Insect Pest Populations Research Articles

A Low-Cost Remotely Configurable Electronic Trap for Insect Pest Dataset Generation

The precise monitoring of insect pest populations is the foundation of Integrated Pest Management (IPM) for pests of plants, humans, and animals. Digital technologies can be employed to address one of the main challenges, such as reducing the IPM workload and enhancing decision-making accuracy. In this study, digital technologies are used to deploy an automated trap for capturing images of insects and generating centralized repositories on a server. Subsequently, advanced computational models can be applied to analyze the collected data. The study provides a detailed description of the prototype, designed with a particular focus on its remote reconfigurability to optimize repository quality; and the server, accessible via an API interface to enhance system interoperability and scalability. Quality metrics are presented through an experimental study conducted on the constructed demonstrator, emphasizing trap reliability, stability, performance, and energy consumption, along with an objective analysis of image quality using metrics such as RMS contrast, Image Entropy, Image sharpness metric, Natural Image Quality Evaluator (NIQE), and Modulation Transfer Function (MFT). This study contributes to the optimization of the current knowledge regarding automated insect pest monitoring techniques and offers advanced solutions for the current systems.

Population dynamics and diversity of pests and natural enemies in various organic rice regimes across different phenological stages in rice

A field study was conducted at the ICAR-Indian Institute of Rice Research to investigate insect pest populations and their natural enemies in different organic rice modules during the rabi 2020 season. Three organic rice regimes, farmers’ practice and untreated control were compared across three phenological stages in rice for the population dynamics of pests and natural enemies of Hemiptera and Hymenoptera. Sampling was done fortnightly for three months using various methods such as visual counting, sticky traps, sweep netting, and D-net. Pest and predator populations peaked during the vegetative stage, while parasitoids peaked during the reproductive stage. Pest population means were highest in untreated control during the reproductive and ripening stages exhibiting the impact of treatments. The predator population was highest in untreated control during the vegetative and reproductive stage, while parasitoid population size was highest in Pseudomonas treatment in the vegetative and reproduction stages of the crop and the Trichoderma treatment in the ripening stage. Predator diversity was highest in untreated control during vegetative and reproductive stages of the crop while parasitoid diversity was maximum during reproductive and ripening stage. Pearson’s correlation coefficient between the population of pests and natural enemies was found to be positive and highly significant.

Impact of Weather Parameters on the Population Fluctuation of Major Sucking Pest in Summer Mung Bean [Vigna radiata (L.) Wilczek

Background: Mungbean may be grown in an extensive range of agro climatic zones in India and across the world. It is a crucial component of our diet. Because of its capacity to fix nitrogen, it also plays a vital role in managing soil fertility. Mung beans are one of the most significant crops for farmers as a cash crop. In order to implement control measures effectively and on schedule, it is crucial to monitor the population dynamics of major sucking pests, such as aphids, jassids and whiteflies in relation of weather parameters. Methods: PDM-139 (Samrat) variety seeds were manually planted 5-7cm deep in the ground. Weekly observations were made from 10 randomly chosen plants Split cage methods were used to record the observations of jassids and whiteflies and aphids from the top and bottom surfaces of the first three trifoliate plants were tallied. Averages population were computed. Result: The incidence of pest population start on the 14-15th standard meteorological weeks which attain their peak population in 19th SMW. The insect-pest population was established positive correlation with the max and min temperature whereas population was negatively correlated with R.H. and Rainfall.

Conservation agriculture compared to conventional tillage improves the trade-off between ground-dwelling arthropod trophic groups for natural pest regulation in cotton cropping systems

Conservation agriculture is an innovative approach based on minimal soil disturbance, soil cover with crop residues, and crop rotation, which increases the biodiversity of soil macrofauna thus contributing to nutrient cycling and soil aggregation. In addition, macrofaunal abundance may play a role at regulating insect pest populations. The study aims to predict the effects of soil management practices (conventional tillage and conservation agriculture) on the abundance of soil macrofauna and herbivore predation in cotton (Gossypium hirsutum L.) based cropping systems. We conducted a field experiment with a randomized complete block comprising two treatments, Conventional Tillage (CT) and Conservation Agriculture (CA), and six replications in a cotton-maize rotation system from 2020 to 2023. Soil monoliths and pitfall traps were installed in both treatments to collect ground-dwelling arthropods, to analyse the influence of soil management practices on their abundance, their trophic groups, and the rate of pest predation by generalist predators. Pest predation rates were assessed using artificial caterpillars made from plasticine. The results showed significant positive effects of soil management practices on herbivory rate, herbivore abundance, predator abundance, omnivore-predator abundance and pest predation rate. The average herbivory rate was 9.8 % in the conservation agriculture plots and 11.6 % in the conventional tillage plots. Overall, the predation rate was 58.9 % in the conservation agriculture plots and 21.8 % in the conventional tillage plots. The abundance of predators and of omnivore-predators were significantly higher in conservation agriculture than in conventional tillage. These findings suggest that conservation agriculture practices improve soil macrofauna and pest regulation, with potential benefits on soil quality and sustainability in cotton cropping systems.

Multigenerational hormetic effects of different insecticides on Spodoptera frugiperda (J.E. smith) (Lepidoptera: Noctuidae)

To protect crops from pest insects, farmers continuously use insecticides, which eventually degrade into residue due to abiotic or biotic factors. These residual effects of pesticides may cause low lethal and/or sublethal impacts on the exposed pest insect populations, leading to the induction of pest resurgence through hormesis and ultimately the development of resistance. Hormesis is a beneficial bi-phasic effect generally characterized by low-dose reproductive stimulation and high-dose inhibition. In the present study, we investigated the impact of low lethal and sublethal concentrations (LC10, LC20, and LC30) of spinetoram, chlorantraniliprole, and thiodicarb on the F0 generation as well as their multigenerational hormesis effects on the F1 and F2 generations of Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). The study focused on reproductive parameters, fecundity, fertility, and life index parameters such as net reproductive rate (R0), intrinsic rate of increase (rm), finite rate of increase (λ), mean length of generation (Tc), and gross reproductive rate (GRR). Fecundity of S. frugiperda increased by 4.82%, 4.63% and 4.58%, while eggs fertility improved by 7.77%, 6.78% and 6.52% at LC10 of thiodicarb, chlorantraniliprole and spinetoram, respectively, from the F1 to F2 generation. Further, interaction analysis (Concentration × Insecticidal treatments) revealed that important vital parameters like pre-oviposition period (POP), oviposition period (OP), post-oviposition period (PtOP), R0,rm,λ, Tc and GRR of F0 were negatively impacted by LC30 of all the tested insecticides and LC20 of only spinetoram. However, LC10 of any of the tested insecticides did not affect these parameters when compared with control. Furthermore, interactive analysis in multigenerational exposure experiments (Concentration × Insecticidal treatments × Generation(s)) showed hermetic effects of LC10 of all tested insecticides which is more positive in F2 as compared to F1 generation. These unwanted positive hermetic effects of low lethal concentrations (LC10) of tested insecticides in offspring of exposed parental population of S. frugiperda indicated its resistance and/or resurgence. Furthernore, present study emphasizes the necessity for additional research to elucidate the underlying mechanisms responsible for these effects.

Seasonal Variations in Population Dynamics of Insect Pests in Tiruvallur District, Tamil Nadu, India

Understanding the complex relationship between seasonal changes and pest dynamics is essential for establishing effective protection methods in contemporary agriculture and guaranteeing long-term agricultural sustainability and food security. The study was conducted in the Tiruvallur District of Tamil Nadu, India, which is characterized by a tropical climate with distinct wet and dry seasons [1]. Shannon-Wiener Index and Simpson's Index biodiversity indices reflected the moderate to high pest diversity of species in the region. Values for Shannon-Wiener indexes ranged between about 1.93-1.95 for different species of insect pests, and Simpson's indexes were found to range between about 0.85-0.86. All these indices indicate a well-balanced insect pest community with high species richness and even distribution, which is necessary to maintain ecological resilience. The findings enrich our understanding of pest ecology in tropical agriculture and provide valuable insights applicable to other regions facing similar issues. The observed seasonal patterns emphasize the importance of ongoing monitoring and adaptive management to tackle the challenges posed by insect pests amid climate variability and agricultural intensification. Additionally, this research offers a thorough framework for comprehending and managing insect pest populations in the Tiruvallur District.

Isolation, morphological characterization, and screening virulence of Beauveria bassiana and Metarhizium robertsii fungal isolates on Galleria mellonella

Background Entomopathogenic fungi exists naturally in plants as an asymptote and have the potential to reduce the population of insect pests through indirect interactions. This study was conducted to detect and characterize the endophytic fungi Beauveria bassiana and Metarhizium robertsii from the rhizosphere soil of tomato plants and their virulence effect on Galleria melonella. Methods From the rhizosphere soil of 40 tomato fields, three Beauveria bassiana and seven Metarhizium robertsii isolates were isolated using the galleria bait method. All fungi isolate were morphologically characterized by their colony color, shape, and surface texture. Isolates with the highest percentages of germination, conidial yield, and radial growth were selected, and their virulence was evaluated on second instar larvae of Galleria melonella under laboratory conditions. Results In this study, Beauveria bassiana showed white colony color and aseptate hyphae, whereas Metarhizium robertsii showed dark green to light green colony color and septate hyphal structures. Maximum spore production and conidial length were obtained by Beauveria bassiana isolate APPRC-27 with 2.67x107 spores ml-1 and 3.24 µm, respectively. Colony radial growth rates ranged from 1.73 to 3.24 mm day-1. The results revealed that the highest mortality rate of Galleria melonella (100%) was obtained by Metarhizium robertsii isolates K-61 and K-102 at a concentration of 1x108 conidial ml-1 at 7 days post-inoculation. The lowest mortality rate was registered by Metarhizium robertsii isolate RST-11. Conclusions In the present study, isolates that produced the most spores and had the highest germination rates were the most virulent to Galleria mellonella second instar larvae. Therefore, virulent entomopathogenic fungi, Beauveria bassiana and Metarhizium robertsii, are promising bioagents for the control of insect pests.

Population suppression with dominant female-lethal alleles is boosted by homing gene drive

BackgroundMethods to suppress pest insect populations using genetic constructs and repeated releases of male homozygotes have recently been shown to be an attractive alternative to older sterile insect techniques based on radiation. Female-specific lethal alleles have substantially increased power, but still require large, sustained transgenic insect releases. Gene drive alleles bias their own inheritance to spread throughout populations, potentially allowing population suppression with a single, small-size release. However, suppression drives often suffer from efficiency issues, and the most well-studied type, homing drives, tend to spread without limit.ResultsIn this study, we show that coupling female-specific lethal alleles with homing gene drive allowed substantial improvement in efficiency while still retaining the self-limiting nature (and thus confinement) of a lethal allele strategy. Using a mosquito model, we show the required release sizes for population elimination in a variety of scenarios, including different density growth curves, with comparisons to other systems. Resistance alleles reduced the power of this method, but these could be overcome by targeting an essential gene with the drive while also providing rescue. A proof-of-principle demonstration of this system in Drosophila melanogaster was effective in both biasing its inheritance and achieving high lethality among females that inherit the construct in the absence of antibiotic.ConclusionsOverall, our study shows that substantial improvements can be achieved in female-specific lethal systems for population suppression by combining them with various types of gene drive.

INFESTATION OF DIFFERENT INSECT PESTS ON NOVEL COTTON CULTIVARS AND THEIR IMPACTS ON COTTON FIBER QUALITY PARAMETERS

Pakistan is the 5th largest producer of cotton in the world. Exports of cotton and textile products have a share of around 60 percent in overall exports of the country. A field experiment was conducted to evaluate the different fiber quality parameters in relation to different insect pest populations. The introduction of this new types of cultivars may satisfy the needs of farmers for better quality and quantity, laborers who harvest crops, and other investors, including those in the cotton sector. A field research was carried out at the Cotton Research Station, Faisalabad, Pakistan, during the year 2023 cotton cultivars (VH-447, FH-1133, BH-228, SLH-94, MNH-S GOLD, BH-227, FH-1214, MNH-1095, VH-442, MNH-1090, RH-BAGHO BAHAR, MNH-1050, and MNH-TP) were evaluated for resistance to sucking pests such as whitefly (Bemisia tabaci); jassid (Amrasca biguttula biguttula); and thrips (Thrips tabaci) as well as bollworms such as pink bollworm (Pectinophora gossypiella); spotted bollworm (Earias insulana; E. vitelli); and American bollworm (Helicoverpa armigera). There were notable variations across the genotypes in terms of the population of sucking and bollworm insect pest infestation, which lowers cotton production and negatively affects fiber quality. FH-1133 showed the lowest average populations of thrips (1.00/leaf), jassid (0.27/leaf), and whiteflies (2.00/leaf), indicating the highest resistance. The average population (9.84%) of pink bollworm larvae in residual boll. The virus percentage on different cotton genotypes recorded after 30, 60, 90, and 120 days was 0.00, 9.00, 14.00, and 19.00%, respectively. The cultivar FH-1133 was observed to be good for all other genotypes of cotton due to its yield (2372.50 kg/acre), and it had the following lint quality attributes: GOT (46.50%), staple length (28.50 mm), fiber fineness (4.70 µg/inch), and fiber strength (33.20 g/tex).

Advancements and Future Prospects of CRISPR-Cas-Based Population Replacement Strategies in Insect Pest Management.

Population replacement refers to the process by which a wild-type population of insect pests is replaced by a population possessing modified traits or abilities. Effective population replacement necessitates a gene drive system capable of spreading desired genes within natural populations, operating under principles akin to super-Mendelian inheritance. Consequently, releasing a small number of genetically edited insects could potentially achieve population control objectives. Currently, several gene drive approaches are under exploration, including the newly adapted CRISPR-Cas genome editing system. Multiple studies are investigating methods to engineer pests that are incapable of causing crop damage or transmitting vector-borne diseases, with several notable successful examples documented. This review summarizes the recent advancements of the CRISPR-Cas system in the realm of population replacement and provides insights into research methodologies, testing protocols, and implementation strategies for gene drive techniques. The review also discusses emerging trends and prospects for establishing genetic tools in pest management.

Morphological Parameters of Sesame in Relation to Susceptibility to Major Sucking Insect Pests

Based on previous field screening data 15 genotypes were selected (based on the number of insect pests population/ plant) to study the role of morphological parameters of sesame. Trichome density, length and width were estimated under microscope with the help of software. The 15 selected genotypes of sesame were studied for finding trichome’s role in host plant resistance against major sucking pests; whitefly Bemisia tabaci), leafhopper (Orocius albicinctus) and mirid bug (Nesidiocoris tenuis) of sesame and the correlation studies revealed that the density of non-glandular trichome showed significant positive correlation with the population of Orocius albicinctus (r= 0.868), Nesidiocoris tenuis (r=0.549) and Bemisia tabaci (r= 0.824) while length and width of non-glandular trichomes and density of glandular trichomes showed non-significant (±) impact on the incidence of tested sucking insect pests.

Seasonal occurrence of the shoot fly complex on Rabi sorghum in the Marathwada area of Maharashtra

The present study was conducted to investigate the variety and abundance of shoot flies in the Postgraduate Experimental Field, Department of Agricultural Entomology, College of Agriculture, Latur Campus, Maharashtra, India, during rabi season 2020-21. Analysis of insect pest population dynamics indicated that Atherigona soccata attained its maximum population density during the 51st standard meteorological week, with an average of 3.60 maggots per quadrat. Correlation studies exhibited that wind speed had a detrimental impact on the population of A soccata maggots. During the first sampling period of the study, Oscinella sp. achieved its peak population density, with an average of 13.00 maggots per quadrat. Link tests revealed a positive link between the relative humidity before noon and the population of Oscinella sp., but a substantial negative correlation was seen between wind speed and the population. The population of Ectecephala sp. reached its highest level during the second sampling week, with an average of 2.33 maggots per quadrat. Correlation studies demonstrated a substantial negative correlation between wind speed and the population of Ectecephala sp.

Investigating the Effects of Bamboo Vinegar as An Organic Pesticide on Insect Pests and the Nutrient Content of Harumanis Mango (MA128), Mangifera indica L.

Chemical pesticides have been widely used in plantations, and their effects have more disadvantages to the environment as well as to humans. Therefore, this study tries to implement organic pesticides using bamboo vinegar. Bamboo vinegar is one of the organic pesticides to control insect pests in plantation crops. The role of this organic pesticide on the insect pests of Harumanis mango is still unknown. Hence, this study aims to determine the impact of applying bamboo vinegar on the insect pests, quality, and nutrient content of Harumanis mango (MA128). Bamboo vinegar was applied in February 2021 during the flowering phase at the Harumanis plot in the Plantation Unit, Universiti Teknologi MARA Perlis. This study used a randomized complete block design with three treatments (spraying intervals) and three replications: T1 (3-day interval), T2 (5-day interval), and T3 (no bamboo vinegar). Sticky traps were installed to determine the population of insect pests in Harumanis mango. Matured fruits have been harvested, and the standard procedure of Harumanis mango postharvest handling has been followed. Then, the fruits were determined for total phenolic content (TPC), total flavonoid content (TFC), vitamin C, and sugar content. Bamboo vinegar significantly reduced the abundance of insects in Harumanis mango. Additionally, the highest TPC was observed from a 3-day interval of bamboo vinegar application. A similar trend was indicated for improving TFC with bamboo vinegar application. Similarly, there was a significantly higher vitamin C and sugar content after bamboo vinegar application compared to the control group. In conclusion, applying bamboo vinegar to Harumanis mango reduced insect pests and increased the quality and nutrient content of the Harumanis mango.

Resistance of Lepidopteran Pests to Bacillus thuringiensis Toxins: Evidence of Field and Laboratory Evolved Resistance and Cross-Resistance, Mode of Resistance Inheritance, Fitness Costs, Mechanisms Involved and Management Options.

Bacillus thuringiensis (Bt) toxins are potential alternatives to synthetic insecticides for the control of lepidopteran pests. However, the evolution of resistance in some insect pest populations is a threat and can reduce the effectiveness of Bt toxins. In this review, we summarize the results of 161 studies from 20 countries reporting field and laboratory-evolved resistance, cross-resistance, and inheritance, mechanisms, and fitness costs of resistance to different Bt toxins. The studies refer mainly to insects from the United States of America (70), followed by China (31), Brazil (19), India (12), Malaysia (9), Spain (3), and Australia (3). The majority of the studies revealed that most of the pest populations showed susceptibility and a lack of cross-resistance to Bt toxins. Factors that delay resistance include recessive inheritance of resistance, the low initial frequency of resistant alleles, increased fitness costs, abundant refuges of non-Bt, and pyramided Bt crops. The results of field and laboratory resistance, cross-resistance, and inheritance, mechanisms, and fitness cost of resistance are advantageous for predicting the threat of future resistance and making effective strategies to sustain the effectiveness of Bt crops.

Neuropeptide natalisin regulates reproductive behaviors in Spodoptera frugiperda

Natalisin (NTL) is a conserved neuropeptide, only present in insects, that has been reported to regulate their sexual activity. In this study, we investigated the involvement of NTL in the reproductive behaviors of a major invasive pest, Spodoptera frugiperda. We identified NTL precursor-encoded transcripts, and evaluated their transcript levels in different stages and tissues of S. frugiperda. The results showed that the NTL transcript level was expressed in both male and female pupae and both male and female adults in the later stage. It was highly expressed in male pupae, 3-day-old male and female adults, and 5-day-old male adults. In different tissues, the expression level is higher in the male and female adult brain and male testis. Immunohistochemical staining of the brain of S. frugiperda female and male adults revealed that three pairs of brain neurons of S. frugiperda adults of both sexes secreted and expressed NTL. To study the role of NTL in reproductive behaviors, NTL was silenced in S. frugiperda male and female adults by RNA interference (RNAi) technology, the results showed that silencing NTL could significantly affect the sexual activity behavior of the adults, reducing the calling rate of females, the courtship rate of males, and the mating rate. In summary, this study emphasizes the important role of NTL in regulating the mating behavior and sexual activity of S. frugiperda in both male and female adults, potentially laying a foundation to employ NTL as a new insect-specific target to control populations of pest insects.

The Increase of Insect Pest Population in Paddy Field Managed with an Ecological Approach using Refugia Plants and Biopesticides

Insect pests can damage plants and act as vectors of diseases such as brown planthoppers which can transmit dwarf virus disease. The presence of insect pests is influenced by the type of variety, planting patterns, and excessive use of chemical pesticides so that insect pests increase and are difficult to control. This research wanted to provide insights into the effectiveness of combining insectary plants and biopesticides as ecological strategies to manage paddy (Oryza sativa Linnaeus) insect pests. The study was conducted in February-April 2024 in Sukodadi Village, Sukodadi District, Lamongan Regency. Method of study was conducted using a combination of direct observation, insect traps, and quantitative analysis to evaluate the impact of refugia plants and biopesticides on insect pest populations in paddy fields. The analysis includes the species diversity index (Shannon-Winner), species evenness index, species richness index (Margalef), dominance index (Simpson) and similarity index (Bray-Curtis). The study obtained 2,687 individual insect pests in paddy fields with refugia and fobio and 1,761 individuals in paddy fields without refugia and fobio. Insect pests were more abundant in paddy fields with refugia and fobio compared to fields without refugia and fobio. Refugia provides alternative habitats and additional resources for insect pests, and the use of biopesticides can create temporary ecosystem imbalances, and increase the population of insect pest.

Comparative Efficacy of Organic Mulching and Organic Neem Oil in the Control of spotted and striped cucumber beetles affecting the growth and yield of Cucumber in Uyo, Akwa Ibom State

A research work was undertaken in the University of Uyo Teaching and Research Farm, Main Campus, Uyo, from March to May during the 2023 cropping season to assess the effect of Organic Mulching and Neem Oil in the Control of Cucumber Beetles (spotted “Diabrotica undecimpunctata” and striped “Acalymma vitatum”) affecting the growth and yield of Cucumber (Cucumis sativum, Saira F1 variety). The experiment was laid out in Randomized Complete Block Design (RCBD). The experimental plot consisted of three (3) replicates with 2 treatments: organic mulch, organic Neem oil application and control. An early maturing variety of cucumber “Saira F1” was used as planting material sown in March which lasted till May. Data on insect pest population count, growth and yield parameters were studied and the data obtained were analyzed and subjected to analysis of variance using Fisher`s Least Significant Difference (LSD) at 5% probability level. The results from insect population count parameters revealed that Neem oil at 100ml application rate which recorded 10.50 and 6.00 was significantly effective in managing spotted and striped cucumber beetles respectively compared to organic mulch (3kg) which recorded 47.00 and 14.00 for spotted and striped cucumber beetles and control unit which had 61.00 and 42.00 for spotted and striped cucumber beetles respectively. Neem oil at 100ml application rate was also more effective in improving the growth and yield of cucumber plant compared to organic mulch. Hence, Farmers in Uyo, Akwa Ibom State should employ Neem oil in managing spotted and striped cucumber beetles in cucumber production as this is a promising botanical insecticide to check the activities of field cucumber beetles thereby bringing their destructive activities to a minimum and also improves yield.

Seasonal Incidence of Major Insect Pests of Chilli and Their Correlation with Weather Parameters

Study Design: Randomised Block Design (RBD) with three (3) replications. Place and Duration of Study: Biswanath College of Agriculture, Assam Agricultural University, Assam,India. The experiment was conducted during Rabi 2022-23. Methodology: Suryamukhi variety of chilli from packages of practices for Organic crops of Assam was used for this investigation. Three sucking pests viz, Aphis gossypii, Scirtothrips dorsalis, Amrasca biguttula biguttula and one fruit borer Helicoverpa armigera was found infesting the chilli plants. Weather parameters such as maximum temperature, minimum temperature, average relative humidity, rainfall and bright sunshine hours were correlated with the insect populations. Results: Aphids were positively correlated with sunshine hours (r=0.503*), thrips showed negative correlation with average relative humidity (r= -0.620*), jassids had a negative correlation with minimum temperature (r=-0.701*) and fruit borer showed negative correlation with sunshine hours (r= -0625**). Rainfall had no significant effect on incidence of pest population in chilli. Conclusion: Insect pest populations are highly influenced by weather parameters. Through this research we can develop new pest management strategies according to their appearance and peak activity period.

On the impact of re-mating and residual fertility on the Sterile Insect Technique efficacy: Case study with the medfly, Ceratitis capitata.

The sterile insect technique (SIT) can be an efficient solution for reducing or eliminating certain insect pest populations. It is widely used in agriculture against fruit flies, including the Mediterranean fruit fly (medfly), Ceratitis capitata. The re-mating tendency of medfly females and the fact that the released sterile males may have some residual fertility could be a challenge for the successful implementation of the SIT. Obtaining the right balance between sterility level and sterile male quality (competitiveness, longevity, etc) is the key to a cost-efficient program. Since field experimental approaches can be impacted by many environmental variables, it is difficult to get a clear understanding on how specific parameters, alone or in combination, may affect the SIT efficiency. The use of models not only helps to gather knowledge, but it allows the simulation of a wide range of scenarios and can be easily adapted to local populations and sterile male production. In this study, we consider single- and double-mated females. We first show that SIT can be successful only if the residual fertility is less than a threshold value that depends on the basic offspring number of the targeted pest population, the re-mating rates, and the parameters of double-mated females. Then, we show how the sterile male release rate is affected by the parameters of double-mated females and the male residual fertility. Different scenarios are explored with continuous and periodic sterile male releases, with and without ginger aromatherapy, which is known to enhance sterile male competitiveness, and also taking into account some biological parameters related to females that have been mated twice, either first by a wild (sterile) male and then a sterile (wild) male, or by two wild males only. Parameter values were chosen for peach as host fruit to reflect what could be expected in the Corsican context, where SIT against the medfly is under consideration. Our results suggest that ginger aromatherapy can be a decisive factor determining the success of SIT against medfly. We also emphasize the importance of estimating the duration of the refractory period between matings depending on whether a wild female has mated with a wild or sterile male. Further, we show the importance of parameters, like the (hatched) eggs deposit rate and the death-rate related to all fertile double-mated females. In general, re-mating is considered to be detrimental to SIT programs. However, our results show that, depending on the parameter values of double-mated females, re-mating may also be beneficial for SIT. Our model can be easily adapted to different contexts and species, for a broader understanding of release strategies and management options.

Long-term suppression of turfgrass insect pests with native persistent entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) can control several important turfgrass insect pests including white grubs, weevils, cutworms, and sod webworms. But most of the research has focused on inundative releases in a biopesticide strategy using EPN strains that may have lost some of their ability to persist effectively over years of lab maintenance and / or selection for virulence and efficient mass-production. Our study examined the potential of fresh field isolate mixes of endemic EPNs to provide multi-year suppression of turfgrass insect pests. In early June 2020, we applied isolate mixes from golf courses of the EPNs Steinernema carpocapsae, Heterorhabditis bacteriophora, and their combination to plots straddling fairway and rough on two golf courses in central New Jersey, USA. Populations of EPNs and insect pests were sampled on the fairway and rough side of the plots from just before EPN application until October 2022. EPN populations increased initially in plots treated with the respective species. Steinernema carpocapsae densities stayed high for most of the experiment. Heterorhabditis bacteriophora densities decreased after 6 months and stabilized at lower levels. Several insect pests were reduced across the entire experimental period. In the fairway, the combination treatment reduced annual bluegrass weevil larvae (59 % reduction) and adults (74 %); S. carpocapsae reduced only adults (42 %). White grubs were reduced by H. bacteriophora (67 %) and the combination (63 %). Black turfgrass ataenius adults were reduced in all EPN treatments (43–62 %) in rough and fairway. Sod webworm larvae were reduced by S. carpocapsae in the fairway (75 %) and the rough (100 %) and by H. bacteriophora in the rough (75 %). Cutworm larvae were reduced in the fairway by S. carpocapsae (88 %) and the combination (75 %). Overall, our observations suggest that inoculative applications of fresh field isolate mixes of endemic EPNs may be a feasible approach to long-term suppression of insect pests in turfgrass but may require periodic reapplications.