Adult Fecundity Research Articles

Survival, development, and reproduction of Aulacorthum solani (Hemioptera: Aphididae) fed on Persicaria lapathifolia.

The foxglove aphid, Aulacorthum solani (Kaltenbach), is a polyphagous economic pest. In this study, A. solani were fed on detached leaves of dockleaf knotweed, Persicaria lapathifolia (L.) Delarbre. Survival, development, and reproduction were studied at constant temperatures of 17, 20, 23, 26, 29, and 32 °C. These data were compared with those of controls fed on Glycines max (L.) Merrill. At 17, 20, 23, and 26 °C, the survival rate of A. solani adults fed on P. lapathifolia were lower than those fed on G. max; the adult longevity, aphid total longevity, and reproduction period were shorter. At 20, 23, and 26 °C, the adult fecundity, intrinsic rate of increase, finite rate of increase, and net reproductive rate of A. solani fed on P. lapathifolia were smaller than those fed on G. max. At 29 °C, the survival rate of A. solani adults fed on P. lapathifolia were higher than those fed on G. max; the adult longevity and aphid total longevity were longer. These results are consistent with our finding that A. solani feed on P. lapathifolia, which is important for studying the host adaptability of A. solani.

Estimating Demographic Parameters for Bearded Seals, Erignathus barbatus, in Alaska Using Close-Kin Mark-Recapture Methods.

Reliable estimates of population abundance and demographics are essential for managing harvested species. Ice-associated phocids, "ice seals," are a vital resource for subsistence-dependent coastal Native communities in western and northern Alaska, USA. In 2012, the Beringia distinct population segment of the bearded seal, Erignathus barbatus nauticus, was listed as "threatened" under the US Endangered Species Act requiring greater scrutiny for management assessments. We sought to estimate requisite population parameters from harvested seals by using close-kin mark-recapture (CKMR) methods, the first such application for marine mammals. Samples from 1758 bearded seals harvested by Bering, Chukchi, and Beaufort Sea communities during 1998-2020 were genotyped, genetically sexed, and aged by tooth annuli. After rigorous quality control, kin relationships were established for 1484 seals including two parent-offspring pairs (POPs) and 25 potential second-order kin pairs. Most of the second-order kin were half-sibling pairs (HSPs), but four were potential grandparent-grandchild pairs (GGPs). There were no full sibling pairs, suggesting a lack of mate fidelity. Mitochondrial DNA analysis identified 17 potential HSPs as paternally related, providing substantial evidence of persistent heterogeneity in reproductive success among adult males. The statistical CKMR model incorporates probabilities associated with POPs, HSPs, and GGPs and assumes known ages and a stable population. Our top model accommodates heterogeneity in adult male breeding success and yields an abundance estimate of ~409,000 with a coefficient of variation (CV) = 0.35, which is substantially greater than the "non-heterogeneity" model estimate of ~232,000 (CV = 0.21), an important difference for managing a harvested species. Using CKMR methods with harvested species provides estimates of abundance with the added opportunity to acquire information about adult survival, fecundity, and breeding success that could be applied to other species of concern, marine and terrestrial.

Life table and feeding behavior of Myzus persicae (Hemiptera: Aphididae) at sublethal concentrations of Afidopyropen, Spirotetramat and sulfoxaflor

AbstractThe green peach aphid Myzus persicae Sülzer is a major insect pest of cruciferous plants, including vegetables such as Chinese cabbage. The objective of the present study was to determine the effects of sublethal afidopyropen and spirotetramat concentrations on the survival and reproduction of M. persicae. In addition, we used an electrical penetration graph (EPG) to study the feeding behavior of M. persicae on Chinese cabbage leaves treated with various concentrations of afidopyropen, spirotetramat and sulfoxaflor. The results showed that sublethal concentrations (LC10 and LC30) of afidopyropen and spirotetramat significantly decreased adult longevity and fecundity. However, sulfoxaflor had no significant effects. Several population parameters, including the net reproductive rate (R0), intrinsic rate of increase (rm), mean generation time (T), finite rate of increase (λ), and doubling time (DT), were significantly decreased only at the LC30 of spirotetramat. According to the EPG feeding behavior analyses, when all three insecticides were applied at LC30, the nonpenetration (NP) waveform significantly increased. The above results can be used as basic data for the well‐planned use of insecticides.

Adaptability of the Soybean Aphid Aphis glycines (Hemiptera: Aphididae) to Temperature and Photoperiod in a Laboratory Experiment.

The soybean aphid, Aphis glycines Matsumura, 1917, is a crucial soybean pest. Cultivated soybean, Glycine max (Carl von Linné) Elmer Drew Merrill, 1917, and wild soybean, Glycine soja Philipp Franz von Siebold & Joseph Gerhard Zuccarini, 1843, are summer hosts of A. glycines. In this study, the development, reproduction, and morphogenesis of A. glycines fed wild soybean (AgFW) were studied at different temperatures and photoperiods. The data were compared with that of A. glycines fed soybean (AgFS). At 20-29 °C, the adult lifespan of the first-third-generation AgFW was shorter than or equal to that of AgFS. Significant differences existed in the adult fecundity and intrinsic rate of increase between AgFW and AgFS. At a 10L:14D h photoperiod, males of AgFW were deposited earlier than, or as early as, males of AgFS. At 17 °C, the gynoparae of AgFW were deposited in proportions greater than or equal to those of AgFS. Based on these results, we concluded that the adaptability of AgFW and AgFS to temperature and photoperiod significantly differs. It is important to understand the life cycle of A. glycines in Harbin, northeast China, and formulate an integrated pest management strategy for A. glycines in the region.

Evaluation of three inert materials in controlling Cowpea weevil (<em>Callasobruchus maculatus</em> F.) on stored cowpea (<em>Vigna unguiculate</em> L.)

Eco-friendly inert materials can be achieved minimizing insect damages, this study was conducted to explore the efficacy of the three inert materials at 20% (w/w) paddy husk ash (PHA), fine dry sea salt and tiny bricks against the cowpea weevil C. maculatus on stored cowpea (V. unguiculata) on the basis of adulticidal effects and asses the influence against germination losses of the seeds. The result exhibited a significant difference (p≤ 0.0001) in their level of weevil attack during the storage. Maximum 100% adult mortality was recorded in the cowpea seeds incorporated with PHA after 96 hours of the treatment followed by dry salt it was observed 94% at the 5th day whereas, tiny bricks killed only 20% weevils as untreated control until 5th day after the treatment. Further, PHA treated seeds much reduced the capable of the egg laying capacity of weevil (9.8± 0.58eggs/ female) as well as minimized the production of new progenies (13.6 ± 0.37) and also there were recorded 0.03% weight loss and zero percent germination losses proving it to be best protectant on stored cowpea. However, significantly (p≤ 0.0001) any adverse effects that, egg laying capacity and new progeny production did not visible in dry salt up to 90 days after the treatments except minimize the germination loss. Among the inert materials used, tiny bricks were found ineffective to cause adult mortality, fecundity and adult emergency in F1 generation (119.8± 1.78), it was further increased production of new weevils obtained following the next F2 generation (1301 ± 0.65) and play down the losses of weight and germination of the seeds. Considering it was noticed tiny bricks treated seeds significantly equivalence with the level of damage by the weevil C. maculatus in untreated control on stored cowpea.

Sublethal effects of emamectin benzoate on biological characteristics and the expression of vitellogenin (SgVg) and its receptor in Sclerodermusguani

Emamectin benzoate (EMB) is a commonly used insecticide for controlling agricultural and forest pests. To facilitate its rational use in integrated pest management (IPM), the sublethal effects of EMB on the development and reproduction of Scleroderma guani were evaluated. Sublethal doses of EMB (LD10 and LD30) significantly reduced the longevity and fecundity of F0 females. In the F1 generation, sublethal doses significantly reduced larval development duration and male longevity but significantly extended female longevity. Additionally, the LD30 treatment significantly decreased the number of laid eggs in F1 females by 20.72% compared with the control group. The net reproductive rate (R0) was significantly declined by the LD30 treatment compared with the control group (CK). Furthermore, the mean generation time (T) was significantly extended in both LD10 and LD30 treatment groups. Compared to the control group, the expression of SgVg and SgVgR genes in the LD10 and LD30 groups was significantly lower, which may be a crucial factor for the reduced fecundity of the females. These results indicate that sublethal doses of EMB significantly reduced adult longevity and fecundity of S. guani. The findings are practical for developing IPM strategies for forestry pests using S. guani and EMB.

Limited Migration From Physiological Refugia Constrains the Rescue of Native Gastropods Facing an Invasive Predator.

Biological invasions have caused the loss of freshwater biodiversity worldwide. The interplay between adaptive responses and demographic characteristics of populations impacted by invasions is expected to be important for their resilience, but the interaction between these factors is poorly understood. The freshwater gastropod Amnicola limosus is native to the Upper St. Lawrence River and distributed along a water calcium concentration gradient within which high-calcium habitats are impacted by an invasive predator fish (Neogobius melanostomus, round goby), whereas low-calcium habitats provide refuges for the gastropods from the invasive predator. Our objectives were to (1) test for adaptation of A. limosus to the invasive predator and the low-calcium habitats, and (2) investigate if migrant gastropods could move from refuge populations to declining invaded populations (i.e., demographic rescue), which could also help maintain genetic diversity through gene flow (i.e., genetic rescue). We conducted a laboratory reciprocal transplant of wild F0 A. limosus sourced from the two habitat types (high calcium/invaded and low calcium/refuge) to measure adult survival and fecundity in home and transplant treatments of water calcium concentration (low/high) and round goby cue (present/absent). We then applied pooled whole-genome sequencing of 12 gastropod populations from across the calcium/invasion gradient. We identified patterns of life-history traits and genetic differentiation across the habitats that are consistent with local adaptation to low-calcium concentrations in refuge populations and to round goby predation in invaded populations. We also detected restricted gene flow from the low-calcium refugia towards high-calcium invaded populations, implying that the potential for demographic and genetic rescue is limited by natural dispersal. Our study highlights the importance of considering the potentially conflicting effects of local adaptation and gene flow for the resilience of populations coping with invasive predators.

A potential trade-off between reproduction and enhancement of thermotolerance in Liriomyza trifolii populations driven by thermal acclimation

The invasive pest, Liriomyza trifolii, poses a significant threat to ornamental and vegetable plants. It spreads rapidly and causes large-scale outbreaks with pronounced thermotolerance. In this study, we developed L. trifolii strains adapted to high temperatures (strains designated 35 and 40); these were generated from a susceptible strain (designated S) by long-term thermal acclimation to 35 °C and 40 °C, respectively. Age-stage, two-sex life tables, thermal preferences, critical thermal limits, knockdown behaviors, eclosion and survival rates as well as expression of genes encoding heat shock proteins (Hsps) were compared for the three strains. Our findings indicated that the thermotolerance of L. trifolii was enhanced after long-term thermal acclimation, which suggested an adaptive plastic response to thermal stress. A trade-off between reproduction and thermotolerance was observed under thermal stress, potentially improving survival of the population and fostering adaptionary changes. Acclimation at 35 °C improved reproductive performance and population density of L. trifolii, particularly by enhancing the fecundity of female adults and accelerating the speed of development. Although the 40 strain exhibited the highest developmental speed and greater thermotolerance, it incurred a larger reproductive cost. This study provides a theoretical framework for monitoring and controlling leafminers and understanding their evolutionary adaptation to environmental changes.

Effect of storage conditions on host egg suitability and the reproductive fitness of Oobius agrili (Hymenoptera: Encyrtidae), an egg parasitoid of the invasive emerald ash borer (Agrilus planipennis) (Coleoptera: Buprestidae).

Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) is an important egg parasitoid of the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). Methods for laboratory-rearing O. agrili have been developed but its mass-production depends on the continuous production and storage of freshly laid EAB eggs as well as diapaused parasitoid progeny (inside parasitized EAB eggs). The purpose of this study was to determine optimal environmental conditions for long-term storage of host eggs as well as diapaused parasitoid progeny. Fresh host eggs and diapaused parasitoid progeny were stored at two low storage temperatures (1.7 and 12.8 °C) and three levels of relative humidity (low ~31%, medium ~74%, and high ~99.9%) for various length of time (15-270 days) and then evaluated for host egg suitability and the reproductive fitness of stored parasitoid progeny. EAB eggs were stored for approximately 30 days without significant reduction of their viability and suitability to O. agrili parasitism at low storage temperatures under high and medium relative humidity. Neither storage temperature or humidity had any significant effects on adult parasitoid emergence for storage durations of up to 270 days. When storage durations were over 120 days, however, both adult parasitoid longevity and fecundity declined approximately 20-30% across all temperature and humidity treatments. Relevance of findings to mass-production and storage of O. agrili for biocontrol is discussed.

Heat Shock Protein 70 Genes Are Involved in the Thermal Tolerance of Hippodamia variegata.

Previous studies have shown that the survival and reproduction of Hippodamia variegata are increasingly harmed by progressive increases in temperature (from 32 °C to 35 °C and 38 °C). In this study, transcriptome sequencing analysis was performed on H. variegata, after being exposed to different temperatures (from 32 to 38 °C) for 24 h, using high-throughput sequencing technology. We found the largest number of differentially expressed genes (DEGs) in the 35 °C vs. 32 °C group (1151) followed by the 38 °C vs. 32 °C group (1054) and then the 38 °C vs. 35 °C group (901), indicating that H. variegata expressed the largest number of newly mobilized genes under medium-high temperature (35 °C). Gene functional analysis showed that a large number of DEGs were involved in "Catalytic activity", "Oxidoreductase activity", "Metabolic pathways", and "Longevity regulating pathway-multiple species" gene groups. We randomly selected nine DEGs for validation using qRT-PCR. The results of qRT-PCR were consistent with the transcriptome data, confirming their reliability. Finally, the RNAi results showed that adult survival, longevity, and fecundity were lower in the group in which gene expression of the heat shock proteins (Hsp70-01 and Hsp68) was suppressed than in the control group (injection ds-GFP) at all the experimental temperatures (32, 35, and 38 °C). Our results indicate the important role of the heat shock proteins (Hsp70-01 and Hsp68) in resistance to high-temperature stress in H. variegata and provide a molecular basis for analyzing its thermotolerance mechanism.

Host Plants and Fertilization Mediated Life History of American Serpentine Leaf Miner, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae).

Herbivorous insects depend on the host plant to optimize their overall reproductive success, and balanced fertilization may alter the plant's quality against herbivory. Life history traits of the Liriomyza trifolii (Burgess) were determined under laboratory conditions using either unfertilized and fertilized plants of bean [Phaseolus vulgaris L. (Fabaceae)], chrysanthemum [Chrysanthemum × morifolium (Asteraceae)], potato [Solanum tuberosum (Solanaceae)], bell pepper [Capsicum annuum (Solanaceae)], and tomato [Solanum lycopersicum (Solanaceae)]. Results indicated that L. trifolii completed development on all studied unfertilized and fertilized plants. Nevertheless, a higher performance of the leaf miner was observed on bean and bell pepper plants compared to the other plants. Furthermore, there was an interaction of the host plant and fertilization with Calcium Aria or Sitam negatively affecting the fitness-related traits of the leaf miner. Application of these fertilizers resulted in delayed immature development of L. trifolii, decreased survival rate, and reduced adult longevity and fecundity. The activity of cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzymes, as well as phenolic, flavonoid, and lignin content were higher in Calcium Aria + Sitam fertilized plants, intermediate in Calcium Aria and Sitam treated plants, and the lower in unfertilized plants. The development and survival of L. trifolii on different host plants, considering fertilization options, become important for deploying cultural control practices against this important pest species.

The low-lethal concentrations of rotenone and pyrethrins suppress the population growth of Rhopalosiphum padi

As an important pest on winter wheat, Rhopalosiphum padi (L.) causes damage to the wheat yield by sucking plant nutrients, transmitting plant viruses and producing mildew. R. padi has been reported to develop resistance to pyrethroids and neonicotinoids. To explore potential alternative approaches for R. padi control, the activity of 10 botanical insecticides was evaluated. Results suggested that the toxicity of rotenone and pyrethrins to R. padi were the highest and near to the commonly used chemical insecticides. When exposed to the low-lethal concentrations (LC10, LC30) of rotenone or pyrethrins for 24 h, the lifespan and fecundity of adults in F0 generation decreased significantly compared to control. The negative effect could also be observed in the F1 generation, including the decreased average offspring, longevity of adult, and prolonged nymph period. The population parameters in F1 generation of R. padi were also inhibited by exposing to the low-lethal concentrations of rotenone or pyrethrins, including the decreased net reproductive rate, intrinsic rate of natural increase, finite rate of population increase, and gross reproduction rate. Co-toxocity factor results showed that mixtures of rotenone and thiamethoxam, pyrethrins and thiamethoxam showed synergistic effect. Our work suggested that rotenone and pyrethrins showed negative effect on the population growth under low-lethal concentrations. They are suitable for R. padi control as foliar spraying without causing population resurgence.

Intergenerational Sublethal Effects of Flonicamid on Cotton Aphid, Aphis gossypii: An Age-Stage, Two-Sex Life Table Study.

Flonicamid is a novel systemic insecticide widely used against aphids. However, the intergenerational sublethal effects of flonicamid on cotton aphid, Aphis gossypii, have not been fully studied. This study aimed to evaluate the sublethal effects of flonicamid on the biological parameters of adult A. gossypii (F0) and its subsequent intergenerational effects on the offspring (F1 generation) through age-stage, two-sex life table analysis. The results of the bioassays indicate that flonicamid exhibits significant toxicity toward adult A. gossypii, as evidenced by an LC50 value of 0.372 mg L-1 after a 48-h exposure period. The longevity, fecundity, and reproductive days of adult cotton aphids (F0) were significantly decreased when treated with the sublethal concentrations of flonicamid. The pre-adult stage exhibited an increase, whereas the adult longevity, total longevity, and fecundity experienced a notable decrease in F1 aphids after the exposure of F0 aphids to sublethal concentrations of flonicamid. Furthermore, the key demographic parameters, including r, λ, R0, and RPd, showed a significant decrease, while the total pre-reproductive period (TPRP) experienced a significant increase in the F1 generation. Collectively, our findings indicate that sublethal concentrations of flonicamid impact the demographic parameters of A. gossypii, resulting in suppression of population growth. This study presents comprehensive information on the overall impact of flonicamid on A. gossypii, which could potentially aid in managing this major pest.

The ZcVg3 Gene Regulates the Reproduction and Lifespan of Female Zeugodacus cucurbitae (Coquillett) Mediated by Short-Term High Temperatures.

Zeugodacus cucurbitae (Coquillett) is a significant pest affecting fruit and vegetables in tropical and subtropical regions, and its development and reproduction are enhanced after exposure to short-term high-temperature stress at 45 °C. Vitellogenin (Vg) is an essential precursor of yolk protein formation in eggs and plays a vital role in the ovarian development of insects. Interfering with the Z. cucurbitae vitellogenin receptor (ZcVgR) gene in short-term high-temperature conditions decreases the fecundity of female adults, while the transcription level of the ZcVg3 gene increases. To elucidate the reproductive function of the ZcVg3 gene and the synergistic relationship among the ZcVgs genes under short-term high temperatures, this study injected siRNA to interfere with the ZcVg3 gene after subjecting Z. cucurbitae to a 1 h treatment at 45 °C and 25 °C. The expression of the ZcVg3 gene was suppressed, leading to the upregulation of the ZcVg1 and ZcVg2 genes, and the expression of the ZcVgR gene was initially decreased and then increased. Silencing the ZcVg3 gene after a 1 h treatment at 45 °C resulted in a reduction of approximately 84.7% and 75.9% in the fecundity and spawning days of female adults compared to the control. The development rate of their ovaries and the ovarian diameter significantly decreased, and their lifespan was reduced by 71%. The ZcVg3 gene plays a crucial role in the reproduction of Z. cucurbitae in short-term high-temperature conditions. The results of this study provide potential targets for the development of RNAi-based techniques for the control of Z. cucurbitae.

Sublethal and transgenerational effects of broflanilide on the citrus red mite, Panonychus citri.

The citrus red mite, Panonychus citri is a serious pest of the citrus industry and has developed resistance to many acaricides. Broflanilide is a novel meta-diamide insecticide that binds to a new site on the γ -aminobutyric acid receptor with high potency against pests. However, little information has been reported about its effect on the citrus red mite. Broflanilide exhibited higher toxicity to female adults and eggs of a laboratory strain of P. citri The median lethal concentration (LC50), 9.769 mg/L and 4.576 mg/L, respectively) than other commonly used acaricides and was also toxic to two P. citri field strains. Broflanilide treatment with LC10, LC20, and LC30 significantly decreased the fecundity and longevity of female adults of F0 P. citri compared with the control. The duration of larva, protonymph, deutonymph and adult, and total life span in the F1 generation were significantly reduced after treatment of F0 with broflanilide. Population parameters, including the intrinsic rate of increase (r) and finite rate of increase (λ), were significantly increased, and the mean generation time (T) of F1 progeny was significantly reduced in the LC20 treatment. The predicted population size of F1 increased when parental female adults were treated with sublethal concentrations. Broflanilide had high acaricidal activity toward P. citri, and exposure to a sublethal concentration significantly inhibited the population growth of F0. The transgenerational hormesis effect is likely to cause population expansion of F1. More attention should be paid when broflanilide is applied to control P. citri in citrus orchards. © 2024 Society of Chemical Industry.

The Effect of Different Thiamethoxam Concentrations on Riptortus pedestris Development and Fecundity.

The stink bug, Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), is a highly destructive pest that significantly damages legume crops in East and South Asia. Neonicotinoid insecticides containing thiamethoxam are widely used to control R. pedestris in soybean fields. However, the current knowledge on the impact of different thiamethoxam concentrations on R. pedestris growth and reproduction is lacking and insufficient. The present study investigated the effects of thiamethoxam on the biological traits of R. pedestris after treatment with LC10 (19.8 mg/L), LC20 (31.6 mg/L), LC30 (44.2 mg/L), LC40 (58.9 mg/L), and LC50 (77.0 mg/L) concentrations. These five thiamethoxam concentrations (LC10~LC50) reduced adult longevity and fecundity in the F1 generation females. Thiamethoxam treatment also significantly decreased the population trend index, intrinsic rate of increase, net reproductive rate, gross reproductive rate, and finite rate of increase and increased the mean generation time. These results show that thiamethoxam hinders and suppresses the development and growth of the F1 population of R. pedestris. Thiamethoxam is recommended for spray control during peak adult emergence, as it not only has a controlling effect on the parental generation but also a negative impact on the F1 generations.

The sublethal concentration of acetamiprid suppresses the population growth of 2 species of wheat aphids, Sitobion miscanthi and Schizaphis graminum (Hemiptera: Aphididae).

Sitobion miscanthi and Schizaphis graminum (Rondani) are the 2 main aphid species that occur simultaneously, causing significant loss to wheat production. Acetamiprid has been used to control a variety of pests, including aphids. In this study, the sublethal effect of acetamiprid on S. miscanthi and S. graminum was evaluated using life-table analyses. The results showed that acetamiprid has a high toxicity to S. miscanthi and S. graminum with a LC50 of 1.90 and 3.58 mg/L at 24 h, respectively. The adult longevity and fecundity of S. miscanthi and S. graminum F0 generation were significantly reduced after being exposed to a sublethal concentration of acetamiprid. Additionally, the sublethal concentration of acetamiprid had negative transgenerational effects on S. miscanthi and S. graminum, which showed a significant decrease in fecundity and population life-table parameters involving age-stage-specific survival rate (sxj), age-specific survival rate (lx), and intrinsic rate of increase (r). Furthermore, the population projections showed that the total population size of S. miscanthi and S. graminum was significantly lower in the aphid group exposed to sublethal concentration of acetamiprid compared to the control group. These results suggest that sublethal concentration of acetamiprid suppresses the population growth of S. miscanthi and S. graminum. This finding is beneficial to the control of wheat aphids, and is important to fully understand the role of acetamiprid in integrated pest management.

The Impact of High-Temperature Stress on the Growth and Development of Tuta absoluta (Meyrick).

Insect life processes and reproductive behaviors are significantly affected by extremely high temperatures. This study focused on Tuta absoluta, which poses a severe threat to tomato cultivars. The effects of intense heat stress on the growth, development, oviposition, and longevity of T. absoluta were investigated. This investigation encompassed various developmental stages, including eggs, pupae, and adults. This study revealed that egg hatching and pupa emergence rates were significantly reduced at a temperature of 44 °C maintained for 6 h. The longevity of adults that emerged after the egg and pupal stages were exposed to 44 °C for 6 h was significantly reduced compared to the control. Notably, there was no significant variation in adult fecundity after egg-stage exposure to high temperatures. However, all treatments exhibited significantly reduced fecundity compared to the control after exposure to high temperatures during the pupal stage. Adult survival rates after exposure to 40 °C and 44 °C for 3 h were 74.29% and 22.40%, respectively, dramatically less than that of the control, which was 100%. However, no significant differences were noted in terms of longevity and egg production. These results offer a better understanding of the complex interactions between extreme temperatures and the life history traits of T. absoluta, thereby offering valuable insights for implementing management strategies to alleviate its impact on tomato crops in response to climate change.

Physical traits and fitness of cold-induced lethargic Diachasmimorpha longicaudata (Hymenoptera: Braconidae) adults

ABSTRACT The chilled adult technique is a suitable strategy for the mass-release of insects for the area-wide management of insect pests. Chilling may have undesirable effects on the released insects. The relationship between physical traits and the effects of cold-induced lethargy on the fitness of Diachasmimorpha longicaudata has not been fully explored. In the present study, we evaluated the relationship between weight, size, and water and lipid content in D. longicaudata subjected to cold-induced lethargy at 9, 6, and 3°C, and the effects of cold induction on the survival, flight ability, and fecundity of parasitoid adults. During gradual chilling from 15°C to 3°C over a 45 min period, we observed that most wasps became lethargic at 9°C. The tibias of wasps that became lethargic at 3°C were larger than those of parasitoids that became lethargic at 9 and 6°C. Body water and lipid contents were higher in lethargic females chilled at 3°C, but no differences were observed in males. Lethargic males experienced reduced flight ability compared with the control, whereas fecundity was reduced only in lethargic females that had been exposed to 3°C. The survival rate was lower in both sexes. Our results suggest that greater body size and higher water and lipid contents delay the onset of cold-induced lethargy, but do not prevent negative effects on survival, fecundity, and flight ability in D. longicaudata. This study will help the advancement of parasitoid-release field programmes that use the chilled adult technique.

Improving quality of stored Trichogramma evanescens (Hymenoptera: Trichogrammatidae) by inducing diapause or quiescence

BackgroundEfficacy of parasitic wasps from the genus Trichogramma to attack the eggs of numerous important pests in various agricultural crops makes them one of the most prevalent biocontrol agents. In Trichogramma, the pre-pupal stage can survive during the cold season in a dormant state (diapause or quiescence). The optimal conditions for the induction of this pause of development during mass rearing to store the parasitoid for a long time in good quality depend on the species. In the present study, four factors [the incubation periods (24 and 48 h), diapause induction temperatures (9 and 11 °C), durations of the diapause induction (from 0 to 6 weeks), and the periods of storage (from 0 to 6 months)], were experimented to force Trichogramma evanescens Westwood, reared on Sitotroga cerealella, to enter diapause or quiescence and estimating their impacts on the efficacy of stored parasitoid.ResultsResults confirmed that the life parameters of T. evanescens as the percentage of adult emergence, female percentage, rates of wing deformation of emerged adults, and fecundity of emerged females were significantly affected by all experimented factors. The pre-storage treatments made it possible to store the parasitoid for at least 2 months at 3 °C, with no much changes in their fitness, the emergence rate of adults reached more than 80%, and the egg-laying efficacy of females reached more than 42 eggs per emerged female, when diapause induction treatments were applied for 5 weeks at 11 °C after 24 h of incubation. Furthermore, there is the possibility of storage for 6 months with an acceptable level of parasitoid’s quality, when diapause induction treatments were applied for 5 weeks at 9 °C after 24 h of incubation, the emergence rate reached 70%, and the number of eggs per female was 52 eggs, while no emergence of adult insects was recorded after 3 months of cold storage without diapause induction treatments.ConclusionTwo storage programs were reached for T. evanescens (depending on the adult emergence rate and fecundity of emerged females). There is a long-term storage (6 months), when diapause was induced at a low temperature (9 °C) after 24 h of incubation. Short-term storage (from 2 to 4 months), when quiescence was induced under a higher temperature of 11 °C after both 24 and 48 h of incubation.