Functional response and biological characteristics of Orius vicinus (Ribaut) (Hemiptera: Anthocoridae) on Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae)

Blattisocius mali (Oudemans), known as a predator of some species of storage pest mites, was reared on frozen eggs of Tyrophagus putrescentiae (Schrank) alone (Tp) but also supplemented with cattail (Tp + cattail) and olive (Tp + olive) pollen. Life table parameters of B. mali were evaluated in the first (G1), eighth (G8) and sixteenth (G16) generation on the three different diets. Survival of the immatures of the predator was not affected by the tested diets, whereas it significantly differed among generations. The highest and lowest mortality was observed in the G8 and G1 generations, respectively, on all diets. Except for the total pre-oviposition period (TPOP) and the adult pre-oviposition period (APOP), all life table parameters of B. mali were affected by the different diets; In G1, supplementation of (Tp) with both pollens significantly increased the fecundity, oviposition period and female life span of B. mali. Population growth parameters of the predator like intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase (λ) significantly increased with the supplementation of (Tp) with cattail pollen. However, in G8 and G16, B. mali reared on the two combinations significantly showed the lowest values of oviposition period, female and male life span and mean generation time (T) (only F8). Except for female and male developmental times and TPOP, other biological parameters of B. mali significantly differ across generations. Adding both pollens to the frozen eggs of the prey mite, significantly decreased fecundity, oviposition period, female and male life span and population parameters such as (r), (T), (λ) of B. mali in G16 compared with G1. With comparison of the effects of diet through the generations on biological and population parameters of B. mali, it is concluded that frozen eggs of T. putrescentiae is strongly advisable for mass-rearing of the predator and mixed frozen diets (containing pollen) is suggested as supplemental diet for establishment of the predator after release.

Bradysia odoriphaga is a major insect pest that infests Chinese chive in northern China. Clothianidin is a second-generation neonicotinoid insecticide that is commonly used against B. odoriphaga. In this study, the effect of sublethal clothianidin concentrations (LC5 and LC10) on key biological characteristics of B. odoriphaga was investigated using an age-stage, two-sex life table method. Bioassays results showed that clothianidin exhibited high toxicity against B. odoriphaga with LC50 of 1.898 mg L-1 following 24 h exposure. The developmental duration of larvae was significantly increased when exposed to the LC5 (0.209 mg L-1) and LC10 (0.340 mg L-1) of clothianidin. No significant effects were observed on the pupal stage, adult pre-oviposition period (APOP), total pre-oviposition period (TPOP), and mean longevities of male and female. The oviposition period and fecundity of B. odoriphaga were reduced in clothianidin-treated groups. Moreover, key demographic parameters, including the intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0), were significantly decreased by the LC5 and LC10 of clothianidin, while no effects were noted on mean generation time (T). Overall, this study showed that sublethal concentrations of clothianidin have a detrimental effect on B. odoriphaga developmental period, fecundity, and life table parameters. Therefore, clothianidin has the potential to suppress the population of B. odoriphaga even at sublethal concentrations.

Demographic toxicology is recommended for toxicity determination of the long term effects of a pesticide since it gives a more accurate and efficient measure of the effect of a pesticide. Thus, in the current study the sublethal effects of pirimicarb (carbamate insecticide) two concentrations of LC30and LC10were used against third instar larvae of Hippodamia variegata (Goeze) in order to determine the effects of the pesticide on demographic parameters of the predator under laboratory conditions. Results showed that pirimicarb did not affect individual life parameters such as development time of larva, pupa, adult longevity, female and male longevity, adult preoviposition period (APOP), and total preoviposition period (TPOP). However, population parameters such as intrinsic rate of increase (r), net reproductive rate (R0), mean generation time (T), and finite rate of increase (λ) was affected by sublethal treatment. For example, intrinsic rate of increase (r) was 0.18 day-1in the controls but it was 0.13 and 0.14 day-1in the treated insects with LC10and LC30concentrations, respectively. Also, there were significant differences between mean generation time (T) of the treatments and the controls i.e. mean generation time of the controls was 29.03 days while mean generation time in the two treatments of LC10and LC30was 33.93 and 31.66 days, respectively. The finite rate of increase was also significantly affected by sublethal effects of the pesticide. The results showed that pirimicarb, even at low concentrations, has potential to adversely affect the predatory ladybird, therefore care should be taken when this insecticide is used in the Integrated Pest Management (IPM) program.

Red spider mite (Tetranychus macfarlanei) is an important pest that severely infests a wide range of crops. Traditionally, chemical pesticides have been employed to control this pest, but their extensive use has led to detrimental side effects against humans including environmental contamination, non-target species destruction, and the development of pesticide-resistant mite populations. This study explores the potential of botanicals, i.e., Bishkatali (Polygonum hydropiper), Telakucha (Coccinia grandis), and Bhimraj (Wedelia chinensis) as a natural and effective solution for managing T. macfarlanei. Bhimraj exhibited more toxicity (LC50 = 1.636 mL of a.i./L) than Bishkatali (LC50 = 2.417) and Telakucha (LC50 = 2.230). Tetranychus macfarlanei were treated with LC50 doses of three botanicals and life table parameters were assessed and compared with control. Although the spider mite successfully completed their development from egg to adult, it took longer time when treated with botanicals. Adult pre-oviposition and total pre-oviposition period was significantly higher in T. macfarlanei treated with botanicals than control. The oviposition period is not significantly different, but the fecundity was higher in control. The eggs per female in T. macfarlanei was significantly reduced when treated with botanicals. The botanicals affected the life table parameters of T. macfarlanei. The net reproductive rate (R0), intrinsic rate of increase (r, day-1), finite rate of increase (λ), and gross reproduction rate (GRR) were lower in T. macfarlanei when treated with botanicals than control. The mean generation time (T, day) was higher in botanicals than control. Finally, it could be concluded that botanicals have significant negative impact on the life table parameters of T. macfarlanei, which could be incorporated into Integrated Mite Management (IMM).

BackgroundTelenomusremus Nixon is an important egg parasitoid of Spodoptera spp. pests and, as such, has potential as a biological control agent. Spodopteralitura (Fabricius) is a significant pest of many economically important crops worldwide. This study was conducted to evaluate the demographic parameters and functional response of T.remus on the S.litura eggs.ResultsT.remus can lay 186.90 eggs/female in the lifetime, adult preoviposition period was 0 days, total preoviposition period was 10.03 days, and the ratio of female and male offspring was 0.495 and 0.421, respectively. In addition, most females emerged from 24 h-old eggs, whereas most males emerged from 48 h-old eggs. The intrinsic rate of increase, finite rate of increase, net reproductive rate, mean generation time, and population doubling time were 0.3506 d–1 1.4199 d–1 92.45 offspring/individua, 12.91 days and 1.98 days, respectively. The net killing rate of T.remus on S.litura was 101.49 eggs/female, indicating the high capacity of T.remus to parasitize S.litura eggs. Moreover, the higher the egg density, the higher the parasitism rate by female T.remus, although there was a trend of parasitism stabilization at an egg density of 100, indicating a type II functional response curve for this parasitoid.ConclusionOverall, these findings suggest that T.remus can be efficiently reared on S.litura eggs and shows potential as biocontrol agent for this economically important pest species.

Simple SummaryIn many Asian countries, Henosepilachna vigintioctopunctata (F.), is seriously harmful to Solanaceae vegetables. With the popularization of green agriculture and the improvement in people’s living standards, biological pest control may become the mainstream. The artificial release of sex pheromones and other methods to delay insect mating, thus affecting population abundance, is an important part of biological control. We took H. vigintioctopunctata collected from Jingzhou, Hubei Province, China, back to the laboratory to establish an experimental population to study the effect of delayed mating on its reproductive behavior. The negative effects on reproduction and changes in population life table parameters, such as net reproductive rate, intrinsic and finite rates of increase, doubling time, and mean generation time, could be estimated by the treatment of delayed mating of males and females, which could be useful for providing important information for pest control in the future.Henosepilachna vigintioctopunctata (F.) is a serious pest of numerous solanaceous crops in many Asian countries. The purpose of this study was to clarify the effects of delayed mating on mating success, fecundity, fertility, pre-oviposition period, oviposition period, adult longevity, and population life table parameters (including net reproductive rate, intrinsic and finite rates of increase, doubling time, and mean generation time) of H. vigintioctopunctata. Beginning three days after emergence for both sexes, mating was delayed an additional 0, 2, 4, 6, or 8 days. We compared the data when mating was delayed for males only with the data when mating was similarly delayed for females only. Reproductive and life table parameters were calculated from the two data sets and compared. The results showed that the preoviposition and oviposition period of adults was significantly reduced by delayed mating, while the preoviposition period was not significantly different in adults mated at older ages. The mating success rate, fecundity, and proportion of hatching eggs decreased with increasing mating age. Longevity was not affected by the age at mating. Mating delay also affected the life table parameters of H. vigintioctopunctata, with a similar trend observed in the net reproductive rate and intrinsic and finite rates of increase, all of which decreased gradually as the number of delay days increased. The population doubling time increased with increases in mating age. The results also showed that delayed mating was an effective measure to consider in controlling H. vigintioctopunctata. It is hoped that our data will provide a scientific basis and contribute technical guidance for forecasting and integrated management of this pest.

Transgenic Bt cotton developed against lepidopteran pests may not be compatible with parasitoid of secondary pests such as Bemisia tabaci which attack many plants such as cotton. In this study, the effects of Bt cotton on the demographic parameters of Encarsia formosa, parasitoid of B. tabaci were assessed. The data were analysed using the age specific, two-sex life table parameters. The results indicated that pre-adult developmental time, the total preoviposition period (TPOP) and the adult preoviposition period (APOP) in the Bt cotton were significantly longer than in the non-Bt cotton. Also, fecundity and body size in both lines were significantly different. The fecundity was 23.64±0.73 and 43.75±0.89 eggs/females in the Bt and non-Bt cotton, respectively. All the population parameters were affected by the Bt cotton. The intrinsic rate of increase (r) was 0.15 day-1 in the non-Bt cotton but it was 0.10 day-1 in the Bt cotton. The finite rate of increase (λ) was 1.11 day-1 in the non-Bt cotton whilst it was 1.08 in the Bt cotton. The net reproductive rate (R0) in the non-Bt cotton was 36.75 but in the Bt cotton these parameters showed 19.62 offspring/individual. Also, the mean generation time (T ) in the non-Bt and Bt cotton was 22.69 and 27.79 days, respectively. The results illustrated, that although transgenic crops are effective tools for management of the target pests, they can adversely affect, either directly or indirectly, the natural enemies dependent on these plants.

Spodoptera frugiperda (J.E. Smith) is an invasive and key pest of maize, which has been recently introduced to South India. There are two strains reported, viz. rice strain and maize strain. Though several diets were tried in different parts of the world, none of them contained rice leaf powder as a component from natural host. Hence a study was conducted to evaluate the biology, nutritional indices, age-stage and two-sex life table to assess the suitability of the different artificial diets for S. frugiperda larval development. Six differently modified artificial diets were tested to evaluate the following biological parameters: duration of larva and pupae, survival of larvae and pupae, pupal weight, sex ratio, fecundity, adult pre-oviposition period, total pre-oviposition period, adult longevity and total lifespan. The following nutritional indices were determined: growth rate, relative growth rate, consumption rate, consumption index, approximate digestibility, efficiency of conversion of ingested food, efficiency of conversion of digested food and metabolic cost. Larval development showed a significant difference among the diets, in relation to the life table parameters. The results indicated that optimal growth, development and food utilisation by S. frugiperda occurred in the mixture of rice leaf powder and chickpea flour-based diet followed by the mixture of maize leaf powder and common bean powder-based diet. Evaluated diets also had a significant effect on the net reproductive rate, gross reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and population doubling time. The values of these parameters were higher in the mixture of rice leaf powder and chickpea flour-based diet followed by mixture of maize leaf powder and common bean powder-based diet. Based on the results, the most adequate diet for rearing in the laboratory was the mixture of rice leaf powder and chickpea flour-based diet.

BackgroundThe predatory mite, Blattisocius mali Oudemans (Mesostigmata: Blattisociidae), feeds on various species of storage mites such as Tyrophagous putresentiae (Schrank). In this study, life table parameters and consumption rates of B. mali were determined when fed on the eggs and larvae of T. putrescentiae as the prey under laboratory conditions.ResultsBased on the age-stage two-sex life table analysis, the total pre-ovipositional period (TPOP) of the predator was considerably lower by feeding on host larvae than that on eggs. Also, mean fecundity (eggs/female) of the B. mali was 2.60-fold higher on host larvae than its eggs. Moreover, the intrinsic rate of increase (r), as the most important parameter was 0.272 and 0.357 day−1, respectively, by host mite eggs and larvae as food. This showed the significantly greater influence of T. putrescentiae larvae than eggs on mass production of the predatory mite. The same trend was observed in finite rate of increase (λ), net reproductive rate (R0), gross reproductive rate. But mean generation times (T) were statistically the same by feeding both host stages. Maximum longevity of male and female individuals was, respectively, 21 and 22 days when eggs were fed. By feeding on larvae as prey, maximum longevity was lowered to 20 days in both predator sexes. However, the net predation rate (C0) and transformation rate from prey population to predator offspring (QP) were significantly higher by feeding on host eggs (97.420 and 3.049) than its larvae (41.3936 and 0.5575), respectively.ConclusionFrom practical biocontrol view, both eggs and larvae of T. putrescentiae can be consumed and therefore controlled by the predatory mite, B. mali. From mass production view, larvae of T. putrescentiae produced a better fitness in the predatory mite than its eggs and can be used in augmentation programs of B. mali.

The effects of milbemectin and spirodiclofen resistance on Phytoseiulus persimilis A.[sbnd]H. (Acari:Phytoseiidae) life table parameters

The small brown planthopper (Laodelphax striatellus (Fallén), Hemiptera: Delphacidae), is an important agricultural pest of rice, and neonicotinoid insecticides are commonly used for controlling L. striatellus. However, the sublethal effects of thiamethoxam on L. striatellus remain relatively unknown. In this study, an age-stage life table procedure was used to evaluate the sublethal effects of thiamethoxam on the biological parameters of L. striatellus. Additionally, activities of carboxylesterase, glutathione S-transferase, and cytochrome P450 monooxygenase in the third instar nymphs were analyzed. The results indicated that the survival time of F0 adults and the fecundity of female adults decreased significantly after the third instar nymphs were treated with sublethal concentrations of thiamethoxam (LC15 0.428 mg/liter and LC30 0.820 mg/liter). The developmental duration, adult preoviposition period, total preoviposition period, and mean generation time of the F1 generation increased significantly, whereas the fecundity of the female adults, intrinsic rate of increase (ri), and finite rate of increase (λ) decreased significantly. The oviposition period was significantly shorter for the insects treated with LC30 than for the control insects. Neither sublethal concentrations had significant effects on the adult longevity, net reproduction rate (R0), or gross reproduction rate (GRR) of the F1 generation. The activities of carboxylesterase, glutathione-S-transferase, and cytochrome P450 monooxygenase increased significantly after the thiamethoxam treatments. These results indicate that sublethal concentrations of thiamethoxam can inhibit L. striatellus population growth and enhance detoxification enzyme activities.

Sulfoxaflor is a novel insecticide belonging to sulfoximine chemical class that can be used to control sap-feeding insects, notably Aphis gossypii Glover. In addition to its acute toxicity, it is also important to consider the possible sublethal effects when establishing a comprehensive understanding of the toxicity of a new insecticide. We assessed the effects of a low lethal concentration (LC25) of sulfoxaflor on biological parameters of A. gossypii adults (F0) and subsequent transgenerational effects, i.e., on the progeny (F1 generation). The data were analyzed using an age-stage life table procedure. The results showed that the longevity and fecundity were not significantly affected by the LC25 of sulfoxaflor in the F0 or F1 generations. In addition, no significant differences were observed on the developmental time of each instar, the adult pre-oviposition period, and on the longevity of F1 individuals. However, the duration of their pre-adult stage and total pre-oviposition period, as well as their mean generation time were significantly increased. These observed effects affected aphid demographic traits; the survival rate, the intrinsic rate of increase (r i ), the finite rate of increase (λ), the net reproductive rate (R0), and the gross reproduction rate (GRR) of the F1 individuals (i.e., from F0 mothers) were significantly lower compared to the control. Our results showed that sublethal effects of sulfoxaflor significantly slowed down A. gossypii population growth; they indicated that effects of sulfoxaflor might be increased (beyond lethal effect) through sublethal effects when concentrations decreased in sulfoxaflor-treated areas after initial application in field.

Sublethal effects of sulfoxaflor on the development and reproduction of the brown planthopper, Nilaparvata lugens (Stål)

Host plant resistance to insects: By N. Panda and G.S. Khush. ISBN 0 85198 963 2. CAB International, Wallingford, UK, 1995. xii+431 pp. Hard-cover £55

Athetis dissimilis (Hampson) has emerged as a serious pest on corn in recent years in China. Understanding the population response of A. dissimilis to temperature will be beneficial for adopting control strategies for this pest. The impact of five constant temperatures (17, 21, 25, 29, and 33 °C) on the life table of A. dissimilis was studied using age-stage, two-sex life table method in the laboratory. The results showed that the developmental time of egg, larva, pupa, and adult decreased when temperature increased from 17 °C to 33 °C. The TPOP (total preoviposition period) decreased with temperature increasing from 17 °C to 29 °C, while the longest APOP (adult preoviposition period) occurred at 21 °C (3.57 d) and the shortest at 33 °C (2.15 d). The fecundity increased from 407.52 to 763.94 eggs as temperatures were raised from 17 to 25 °C, but decreased at temperatures from 25 °C to 33 °C. The intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) increased as temperatures increased from 17 to 25 °C, then decreased when temperatures exceeded 25 °C. In contrast, the mean generation time (T) decreased as temperatures increased from 17 to 33 °C. Based on the estimated data, the highest female age-stage-specific fecundity (fx) and age-specific fecundity (mx) were 81.91 and 45.04 eggs, respectively, at 25 °C. The age-stage life expectancy (exj) of all stages decreased as the temperature increased. The reproductive value (vxj) increased gradually with age and stage. The developmental rates of A. dissimilis between 17 to 29 °C fit the linear equation y = -0.01315 + 0.001303x, with a coefficient of determination (R2) of 0.9314. In conclusion, our finding clearly states that A. dissimilis has the greatest population increase at 25 °C, and this may help develop appropriate pest management strategies.