricultural crops, is often managed through the use of chemical pesticides. However, the use of chemical pesticides can have negative impacts on human health and the environment, making it important to find sustainable and alternative approaches to effectively manage this pest. One promising solution is the use of inhibitors that hinder the activity of proteases in the insect's digestive tract. Many digestive proteases, such as chymotrypsin, are produced as inactive zymogens with N-terminal pro-regions, which act as intramolecular chaperones and inhibitors of cognate catalytic regions. The present study aimed to utilize various bioinformatics tools to identify the physicochemical properties, secondary structures, and topology of chymotrypsin from S. exigua. Furthermore, we evaluated the potential of peptide inhibitors derived from the pro-region of zymogens that could be utilized as mimetic inhibitors for chymotrypsin in S. exigua. Homology molecular modeling was performed using SWISS-MODEL, and the validation of the predicted model was done by various programs. Molecular docking studies between five homologous species-derived protease inhibitors and the predicted model following by molecular dynamics (MD) simulation coupled with Molecular Mechanics Poisson–Boltzmann Surface Area (MMPBSA) calculations were also applied and the analysis of peptides/enzyme interactions revealed the antagonistic capacity of two screened inhibitors against S. exigua chymotrypsin. Protein-protein interaction networks demonstrated that chymotrypsin from S. exigua interacted with eleven other proteins in a high confidence score. Active site analysis revealed that S219, D230, and H232 serve as catalytic residues. These findings demonstrate a central role for computational methods in designing a potent inhibitor peptide that is highly specific and selective to its mature enzyme. Our study could be promising for future insecticide designs used in S. exigua control.

Applying reduced doses of pesticides has advantages such as resistance management, environmental pollution reduction, and control costs. Very few studies show that passing the water used for pesticide applications through a magnetic field can improve the pesticides' efficiency. In this study, the effect of a magnetic field on the acaricidal activity of spirodiclofen was evaluated against Tetranychus urticae. Treatments included distilled water and well water for preparing the suspensions after passing through a constant magnetic field of 0.42 Tesla. Furthermore, additional treatments were made by passing the prepared suspensions through the magnetic field. Mites were counted right before the sprays on days 7, 14, and 21. The treatment efficiencies were calculated by using the Henderson-Tilton formula. Except for 2 of 12 cases in which the efficiencies were negative, in the rest of the experiments, the magnetic field enhanced the efficiency of the studied acaricide. The highest values were recorded for two treatments including magnetizing the mixture of well water and acaricide treatment and magnetized distilled water plus acaricide treatment between days 7 to 21 (approximately 77 %). This study suggests the usefulness of magnetic fields as an environmental-friendly method to increase the effectiveness of the studied plant protection agent.

Codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae) is the key insect pest of apple orchards in Iran. This study was conducted in the main apple-growing regions of East Azarbaijan Province to generate potential habitat suitability maps of C. pomonella using MaxEnt modeling and to determine the importance of vegetation index in improving the accuracy of these models. Field surveys for collecting the occurrence data of codling moth were conducted during three growing seasons, 2017 - 2019. The activity of codling moth adult males was monitored using delta-shaped traps baited with female sex pheromone. Fifteen environmental variables were considered as potential predictors for estimating codling moth distribution. These variables were categorized into topographic, climatic, and remote sensing variables. A MaxEnt modeling algorithm was used to predict the distribution of codling moth. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC). By using the topographic, climatic, and topographic+climatic variables, the AUC values were 0.840, 0.951, and 0.938, respectively. The model including normalized difference vegetation index (NDVI) had the highest AUC value (0.99), which strongly supports model predictive power and indicates the importance of vegetation index in codling moth distribution modeling. NDVI was the most contributed variable in the model followed by precipitation of September, slope, minimum temperature of May, and mean temperature of April. The distribution map obtained in MaxEnt provides an important tool for identifying potential risk zones of codling moth. This map can assist managers in forecasting and planning control measures and therefore, effective management of current infestations of codling moth.