فصلنامه تحقیقات آفات گیاهی
سال دهم شماره 3 (پاییز 1399)

Spodoptera cilium Guenee is one of the pests of grasses in the landscape of the southern regions of Iran and many countries of the world. In this study, the effects of some insecticides, including, indoxacarb, fanvalerate, diflubenzuron, Imunit® (Alpha Cypermethrin +Teflubenzuron) and Bt were investigated against larvae of S. cilium in laboratory and field conditions. The laboratory bioassays were performed by leaf dipping method at 250C, 60±5% RH, and 16:8 light: dark conditions. The results indicated the LC50 values from low to high of imunit®, indoxacarb, diflubenzuron and fanvalerate, 48 h after lavae exposure were 27.7, 60, 187.8 and 1057.0 ppm, respectivley. In the second experiment, grass leaves were treated with recommended and half recommended concentration of tested insecticides using leaf dipping method. Then, the mortality of second and fourth instar larvae were counted daily up to five days. A day after exposure, the highest mortality percentage of the second instar larvae was related to the recommended concentration of indoxacarb, fenvalerate and imunit®, respectively, with 99.0±1.0, 92.0±2.3 and 89.0±1.0%, respectively. In this time, the highest mortality level of fourth instar larvae was related to the recommended concentration of imunit® and indoxacarb with the mortality of 58.0±2.0% and 56.0±5.9%, respectively. The greatest reduction in the damage percentage in the field test was reported 19 days after spraying is related to the recommended concentration of indoxacarb, and imunit® with 6.0±1.0 and 28.0±0.0%, respectively. According to our results, immunit and indoxacarb have been shown to control the population and reduce the damage of S. cilium, and can be used in this pest control programs.

The dubas bug, Ommatissus lybicus Bergevin, is a key pest of date palm, Phoenix dactylifera L. in Iran. This study was conducted in a date palm orchard in Farashband (Fars Province) to investigate the different sampling methods and population fluctuations of dubas bug nymphs in first generation. The results showed that the nymphs emerged at early April, their population density reached to peak at 30 April, and finally declined to a few numbers at early June. Results showed that there was a significant correlation between different sampling methods. Using correlation analysis, it was shown a high and significant correlation between nymph densities on mature date palm and on offshoots (R2=0.96). Results showed that yellow sticky traps could be a relatively appropriate variable to estimate population densities on date palms. Also, results showed that the honeydew secretion begun approximately three weeks after nymphal emergence, however its peak was happened one week after the peak of nymph densities. Regression analysis of Taylor model showed that in exception of one sampling method, all other three sampling methods were significant. Based on R2 and P of regression analysis, Iwao’s model was more appropriate than Taylor model for sampling of dubas bug honeydew. In order to determine the optimal sample size, the Green's and Kuno's method with constant accuracy of 0.2 were used. Based on Green's method, whenever the average density of dubas bug on mature and offshoot date palm leaflet is 10, the number of required samples with a precision level of 0.2 would be 38 and 47 leaflets, respectively. Whenever the average density of this pest in each yellow card is 200, the number of required samples would be 19 cards.

The use of pesticide mixtures is one of the effective ways to reduce spraying costs, reduce their consumption and prevent resistance development in the pest’s population. However, due to the potential hazards, before any recommendation to mix pesticides, the need for mixing and its physical and chemical compatibility should be carefully considered. In this study, due to the synchronicity of aphid control with acari pests, the insecticidal performance of mixtures of imidacloprid (SC 35%) with fenpyroximate (SC 5%), spirodiclofen (SC 24%) and etoxazole (EC 10%) were investigated on third instar nymphs of melon aphid, A. gossypii. Furthermore, the activity levels of detoxifying enzymes esterase and glutathione S-transferase was measured in treated insects with these compounds. Bioassay tests were performed with a Potter spray tower method. LC50 value of the imidacloprid alone and in combination with each of the acaricides of fenpyroximate, spirodiclofen and etoxazole were 45.41, 84.91, 44.65 and 48.94 mg/l, respectively. In addition, by estimating the Combination Index (CI), a synergistic effect was observed in the mixture of imidacloprid with each of the acaricides and the highest synergistic activity occurred at concentrations higher than LC30. In mixed treatments, the CI index decreased with increasing concentration. The results of detoxifying enzyme activities showed that the activity levels in mixture of imidacloprid: fenpyroximate and imidacloprid: spirodiclofen were higher than that of imidaloprid alone and mixture of imidacloprid: etoxazol. In this study, the lowest CI index at LC50 concentration, were for binary mixture of imidacloprid: etoxazol (0.529) and imidacloprid: spirodiclofen (0.545) that exhibited high synergistic effect. The results of this study showed that the effectivness of imidacloprid (SC) was increased for control melon aphid, when mixed with the tested acaricides. However, the mixture of imidacloprid: etoxazole showed the highest insecticidal performance.

Carob moth is the most important pest of pomegranate in some countries including Iran. The use of sex pheromones is one of the methods to monitor and control of this pest. The major component of the carob moth sex pheromone ((Z, E) -9,11,13-Tetradecatrienal) is unstable, and the effectiveness of its mimic ((Z, E) -7,9,11-Dodecatrienyl format) is less than the sex pheromone. Nanotechnology can play an important role in increasing the efficiency of pheromones through gradual release. In this study, with the aim of increasing the stability of the sex pheromone in garden conditions, in addition to prepare the nanocapsule containing the major component of the sex pheromone, an experiment was conducted in a factorial design based on completely randomized blocks with two factors, including type of attractor (sex pheromone nanocapsule and commercial dispenser of mimic sex pheromone) and replacement time attractor (including one, two, four, and eight weeks). According to results, nanocapsule formulation had better performance than the mimic sex pheromone. The mean number of males attracted to nanocapsule at times of replacement attractor including one, two, four, and eight weeks were 1.93, 1.74, 1.51, and 0.6 insects per day, respectively, and to mimic sex pheromone at the mentioned times were 1.17, 0.89, 0.56, and 0.14 insects per day, respectively. Also, nanocapsule and mimic sex pheromone were able to attract insects for 49 and 21 days, respectively. According to the results of this study, the sex pheromone nanocapsule is recommended to monitor and control of this pest.

The effect of new formulations of Neem, Neemarin® and metaldehyde on slug, A. agrestis was evaluated in laboratory and greenhouse conditions. In bioassay experiments, the leaves of the ornamental plant (Spathiphyllum wallisii Regel) were dipped in different concentrations of neem and Neemarin®, and then same-age immature slugs were released on the leaves and their mortality and feeding were determined up to 14 days. The LC50 values for Neem and Neemarin® were estimated 34.1 and 22.5 ml/lit, respectively, and relative toxicity of Neemarin® was 1.59 times of /more than Neem. The greenhouse experiments were conducted in RCD with 4 treatments, and the maximum effect of the treatments was obtained for metaldehyde with a mean of 95.75% after 15 days compared to the Neem and Neemarin® with 47.85% and 51.63% mean mortality, respectively. Also, the effect of Neem and Neemarin® on the nutrition was 1.72 g and 1.9 g, respectively, in comparison with control (9 g) and the percentage of egg hatching significantly decreased compared to the control. According to the results, Neem and Neemarin® compounds in the concentrations 34.1 and 22.5 per thousand, respectively, and up to ten times on leaves of S. wallisii had a negative effect on the nutrition of A. agrestis and reduced the damage in greenhouse conditions. This effect with increasing age and body size of the slug and subsequent increase in concentration was maintained. However, they were less lethal than methaldehyde.

Alfalfa weevil, Hypera postica Gyllenhal is the most important pest of alfalfa fields in Iran. Main damage is related to larvae by feeding on plant leaves especially on first cutting. In this study, mortality of alfalfa weevil larvae and adults and damage reduction on plant leaves were assessed by using the recommended concentrations of some combinatory and botanical insecticides including lufenuron+ emamectin benzoate (Proclaim fit®), lufenuron+fenoxycarb (Lufox®), thiacloprid+deltamethrin (Proteus®), and azadirachtin (Neem-Azal®). Numerous observations were made on the mortality of insect larvae and adults and also the number of damaged (eaten) leaves of plants on one day before spraying (control) and 1, 3, 7, and 15 days after spraying. A factorial experiment with RCB design was adopted with three replications in Nagadeh suburbs in the spring 2018. Results showed that there was a significant difference in efficacy of used insecticides with control. lufenuron+emamectin benzoate and lufenuron+fenoxycarb had higher lethality on larvae with more than 95% after 15 days of treatment. Lufenuron+fenoxycarb along with lufenuron+emamectin benzoate and azadirachtin imposed more mortality adult alfalfa weevils. There were no statistically significant differences on the percent damages of larvae and adults among azadirachtin, lufenuron+emamectin benzoate and lufenuron+fenoxycarb treatments after 15 days. Considering the economic importance of weevil larvae especially in the first cut and the results of mortality and damage percent in different treatments, azadirachtin can be recommended as the most appropriate option in damage control of alfalfa weevil.

In the present study, sublethal effects (LC10 = 255, LC20 = 3702 and LC30 = 25461 conidia/ml) of entomopathogenic fungus, Beauveria bassiana Bals. (Vuill.) on the biological attributes of Cotton aphid, Aphis gossypii Glover, was evaluated under laboratory conditions (25 ± 1 °C, relative humidity of 65 ± 5% and a light period of 16 h.). Data analysis was performed using the Age-stage two sex life table theory. Based on the results obtained, although sublethal concentrations had no significant effects on the female longevity, but their effects on the fecundity of treated individuals was significant. In addition to the treated individuals, we also present data supporting that the sublethal effects could carry over to their offspring. The lowest recorded value for pre-adult development of A. gossypii was observed at LC30 (4.36 day). Furthermore, the lowest value for duration of total pre-ovipositional period (TPOP) was also recorded at this sublethal concentration (4.60 day). The highest mortality of immature stages was recorded at LC30 (24.24 %). Different treatments had significant effects on the intrinsic (r) and finite (λ) rates of increase. The results obtained could be helpful for increasing efficiency of entomopathogenic fungi in management programs of different pests.