Journal of Entomological Society of Iran
Year:2019 | Volume:39 | Issue:3|Papers Count:11

The cotton mealybug, Phenacoccus solenopsis Tinsley, is a phytophagous insect with high populations causing serious damage to the Chinese hibiscus shrubs (Hibiscus rosa-sinensis L. ) from south of Iran. This research was conducted to determine the host preference of Aenasius bambawalei Hayat when had choice or no-choice access to different stages of cotton mealybug. Moreover, biological characteristics and body size of wasps when reared on third nymphal instar and adult females was studied under laboratory condition. According to the results, female wasps did not parasitize the first nymphal stage. The second nymphal stage was parasitized without any adult wasp emergence. The results revealed that the percentage of mealybug mummified, and sex ratio (% female) was significantly higher when mealybug hosts were parasitized at adult females compared to third nymphal stage, in both choice and no-choice access. The developmental times (days) and body size (hind tibia length and antenna length) of A. bambawalei females and males developing in cotton mealybug adult female was significantly longer than those reared on third nymphal instar. The results indicated the high control ability of A. bambawalei, on the older growth stages of cotton mealybug. It is hoped that this parasitoid wasp can be used as a biological agent to control Ph. solenopsis, on the Chinese hibiscus shrubs, H. rosa-sinensis.

The volatiles emitted by herbivorous insects and herbivore-damaged plants play an important role in foraging behaviour of parasitoids that lead to host location of parasitic wasps. The olfactory response of Habrobracon hebetor (Say ) (Hymenoptera: Braconidae ) to volatile compounds of larvae and larval faeces of Helicoverpa armigera (Hü nber) (Lepidoptera: Noctuidae ), corn ear and tomato fruits both infested and un-infested by cotton bollworm was studied using a double sided Y-shaped olfactometer in laboratory conditions. Results showed that parasitoid wasps were significantly more attracted to compounds emitted by larvae and larval faeces of the cotton bollworm. Response of parasitoid wasps to volatiles of larvae in comparison with infested tomato and corn ear indicated that 71. 74% and 68. 09%of wasps were attracted to odors of host larvae, respectively. Wasps did not show response to the odors released from un-infested tomato fruit and corn ear. There was no significant difference in attraction of parasitoid wasps to faeces of larvae that fed on tomato and corn ear. Our results indicated that volatile compounds produced by fifth instar larvae and larval faeces of H. armigera are important agents for attracting parasitoid wasps.

Trichogramma evanescens Westwood is one of the most important biological control agents of lepidopteran pests. This parasitoid is widely distributed throughout Iran. Present study was conducted to assay influence of the age of Ephestia kuehniella Zeller egg on the number of parasitized eggs, developmental time, sex ratio, progeny longevity and fecundity of T. evanescens. Individual mated female parasitoids (<24 h age) were provided with 12, 24, 36, 48 and 60 hours eggs of E. kuehniella in nochoice experiments. Mean number of parasitized eggs were 32. 40 ± 0. 04, 29. 80 ± 0. 05, 26. 93 ± 0. 16, 23. 83 ± 0. 06 and 18. 91 ± 0. 04, respectively. The obtained results showed that different egg ages had a significant effect on the developmental time, sex ratio, progeny longevity and fecundity of the parasitoid wasp. Data analysis demonstrated significant decreasing of net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ ) with increasing the age of eggs. The highest values for r and λ were 0. 390 ± 0. 006 day-1 and 1. 47 ± 0. 008 days, respectively in the eggs with 12h egg. The results of the current study indicated that the egg age is one of the most important factors on life table parameters of T. evanescens and the eggs of E. kuehniella with 12h age are the most suitable eggs for development, reproduction and mass rearing of T. evanescens.

Life history attributes of Habrobracon hebetor Say were investigated at six thermal regimes (20, 22. 5, 25, 27. 5, 30 and 32. 5 º C, 65± 5 % RH and a photoperiod of 16: 8 h L: D) using Galleria mellonella L. larvae as lab host. About 80-250 fresh eggs of the parasitoid (Cohort) were reared under different thermal treatments. Incubation period of male and female eggs reduced significantly from 4. 12 and 3. 45 days at 20 º C to 1. 25 and 1. 06 days at 27. 5 º C, respectively. Larval development was 7. 00 and 6. 81days for male and female larvae at 20 º C and decremented to 2. 43 and 2. 47 days at 32. 5 º C, respectively. Similarly, the longest and the shortest male and female pupal duration was observed at 20 º C (16. 12 and 18. 27 days) and 32. 5 º C (5. 05 and 5. 02 days), respectively. Adult male and female longevity was longest (42. 83 and 58. 44 days) at 20 º C and shortest (16. 05 and 14. 02 days) at 32. 5 º C, respectively. Population parameters including R0, r, and λ ranged between 4. 98-28. 81 offspring, 0. 0378-0. 2001 d-1 and 1. 0351-1. 2065 d-1, respectively, when temperature increased from 20 to 27. 5 º C, proving about 5 folds enhancement in r. Generation time was 42. 50 days at 20 º C and decreased to 15. 16 days at 32. 5 º C, respectively. Female wasp required at least 2. 62 days at 27. 5 º C and maximum 8. 18 days at 20 º C to start oviposition. It is concluded that the population characteristics of H. hebetor were statistically superior at 27. 5 º C compared with those in other treatments and considering economy of rearing, 27. 5 º C along with 65± 5 and 16: 8 L: D h would be the optimum conditions for its propagation on G. mellonella larvae.

The orange pulvinaria scale, Pulvinaria aurantii Ckll. is the most important scale of citrus in the northern Iran. The lethal effects of chlorpyrifos, pyripropoxyfen, acetamiprid and palazin, alone and in combination with emulsifying oil, were evaluated on first-instar nymphs of P. aurantii. The experiment was conducted under natural condition in a randomized complete block design with 3 replications and 10 treatments, and treatments effect was compared 1, 7, 14 and 21 days after spraying. Moreover, the effect of these insecticides was investigated on duration of immature stages and female longevity of Cryptolaemus montrouzieri Mulsant. The activity of some detoxification enzymes (alpha-esterase, beta-esterase and glutathion-S-transferase) in third instar larvae was evaluated. The experiments on the ladybird were conducted under laboratory conditions at 26± 1º C, 75± 5% RH and a photoperiod of 14: 10 (L: D) h. The treatments with acetamiprid + oil, pyripropoxyfen + oil, chlorpyrifos + oil and palazin + oil had the highest mortality on first nymphal instar of the scale. The longest incubation period of C. montrouzieri was in chlorpyrifos treatment (8. 13 days), and the shortest was in control (4. 80 days). Moreover, among treatments the female longevity of C. montrouzieri was the longest in control (96. 60 days), and shortest in chlorpyrifos treatment (53. 50 days). Chlorpyriphos and acetamipirid caused the highest reduction in alpha-esterase and glutathion-S-transferase activities of the third larval instar of C. montrouzieri, respectively. Also, palizin had less negative effect on the activity of beta-esterase in comparison with other tested insecticides. The results of this study indicated that among tested compounds, palizin in combination with the oil is a suitable compound to control of the orange pulvinaria scale.

In this research, barley aphids in Mahidasht region of Kermanshah province were identified. Spatial distribution type and statistics for corn leaf aphid, Rhopalosiphum maidis (Fitch) were also studied and sequential sampling models were developed. Regular weekly sampling was carried out in 2015, 2016 and 2017. Each sampling date, 100 tillers were randomly visited and aphids were transferred to the laboratory for counting and identification. Taylor’ s power law was used to determine spatial distribution type and statistics and sequential sampling models were developed according to Green (1970). Results revealed feeding of five species of aphids on barley including greenbug, Schizaphia graminum, rose-grain aphid, Metopolophium dirhodum, the English grain aphid, Sitobion avenae, corn leaf aphid, R. maidis and bird cherry-oat aphid, R. padi. Corn leaf aphid was more abundant during the season with 93. 8%, 94. 2% and 93. 2% of aphids collected in 2015, 2016 and 2017, respectively. Low populations density of the other four species was observed every three years. Spatial distribution type of corn leaf aphid in barley field was determined as cumulative (b = 1. 45). Sample size required in models with precision levels of 0. 1 and 0. 25 at mean aphid densities observed in the barley field (1. 02-44. 32 aphids per tiller) was 70-524 and 11-84 tillers, respectively. In conclusion, sequential sampling model developed at the precision level of 0. 1 was evaluated time consuming due to large sample size required, but the model at pest management precision level (0. 25) was recommended for monitoring leaf corn aphid in barley fields.

In this research, barley aphids in Mahidasht region of Kermanshah province were identified. Spatial distribution type and statistics for corn leaf aphid, Rhopalosiphum maidis (Fitch) were also studied and sequential sampling models were developed. Regular weekly sampling was carried out in 2015, 2016 and 2017. Each sampling date, 100 tillers were randomly visited and aphids were transferred to the laboratory for counting and identification. Taylor’ s power law was used to determine spatial distribution type and statistics and sequential sampling models were developed according to Green (1970). Results revealed feeding of five species of aphids on barley including greenbug, Schizaphia graminum, rose-grain aphid, Metopolophium dirhodum, the English grain aphid, Sitobion avenae, corn leaf aphid, R. maidis and bird cherry-oat aphid, R. padi. Corn leaf aphid was more abundant during the season with 93. 8%, 94. 2% and 93. 2% of aphids collected in 2015, 2016 and 2017, respectively. Low populations density of the other four species was observed every three years. Spatial distribution type of corn leaf aphid in barley field was determined as cumulative (b = 1. 45). Sample size required in models with precision levels of 0. 1 and 0. 25 at mean aphid densities observed in the barley field (1. 02-44. 32 aphids per tiller) was 70-524 and 11-84 tillers, respectively. In conclusion, sequential sampling model developed at the precision level of 0. 1 was evaluated time consuming due to large sample size required, but the model at pest management precision level (0. 25) was recommended for monitoring leaf corn aphid in barley fields.

Tomato leafminer, Tuta absoluta has invaded Iran in recent years and rapidly turned into an important pest of tomato crops in open fields and greenhouses. Tomato is the preferred host of the pest. However, preliminary observations have shown that it can feed and reproduce on the other Solanaceous crops like eggplant and potato. In his study, the fitness of tomato leafminer has been investigated on fifteen commonly cultivated eggplant genotypes including Ghasri Dezful, Paboland Yazd, Mahali Jahrom, Shendabad, Dastgerd Esfahan, Sarkhoun Bandarabas, Chahboland Neishabur, Ghalami Varamin, Black Beauty, Blacky, Yalda, Lady, Linda, Lima and Kime in a greenhouse with the mean daily temperature of 25 ± 2° C, 60 ± 5% Relative Humidity and a natural photoperiod during the May and June. The ovipositional preference of females and some biological parameters like development times and survival rates of egg, larva and pupa, pupal weight and sex ratio have been evaluated on the plant genotypes using free-choice and no-choice tests. Significant differences have been revealed in the number of daily oviposited eggs on both potted plants and excised leaves and in all biological parameters except pupal weight and sex ratio among the eggplant genotypes throughout the experiments. The ovipositional preference of the females was significantly correlated and negatively correlated respectively with chlorophyll content of the leaves of eggplant genotypes (P < 0. 01) and with trichome density on the underside of the entire leaf surface (P < 0. 05). The eggplant genotypes were clustered into three main categories of resistant (Kime), semi-resistant (Black Beauty and Blacky) and semi-susceptible (other genotypes) using Ward-1963 hierarchical clustering method. The observed differences among the examined genotypes can be used in cropping systems for designing of eggplant breeding and tomato leafminer management programs.

The mealybug destroyer, Cryptoleamus montrouzieri Mulsant is the most important natural enemy of the mealybugs. Increasing knowledge regarding ecological compatibilities of the natural enemies lead to increase their efficacy for controlling the pests. In this study, the effect of temperature as the most effective environmental factor on development of the mealybug destroyer was studied. Developmental time of incubation period, all larval instars, pupal period, and overall immature stages of the mealybug destroyer were recorded in temperatures ranging 15-35° C, 50-60% RH, and a photoperiod of (L: D) 16: 8h. According to the ANOVA, temperature affected significantly developmental time of the mealybug destroyer at 1% probability level and increasing temperature lead to decreasing developmental time. Degree-Day and Ikemoto-Takai linear models were used to describe temperature-dependent development of the mealybug destroyer. While, both of the linear models had shown an acceptable fit to data, because of better statistical criteria, estimation of the Ikemoto-Takai linear model was considered for thermal indices. Estimated values for thermal requirement of incubation period, 1 st nd, 2 rd, 3, and 4 th larval instars, total larval period, pupal period and overall immature stages of the C. montrouzieri were 45. 38, 43. 67, 53. 04, 113. 27, 256. 89, 143. 29 and 483. 59 degree-days, respectively. Moreover, the values of the lower temperature threshold for the mentioned developmental stages were 9. 79, 10. 74, 10. 28, 9. 67, 10. 06, 10. 07, 9. 18 and 9. 64° C, respectively, using Ikemoto and Takaei linear model. According to the results, clarifying some aspects of thermal characteristics of the mealybug destroyer, would increase our knowledge to improve biological control program of the mealybugs.

Brevicoryne brassicae (L. ) is one of the most damaging pests of canola in Iran. Digestive amylolytic and proteolytic activities of adult aphids were evaluated on eight canola cultivars (Opera, SLM046, RGS000, Okapi, Delgan, Licord, H19, and Modena) using starch and azocasein substrates, respectively. The experiment was conducted at 25 ± 1° C, 65 ± 5% RH and a 16: 8 h (L: D) photoperiod. Amylolytic activity was the lowest on Licord and highest on SLM046. The lowest proteolytic activity was on Okapi and Opera, and highest activity was on Delgan. The results indicated that canola cultivars influence on digestive physiology of this aphid.

During May 2019, a study in Shirvā n city (North Khorasan province) to investigate the infestation of livestock farms with various insect species was carried out. In this study, large quantities of flies belonging to the Sphaeroceridae family were collected using light traps. The genus and species of these flies were identified as Coproica vagans (Haliday, 1833). This species is a new record for the Iranian insect fauna.