Field Pests Research Articles

Evaluation of Maize Varieties for Resistance to Field Pests: Fall Armyworm (Spodoptera frugiperda JE Smith) and Stem Borer in a Tropical Rainforest Agro-Ecology

Aims: To evaluate newly improved maize varieties for fall armyworm and stem borer resistance and determine the relationship among traits for increased productivity in a rainforest location in Nigeria.
 Study Design: The experiments were laid out in a 10 x 10 triple lattice design with three replications and Randomized Complete Block Design (RCBD) in four replicates.
 Place and Duration of Study: Field experiments were conducted during the late seasons of 2018 and 2019 at Obafemi Awolowo University Teaching and Research Farm, Ile Ife, Osun State, Nigeria.
 Methodology: Hundred newly improved maize varieties were evaluated during the late season of 2018 for fall armyworm resistance, while ten stem borers resistant varieties were evaluated during the late season of 2019. Data were collected on emergence, flowering, vegetative, armyworm, and grain yield traits. Data collected were subjected to analysis of variance (ANOVA), descriptive statistics, correlation and cluster Analysis.
 Results: Differential responses for resistance to fall armyworm traits were observed for all the varieties evaluated. Fall armyworm trait was observed to be negatively correlated with emergence percentage and ear number and positively correlated with flowering traits and moisture content. Furthermore, the results from the stem borer varieties evaluation indicated varietal differences for emergence percentage, plant height, ear height and kernel number. Stand count, ear number and weight per plot, moisture content had a significant positive correlation with yield while days to tasseling and silking and kernel row number had a significant negative correlation with yield.
 Conclusion: The best resistant varieties to fall armyworm were F2SCA 1413-36, ACR. 06 TZL COMP. 3C4 and 2013 TZEE-W POP STR with 6.01 tons/ha, 5.11 tons/ha, and 4.87 tons/ha of yield respectively while that of stem borer were TZBR Comp 1 –W C2 and Ama TZBR-W C4 with grain yield of 3.7 tons/hectare and 3.5 tons/hectare respectively.

Ecology and distribution of Leptospira spp., reservoir hosts and environmental interaction in Sri Lanka, with identification of a new strain.

Leptospirosis is a neglected zoonotic disease and one of the leading causes of zoonotic morbidity and mortality, particularly in resource-poor settings. Sri Lanka has one of the highest disease burdens worldwide, with occasional endemic leptospirosis outbreaks (2008, 2011). Rodents are considered the main wildlife reservoir, but due to a scarcity of studies it is unclear which particular species contributes to bacterial transmission and reservoir maintenance in this multi-host multi-parasite system. Several rodent species act as agricultural pests both in rice fields and in food storage facilities. To unravel the interactions among the small mammal communities, pathogenic Leptospira spp. and human transmission pathways, we collected animals from smallholder food storage facilities, where contact between humans and small mammals is most likely, and screened kidney tissue samples for Leptospira spp. using PCR. Samples were collected in three climatic zones along a rainfall gradient. Pathogenic Leptospira spp. were detected in small mammal communities in 37 (74%) out of 50 sampled farms and 61 (12%) out of 500 collected individuals were infected. The small mammal community was comprised of Rattus rattus (87.6%), Suncus shrews (8.8%), Bandicota spp. (2.8%) and Mus booduga (0.8%). Three pathogenic Leptospira spp. were identified, L. borgpetersenii (n = 34), L. interrogans (n = 15), and L. kirschneri (n = 1). Suncus shrews were commonly infected (32%), followed by B. indica (23%) and R. rattus (10%). L. borgpetersenii strains similar to strains previously extracted from human clinal samples in Sri Lanka were detected in R. rattus and Suncus shrews. L. interrogans was observed in R. rattus only. A single L. kirschneri infection was found in M. booduga. The presence of human pathogenic Leptospira species in an agricultural pest rodent (R. rattus) and in commensal shrews (Suncus) calls for management of these species in commensal settings. Further investigation of the interplay between pathogen and reservoir population dynamics, overlap in geographic range and the extent of spill-over to humans in and around rural settlements is required to identify optimal management approaches.

Exploring the Antioxidant and Bioinsecticidal Activity of Spontaneous Flora Vegetal Extracts for Plant Protection and Prevention of Soil Contamination

The purpose of this article was to evaluate the application of different plant extracts with bioinsecticidal action and antioxidant activity for plants and soil protection, by substitution of the application of synthetically formulated pesticides with eco-friendly compounds. In this framework, this research focused on the utilization of plant extracts from the spontaneous flora of Moldova (Romania) as bioinsecticides for the control of field pests of the species Leptinotarsa decemlineata and their antioxidant activity. Plant extracts of oregano (Origanum vulgare), yarrow (Achillea millefolium), wormwood (Artemisia absinthium), and cowslip (Primula veris) were assessed for their antioxidant activity by the microplate spectrophotometric-based method (for polyphenols and flavonoids content and for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenger activity) and were characterized by FTIR spectroscopy spectra. To evaluate the bioinsecticidal properties of the plant extracts, the mortality (%) and neuroleptic manifestations appearing in the middle of the monitoring period for larvae and adults of the Leptinotarsa decemlineata species were identified. Mortality (%) was statistically analyzed using a one-way analysis of variance (ANOVA) and the resulting experimental results were compared with the LSD-Fisher’s test (p < 0.05). The highest mortality (%) was observed after 24 h of treatment with extracts of Origanum vulgare at 100% concentration, while the maximum effect was recorded after 48 h for Origanum vulgare at 60% and 100% concentrations.

Identification of noble candidate gene associated with sensitivity to phytotoxicity of etofenprox in soybean

Phytotoxicity is caused by the interaction between plants and a chemical substance, which can cause critical damage to plants. Understanding the molecular mechanism underlying plant-chemical interactions is important for managing pests in crop fields and avoiding plant phytotoxicity by insecticides. The genomic region responsible for sensitivity to phytotoxicity of etofenprox (PE), controlled by a single dominant gene, was detected by constructing high density genetic map using recombination inbred lines (RILs) in soybean. The genomic region of ~ 80 kbp containing nine genes was identified on chromosome 16 using a high-throughput single nucleotide polymorphism (SNP) genotyping system using two different RIL populations. Through resequencing data of 31 genotypes, nonsynonymous SNPs were identified in Glyma.16g181900, Glyma.16g182200, and Glyma.16g182300. The genetic variation in Glyma.16g182200, encoding glycosylphosphatidylinositol-anchored protein (GPI-AP), caused a critical structure disruption on the active site of the protein. This structural variation of GPI-AP may change various properties of the ion channels which are the targets of pyrethroid insecticide including etofenprox. This is the first study that identifies the candidate gene and develops SNP markers associated with PE. This study would provide genomic information to understand the mechanism of phytotoxicity in soybean and functionally characterize the responsive gene.

Rice skipper, Pelopidas thrax (hubner) (Hesperiidae: lepidoptera): An emerging insect pest in rice fields in Egypt, host plants, population fluctuation, damage and related natural enemies

Rice (Oryza sativa L.) is a very important food crop in Egypt, particularly with shortage of wheat production for consumers. Insect pests are one of challenges against high yield productivity. Experiments and observations conducted at rice fields at Sakha Agricultural Research Station, Egypt during 2019, 2020 and 2021 seasons revealed occurrence of an emerging insect pest; rice skipper, Pelopidas thrax (Hubner) (Hesperiidae : Lepidoptera) . Larvae of skipper fed upon leaves of rice, barnyardgrass and juncle rice. Adult activity was low in June - July, increased by mid-August, and maximum by late August, and throughout September, with 3-4 seasonal peaks. In general, the damage in rice plants was low, so, the simulation technique, based upon removing certain areas of the flag leaves, was adapted. The treatments (removed areas); 0, 25, 50, 75 and 100 %. Induced reductions of 4.47-23.05% filled grain percentage, 2.07-6.61% in 1000-grain weight, and 5.95-31.86% in grain yield respectively. Seven parasitoid species were recorded. They are Trichogramma evanescens (on skipper eggs), Telenomus sp. (eggs), Chelonus sp. (egg-larva), Anomalon sp. (larvae), Cotesia ruficrus (lavae), Brachymeria sp. (pupae), and Exorista sp. (larvae). Also, two insect predators were found associated with P. thrax; Anatrichus pygmaeus, Paederus alfierii as well as the spider, Argiope trifasciata. Till now, Pelopidas thrax (Hubner) is considered a minor pest. Because of expected climatic changes and disturbances in rice ecosystem due to excessive use of pesticides, this skipper may become a major insect pest. Further studies are required to reveal additional biological and ecological aspects of this emerging insect.

MicroRNA-263b confers imidacloprid resistance in Sitobion miscanthi (Takahashi) by regulating the expression of the nAChRβ1 subunit

The Chinese wheat aphid Sitobion miscanthi (CWA) is an important harmful pest in wheat fields. Imidacloprid plays a critical role in controlling pests with sucking mouthparts. However, imidacloprid-resistant pests have been observed after insecticide overuse. Point mutations and low expression levels of the nicotinic acetylcholine receptor β1 (nAchRβ1) subunit are the main imidacloprid-resistant mechanisms. However, the regulatory mechanism underlying nAChRβ1 subunit expression is poorly understood. In this study, a target of miR-263b was isolated from the 5'UTR of the nAchRβ1 subunit in the CWA. Low expression levels were found in the imidacloprid-resistant strain CWA. Luciferase reporter assays showed that miR-263b could combine with the 5'UTR of the nAChRβ1 subunit and suppress its expression by binding to a site in the CWA. Aphids treated with the miR-263b agomir exhibited a significantly reduced abundance of the nAchRβ1 subunit and increased imidacloprid resistance. In contrast, aphids treated with the miR-263b antagomir exhibited significantly increased nAchRβ1 subunit abundance and decreased imidacloprid resistance. These results provide a basis for an improved understanding of the posttranscriptional regulatory mechanism of the nAChRβ1 subunit and further elucidate the function of miRNAs in regulating susceptibility to imidacloprid in the CWA. These results provide a better understanding of the mechanisms of posttranscriptional regulation of nAChRβ1 and will be helpful for further studies on the role of miRNAs in the regulation of nAChRβ1 subunit resistance in homopteran pests.

Field pest monitoring and forecasting system for pest control.

Insect pest is an essential factor affecting crop yield, and the effect of pest control depends on the timeliness and accuracy of pest forecasting. The traditional method forecasts pest outbreaks by manually observing (capturing), identifying, and counting insects, which is very time-consuming and laborious. Therefore, developing a method that can more timely and accurately identify insects and obtain insect information. This study designed an image acquisition device that can quickly collect real-time photos of phototactic insects. A pest identification model was established based on a deep learning algorithm. In addition, a model update strategy and a pest outbreak warning method based on the identification results were proposed. Insect images were processed to establish the identification model by removing the background; a laboratory image collection test verified the feasibility. The results showed that the proportion of images with the background completely removed was 90.2%. Dataset 1 was obtained using reared target insects, and the identification accuracy of the ResNet V2 model on the test set was 96%. Furthermore, Dataset 2 was obtained in the cotton field using a designed field device. In exploring the model update strategy, firstly, the T_ResNet V2 model was trained with Dataset 2 using transfer learning based on the ResNet V2 model; its identification accuracy on the test set was 84.6%. Secondly, after reasonably mixing the indoor and field datasets, the SM_ResNet V2 model had an identification accuracy of 85.7%. The cotton pest image acquisition, transmission, and automatic identification system provide a good tool for accurately forecasting pest outbreaks in cotton fields.

Sorghum Production in Northern Namibia: Farmers’ Perceived Constraints and Trait Preferences

Sorghum (Sorghum bicolor [L.] Moench) is a valuable crop in the dry regions of the world, including Namibia. Due to the intensity and recurrence of drought and heat stress in the traditional sorghum growing areas, there is a need to breed and deploy new generation farmer-preferred and climate-smart cultivars to serve the diverse value chains. Therefore, the objectives of this study were to assess the present state of sorghum production in northern Namibia and document farmers’ perceived production constraints and trait preferences in new varieties to guide drought-tolerance breeding. A survey was conducted using a participatory rural appraisal in the following six selected sorghum-growing constituencies in Namibia: Kapako and Mpungu (Kavango West Region), Eenhana and Endola (Ohangwena Region), and Katima Mulilo Rural and Kongola (Zambezi Region). Data were collected using a structured questionnaire involving 198 farmers in 14 sampled villages across the regions. Results revealed variable trends in sorghum production among respondent farmers when disaggregated by gender, age, number of households, education level, cropping systems, types of varieties grown, and perceived production constraints. An equal proportion of male and female respondent farmers cultivate sorghum, suggesting the value of the crop to both genders in Namibia. Most respondent farmers (63.6%) were in productive age groups of <40 years old. In the study areas, low-yielding landrace varieties, namely Ekoko, Okambete, Makonga, Kamburo, Nkutji, Katoma, Fuba, Dommy, Kawumbe, and Okatombo, were widely cultivated, and most of the farmers did not use chemical fertilizers to cultivate sorghum. Farmers’ perceived sorghum production constraints in the study areas included recurrent drought, declining soil fertility, insect pest damage, high cost of production inputs, unavailability of improved seed, lack of alternative improved varieties with farmers’ preferred traits, lack of organic manure, limited access to market and limited extension service. The key farmers’ preferred traits in a new sorghum variety included high grain yield, early maturity, and tolerance to drought, in the field and storage insect pests. The study recommends genetic improvement and new variety deployment of sorghum with the described farmers-preferred traits to increase the sustainable production of the crop in Namibia.

Knowledge and Practices of Vegetables Insect Pest Managements in Banganga Municipality of Kapilvastu District

A study was carried out in Banganga Municipality of Kapilvastu district to know the farmer's knowledge, practices, and management method used in insect pests of vegetables. The survey involved 160 randomly selected farmers who were interviewed using semi-structured questionnaires and also evaluated based on direct field observation. The data were analyzed using SPSS and Microsoft-Excel. Tomato, potato, chili, cauliflower, cabbage, garlic, and onion were major vegetables grown by the farmers during the winter season and cucumber, bottle gourd, bitter gourd, sponge gourd, tomato, chili, brinjal during the summer season. Aphids, cabbage butterfly, pumpkin beetle, tomato leaf miner, cutworm, and tomato fruit borer were the major pests in vegetable field. Knowledge of vegetable farmers regarding insect pest identification was also observed i.e., 86% of respondents identified insect pest by the help of Junior Technical Assistance and agro-vets, and 10% of respondents identified insects by their own knowledge. About 60% of respondents were found using chemical pesticides such as; chlorpyrifos, cypermethrin, imidacloprid, alphamethrin etc. to control pests, 4% of respondents were using botanical plant extract i.e., jholmal, neem extract, cow urine and 24% were using cultural methods such as crop rotation, mulching, tillage operation. Only a few farmers' groups were found to know about IPM, biological pest management practices, and conservation of natural enemies.

The effect of pine trees surrounding wheat fields on the infestation of wheat sunn pest, Eurygaster integriceps in Shahr-e-Rey/Tehran region

The sunn pest, Eurygaster integriceps Put. (Hem.: Scutelleridae) is one of the most important pests of wheat in Iran and the Middle East. At present, the control of this pest in the country is based on chemical control, which due to the limitation of using chemical pesticides, the use of other eco-friendly control methods, including the cultivation of companion plants is considered. Therefore, in this study, the effect of windbreakers, especially pine trees, around wheat fields, on the infestation of the sunn pest was investigated during 2019 and 2020. In this experiment, three treatments were considered in three replications, including three areas surrounded by pine trees, three areas surrounded by non-pine trees, and three areas without windbreakers. In each area, sampling of the mother's bug was performed several times by quadrate and insect net during an outbreak of pest in two consecutive years. Furthermore, the correlation of meteorological parameters with the pest density at sampling dates in different treatments was investigated. As well as, in the laboratory studies, the repellency of pine essential oils on the adult insect was tested in three concentrations, including LC10, LC25, LC50 by olfactometer and wind tunnel. The results of field sampling showed that the density of the pest in fields with windbreakers, especially pine windbreakers, was much lower than the farms without windbreakers in both years. Bioassay results showed that pine trees essential oils have a high lethal effect on adult bug, and the values of LC50, LC25 and LC10 were 362, 82 and 21 µl/l of air, respectively. The results also showed that increasing the concentration of essential oils increased the rate of repellency. The results of the correlation of meteorological parameters with adult bug density showed that in all treatments, there was a positive and significant correlation between sunn pest density and wind direction in both studied years. Therefore, based on this study's results, planting of pine trees around wheat fields can reduce infestation of sunn pest, and the repellency properties of the volatile compounds of this plant on the pest are probably adequate.

Nanoparticle facilitated stacked-dsRNA improves suppression of the Lepidoperan pest Chilo suppresallis

BackgroundIn recent years, gene knockdown technology using double-stranded RNA (dsRNA) has been widely used as an environment-friendly pest control strategy, but its instability and limited cellular uptake have limited its overall effect. Studies have shown that the efficiency of single dsRNA can be improved by using various nanomaterials. However, the effect of stacked-dsRNA wrapped by nanomaterial on pests remains unclear. In the present study, both CYP15C1 and C-factor genes were cloned from the midgut of C. suppressalis, and the transcript of C-factor is most highly expressed in heads. Feeding a dsCYP15C1 or dsC-factor - nanomaterial mixture can downregulate the gene expression and significantly increase larval mortality. More importantly, feeding the stacked-dsRNA wrapped by nanomaterial can significantly increase the mortality of C. suppressalis, compared with feeding dsCYP15C1 or dsC-factor - nanomaterial mixture alone. These results showed that CYP15C1 and C-factor could be potential targets for an effective management of C. suppressalis, and we developed a nanoparticle-facilitated stacked-dsRNA strategy in the control of C. suppresallis. Our research provides a theoretical basis for gene function analysis and field pest control, and will promote the application of RNAi technology in the stacked style of pest control.

Agroecosystem complexity of Surjan and Lembaran as local farming systems effects on biodiversity of pest insects

Abstract. Trisnawati DW, Nurkomar I, Ananda LK, Buchori D. 2022. Agroecosystem complexity of Surjan and Lembaran as local farming systems effects on biodiversity of pest insects. Biodiversitas 23: 3619-3629. Farming systems can influence the diversity and abundance of insect pests. This study was conducted to determine the effect of Surjan and Lembaran farming systems on the diversity and abundance of insect pests in Kulon Progo, Yogyakarta. The field survey was conducted in three Surjan paddy fields and three Lembaran paddy fields in Panjatan Subdistrict, Kulon Progo Regency. The sampling of pests was collected using four kinds of traps, such as sweeping net, yellow sticky trap, pitfall trap, and yellow pan trap. The traps were set twice in the vegetative phase and twice in the generative phase. The results showed that the abundance of pests in Surjan paddy fields was not different from that in Lembaran paddy fields. However, the number of pest species in Surjan paddy fields was higher than in Lembaran paddy fields. In addition, the structure and composition of pests in both farming systems were significantly different. Hemiptera was the most common insect in both farming systems, with dominant pest species of Nephotettix virescens and Nilaparvata lugens.

Expression of Modified Snowdrop Lectin (Galanthus nivalis Agglutinin) Protein Confers Aphids and Plutella xylostella Resistance in Arabidopsis and Cotton.

Cotton is a major fiber crop in the world that can be severely infested by pests in agricultural fields. Identifying new insect-resistance genes and increasing the expression of known insect-resistance genes are imperative in cultivated cotton. Galanthus nivalis agglutinin (GNA), a lectin that is toxic to both chewing and sucking pests, is mainly expressed in monocotyledons. It is necessary to improve the expression of the GNA protein and to test whether the lectin confers insect resistance to dicotyledons plants. We report a modified GNA gene (ASGNA) via codon optimization, its insertion into Arabidopsis thaliana, and transient expression in cotton to test its efficacy as an insect-resistance gene against cotton aphids and Plutella xylostella. The amount of ASGNA in transgenic plants reached approximately 6.5 μg/g of fresh weight. A feeding bioassay showed that the survival rate of aphids feeding on the leaves of ASGNA transgenic plants was lower than those of aphids feeding on the leaves of non-optimized GNA (NOGNA) transgenic plants and wild-type plants. Meanwhile, the fertility rate was 36% when fed on the ASGNA transgenic plants, while the fertility was 70% and 95% in NOGNA transgenic plants and wild-type plants. Correspondingly, the highest mortality of 55% was found in ASGNA transgenic lines, while only 35% and 20% mortality was observed in NOGNA transgenic plants and wild-type plants, respectively. Similar results were recorded for aphids feeding on cotton cotyledons with transient expression of ASGNA. Taken together, the results show that ASGNA exhibited high insecticidal activity towards sap-sucking insects and thus is a promising candidate gene for improving insect resistance in cotton and other dicotyledonous plants.

An expert system for insect pest population dynamics prediction

Avocado (Persea americana) production is increasing in Kenya, with both small and largeholder farming for domestic and export markets. However, one of main challenges that limit production is infestation by insect pests, notably the oriential fruit fly Bactocera dorsalis and Ceratitis spp. fruit flies, which cause direct crop losses and are indirectly responsible for non-tariff trade barriers due to stringent export requirements. Data on weekly pest trap counts were collected between September 2017 and December 2020 within orchards in avocado plantations. Fuzzy neural network (FNN) were used to model the population dynamics of B. dorsalis and Ceratitis spp. Weekly pest counts, rainfall, average temperature, relative humidity and avocado plant physiological stages were used for predictive modeling in different orchards. The performance of the resulting models was evaluated using coefficient of determination (R2), mean absolute error (MAE), mean relative approximation error (MRAE) and root mean squared error (RMSE). FNN models achieved satisfactory results in predicting the dynamics of the pests in the orchards, with most of the models obtaining R2 > 0.85. We demonstrated how FNN models can be used as predictive tools for managing and controlling fruit fly pest populations in these plantations, and how they may be suitable to predict fruit fly or other pests in similar cropping systems. Once the input variables are known, they can be loaded into the FNN models to predict field pest populations, and based on threshold values, allow for implementation of timely and adequate control measures such as the use of biopesticides.

Diagnostic Appraisal of the Sorghum Farming System and Breeding Priorities in Sierra Leone

Understanding demographic structures, production constraints, and trait preferences is essential for setting up crop breeding goals and enhancing adoption strategies for new varieties. The objective of this study was to document the sorghum (Sorghum bicolor L. Moench) production constraints and preferred sorghum traits to guide breeding in Sierra Leone. A participatory rural appraisal was used to collect data from 210 farmers across seven districts in Sierra Leone in 2019. Results showed that all sorghum varieties in cultivation are landraces. Poor access to fertilizer (91%), lack of suitable varieties (85%), poor agronomic knowledge (79%), low yielding varieties (78%), storage pests (75%), field pests (67%), low soil fertility (52%), lack of market (49%), sorghum disease (43%), drought (16%), and heavy rainfall (12%) are key production constraints limiting sorghum production. Farmers expressed interest in adopting new varieties with high yield (99%), disease (84%) and pest (81%) resistance, drought tolerance (50%), white grain (59%), and short height (53%). The prioritized traits will form the basis for farmer-oriented sorghum breeding.

EVALUATING REPRODUCTIVE ABILITY OF THE RICE WEEVIL (PICIA MESOPOTAMICA) AT DIFFERENT TEMPERATURES ON RICE

Rice (Oryza sativa L.) is one of the most important grain crops in Iraq. This crop is plagued by several significant pests, including the rice weevil aquatic (Picia mesopotamica) which is a serious pest in rice fields. This study was conducted out to learn more about the biological and environmental factors that influence how this insect survives and poses a threat to rice crops in the field. The results of reproductive ability revealed that temperature seems to have a significant impact on females' life cycles and survival rates during the first reproduction. Female egg productivity rates were found to be regulated by temperature, with the lowest rate occurring later in the female's life cycle. Moreover, the average age at the first reproduction of the female was 21 and 10 days at temperature 30°C and the highest rate of 30 and 19 days at temperature 20°C respectively and the highest average number of eggs 294.20 eggs/female at the temperature was 30°C. Further, the lowest average age of the female at first reproduction was 10 days at 30°C and the highest was 19 days at 20°C. The results also indicated the apparent effect of the tested temperatures on the net compensation rates of the insect females with the lowest being 8.793 females/generation at 35°C with the highest112.68 females/generation at30°C and the lowest average generation length 57.68 days at temperature. The population grew at an exponential rate of 0.035 females per day at 30°C, while the population grew at the slowest pace of 0.008 females per day at 35°C. Despite of the effect of temperature on other biological aspects of rice weevils requires more research. We found that temperature has a clear effect on the rice weevils reproductive activities on rice plants, and this research could be crucial in developing a successful pest management method.

Association between landscape composition and the abundance of predator and herbivore arthropods in Bt and non-Bt soybean crops

Cropland expansion has been occurring over the last century, especially in South America, displacing non-crop areas mainly with soybean. Changes at a landscape level were followed by changes at a local scale, such as the adoption of insect-resistant transgenic crops. The homogenization of agroecosystem composition and agronomic practices have a great impact on arthropod predators and herbivore insects, which has not been quantified to a great extent in South America. We evaluate the effects of cover composition (1 km radii) as a landscape variable, and Bt adoption as a local variable on the quantity of the main predators and pests in soybean fields in Uruguay. Over a two-year period, we sampled 60 soybean fields with sweep net and beating sheet. We found that Bt and non-Bt soybean fields did not differ in the number of predators and stink bugs, while Bt fields were associated with less caterpillars’ abundance. The proportion area of soybean negatively affected the quantity of some predators in this crop. In contrast, the landscape cover with natural grassland, commercial forest and maize positively affected some of these beneficial organisms. The number of stink bugs in soybean was highly affected by the surrounding cover composition. Arthropod responses depend on soybean’s phenological period. We demonstrate the effects of the agriculturalization process on soybean predators and pests, suggesting that Bt adoption does not affect predators and each vegetation cover impacts them differentially. Different non-crop landscape cover and the abundance of predators in the field margin are positively associated with the abundance of predators in soybean fields.

Phenotypic plasticity of predatory mite Amblyseius orientalis in response to diet switch

Phenotypic plasticity, especially the ability to switch to new dietary sources is essential to invertebrates for survival and reproduction in variable environments. Amblyseius orientalis Ehara (Acari: Phytoseiidae) is an effective predatory mite to control spider mites in orchards, whereas its preys or artificial diets used in mass rearing productions are distinct from the field pests. It’s unknown if predator performance could recover immediately after diet change from rearing condition to pest management. In this study, we assessed life-history performances and predation in four populations of A. orientalis which were fed by two preys (Tetranychus urticae and Carpoglyphus lactis) in respective parental and offspring generations to evaluate the phenotypic plasticity and dietary adaptation of A. orientalis progeny. The results showed that prey species switching in two generations had great influence on predator’s developmental time and longevity. The longevity of A. orientalis reduced from 32.98 to 24.22 days while parent and progeny feeding on different preys. However, the sex ratio, fecundity, prey consumptions of progeny were not different among four populations. The sex ratio of four populations of A. orientalis also showed the consistence of a female-biased trend from 1.57 to 1.75, and the lifetime reproductions were almost equivalent from 25.82 to 28.06 eggs per female. Prey consumptions were similar among A. orientalis females and changed between 21.41 to 23.23 eggs per day. Overall, our study demonstrated that A. orientalis has higher fitness plasticity and does not need long time to adapt the new diet, therefore it can be applied as an outstanding biocontrol agent in pest management after diet change from production to the field.

Impact of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), invasion on maize and the native Spodoptera litura (Fabricius) in East Java, Indonesia, and evaluation of the virulence of some indigenous entomopathogenic fungus isolates for controlling the pest

BackgroundThe fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an invasive alien species in Indonesia. This study aimed to assess the impact of its invasion in Indonesia by measuring the damaged area caused by the pest in maize fields located across East Java and simultaneously determine whether S. frugiperda outcompetes the native Asian armyworm Spodoptera litura (Fabricius). Secondly, the virulence of 14 entomopathogenic fungus (EPF) isolates against S. frugiperda larvae was evaluated in an effort to find effective biocontrol agent candidates.ResultsThe damaged area caused by S. frugiperda was generally higher than that caused by S. litura during the survey period from August 2019 to December 2021. It indicated that S. frugiperda may have dominated the native armyworm and become the primary key pest of maize in Indonesia. Based on a single-concentration assay (106 conidia ml−1), the tested EPF isolates displayed varying degrees of virulence against S. frugiperda larvae, causing larval mortality of 3.5 to 71% at 10-day post-treatment, with the highest mortality rates provided by Beauveria bassiana sensu lato and Trichoderma asperellum sensu lato. At a concentration of 108 conidia ml−1, B. bassiana s.l. and T. asperellum s.l. elicited high larval mortality of 76 and 81%, respectively, at 10-day post-treatment. Nevertheless, the probit analysis based on a concentration–response assay revealed that T. asperellum s.l. had lower LC50 and LC90 values than B. bassiana s.l.ConclusionsThe attack and invasion of S. frugiperda seem to be a continual threat to the maize agro-ecosystem in Indonesia. As a consequence, Indonesia should mitigate and be well-prepared for future outbreaks of S. frugiperda. Indigenous EPF isolates used in this study may act as promising biocontrol agents of S. frugiperda, especially T. asperellum s.l. This study also serves as the first report documenting the direct lethality of Trichoderma fungus on S. frugiperda larvae.

Spatial Distribution of Cotton Bollworm in Southeastern Shores of the Caspian Sea, Golestan Province, Iran

Cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), is one of the major pests in the cotton fields, and threatens the sustainability of cotton production due to its polyphagous and cosmopolitan behaviors. Risk levels of moth distribution depend on spatial-temporal changes. Therefore, this study aimed at performing spatial-temporal analysis of H. armigera moth population in the southeastern area of the Caspian Sea (Golestan province, Iran) using the Geographic Information System (GIS). Almost weekly data (7-10 days), the moth distributions of H. armigera were collected from 65 cotton fields from May 30, 2020, to September 17, 2020. The moth’s population maps of H. armigera were estimated using an Inverse Distance Weighting (IDW) interpolation method. Spatial autocorrelations and data clustering for the moth populations were performed by Moran's I analysis to highlight moth population hotspots on the shores of Caspian Sea. The result of the spatial analysis showed that moth of H. armigera distributed aggregation pattern during the cotton growing season. Interpolated maps (IDW) of H. armigera moth showed that almost all of the hotspots were located in the southeastern areas of the Caspian Sea.