Pupal Survival Research Articles

Ecology of outbreak populations of the western spruce budworm

AbstractWe sampled outbreak populations of western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae), between 1997 and 2016 in Douglas‐fir forests in the interior of British Columbia, Canada. Annual rates of change in population densities were correlated with generation survival, modulated by egg recruitment via dispersal of moths. Most temporal variation in generation survival was the result of variation in survival of small, non‐feeding larval stages. Survival rates of feeding larval and pupal stages determined the magnitude of generation survival but contributed little to temporal trend. Survival of small larvae was the product of density‐related losses of larvae dispersing to and from hibernation sites and weather‐related stress caused by warm temperatures in late summer and early spring. Overwinter survival improved in cooler years and at higher elevations. Survival of feeding larvae and pupae was associated with mortality by natural enemies, in particular a few species of dominant, ubiquitous endoparasitoids, and an episodic, virulent baculovirus. Recruitment of eggs indicated emigration of gravid moths independent of defoliation but proportional to density of local moths. During periods of increasing and decreasing population densities over a large outbreak area, a marked differential in adult densities among locations resulted in greater than expected per‐capita egg recruitment to areas of relatively low density and vice versa, indicative of net exchange of gravid moths from high‐ to low‐density populations. The result was homogenization of egg densities among locations, apparent synchrony of the outbreak at the large scale, and extended duration of the outbreak at some locations, despite declining generation survival. These results are compared with field studies of the closely related spruce budworm, Choristoneura fumiferana. We suggest our interpretation applies more generally and outbreaks of conifer‐feeding budworms are maintained for several years by compensatory survival of sequential life‐history stages and spatio‐temporal smoothing of densities via dispersal of gravid moths. Parasitoids and pathogens can cause sudden declines in densities, but populations inevitably wane as a result of cumulative degradation of their resource. The interaction and temporal sequence of bottom‐up and top‐down factors explain the similarities and differences in outbreak characteristics within‐ and among‐budworm species.

Climatic and edaphic characteristics constrain the distribution of the quarantine pestAnastrepha grandis

AbstractThe South American cucurbit fruit fly,Anastrepha grandis(Macquart) (Diptera: Tephritidae), is an economically important pest of cucurbits and is classified as a quarantine species in many countries. In Brazil,A. grandishas a limited distribution; it is absent from northern and northeastern Brazil and distributed discontinuously in other parts of the country. To indirectly evaluate the influence of climatic and edaphic variables on the occurrence ofA. grandis, we used data based on 4 years of cucurbit fruit collections from all mesoregions of the state of São Paulo. Our results show evidence thatA. grandisis constrained by a minimum air temperature above 12 °C, low (<20 °C) and high (>29 °C) maximum air temperature, and by low rainfall and relative humidity, occurring at altitudes from 520 to 780 m. More importantly,A. grandiswas not collected in central to western São Paulo, where sandy soil and low soil water availability predominate and the climate is hot and dry. Our findings suggest that soil texture and moisture may be limiting factors for pupal survivorship ofA. grandis, and consequently edaphic characteristics should be taken into account in studies on its geographical distribution. Based on our results, central to western São Paulo state can potentially be classified as an area of low pest prevalence. Moreover, in countries where cucurbit species are cultivated in such conditions, it is not likely thatA. grandiscould become established.

Multi-generational exposure to fipronil, 2,4-D, and their mixtures in Chironomus sancticaroli: Biochemical, individual, and population endpoints

Conventional farming delivers a range of pesticides to aquatic ecosystems leading to implications for the indigenous species. Due to the multiple applications and persistence of molecules, organisms may be exposed for a prolonged period over multiple generations. The present study outlines a full life-cycle design over three generations of Chironomus sancticaroli exposed to the insecticide fipronil, the herbicide 2,4-D, and their mixtures. The experiment started with newly hatched larvae from the parental generation and lasted with the emerged adults from the second generation. Five nominal concentrations of fipronil and 2,4-D were tested, as well as six combinations of both pesticides. As additional responses, the total carbohydrates and the lipid classes were evaluated in the parental generation. The first and second generations were more susceptible to the tested compounds compared with the parental ones. Survival of larvae and pupae was decreased by both pesticides and their mixtures along with the generations. Only fipronil impaired the survival of emerged adults. Both pesticides (isolated and in the mixture) altered the emergence and the fraction of males and females. Moreover, the number of eggs produced, and their hatchability decreased. Only one combination of the pesticides increased the content of carbohydrates. Fipronil, 2,4-D, and its mixture altered the profile of the lipid classes. All mixture treatments and the three highest concentrations of fipronil extinguished the population of C. sancticaroli at the end of the first generation. In the remaining treatments with the insecticide, the population did not survive the second generation. Only three concentrations of 2,4-D and the control persisted until the end of the experiment. The results indicate that a prolonged exposition to these pesticides may disrupt the natural populations of exposed organisms with consequences to ecosystems' functioning, considering the importance of chironomids to aquatic and terrestrial environments.

Inhibition of Aedes aegypti DNA topoisomerase II by etoposide: Impact on survival and morphology of larvae and pupae

DNA topoisomerase II enzymes maintain DNA stability during vital processes, such as genome replication, transcription and chromosomal segregation during mitosis and meiosis. In the present work, we analyzed functional aspects of the DNA topoisomerase II (AeTopII) enzyme of the mosquito Aedes aegypti. Here, we show that AeTopII mRNA is expressed at all stages of mosquito development. By in situ hybridization, we found that the AeTopII mRNA is concentrated along the ovarian follicular cells as well as in the region of the follicles. The observed expression profiles likely reflect increased topoisomerase II cellular requirements due to the intense ovarian growth and egg production following blood feeding in Ae. aegypti females. The drug etoposide, a classic inhibitor of topoisomerase II, was used for in vivo testing with 2nd stage larvae, in order to investigate the functional importance of this enzyme in Ae. aegypti survival and development. Inhibition of topoisomerase II activity with etoposide concentrations ranging from 10 to 200 μM did not leads to the immediate death of larvae. However, after 10 days of observation, etoposide treatments resulted in 30–40% decrease in survival, in a dose dependent manner, with persisting larvae and pupae presenting incomplete development, as well as morphological abnormalities. Also, approximately 50% of the treated larvae did not reach the pupal stage. Thus, we conclude that AeTopII is a vital enzyme in the development of Ae. aegypti and its sensitivity to inhibitors should be explored for potential chemical agents to be used in vector control.

Ambient Humidity Affects Development, Survival, and Reproduction of the Invasive Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), in China.

Ambient humidity can directly affect the water balance in insects. The migratory fall armyworm, Spodoptera frugiperda Smith, has spread to more than 60 countries and regions in Africa, Asia, and Oceania that have a great difference in average ambient humidity. Understanding the effects of ambient humidity changes on its development, survival, and reproduction can help to predict its population dynamics in different habitats. Therefore, we evaluated the effects of atmospheric relative humidity (RH) on the development, survival, and reproduction and soil moisture on the pupation and emergence of fall armyworm. As a result, survival and pupal mass increased significantly with increasing RH. Among the five RHs tested, 80% RH was the most suitable for fall armyworm with the highest intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0). The population growth at the different RHs in decreasing order was 80 > 100 > 60 > 40 > 20%. A relative moisture (RM) of soil from 6.80 to 47.59% was suitable for fall armyworm pupation, survival, and eclosion, but fall armyworm could not pupate normally in soil with 88.39 and 95.19% RM. The survival and emergence rate of fall armyworm pupae were reduced by irrigation that increased the RM after the mature larvae entered the soil. These findings may be helpful for refining laboratory rearing protocols, population forecasting, and management of fall armyworm.

Effects of intraguild interactions on Anticarsia gemmatalis and Chrysodeixis includens larval fitness and behavior in soybean.

BACKGROUNDCrop pest management requires an understanding of the complex interactions among species that potentially impact crop yield. In soybean, the velvetbean caterpillar, Anticarsia gemmatalis (Hübner), and the soybean looper, Chrysodeixis includens (Walker), are described as key pests, sharing the same feeding guild. We assessed the intraguild interactions of these species under laboratory conditions. Fitness cost study was conducted to examine the influence of competition on insect development. A video tracking system was used to evaluate behavioral parameters during larval interactions in scenarios with and without food availability.RESULTSIn the fitness cost assay, pupal weight was not significantly affected, regardless of sex. However, larval and pupal survival were influenced by the competition, especially in third versus fifth instar scenarios. We detected 40.00% cannibalism and 46.67% predation when A. gemmatalis and C. includens third instars competed with A. gemmatalis fifth instar, respectively. Distance moved, distance between larvae, body contact (food available) and frequency in food of C. includens larvae were negatively affected by interactions. Anticarsia gemmatalis larvae showed highly active behavior, moving twice or more the distance compared to C. includens larvae, and A. gemmatalis spent more time in body contact with food.CONCLUSIONOur results suggest that A. gemmatalis has a competitive advantage over C. includens. This study provides important information regarding lepidopteran behavior in soybean. We recommended that additional studies are necessary to understand the effects of interactions, especially in field conditions.© 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Larval diet affects development and reproduction of East Asian strain of the fall armyworm, Spodoptera frugiperda

In December 11, 2018, the fall armyworm (FAW), Spodoptera frugiperda invaded China and has since impacted local maize, sorghum and other crops. Here, we draw on laboratory experiments to show how different host crops (i.e., maize, sorghum, wheat and rice) and artificial diet affect larval growth and adult reproduction of one local FAW strain. Larval diet affected development duration, pupation rate, survival and emergence rate of pupae, and S. frugiperda adult fecundity. FAW attained the slowest larval development (19.4 days) on sorghum and the fastest (14.1 days) on artificial diet, with larvae attaining 99.6% survival on the latter food item. On rice, FAW larvae attained survival rate of 0.4% and were unable to pupate successfully. Pupation rate and pupal survival varied substantially between artificial diet and live plantlets at different phenological stages. Pupal weight was the highest (0.26 g) on artificial diet and the lowest (0.14 g) on sorghum, while FAW females reached the highest fecundity (699.7 eggs/female) on 2-leaf stage maize. Egg hatching rate equaled 93.6% on 4- or 5-leaf stage maize and 36.6% on artificial diet. FAW intrinsic rate of natural increase and the finite rate of increase varied between larval diets, reflecting how young maize leaves are the most suitable diet. Our findings can help to refine laboratory rearing protocols, devise population forecasting models or guide the deployment of ‘area-wide’ integrated pest management (IPM) modules in FAW-invaded areas of China and other Asian countries.

Mechanisms of DEET gustation in Drosophila

DEET is the most widely used active ingredient in insect repellents and offers protection against insect bites. We previously reported that DEET suppresses the feeding behavior of Drosophila, which is guided by gustatory receptors (GRs) in bitter-sensing gustatory receptor neurons. Here, we sought to identify new candidates using egg-laying assays. Upon screening all GR mutants, GR89a was identified as a potential DEET receptor. Gr89a mutants exhibited reduced oviposition avoidance, feeding avoidance, and electrophysiological responses compared to Gr32a, Gr33a, and Gr66a mutants. However, GR89a was found to modulate DEET avoidance, as demonstrated by genetic and RNA interference assays. Furthermore, we found that DEET ingestion severely affected larval and pupal development and survival, and therefore may act as an effective larvicide.

Photoregime Affects Development, Reproduction, and Flight Performance of the Invasive Fall Armyworm (Lepidoptera: Noctuidae) in China.

The migratory fall armyworm, Spodoptera frugiperda (Smith), has become a worldwide agricultural pest. In this study, the effects of photoregime on the development, reproduction, and flight performance of fall armyworm were assessed based on two-sex life tables, ovarian and testis anatomy, and flight mill tests. The results indicated that photoregime had a significant effect on developmental duration of fall armyworm individuals, pupal survival and emergence, and adult fecundity. Among seven photoregimes tested, the 16:8 (L:D) h photoregime was the most suitable for fall armyworm fitness with the shortest pre-oviposition period and mean generation period (T), highest mating frequency and mating rate of female moths, largest intrinsic rate of natural increase (rm) and finite rate of increase (λ), and highest net reproduction rate (R0). Population growth for seven different photoregimes in decreasing order was 16:8 (L:D) h > 8:16 (L:D) h > 12:12 (L:D) h > 10:14 (L:D) h > 14:10 (L:D) h > 0:24 (L:D) h > 24:0 (L:D) h. The ovarian development level, mating frequency, and testis size did not significantly differ between long (16:8 (L:D) h) and short (10:14 (L:D) h) illumination. Photoregime had a significant effect on mass loss during flight of adults, but not on flight velocity, flight duration, and flight distance. These findings can be used to refine laboratory rearing protocols, accurately predict seasonal changes in population dynamics and should help improve regional forecasts and management of the fall armyworm.

Combined effects of elevated CO2 and temperature on multitrophic interactions involving a parasitoid of plant virus vectors

Atmospheric concentration of carbon dioxide (CO2) is predicted to double by late twenty-first century, likely increasing global temperature by 2.2 °C. Elevated CO2 (eCO2) and temperature (eT) affect agricultural crops as well as pests and their natural enemies. Changes in any part of multitrophic systems due to environmental factors can affect pest infestation and disease dynamics, as well as the effectiveness of biological control programs. Our study evaluated the effects of eCO2 and eT combined on the performance of the parasitoid Aphidius colemani Vierick (Hymenoptera: Braconidae) when its aphid host Rhopalosiphum padi L. (Hemiptera: Aphididae) was exposed to non-infected or Barley yellow dwarf virus (BYDV–PAV) infected wheat (Triticum aestivum L., Poaceae). Using controlled environment chambers, plant physiology and parasitoid performance were examined under ambient (aCO2a aCO2 = 400 ppm, aT = 20 °C) and elevated (eCO2e eCO2 = 800 ppm, eT = 22 °C) conditions. Virus infection reduced plant biomass and chlorophyll content more pronouncedly under eCO2&eT. Developmental time from oviposition to adult emergence of A. colemani significantly decreased under eCO2&eT, on virus-infected and non-infected plants. However, parasitism rate, sex ratio and pupal survivorship remained unchanged under eCO2&eT, regardless of virus infection. Therefore, we incline to suggest that the biocontrol of R. padi by A. colemani will continue being effective in a future climate with similar conditions as studied here. This study provides empirical data on a particular tritrophic system (plant-pest-parasitoid) affected by plant virus and eCO2&eT, essential to complement scientific knowledge about the impact of climate change on complex interactions of agro-ecosystems.

Susceptibility of Zoysiagrasses to the Fall Armyworm (Lepidoptera: Noctuidae)

Abstract Growth and developmental parameters of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), were evaluated on 41 new zoysiagrass taxa (Zoysia spp. Willd.), which belong to an increasingly popular group of warm-season turfgrasses, in comparison with 5 commercially available zoysiagrass taxa and 1 known susceptible Paspalum L. taxon. Results from two no-choice growth chamber trials indicated that the new Zoysia japonica Steud. taxa were unfavorable for the development of fall armyworm larvae in general compared with the susceptible Paspalum taxon. This was evidenced by significantly lower larval and pupal weights and survival and longer time to pupation and adult emergence, pointing to antibiosis in these zoysiagrass taxa. The new Zoysia matrella (L.) Merr., Zoysia macrostachya Franch. & Sav., and Zoysia sinica Hance taxa seemed more favorable than Z. japonica taxa, as evidenced by numerically higher larval and pupal weights and survival and shorter duration to pupation and adult emergence. Taxa that consistently showed low larval survival were identified for further testing.

Effects of Larval Population Density and Food Type on the Life Cycle of Musca domestica (Diptera: Muscidae).

Larval density is an important factor modulating larval resource-acquisition, influencing development of insects. This study aimed to evaluate the effect of larval density and substrate content on some life-history parameters of Musca domestica Linnaeus, 1758 (Diptera: Muscidae). This research was carried out from March 2019 through September 2019 at Animal Physiology Laboratory of Ondokuz Mayıs University, Samsun, Turkey. Groups of 25, 100, 200, and 400 newly hatched M. domestica larvae were transferred to a polyethylene cup filled with different substrates (i.e., wheat bran, poultry meal, soybean meal) and kept at 25°C, 62% RH with a photoperiod of 12:12 (L:D) h. A two-way analysis of variance (Two way ANOVA) was used to analyze the data on the percentage of pupal and larval survival development time, pupal, and adult weight to evaluate the effect of density and rearing substrate. In this study, increasing larval density and nutrient content of food led to changes in the larval and pupal development time of M. domestica. The results also indicated that the weight of pupae and adult survival was negatively affected by increasing larval density. The wheat bran diet was superior to the other diets for all parameters tested. Our study indicated that life history parameters of Musca domestica are affected by the rearing conditions.

Effect of entomopathogenic fungi introduced as corn endophytes on the development, reproduction, and food preference of the invasive fall armyworm Spodoptera frugiperda

Fall armyworm (FAW), Spodoptera frugiperda, is a migratory polyphagous pest that causes major damage to economically important cultivated grasses, such as corn. Native to the neotropics in America but recently reported as an invasive pest in Africa and Asia, FAW imposes a serious threat to food security and sustainable crop productivity due to lack of effective management. In this study, the introduction of entomopathogenic fungi as endophytes was explored as an alternative more sustainable management strategy against FAW in corn. The study determined (1) the effect of isolates and inoculation methods on the ability of entomopathogenic fungi to colonize corn plants, and (2) the effect of colonized plants on S. frugiperda survival, development, reproduction, and food preference. Although all tested isolates (twelve of Beauveria bassiana and one each of Metarhizium anisopliae and Metarhizium robertsii) colonized inoculated plants, there was a highly significant interaction between isolates and inoculation methods. Highest plant colonization was obtained by Beauveria bassiana isolate (LPSc 1098) using foliar spray. Endophytic B. bassiana caused significant reductions in larval and pupal survival, length of different developmental stages, total S. frugiperda lifespan, and leaf area consumed by third instar larvae. Plant colonization also significantly reduced female longevity, fecundity, and fertility. This is the first report for the negative effects of endophytic B. bassiana on S. frugiperda growth, reproduction, and food preference. Our results highlight the promising potential of incorporating entomopathogenic fungi as endophytes in integrated pest management practices to protect corn against FAW if their efficacy is also confirmed under field conditions.

Acute and Chronic Toxicity of Indoxacarb in Two Populations of Plutella xylostella (Lepidoptera: Plutellidae).

The diamondback moth, Plutella xylostella (Linnaeus, 1758), is one of the main pests of brassicas, and various insecticides, such as indoxacarb, are used to control it. However, frequent insecticide applications favor the selection of resistant individuals. Thus, the residual and sublethal effects of indoxacarb in two populations of P. xylostella, one collected in the field (FP) and one from the laboratory (LP), were evaluated and compared. The objective of this research was to investigate the toxicity of indoxacarb at residual and sublethal levels in a field population of P. xylostella from Brazil and a population from the laboratory. Leaf-dip bioassays showed high toxicity, with LC50 values after 48 h of 3.7 and 6.9 mg/liter for the LP and FP, respectively. Sublethal effects were indicated by significant reduction in the survival of larvae, pupae, and offspring. There was an increase in foliar consumption and a decrease in adult survival in the LP, and a decrease in fecundity in the FP. For the LP and FP population, the mean values for R0, rm, and λ for the control treatment were significantly higher than for the treatment groups (CL15 and CL25). Exposure of larvae to sublethal indoxacarb concentrations significantly reduced larval and pupal survival. Larval and pupal survival decreased as the indoxacarb concentration increased. Fecundity was significantly lower for the FP at LC15 (96.2 eggs per female) and LC25 (69.2 eggs per female) concentrations compared with the other treatments.

Changes in the Biological Characteristics of Plutella xylostella Using Ethanolic Plant Extracts

The indiscriminate use of synthetic insecticides has led to the emergence of resistant populations of Plutella xylostella L. (Lepidoptera: Plutellidae), hindering its control and causing economic damage to brassica production. Thus, in order to seek control alternatives, this study aimed at assessing the bioactivity of the ethanolic extracts of Schinus terebinthifolius (Anacardiaceae), Annona coriacea (Annonaceae), Annona crassiflora (Annonaceae), and Serjania marginata (Sapindaceae) on the life cycle of P. xylostella. Cabbage leaf discs were immersed in the treatments at a concentration of 10 mg/mL and given daily to the larvae. Larval and pupal duration and survival, pupae weight, the longevity of males and females, number and survival of eggs, incubation period, and days of oviposition parameters were evaluated. All extracts differed significantly from the control in terms of larval and pupal duration, pupal survival, and pupae weight. All the extracts prolonged the larval and pupal period of P. xylostella. Only A. coriacea did not differ significantly from the control in terms of larval survival, and the highest larval mortality was observed in the treatment with S. marginata (50%). Pupal survival, pupae mass, oviposition period, and egg survival were reduced in all treatments with ethanolic extracts. The treatments with Annona and S. marginata species have reduced the number of eggs. Treatments with S. terebinthifolius and S. marginata have reduced the incubation time of eggs. Thus, the treatments with ethanolic plant extracts act on the life cycle of P. xylostella negatively impacting the biological parameters evaluated.

Effects of a Meridic Diet Supplemented with Cotton Leaf Tissue on Bollworm Fitness

Rearing bollworm, Helicoverpa zea (Boddie), on synthetic diets for use in laboratory bioassays is a common practice around the world. Little is known about how insect diets currently utilized for bollworm rearing have been altered from their original nutrient composition and the implications this might have on insect fitness. Therefore, this study assessed notable shortcomings of a commonly used meridic diet by exposing bollworms to cotton (Gossypium hirsutum L) leaf tissue for short periods during early development to determine effect on larval and pupal survival and weights. Mean survival of larvae ranged from 60% when bollworms were exposed to Bt cotton leaves for 7 days to 100% on meridic diet. Mean pupation ranged from 58 to 97%, which closely mimicked survival of larvae at 7 days. Insect larvae reared on meridic diet through 7 days were fitter relative to those exposed to cotton leaf tissue, having greater larval weight and survival than other treatments. Conversely, pupal weight of bollworms exposed to meridic diet for the same 7-day period tended to lag behind those exposed to cotton leaf tissue. However, any fitness benefit gained from rearing larvae on leaf tissue might be offset by increased mortality before the pupal stage. The experiment demonstrated that larval and pupal fitness were impacted by supplementing meridic diet with leaf tissue, but additional research is needed to further investigate effects through multiple generations.

Physico-chemical bases of resistance in maize against shoot fly, Atherigona naqvii Steyskal during spring season in north India

Host plant resistance is one of the most promising alternatives to insecticides to manage the shoot fly, Atherigona naqvii Steyskal, which is a major biotic constraint to spring sown maize in northern India. In present studies, Nineteen maize inbreds selected from diverse sources were characterized for resistance traits against shoot fly under its natural infestation using moistened fishmeal. Though the antixenosis to shoot fly for oviposition was not observed in the test genotypes. But, the presence of significant variation in the deadhearts incidence revealed the existence of relative amount of resistance among the test genotypes. The Tolerance (measured in the terms of less proportion of deadhearts out of total shoot fly incidence (leaf injury + deadhearts)) and Antibiosis (in terms of larval and pupal weight, duration and survival) were recognized as key mechanisms of this resistance. Tolerance to shoot fly was significantly more in resistant inbreds, SO1SHYQBBB13B, HK12-6-2-4, DMSC 28, CM 143 and Winpop 8 (29.46–36.56%) in comparison to the susceptible genotypes SE 563 and LM 16 (46.31–47.44%). The correlation and stepwise regression analyses revealed that the more seedling vigor, less leaf area, less number of leaves and thin stem had significant impact on the shoot fly deadhearts incidence and provided resistance against this pest. The total soluble sugars (TSS), proteins and amino acids were significantly higher in the susceptible inbreds; whereas, total phenols and tannins; and activities of defensive enzymes viz. phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) were significantly higher in resistant inbreds. Further, the stepwise regression revealed that the larval period, per cent pupation, pupal weight female, pupal weight male and adult emergence of shoot fly were significantly influenced by PAL activity, which explained 71.5, 82.9, 47.0, 29.8 and 39.9% of their total variation, respectively. PPO activity significantly influenced the pupal period (R2 = 59.7%) whereas, the larval weight was significantly influenced by amino acids (R2 = 56.9%), proteins (R2 = 10.2%) and TSS (R2 = 7.7%). So, the correlation and regression analyses revealed that these physico-chemical characters of the maize inbreds can be utilized as reliable markers traits to identify resistant sources to develop shoot fly resistant maize hybrids.

Detecting the population dynamics of an autosomal sex ratio distorter transgene in malaria vector mosquitoes.

The development of genetically modified (GM) mosquitoes and their subsequent field release offers innovative and cost‐effective approaches to reduce mosquito‐borne diseases, such as malaria. A sex‐distorting autosomal transgene has been developed recently in G3 mosquitoes, a laboratory strain of the malaria vector Anopheles gambiae s.l. The transgene expresses an endonuclease called I‐PpoI during spermatogenesis, which selectively cleaves the X chromosome to result in ~95% male progeny. Following the World Health Organization guidance framework for the testing of GM mosquitoes, we assessed the dynamics of this transgene in large cages using a joint experimental modelling approach.We performed a 4‐month experiment in large, indoor cages to study the population genetics of the transgene. The cages were set up to mimic a simple tropical environment with a diurnal light‐cycle, constant temperature and constant humidity. We allowed the generations to overlap to engender a stable age structure in the populations. We constructed a model to mimic the experiments, and used the experimental data to infer the key model parameters.We identified two fitness costs associated with the transgene. First, transgenic adult males have reduced fertility and, second, their female progeny have reduced pupal survival rates. Our results demonstrate that the transgene is likely to disappear in <3 years under our confined conditions. Model predictions suggest this will be true over a wide range of background population sizes and transgene introduction rates. Synthesis and applications. Our study is in line with the World Health Organization guidance recommendations in regard to the development and testing of GM mosquitoes. Since the transgenic sex ratio distorter strain (Ag(PMB)1) has been considered for genetic vector control of malaria, we recorded the dynamics of this transgene in indoor‐large cage populations and modelled its post‐release persistence under different scenarios. We provide a demonstration of the self‐limiting nature of the transgene, and identified new fitness costs that will further reduce the longevity of the transgene after its release. Finally, our study has showcased an alternative and effective statistical method for characterizing the phenotypic expression of a transgene in an insect pest population.

Life cycle of cabbage caterpillar, Pieris brassicae Linn. (Lepidoptera: Pieridae) on cabbage leaves in Talwandi Sabo (Punjab)

Study on different biological parameters of cabbage caterpillar, Pieris brassicae was carried out in Guru Kashi University, Talwandi Sabo (Punjab) during 2018-19. The average incubation period of eggs was recorded as 4.3 days. The freshly laid eggs of the caterpillar were light yellow that turned grayish black prior to hatching. The average duration different larval instars, namely 1st, 2nd, 3rd, 4th, and 5th, lasted for 4.6, 5.9, 3.5, 3.1 and 4.3 days, respectively. The full grown larvae stopped feeding before pupation, which took place on rough surface i.e. muslin cloth. Total larval and pupal periods were recorded as 21.45 and 10.95 days, respectively. The females were longer lived than the males with average longevity of 9 and 8.15 days, respectively. The male to female sex ratio was 1:1.56. The fecundity of female was observed to be 163 eggs/female and the per cent hatchability 96.82. Larval and pupal survival was observed as 87 and 95 percent, respectively. Total life cycle of male and female was 45 and 46.5 days respectively. On an average, the 1st, 2nd, 3rd, 4th and 5thinstar larvae measured 6.45, 13.3, 21.65, 33.65 and 40.75mm in length, respectively. The larval width of the corresponding instars were1.0, 2.0, 2.6, 3.75 and 4.75mm in breadth. The length and breadth of pupa were measured as 25.65±0.48 and 6.55±0.51mm, respectively and the body lengths of adult male and female were 21.95 and 22.8mm respectively. The breadth of fore and hind wings of male was 30.6 and 25.6mm and those of females was 32.25 and 26.7mm, respectively.

Within-tree Distribution and Survival of the Eucalyptus Longhorned Borer Phoracantha semipunctata (Coleoptera: Cerambycidae) in a Mediterranean-Type Ecosystem.

The attack patterns, infestation success and larval development of woodborers within living trees are complex and are largely shaped by host tree characteristics. Following a severe drought in a native eucalypt forest where outbreak densities of a native Australian beetle, the eucalyptus longhorned borer (Phoracantha semipunctata), occurred, a tree dissection study was conducted in Australia. This involved felling 40 trees each of jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) that were cut into 1-m sections and neonate larval galleries, larvae in pupal cells and adult borer emergence were measured and added to give total numbers per tree to determine the within-tree distribution and survival of P. semipunctata. There was a significant impact on larval survival in both species, in contrast, pupal survival remained high. Within-tree distribution of P. semipunctata was directional with borer emergence and incidence of larval galleries both negatively associated with tree section height above the ground and positively associated with section diameter and bark thickness, reaching a maximum towards the base of trees. High incidence and survival in lower thicker tree sections indicate a more conducive environment for larval development, in contrast to poor larval survival in smaller thinner sections at the top of trees. The dependence of larval survival on tree characteristics controlling the within-tree distribution of borer emergence is emphasized, and needs to be considered when estimating the spread of borer populations during outbreaks.