Pre-adult Development Time Research Articles

Effects of Elevated CO2 on the Fitness Parameters of Individually- and Group-Reared Agasicles hygrophila (Coleoptera: Chrysomelidae).

Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae) is a natural enemy of Alternanthera philoxeroides (Mart.) Griseb (Amaranthaceae: Alternanthera), a worldwide invasive weed. Elevated atmospheric CO2 concentrations may have significant impacts plants, herbivorous insects, and natural enemies. To assess the concurrent effect of elevated CO2 on the development time, fecundity, and population parameters of A. hygrophila, the age-stage, two-sex life table was used to understand the fitness and population parameters of individually-reared and group-reared A. hygrophila under elevated CO2 concentration. In individually-reared population, the development time of preadults, adult pre-oviposition period, and total pre-oviposition period of A. hygrophila in the elevated CO2 (eCO2, 750 ppm) treatment were shorter than those in the ambient CO2 (aCO2, 420 ppm) treatment. In group-reared population, the developmental time of preadults, female adult longevity, female proportion, adult pre-oviposition period, and total pre-oviposition period of A. hygrophila in eCO2 were longer than those in aCO2. Additionally, in both individually-reared and group-reared population, fecundity and oviposition days of A. hygrophila in eCO2 were higher than those in aCO2, and a higher intrinsic rate of increase, finite rate of increase, and the net reproductive rate of A. hygrophila were observed at eCO2. Moreover, shorter preadult development time, adult pre-oviposition period, total pre-oviposition period, male adult longevity, and higher fecundity were found in group-reared cohort at both aCO2 and eCO2. The results indicates that elevated CO2 has effects on the growth and reproduction of A. hygrophila, and the population growth rate of group-reared was faster and produced more offspring.

Evaluation of Hemp (Cannabis sativa) (Rosales: Cannabaceae) as an Alternative Host Plant for Polyphagous Noctuid Pests.

Hemp (Cannabis sativa L.) is a reemerging crop in the United States with increasing outdoor acreage in many states. This crop offers a potential host for polyphagous, defoliating lepidopteran pests currently present in Louisiana. The ability of soybean looper [Chrysodeixis includens (Walker)] (Lepidoptera: Noctuidae), fall armyworm [Spodoptera frugiperda (J.E. Smith)] (Lepidoptera: Noctuidae), and beet armyworm [Spodoptera exigua (Hübner)] to develop and reproduce on hemp was investigated in this study. Insects were reared on two hemp varieties, Maverick and Pipeline, as well as documented host plants soybean [Glycine max (L.) Merr.] (Fabales: Fabaceae) variety UA5414RR and cowpea [Vigna unguiculata (L.)] (Fabales: Fabaceae) variety Quickpick Pinkeye. Larvae of all three species reared on 'Maverick' had significantly faster preadult developmental times compared to the other hosts. Chrysodeixis includens larvae fed excised leaves of 'Maverick' and 'Pipeline' experienced higher intrinsic and finite rates of increase, higher net reproductive rates, and faster mean generation and doubling times. Spodoptera frugiperda larvae reared on 'Maverick', 'Pipeline', and 'UA5414RR' had higher intrinsic and finite rates of increase, higher net reproductive rates, and faster mean generation and doubling times compared to 'Quickpick Pinkeye'. Spodoptera exigua larvae had the highest survivorship on 'Maverick' and similar, positive lifetable statistics when reared on 'Maverick' and 'Pipeline'. The results of this study indicate hemp is an alternative host plant that has the potential to influence the population dynamics of C. includens, S. frugiperda, and S. exigua in Louisiana agroecosystems they co-occur in.

Meet Me Halfway: Will Photoperiodic Responses of Interpopulation Hybrids of the Brown Marmorated Stink Bug Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae) Promote or Constrain Subsequent Invasions?

Biological invasions often result from multiple invasion events. In the case of several subsequent invasive episodes, ‘newcomers’ are usually poorly adapted to local environmental conditions in contrast to the representatives of the already-established invasive population of the same species. Therefore, the mode of inheritance of life-history features determining the survival and performance of interpopulation hybrids is an important component of invasiveness. We investigated the mode of inheritance of the photoperiodic response in the brown marmorated stink bug, Halyomorpha halys, by crossing between the native population of South Korea and the invasive population of the Black Sea coast of Russia. The aim of this study was to predict the overwintering potential of the progeny from possible crosses between representatives of the native and invasive populations. The pre-adult development time and the incidence of winter adult diapause in the progeny of the interpopulation crosses were close to the average of the values recorded in ‘pure’ (unmixed) crosses. Female and male genotypes were equally important in the determination of these characters. Such a mode of inheritance is most likely determined by a polygenic control and would only partially promote subsequent invasion events from the native South Asian range of H. halys into Europe.

The effects of storage temperature, food, and humidity on survival and progeny of Neoseiulus bicaudus

AbstractNeoseiulus bicaudus Wainstein (Acari: Phytoseiidae) is a beneficial predatory mite to control spider mites. To evaluate the suitable storage conditions of N. bicaudus, the survival of adult females was observed under different combinations of low temperature (3, 6, 9, or 12°C), food (F) or no food (NF), and high (H) or low (L) humidity conditions for 7, 14, 21, 28, and 35 d. Predator mites’ longevity and survival time of 50% and 80% individuals (ST50,80) were measured and compared between treatments. After storage, female and male living mites were paired at 26°C. The progeny parameters were evaluated after storage. Results revealed that survival rate decreased as storage temperature decreased. At 3 and 6°C, fewer mites survived after 28 d. At 9°C, ~50% of the females survived in the FH treatment after 35 d. At 12°C, >80% survived 7–35 d in the FH treatment. Moreover, longevity and ST50,80 were significantly greater in the FH treatment than in the FL or NFH treatments at 3, 9, and 12°C. The highest longevity (48.6 ± 3.7 d) and ST50 (51.6 d) occurred at 12°C in the FH treatment. There was no effect on progeny hatching or survival rates when adults were stored at 9 or 12°C for 28 d. At 9°C, the total preadult development time was 4.20–5.25 d. At 12°C, the total development time was 4.87–4.93 d and there was no significant difference between the storage treatment and control group. These results demonstrated that N. bicaudus females can be successfully stored at 9°C for ~21 d and 12°C for ~28 d with little effect on adult survival or progeny parameters.

Evolution of reproductive traits have no apparent life-history associated cost in populations of Drosophila melanogaster selected for cold shock resistance

BackgroundIn insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits. Adaptation to cold stress can, in principle, involve modification of reproductive traits and physiological responses. Reproductive traits carry a substantial cost; and therefore, the evolution of reproductive traits in response to cold stress could potentially lead to trade-offs with other life-history traits. We have successfully selected replicate populations of Drosophila melanogaster for increased resistance to cold shock for over 33 generations. In these populations, the ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection. These populations have evolved a suite of reproductive traits including increased egg viability, male mating ability, and siring ability post cold shock. These populations also show elevated mating rate both with and without cold shock. In the present study, we quantified a suite of life-history related traits in these populations to assess if evolution of cold shock resistance in these populations comes at a cost of other life-history traits.ResultsTo assess life-history cost, we measured egg viability, mating frequency, longevity, lifetime fecundity, adult mortality, larva to adult development time, larvae to adults survival, and body weight in the cold shock selected populations and their controls under two treatments (a) post cold chock and (b) without cold shock. Twenty-four hours post cold shock, the selected population had significantly higher egg viability and mating frequency compared to control populations indicating that they have higher cold shock resistance. Selected populations had significantly longer pre-adult development time compared to their control populations. Females from the selected populations had higher body weight compared to their control populations. However, we did not find any significant difference between the selected and control populations in longevity, lifetime fecundity, adult mortality, larvae to adults survival, and male body weight under the cold chock or no cold shock treatments.ConclusionsThese findings suggest that cold shock selected populations have evolved higher mating frequency and egg viability. However, there is no apparent life-history associated cost with the evolution of egg viability and reproductive performances under the cold stress condition.

Age-stage two-sex life table analysis of Eristalinus aeneus (Diptera, Syrphidae) reared with two different larval media.

Eristalinus aeneus (Scopoli, 1763) is a suitable candidate for artificial rearing due to its pollination efficiency and subcosmopolitan distribution. However, the high mortality found at the larval stage of this species needs to be overcome. In this research, two different larval media were used to study the life cycle of E. aeneus: brewery spent grain (BSG) from a local craft-beer factory and soaked oat grains (SOG). The age-stage, two-sex life table method was used to analyze the results, which were compared using the paired bootstrap test. The greatest mortality was found at the larval stage with both media. Individuals fed on SOG presented a shorter preadult developmental time (22.05 days) than those reared with BSG (26.97 days). This fact had a direct impact on the total preoviposition period, it being shorter with SOG (34.36 days) than BSG (38.29 days), although the second provided a larger total number of eggs (19,242 eggs) and a faster adult maturation (10.67 days). The population parameters indicated that both populations will display a positive growth under the studied conditions, being the mean generation time (T) significantly shorter when using SOG (38.71 days) than BSG (45.95 days). Despite the preadult results pointing to SOG being a more efficient medium, the promising fecundity values provided by BSG, as well as it's lower cost and ecological benefits, suggest that this second medium could be improved and used as an alternative to SOG in the near future.

Sublethal and transgenerational effects of afidopyropen on biological traits of the green peach aphid Myzus persicae (Sluzer)

The green peach aphid, Myzus persicae (Sulzer), is a cosmopolitan agricultural pest and causes great damages each year. Afidopyropen is a novel insecticide with high efficacy against even the insecticides resistant M. persicae. However, the sublethal and transgenerational effects of afidopyropen on M. persicae is not clear. In the present paper, sublethal and transgenerational effects of afidopyropen on biological traits of M. persicae were determined based on the age-stage, two-sex life table theory. The afidopyropen was more toxic against M. persicae than other widely used insecticides, with LC50 of 0.086 mg/L. The treatment with LC5, LC15 and LC25 concentrations of afidopyropen remarkably reduced the longevity and fecundity of F0M. persicae by 15.9–64.4% and 24.3–76.7%, respectively, compared with those of the control. The life history traits of F1 generation including the pre-adult development time, mean total longevity, pre-adult survival rate, total pre-oviposition period and fecundity were significantly affected after treatment of the F0 with afidopyropen, and the population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) were also remarkably decreased, while the mean generation time (T) was extended by 6.94%. Among four development and reproduction related genes investigated, JHEH was downregulated by 31.8–38.0% in the afidopyropen treated F0 generation, while the EcR and JHAMT were overexpressed and the Vg was significantly downregulated in F1 generation compared to the control group. All these data indicated that the afidopyropen had significant sublethal and transgenerational effects on M. persicae. These results provide insights into comprehensively understanding of the insecticidal effects of afidopyropen on M. persicae as well as the management of resistant M. persicae.

Impact of maternal age on performance of the progeny in Galleria mellonella (L., 1758) (Lepidoptera: Pyralidae)

Maternal age is the age of an insect at the time of depositing an egg and is an important factor impacting on the properties of the progeny. This study determined the influence of maternal age on the preadult total development time, larval development time, pupal development time, pupal weight and adult longevity of Galleria mellonella (L., 1758) (Lepidoptera: Pyralidae). This study was conducted in 2018 in the Biology Laboratory of Science Teaching, Sinop University. The insects were grouped into four groups (1, 5, 10 and 15 d-old) and they were kept under laboratory conditions (28 ± 2°C and 65 ± 5% RH and continuous darkness). Larval development time, total preadult development time and longevity decreased with maternal age whereas pupal development time increased. Although the development time of the progeny of younger females lasted longer, total longevity increased. Although, the progeny of younger females had increased longevity, progeny of older females was advantaged in terms of development time.

Effects of prolonged mass rearing on life history traits of Habrobracon hebetor (Hymenoptera: Braconidae)

Long-term mass rearing of parasitoids under laboratory conditions may affect their quality. We studied the quality of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) reared for more than 20 generations (G) using two-sex life table parameters. We found that G2 had the longest pre-adult development time (12.4 d) and the highest fecundity (1304.00 eggs/female) compared with the other generations. While no significant differences in the intrinsic rate of increase (r) and net reproductive rate (R 0) were found among G4, G6, G8, G15, and G20, the highest values of r (0.3273 day−1) and R 0 (436.28 eggs/individual) as well as the shortest mean generation time (T) were observed in G10. In addition, significant differences in sex ratio (F/F + M) were observed among different generations, ranging from 17% in G2 to 60% in G10. These results suggest that up to a certain number of generations (G10), the quality of H. hebetor significantly increased without adding field-collected parasitoids or changing the factitious host. To maintain the quality of the colony beyond this point, it should be rejuvenated by periodically adding field-collected individuals.

Effect of Temperature on Life History and Parasitization Behavior of Trichogramma achaeae Nagaraja and Nagarkatti (Hym.: Trichogrammatidae).

Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) is currently used as biological control agent for several lepidopteran pests. Knowledge of thermal requirements is essential to optimize its rearing procedures and inundative releases. The biological characteristics and two-sex life table parameters of T. achaeae were determined at five constant temperatures (15, 20, 25, 30, and 35 °C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. T. achaeae was able to develop and survive from 15 °C to 30 °C, but not at 35 °C. Temperature significantly affected the preadult development time and adult longevity, decreasing when temperature increased from 15 °C to 30 °C. Temperature significantly altered the sex ratio, being female biased between 15 °C and 25 °C. Age-stage, two-sex life table analysis indicated that net reproductive rate (R0) was highest at 20 °C. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased with increasing temperature, while the mean generation time (T) decreased significantly. In addition, functional response of T. achaeae was studied, being significantly affected by temperature and host egg density, displaying a Holling type-I at 15 °C and a Holling type-II at 25 °C. The relevance of these results is discussed for the use of T. achaeae as biological control agent.

Fotoperiyodun Acanthoscelides obtectus Say (Coleoptera: Bruchidae)’un gelişim süresi, eşey oranı ve verimine etkisi

In the trials, the influence of photoperiod on the development time, sex ratio, and fecundity of Acanthoscelides obtectus were examined. The trials were carried out in five different photoperiod regimes including 0L:24D [continuous darkness (CD)], 6L:18D (6 hours of light, 18 hours of dark), 12L:12D (12 hours of light, 12 hours of dark), 18L:6D (18 hours of light, 6 hours of dark), 24L:0D [continuous light (CL)] with a temperature of 25±2 ºC and 60±5% relative humidity. The shortest pre-adult development time was determined under CD conditions. While the development period lasted 26.33±0.88 days under CD conditions, it lasted for 35.33±0.66 days under CL conditions. Although the sex ratio did not differ much, CL conditions were in favor of males. The lowest female fecundity was determined under CL and 18L:6D conditions. Fecundity did not differ significantly under CD and 6L:18D, while it decreased significantly under 12L:12D, 18L:6D, and CL conditions. Especially, when CL and CD were compared with each other, statistically significant difference was observed.

Age-Stage, Two-Sex Life Tables of Anthocoris minki pistaciae (Hemiptera: Anthocoridae) Reared on Agonoscena pistaciae (Hemiptera: Aphalaridae) at Three Constant Temperatures

Agonoscena pistaciae Burckhardt & Lauterer (Hemiptera: Aphalaridae) is the most important pest of pistachio trees in Iran and the world. Anthocoris minki pistaciae Wagner (Hemiptera: Anthocoridae) is a predator of A. pistaciae. Biological characteristics of this predatory bug were determined at three constant temperatures (17, 26 and 30 ± 2°C), 55 ± 5% R.H., and a photoperiod of 16:8 h (L:D). Data were analyzed by age-stage, two-sex life table to assess the variable developmental rates. Pre-adult developmental time of this predator at 17, 26 and 30°C were 24.5, 15.2 and 14.2 d, respectively. Adult longevities were 61.8, 51.9 and 43.7 d for males, and 60.3, 49.2 and 43 d for females at 17, 26 and 30°C, respectively. Fecundity at 17, 26 and 30°C were 50.3, 51.9 and 41.6 eggs/female, respectively. Intrinsic rates of increase (r) were 0.0707, 0.1042 and 0.1102 d–1 at 17, 26 and 30°C, respectively. The mean generation time (T) was 27.3 d (the shortest time) at 30°C and 42 d (the longest time) at 17°C. The net reproductive rate (R0), the age-stage-specific fecundity (fxj), age-specific fecundity (mx) and age-specific maternity (lxmx) at 26°C were higher than those at 17 and 30°C. This research suggests that this predator can retain higher population densities at 26°C than at the other temperatures tested. Results of this study provide the biological basis for using A. minki pistaciae in a biological control program against A. pistaciae in pistachio orchards.

Temperature-Dependent Demography and Population Projection of Tamarixia radiata (Hymenoptera: Eulophidea) reared on Diaphorina citri (Hemiptera: Liviidae).

Tamarixia radiata Waterson (Hymenoptera: Eulophidea) is the principal natural enemy used for the control of the major citrus pest Diaphorina citri Kuwayama (Hemiptera: Liviidae). In this study, we collected the life-history data of T. radiata at four different temperatures (20, 27.5, 30, and 35°C) and analyzed them by using the age-stage, two-sex life table. The longest preadult developmental time (16.53 d) was observed at 20°C, whereas the shortest one was 7.29 d at 35°C. The preadult development rate was well-fitted to a linear equation. The lower threshold temperature (T0) was 7.85°C and the thermal summation (K) was 193.36 degree-day. The highest fecundity (F) was 322.7 eggs per female was at 27.5°C, whereas the lowest one was 10.8 eggs per female at 35°C. The net reproductive rate (R0) were 70.97, 169.42, 55.70, and 3.25 offspring at 20, 27.5, 30, and 35°C, respectively; the intrinsic rate of increase (r) were 0.1401, 0.3167, 0.3517, and 0.1143 d-1, respectively. The highest values of fecundity, net reproductive rate, intrinsic rate of increase, and finite rate of increase were observed at 27.5°C. The relationships among F, R0, Nf, and N in all treatments were consistent with R0=F×(Nf/N). The age of peak reproductive value was close to the total preoviposition period in all treatments. Population projections based on the age-stage, two-sex life table showed the dynamics of stage structure and its variability. Faster population growth was observed at 27.5 and 30°C.

Productivity of Neoseiulus bicaudus (Acari: Phytoseiidae) Reared on Natural Prey, Alternative Prey, and Artificial Diet.

The predatory mite, Neoseiulus bicaudus (Wainstein), is a potential biological control agent against spider mites and thrips. The objective of this experiment was to compare the effects of three diets on the life table of N. bicaudus. The three diets were 1) Tetranychus turkestani (Ugarov & Nikolskii) (Acari: Tetranychidae), the natural prey of N. bicaudus; 2) Tyrophagus putrescentiae (Schrank) (Acari: Acaridae), an alternative prey; and 3) artificial diet primarily consisting of decapsulated shrimp cysts, egg yolk, and honey. The computer simulation was used to project the population growth of N. bicaudus fed on different diets. The preadult developmental time (3.83 d) of N. bicaudus was shortest, and the intrinsic rate of increase (r = 0.2782 d-1) and the net reproductive rate (R0 = 18.98 offspring) were highest when reared on the alternative prey Ty. putrescentiae. The total development time (7.37 d) was longest, and the population parameters were the lowest (r = -0.0081 d-1, R0 = 0.85 offspring) when N. bicaudus was reared on artificial diet. The population projection showed that the population of N. bicaudus reared on Ty. putrescentiae could increase fast. Our results showed that the Ty. putrescentiae was the most suitable prey for mass rearing of N. bicaudus. The artificial diet could not support the N. bicaudus population and needs to be improved.

Direct and correlated responses to bi-directional selection on pre-adult development time in Drosophila montana

Selection experiments offer an efficient way to study the evolvability of traits that play an important role in insects’ reproduction and/or survival and to trace correlations and trade-offs between them. We have exercised bi-directional selection on Drosophila montana flies’ pre-adult development time under constant light and temperature conditions for 10 generations and traced the indirect effects of this selection on females’ diapause induction under different day lengths, as well as on the body weight and cold tolerance of both sexes. Overall, selection was successful towards slow, but not towards fast development. However, all fast selection line replicates showed at the end of selection increased variance in females’ photoperiodic diapause response and about one hour increase in the critical day (CDL), where more than 50% of emerging females enter diapause. Indirect effects of selection on flies’ body weight and cold-tolerance were less clear, as the flies of the slow selection line were significantly heavier and less cold-tolerant than the control line flies after five generations of selection, but lighter and more cold-tolerant at the end of selection. Changes in females’ diapause induction resulting from selection for fast development could be due to common metabolic pathways underlying these traits, collaboration of circadian clock and photoperiodic timer and/or by the interaction between the endocrine and circadian systems.

Geographical variation in life-history traits suggests an environmental-dependent trade-off between juvenile growth rate and adult lifespan in a moth.

Life-history theory predicts a trade-off between the juvenile growth rate and adult traits related to survival. However, this hypothesized negative correlation is difficult to test robustly because many trade-offs are mild, and environmental variables, such as changes in nutrient availability, can ameliorate the trade-off or make it more pronounced. Thus, it is reasonable to expect that the expression of the trade-off can be condition-dependent. In the present study, we first examined the pre-adult life-history traits of the cotton bollworm, Helicoverpa armigera, collected from northern, central, and southern China at different temperatures. We found that the northern China population has a significantly shorter pre-adult developmental time and higher growth rate than the southern China population as a result of adaptation to the decreased seasonal length. Then, we tested for a trade-off between the juvenile growth rate and adult lifespan in different temperature and nutrient conditions. We found a negative relationship between juvenile growth rate and adult lifespan under starvation or desiccation conditions; however, a continuous supply of sugar can diminish or obviate the apparent negative relationship, in which the adult lifespan did not show a significant difference in most of the comparisons. These results suggested a resource-mediated trade-off may exist between juvenile growth rate and adult lifespan. However, the adult size may have some positive effect on the lifespan under starvation and desiccation conditions, which may affect the expression of trade-off.

Toxicity and Sublethal Effects of Selected Insecticides on Life Parameters ofEncarsia formosa(Hymenoptera: Aphelinidae), a Parasitoid ofTrialeurodes vaporariorum(Hemiptera: Aleyrodidae)

Abstract The sublethal effects of buprofezin, abamectin, and a plant-derived extract from aerial portions of Echinophora platyloba DC (Umbelliferae) on the mortality, developmental time, adult longevity, and fecundity of the parasitoid Encarsia formosa Gahan were studied. Laboratory bioassays determined that the median lethal concentrations (LC50) of abamectin, buprofezin, and the Echinophora platyloba extract were 724.2, 1,202.9, and 894.4 mg/l for larvae, 971.4, 1,380.2, and 1,287.0 mg/l for pupae, and 306.2, 3,309.1, and 831.7 mg/l for adults, respectively. Preadult development time was reduced following exposure to sublethal concentrations (LC30) of all insecticides (P 0.05). However, ...

Biology, natural enemies and damage of the sugarcane whitefly (Neomaskellia andropogonis) (Homoptera: Aleyrodidae) in Iran

AbstractAn outbreak of the sugarcane whitefly (Neomaskellia andropogonis Corbett) recently occurred in sugarcane fields in Khuzestan Province of Iran. This pest sucks plant sap producing large amounts of honeydew. In Khuzestan Province, populations of all developmental stages increase from early August until late November. At this time, when sugarcane is at the ripening stage, nymphs suck the sap, and in cases of severe infestation, retard the growth of sugarcane plants. In this study, we investigated the biology of the pest on different cultivars of sugarcane and under different temperatures. Also, we conducted experiments to determine the damage caused by the pest in the field. Mean pre-adult developmental times were 24.09, 28.06, 27.27 and 26.64 days on CP69-1062, CP57-1062, CP48-103 and NCO-310 cultivars, respectively, and only female progeny were produced. Mean longevity of females on the four cultivars was 6, 8.49, 4.15 and 4.60 days, respectively. Adult females laid an average of 61.80, 58.80, 41.10 and 39.38 eggs on the four cultivars, respectively. Results show that the optimum temperature for development of different stages of N. andropogonis is 30±1°C during the day and 25±1°C at night, and at this temperature, egg and nymphal duration (including first, second, third instars and pupae) and adult longevity were 6.2, 17.0 and 7.6 days, respectively. Females of cultivar CP69-1062 laid an average of 50.09 eggs. Analysis of data on the quality of damage (including Brix, pol and refined sugar factors) shows that damage was inversely and significantly correlated with the number of infested leaves. Whitefly damage differed among cultivars; and, based on the quality of damage, early maturing cultivars were more susceptible to whitefly damage. We collected two parasitoid wasps from nymphs—Encarsia inaron (Walker) (Hym.: Aphelinidae) and Eretmocerus delhiensis Mani (Hym.: Aphelinidae). To the best of our knowledge, this is the first study to assess the biology, damage and natural enemies of N. andropogonis on sugarcane in Iran.

The effect of some cucumber cultivars on the biology of Aphis gossypii Glover (Hemiptera: Aphididae)

The development, reproduction, and population growth parameters of cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), were studied on three different Cucumis sativus cultivars (Beith Alpha Balikesir, B.T. Bursaalpha, Beith Alpha MR,) under controlled conditions (25 ± 1 °C, 65 ± 5% RH, and a photoperiod of 16:8 (L:D) h. Life table parameters were estimated according to age-stage, two-sex life table method. Results indicated that the Bt Balikesir are favorable hosts for A. gossypii because of the shorter preadult developmental time, lower preadult mortality rate, and higher total fecundity on this cultivar. The intrinsic rate of increase (r = 0.4214 d-1), the net reproduction rate (R0 = 51.80 offspring), and the finite rate of increase (λ = 1.5242 d-1) values were higher on the Bt Balikesir. The effect of cucumber cultivars on the biology of A. gossypii was determined as significant and it was found that cv. Bt Balikesir was the most convenient cucumber cultivar in terms of the life cycle of A. gossypii. For an ecological and economic pest control, against aphids use of resistant or less favourable crop cultivars is considered one of the important components of integrated pest management. Therefore, results acquired might be used in pest management program that will be prepared for this aphid.

Demographic Parameters of Lipaphis erysimi (Hemiptera: Aphididae) on Different Cultivars of Brassica Vegetables.

Demographic parameters of the turnip aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae), which is a serious pest of Brassica crops worldwide, were evaluated on five major Brassica vegetables (three varieties of Brassica oleraceae (Linnaeus) (Brassicaceae: Brassicales); kohlrabi, cabbage and ornamental cabbage, and two subspecies of Brassica rapa (Linnaeus) (Brassicaceae: Brassicales); Chinese cabbage and bak choi). The study was carried out under laboratory conditions at 25 ± 1°C, 70 ± 5% RH and 16:8 (L:D) h. Preadult developmental time, survival rate, female longevity, reproduction, and life table parameters were evaluated according to the age-stage specific life table method. The highest population growth parameters, i.e., net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were recorded on kohlrabi (R0 = 30.45 offspring, r = 0.2174 d-1, λ = 1.2429 d-1). These parameters were the lowest on Chinese cabbage (R0 = 13.00 offspring, r = 0.1503 d-1, and λ = 1.1621 d-1) and bak choi (R0 = 16.30 offspring, r = 0.1614 d-1, λ = 1.1752 d-1). The results attained from population growth parameters, together with population projection estimation based on the age-stage, two-sex life table theory, indicated that both Chinese cabbage and bak choi were less suitable hosts for turnip aphids and should be considered as a possible source for developing resistance in breeding programs and integrated pest management strategies.