فصلنامه تحقیقات حشره شناسی
سال پنجم شماره 1 (پیاپی 17، بهار 1392)

Grape cicada Cicadatra alhageos (Kolenati, 1857) is known as one of the important pests in Iran. Two other species of cicadas, Chloropsalta ochreata (Melichar, 1920) and Chloropsalta smaragdula Haupt, 1920 have also been reported on Grape in Iran which both resembles very similar to C. alhageos and diagnosing them is only possible by comparing their male genitalia. In this study, the morphometric variation among the three species was investigated base on their wing shapes. The analyses showed that the length ratio of two portions of veins CuA1 and M1+2 were the most important characters for distinguishing the three species in the field.

Alfalfa (Medicago Sativa) is one of the most important forage plants in Iran. Several pests like aphids cause damage to these plants. One of the important aphids is the spotted alfalfa aphid (Therioaphis trifolii). In order to study the genetic variation of this pest, samples were taken from alfalfa fields of different provinces of Iran (Kerman, Fars, Kohkiloieyeh, Lorestan, Hamadan, Kermanshah, Kurdistan, West Azerbaijan, Markazi and Esfahan provinces) during 2007-2009. Seven RAPD primers were used in PCR test. At the range of 200-400 bp., 68 bands out of 88 had polymorphism. The primers A11 and CO4 had the highest polymorphisms that were 77.78 and 73.68 percent respectively. The related dendrogram showed 3 clusters and the second cluster had two sub clusters. In this research genetic differences were seen between collected samples from various regions, but no relationship was observed between these differences and altitudes, longitude, and position of the sampling locations.

During the past few decades, many investigations have been conducted on different plant products in order to obtain safer and effective alternatives for chemical insecticides to control stored product insects. In the present study, the effects of essential oils from fennel, Foeniculum vulgare Miller (Apiaceae), Wall germander, Teucrium polium Boiss. (Lamiaceae) and Summer savory, Satureja hortensis L. (Lamiaceae) were investigated on behavioral and reproductive activity and adult emergence of cowpea seed beetle, Callosobruchus maculatus at 28±2 °C and 60±5% R.H. in dark condition. The results indicated that the repellent activity of essential oils on beetles increased by increasing oil concentration. At the highest concentration (23.08 μl L-1 air), the mean repellencypercentages of fennel, Wall germander and Summer savory oils were 66.82, 84.93 and 95.92% on males and 59.28, 76.06 and 88.8 % on females, respectively. Males were more susceptible to repellent activity of oils than females. The essential oils of Summer savory and fennel had the most and the least repellent activity, respectively. The results indicated that reproductive activity of cowpea seed beetle decreased by increasing oil concentration. At the highest concentration (45.45 μl L-1 air), oviposition deterrence of fennel, wall germander and summer savory oils were 70.89, 63.69 and 56.85%, respectively. At this concentration, the oils caused 76.16, 68.87 and 55.63% deterrencyon F1 adult emergence, respectively. The deterrency of fennel oil on oviposition and F1 adult emergence was significantly higher than two other oils. The results suggested that the essential oils especially that of fennel had an adverse effect on embryonic and larval development, resulting in the reduction of oviposition and F1 progency production.

Callosobruchus maculatus Pic. (Col., Bruchidae) is one of the main pests inside the stores and farms. The effects of light (absolute darkness and light) and temperature (20, 25 and 30C) on growth of C. maculatus were investigated. The experiment was conducted in 6 treatments using a factorial completely randomized design. The results showed that females under the conditions of 30ºC and complete darkness, the life stages of the pest passed in 40 days and under the conditions of 20ºC and complete light, the life stages passed in 86 days. The pre-adult period of females was 78.09 days under 20ºC and complete light, but it was 22 days in 30ºC and compelet darkness.

The relationship between densities of leaf trichomes and number of sweetpotato whitefly, Bemisia tabaci (Gennadius) was investigated on six genotypes of upland cotton, Gossypium hirsutum L. (Mehr, Varamin, Sahel, Khordad, Okra and Red okra) genotypes and one genotype of sea island cotton, Gossypium barbadence (Termus 14) at Cotton Research Station Kashmar, east of Iran, during cropping season in 2009. The result indicated that Termus 14 supported the highest numbers of eggs, nymphs and adults, and also had the highest numbers of trichomes compared to other genotypes.While the genotypes Okra and Red okra with the least numbers of trichomes on leaf surface suppprted the least numbers of various stages of whitefly. Therefore, there was asignificant and positive relationship between leaf trichome densities and whitefly population. It is concluded that the genotypes with glabrous leaves cotton may reduce the whitefly population on cotton.

Although herbivores often encounter with many predator types, most experimental predation studies have focused on the effects of single predator on its prey. Recent researches have presented new insight about the effects of multiple predators on their preys. The effects of different types of predators may affect the population of prey in a quite complex way. To perceiving the influence of combined usage of predators on consumption ratio, we investigated the intraguild predation (IGP) between 3rd instar larvae of Episyrphus balteatus De Geer (Diptera: Syrphidae) with the 2nd and 3rdinstar larvae of Hippodamia variegata Goeze (Coleoptera: Coccinellidae) on the sweet pepper seedlings in the presence of 3-days old nymphs of cotton aphid, Aphis gossypii Glover (Hem.: Aphididae). Predator rearing and IGP experiments were carried out under laboratory conditions (22± 2°c, 60±10% RH and 16L: 8D photoperiod). The treatments included 2nd and 3rd instar larvae of H. variegata and 3rd instar larvae of E. balteatus alone, their combinations and control (without predators). All experiments had 10 replicates. The expected and observed proportions of killed aphid were calculated for each treatment. Comparison of these proportions indicated that the probabilityof aphid predation is reduced in multiple treatments than single usages. In the most cases, the third instar larvae of E. balteatus alone were more efficient than H. variegata 2nd and 3rd instar larvae both in combined and single situations.

In recent years, rearing and releasing of Orius bugs to control small pests such as thrips and aphids has been increased. These studies were carried out to investigate the oviposition rate and longevity of adult females of Orius albidipennis, fed on three different food regimes (eggs of Sitotroga cerealella in addition to corn pollen, eggs of Sitotroga cerealella in addition to date pollen and Sitotroga cerealella's eggs) and two different oviposition substrates (Bean pod and Geranium leaf) under laboratory conditions (25±2°c, 65±5% RH, 16L:8D photoperiod). Results showed a significant differance in the mean number of laid eggs under conditions of various food regimes. There was an increase in oviposition rate of O. albidipennis, when fed on Sitotroga cerealeala's eggs supplementedwith corn pollen (82.7±1.76). The longevity of adult females of O. albidipennis was also not significantly different on these three food regimes. The mean number of laid eggs on two different oviposition substrates showed no significant difference; so the both substrates are suitable for rearing O. albidipennis.

Adults of many parasitoid insects need carbohydrates as a source of energy. Carbohydrate feeding increases the longevity, fertility and parasitism rate, significantly. In this study, the effect of different concentrations (0, 10, 30, 50, and 70 percent) of three sugars in the absence of the Mediterranean flour moth larvae was evaluated on the male and female adults of the parasitoid wasp, Habrobracon hebetor Say (Hym.; Braconidae), under laboratory conditions (25±2ºC; 60±5% R.H., L14:D10). Based on the obtained results and compare to the control (distilled water), sugar feeding treatments were significantly increased the male and female adult longevity of the parasitoid wasp.In the case of glucose, male and female adults mean longevity was significantly lower than those of two other sugars. Thus, the suitability of sugars was ordered as fructose> sucrose> glucose. For males, the optimum concentration of all three sugars was 50 percent, but for females, the optimum concentrations were 30 percent of fructose, 50 percent of sucrose, and 70 percent of glucose, respectively. Furthermore, the response of adult longevity to different concentrations of fructose had a more stable trend comparing the two other sugars. Orthogonal comparison of adult male's longevityversus females showed that no significant difference between the overall means of males and females longevity was observed. It means that both sexes had the same longevity. Based on the overall ANOVA results, sugar concentrations affected the male longevity more than that of females. These differences attributed to differential nutritional requirements and behaviors of males and females. The above-mentioned results indicate the importance of sugar feeding by adult H. hebetor.