Effect of feeding and male presence on some biological characteristics of female Trichogramma brassicae (Hymenoptera: Trichogrammatidae)

Low prominence of natural enemies can cause suboptimal success in biological control programs. In present study, the effects of honey feeding and the availability of males were studied on the biological characteristics of Trichogramma brassicae Bezdenko. Four treatments were considered: male was available for female for merely 24 h, either with or without honey; male was continuously presented for females, either with or without honey. Twenty pairs (1 female à 1 male) of newly emerged parasitoids were placed in glass tubes and considered as the treatments. Mortality of females was recorded daily in order to indicate longevity. To determine fecundity, the emergence rate and female progeny percentage, 150 fresh Sitotroga cerealella Olivier eggs were provided for each female in the entire treatments on a daily basis. Results indicated that interaction between adult nutrition and male presence was insignificant (P > 0.01) and did not influence any of biological characteristics. Adult nutrition was more important than male presence. Honey-fed females lived 5-folds longer than the unfed females. Longevity was not significantly influenced by male presence. Fecundity of honey-fed females was 67 and 70.2 eggs; however, 18.4 and 19 eggs for unfed females. Continuous presence of male did not change fecundity. There were no significant differences in the emergence rate in all treatments and it was more than 90% for the entire treatments. Long-lived females produced more males. Percentage of female progeny was not influenced by period of male presence. Therefore, quality of parasitoids was more persuaded by diet provided rather than the period of male presence

Comparative life table of Aphis craccivora (Hem.: Aphididae) on host plant, Robinia pseudoacacia under natural and laboratory conditions

-The cowpea aphid, Aphis craccivora Koch, is an important pest of Robinia pseudoacacia Frisia. Life table parameters of A. craccivora were determined under natural (16- 33ºC and 32-89% RH, respectively) and laboratory (25 ± 1ºC, RH of 70 ± 5% and a photoperiod of 16:8 h (L: D) conditions. The data were analyzed using the age-stage, two-sex life table theory. Each experiment was replicated 45 times for each condition. There was significant differences between the survivorship, fecundity and longevity of the A. craccivora in laboratory and natural conditions. Under natural conditions, A. craccivora had a significant shorter nymphal developmental time, adult longevity and life span than those reared under laboratory conditions. However, the intrinsic rate of increase (r), net reproductive rate (R0), the finite rate of increase (λ) and gross reproductive rate (GRR) under laboratory conditions, were higher than those obtained in field, the higher mean generation time (T) was found in the field. All in all, the results of this study showed that two different conditions (field and laboratory) had significant influence on developmental times and life table parameters of A. craccivora and it is hard to escape the obvious conclusion that we must prevent the unsuitable extrapolation of laboratory results to field applications. The results obtained here, could also help us to understand the population dynamics of A. craccivora under field condition and to develop effective integrated pest management (IPM) programs

Comparative life table parameters of beet armyworm, Spodoptera exigua (Lep.: Noctuidae), on four commercial sugar beet cultivars

Life table parameters of the beet armyworm, Spodoptera exigua (Hübner), on four sugar beet cultivars (Renger, FD0005, Dorothea and Shirin) were studied in laboratory at 27 ± 1°C, 60 ± 5% RH and a photoperiod of 16L: 8D hours. The larvae successfully developed on all cultivars. The shortest and longest total developmental time were recorded on FD0005 and Renger, respectively. The development index (D.I.) of larval period varied from 4.90 to 5.97 on Renger and Shirin, respectively. The life expectancy (ex) was 26.94, 31.39, 30.51 and 30.16 days on the cultivars respectively at the beginning of life. Life table entropy (H) indicated the survival schedule of S. exigua was convex (type I) on all sugar beet cultivars. The gross fecundity ranged from 1499.93 to 2034.67 eggs on Dorothea and FD0005, respectively. The lowest value of net reproductive rate (R0) was recorded on Renger (253.59 females per female per generation). The intrinsic rate of increase (rm) ranged from 0.2235 on Renger to 0.2309 dayâ1 on FD0005. The mean generation time (T) was found to be significantly different on sugar beet cultivars. Fitting adult survival data to Weibull frequency distribution indicated that the adult survival curve was type I on all cultivars suggesting that the mortality was higher in old individuals. The cultivar Renger was less suitable in comparison with other cultivars in the laboratory. These results provided important information on the effect of four commercial sugar beet cultivars on population growth potential of S. exigua

The first report of Microplitis fulvicornis (Hym.: Braconidae: Microgastrinae) as a parasitoid of Spodoptera exigua (Lep.: Noctuidae) from Iran

طی انجام پژوهشی روی جدول زندگی صحرایی شب‌پره Spodoptera exigua (Hübner) در استان خراسان رضوی، زنبور پارازیتوئید Microplitis fulvicornis (Wesmael) متعلق به خانواده Braconidae جمع‌آوری شد. افراد این زنبور از داخل لاروهای سن سوم S. exigua خارج شدند. نام علمی این زنبور توسط نگارنده آخر تأیید شد. این گونه برای اولین‌بار از ایران گزارش می‌شود

A laboratory and field condition comparison of life table parameters of Aphis gossypii Glover (Hemiptera: Aphididae)

Life table studies are essential tools for understanding population dynamics. The life table parameters of Aphis gossypii Glover (Hemiptera: Aphididae) feeding on the host plant, Hibiscus syriacus L. were studied under laboratory (25±1°C and relative humidity of 65±5% and a photoperiod of 16L : 8D h) and field conditions (23–43°C, and relative humidity of 27–95%). The data were analysed using the age-stage, two-sex life table theory. The life table studies were started with 50 and 40 nymphs in laboratory and field conditions, respectively. Under laboratory conditions, A. gossypii reared on H. syriacus had a higher survival rate, fecundity, and longevity than those reared under field conditions. When reared under field conditions, A. gossypii had a longer nymphal developmental time, shorter adult longevity, and lower fecundity than those reared under laboratory conditions. The intrinsic rate of increase (r), net reproductive rate (R0), and the finite rate of increase (λ) under laboratory conditions, were higher than those obtained under field conditions. Nevertheless, there were no significant differences in the mean generation time T (days) between field and laboratory conditions. In the present study, the results clearly showed that life table parameters of A. gossypii were significantly different under field and laboratory conditions. These results could help us to understand the A. gossypii population dynamics under field conditions. The results could also help us make better management decisions for economically important crops

Modeling temperature-dependent development and demography of Adalia decempunctata L.(Coleoptera: Coccinellidae) reared on Aphis gossypii (Glover) (Homoptera: Aphididae)

Development and demography of Adalia decempunctata L. were studied under laboratory conditions at seven constant temperatures (12, 16, 20, 24, 28, 32 and 36°C). First instar larvae failed to develop to second instar at 12°С and no development occurred at 36°C. The total developmental time varied from 47.92 days at 16°C to 15.94 days at 28°C and increased at 32°C. The lower temperature thresholds of 11.05 and 9.90°C, and thermal constants of 290.84 day-degree and 326.34 day-degree were estimated by traditional and Ikemoto- Takai linear models, respectively. The lower temperature threshold (Tmin) values estimated by Analytis, Briere-1, Briere-2 and Lactin-2 for total immature stages were 11.99, 12.24, 10.30 and 10.8°C, respectively. The estimated fastest developmental temperatures (Tfast) by the Analytis, Briere-1, Briere-2 and Lactin-2 for overall immature stages development of A. decempunctata were 31.5, 31.1, 30.7 and 31.7°C, respectively. Analytis, Briere-1, Briere-2 and Lactin-2 measured the upper temperature threshold (Tmax) at 33.14, 36.65, 32.75 and 32.61°C. The age-stage specific survival rate (sxj) curves clearly depicted the highest and lowest survival rates at 16 and 32°C for males and females. The age-specific fecundity (mx) curves revealed higher fecundity rate when fed A. gossypii at 24 and 28°C. The highest and lowest values of intrinsic rate of increase (r) were observed at 28 and 16°C (0.1945 d–1 and 0.0592 d–1, respectively). Also, the trend of changes in the finite rate of increase (λ) was analogous with intrinsic rate of increase. The longest and shortest mean generation time (T) was observed at 16 and 28°C, respectively and the highest net reproductive rates (R0) was estimated at 24 and 28°C. According to the results, the most suitable temperature seems to be 28°C due to the shortest developmental time, highest survival rate, and highest intrinsic rate of increase

Cellular energy allocation in the predatory bug, Andrallus spinidens Fabricius (Hemiptera: Pentatomidae), following sublethal exposure to diazinon, fenitrothion, and chlorpyrifos

It is necessary to study the biochemical changes in insects exposed to toxicants if we want to predict the potential of various chemicals on the natural enemy. Physiological energy, as a biochemical biomarker, may be affected by many pesticides including organophosphate compounds. Therefore, in this study, the sublethal effects of diazinon, fenitrothion, and chlorpyrifos on the cellular energy allocation (CEA) of the predatory bug, Andrallus spinidens Fabricius (Hemiptera: Pentatomidae), a potential biological control agent, was studied on 5th-instar nymphs. Among the energy reserves of the A. spinidens nymphs, only total protein was significantly affected by pesticide treatments, and the highest value was observed in chlorpyrifos treatment. The energy available (Ea) and energy consumption (Ec) in A. spinidens were significantly affected by these pesticides. In exposed bugs, these parameters were affected by fenitrothion and chlorpyrifos more than diazinon. The activity of the electron transport system (ETS) in the Ec assay showed that A. spinidens exposed to chlorpyrifos had the highest rate of oxygen consumption. Although, there was no significant change in CEA, the insecticides caused a marked change in the physiological balance of A. spinidens. The results suggested that the adverse effect of these insecticides on A. spinidens should be considered in Integrated Pest Management (IPM) programs