فصلنامه تحقیقات آفات گیاهی
سال سیزدهم شماره 3 (پاییز 1402)

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.

Indiscriminate use of chemical insecticides has caused the outbreak and resistance of pests. Plant extracts can be a suitable alternative to common pesticides today. In this research, the lethality effect of Calotropis procera plant extract was tested by the contact method (leaf dipping) on different biological stages (first-instar nymphs and adults) on the greenhouse whiteflies, as well as the repellent effect of the extract on same-age adults in two times, consist of six and 24 hours after treatment. The experiment was conducted based on a completely randomized design with five concentrations of plant extract in four replications and 20 same-aged individuals in each replicate (for the lethality test (and 50 same-age adults (for the repellency test (in different concentrations. In these experiments, mortality of first instar nymphs was checked after 24 and after 72 hours for adult forms. The lethal concentration of 50% on the first instar nymphs and adults were 8805.110 and 7281.697 mg/L, respectively. According to the results, this extract was a lethal compound for both tested instars of greenhouse whitefly. Also, the repellent concentration of 50% of this extract was estimated at 1902.593 mg/L in adults. The repellency effect was also significant. The results show that with an increase in concentration, mortality and repellency will increase and this extract has insecticidal and repellency properties.

The entomopathogenic fungus Beauveria bassiana is an important and universal biological control agent that is used to control many important pests such as cabbage aphid Brevicoryne brassicae. Main limitation of the use of this fungus is environmental persistence to initiate epidemics in susceptible host populations. In this research, the lethal effects of two isolates of the entomopathogenic fungus on adults and second instar nymphs of cabbage aphid and the stability of the entomopathogenic fungus and its nanocomposite formulation against UV-C radiation were investigated. The LC50 value of the cabbage aphid adults was equal to 2.5×105 in WE209 isolate and 9.8×104 spores/ml in WE277 isolate. The LC50 values in the second instar nymphs were 6.4×105 and 3.2×105 spores/ml, respectively. Spore germination after 2 and 3 h exposure to ultraviolet radiation equals to zero for both times in WE209 isolate and 6 and 32%, respectively in WE277 isolate. However, these values were 12% and 37% for WE209 and 65% and 38%, respectively for WE277 base on nanocomposite. These results showed that the nanocomposite of the entomopathogenic fungus B. bassiana based on montmorillonite/salep can be effectively used to increase the stability and as a result, increasing the virulence of the fungus.

In this study, the biological and population growth parameters of the green peach aphid, Myzus persicae Sulzer and the functional response of the green lacewing Chrysoperla carnea Stephens were investigated on two pepper cultivars (Jalapeno and Elegant) in two soil and hydroponic cultivation systems at 25±2 ˚C, 65±5 % RH and 16:8 (L:D) h. The highest values of intrinsic rate of increase (r) and net reproductive rate (R0) of the aphid were estimated on Jalapeno in soil cultivation (0.281d-1 and 62.89 per generation, resp.) and the lowest values were on Elegantin in hydroponic cultivation (0.174 d-1 and 34.14 per generation, resp.). The third instar larvae of C. carnea exhibited functional response type II on all treatments. The attack rate (a) of predator varied from 0.0422 to 0.0674 h-1 and handling time (Th) ranged from 0.1915 to 0.2191 h on different treatments. The results revealed that cultivar Jalapeno in soil cultivation system, with the highest r value, is a relatively desirable cultivar for the growth and feeding of M. persicae. In contrast, cultivar Elegant in hydroponic cultivation system with the lowest value of r is less desirable for M. persicae. Also, according to the results of functional response, Elegant and Jalapeno in hydroponic cultivation, compared to the soil cultivation system, have more suitable quality for biological control of this pest.

The leafhopper, Orosanga japonicus )Melichar( upon sucking sap from the plant deposits a lot of honeydew on the leaves, attracts sooty mold, and blackens the leaves, fruits and branches. The use of monitoring and control methods is an urgent need because of lack of knowledge on the behavior of O. japonicus. Therefore, during the years 2021 and 2022, the attraction of this leafhopper was investigated to the sticky cards with various colors including white, yellow, red, blue, and green. Similarly, the light traps equipped with energy-efficient lamps of different spectrums such as UV, white, yellow, red, and green light was also considered for this investigation. The experiments were performed from the onset up to the end of this insect’s activity in citrus orchards. According to the results, O. japonicus adults were attracted and captured mostly by the UV light traps with means of 1437.3±89.7 and 299.6±18.2 in the first and second years of survey, respectively in comparison with other lamp colors used. On the other hand, the attraction of the leafhopper to the cards showed that the white and blue cards attracted more insects with means of 24.5±5.3 and 17.1±2.1 respectively in two-year of survey, compared to green, red, and yellow cards used. This preliminary information on population monitoring of this pest may pave the path for future management of O. japonicus.

Amblyseius swirskii Athias-Henriot is one of the major biological control agents used in biological control programs for a variety of pests. However, before using a natural enemy in a biocontrol program, it is essential to know its effectiveness. In this study, the age-stage, two-sex predation rate of A. swirskii was determined on Frankliniella occidentalis (Pergande) under laboratory conditions at 25 ± 1 °C, relative humidity of 60 ± 5%, and a 16: 8 h (L: D) photoperiod. The means and standard errors of the predation parameters were estimated using the bootstrap resampling procedure. According to the obtained results, the age-stage specific predation rate (cxj) of female adulte of the predator was higher than the other stages. Their predation rates were zero for the non-predatory stages (e.g., egg and larva). The value of net predation rate (C0), the mean number of prey consumed by an average individual predator during its entire life span, on F. occidentalis was 159.25 preys/predator. In addition, the value of finite predation rate (ω) and stable predation rate (Ψ) were 2.635 preys/predator/day and 2.208 preys/predator, respectively. The value of transformation rate (Qp), the mean number of prey that a predator needs to consume to produce an offspring, was 8.39 prey. Consequently, the obtained results in this study could provide important information in the design of a comprehensive program for controlling F. occidentalis by predatory mite, A. swirskii on crops.

The melon aphid, Aphis gossypii Glover is one of the most important pests in pepper fields and greenhouses, which is of special economic importance due to its wide distribution and large host range. In this research, biological and reprodutive parameters of A.gossypii on two pepper cultivars (Poblano and Paprika) treated with salicylic acid, were investigated at laboratory conditions (25 ± 2 ˚C, 65 ± 5 % RH, and a photoperiod of 16L: 8D h). According to the results, the use of salicylic acid in both cultivars had a significant effect on most of the demographic parameters of the A.gossypii, compared to the control (spraying with distilled water) and decreased its life span, life cycle length, and Survival. The lowest and highest lifespan were 5.91 days (salicylic acid treatment in Paprika) and 10.25 days (control treatment in Poblano), respectively. Also, the use of this hormone had a significant effect on the reducing gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) of the aphid. The minimum and maximum values of r  were obtained in salicylic acid treatment on Paprika and control treatment on Poblano (0.2570 and 0.4046 d-1 respectively). So, salicylic acid can considerably reduce biological and reprodactive parameters of A.gossypii in pepper and can be used in integrated pest management programs of melon aphid.