Brown Stink Bug Research Articles

Euschistus heros: Economic injury level and economic threshold of early maturing carioca common bean cultivar

Early maturing common-bean cultivars lack information referring to Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae) feeding damage assessment. This information is pertinent towards establishing economic threshold for an integrated pest management program. The aim of this study was to analyze the relationship, between the density of stink bugs and the degree of injuries towards the pod and grain production, quantity and quality, of the IPR Curió cultivar. The experiments were conducted during two seasons at the IDR-Paraná in Londrina, Paraná, in field conditions. The experimental design was randomized blocks with five repetitions. The treatments were: 0 (control); 1; 2; 3; 4; 5 E. heros m-1. The evaluated variables were number of grained and flat pods; healthy, damaged and aborted grain mass; grain yield. The economic injury level (EIL), economic threshold (ET) and spraying efficiency influence on the ET were calculated. The total number of grained pods was not affected. More than three brown stink bugs, during the summer season, significantly increases flat pod output. The rainy season resulted in greater aborted grains. Increasing E. heros densities, during the summer season, significantly reduces the healthy grain output. The damaged grain mass doubles at higher than one E. heros population densities. The total grain mass produced was not affected. During the summer season, each E. heros reduces 11% of healthy grain output, and during the rainy season 6%. During the summer season was 1.50 of E. heros m-1 and for the rainy season 1.00 E. heros m-1. The spraying efficiency should directly affect the EIL, modifying the value, thus better resembling the field conditions.

Electropenetrography Study of Euschistus heros (F.) (Heteroptera: Pentatomidae) Nymphs Feeding on Vegetative Soybean Structures.

The study aimed to understand the feeding behavior of Neotropical brown stink bug nymphs Euschistus heros (F.) on soybean plants during vegetative stage through electropenetrography (EPG) technique. Three distinct phases were identified: non-feeding, pathway, and ingestion. Waveforms representing these phases were consistent across nymphal instars and plant structures, and named Np, Eh1, and Eh2, respectively. Biological interpretations of the waveforms were proposed by integrating visual observations, comparisons with adult waveforms, and histological studies. The waveforms Np, Eh1, and Eh2 were associated with resting/walking, initial stylet-plant contact, and xylem sap ingestion, respectively. Notably, nymphs showed a higher number of Eh1 events and longer durations when feeding on petioles compared to leaves, particularly in younger instars. However, differences between instars diminished in older nymphs. Fifth instars consistently exhibited the highest Eh1 values, and displayed longer xylem ingestion durations compared to other instars. Second instars demonstrated increased xylem ingestion events on petioles compared to leaves. Across plant structures, on petioles, nymphs generally showed longer xylem ingestion durations than on leaf surfaces. Fifth instar consistently had the longest ingestion durations overall. Additionally, statistical differences in xylem ingestion duration were observed between instars within each plant structure, with fifth instars displaying the longest durations. These findings offer valuable insights into the feeding behavior of E. heros nymphs, which could inform the development of more effective pest management strategies for soybean crops.

Field abundance and spatial patterns of ear-feeding insect pests in relation to levels of defective kernels in processing sweet corn.

In this study, we investigated the within-field distribution of sweet corn insect pests in relation to adjacent habitats and determined the level and specific causes of defective kernels affecting the quality of the final product at the processing cannery. Sap beetles [primarily Carpophilus lugubris (Murray, 1864) (Coleoptera: Nitidulidae)] and stink bugs [primarily Euschistus servus (Say) ((Heteroptera: Pentatomidae)] infested 27.6% and 73.6% of the fields, respectively. Densities of stink bugs were highest along field edges adjacent to wheat, soybean, vegetable crops, and woodlots. Levels of kernel injury were consistently higher in truckloads of ears harvested first from the outer rows. Earworm damage was confined to the ear tip and had no measurable impact on the quality of the final product. Sap beetles and blemished kernels were the major causes of defective kernels in the cannery, even though stink bugs were more abundant in the fields. Defective kernels were more positively related to physiological blemishes than to other causal factors. For all fields, defective kernel levels averaged less than 1%, resulting in excellent quality of the processed product throughout the entire season. Results provided a better understanding of the quality control issues, resulting in practical implications for improvements in field monitoring and decision-making in the cannery to minimize grading problems.

Competition between brown stink bug (Hemiptera: Pentatomidae) and corn earworm (Lepidoptera: Noctuidae) in field corn.

Interspecific competition is an important ecological concept which can play a major role in insect population dynamics. In the southeastern United States, a complex of stink bugs (Hemiptera: Pentatomidae), primarily the brown stink bug, Euschistus servus (Say), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), are the 2 most common pests of field corn, Zea mays L. (Poales: Poaceae). Stink bugs have the greatest potential for economic injury during the late stages of vegetative corn development when feeding can result in deformed or "banana-shaped" ears and reduced grain yield. Corn earworm moths lay eggs on corn silks during the first stages of reproductive development. A 2-year field study was conducted to determine the impact of feeding by the brown stink bug during late-vegetative stages on subsequent corn earworm oviposition, larval infestations, and grain yield. Brown stink bug feeding prior to tasseling caused deformed ears and reduced overall grain yield by up to 92%. Across all trials, varying levels of brown stink bug density and injury reduced the number of corn earworm larvae by 29-100% and larval feeding by 46-85%. Averaged across brown stink bug densities, later planted corn experienced a 9-fold increase in number of corn earworm larvae. This is the first study demonstrating a competitive interaction between these major pests in a field corn setting, and these results have potential implications for insect resistance management.

Attracting Scelionidae egg parasitoids to enhance stink bug egg parasitisation in soybean crops using methyl salicylate and (E,E)-α-farnesene.

Plant volatile organic compounds (VOCs) play a crucial role in mediating interactions between plants, herbivores and natural enemies. Among these VOCs, methyl salicylate and (E,E)-α-farnesene are emitted as herbivore-induced plant volatiles (HIPVs) by soybean plants in response to feeding by the brown stink bug Eushistus heros. These HIPVs function as synomones, influencing the foraging behaviour of the egg parasitoid, Telenomus podisi, the main natural enemy of E. heros, one of the major soybean pests in Brazil. Laboratory experiments showed that two soybean cultivars, BRS 7580 and BRS 7880, produced similar qualitative blends of HIPVs, with methyl salicylate, (E,E)-α-farnesene and (Z)-3-hexenyl acetate being produced by both cultivars. Soybean cultivar BRS 7580 produced a significant lower amount of HIPVs compared to BRS 7880 but this difference did not affect the attractiveness of the egg parasitoid Telenomus podisi. Field experiments using these two cultivars and synthetic applications of methyl salicylate and (E,E)-α-farnesene showed a substantial increase in egg parasitism in all treated areas. Parasitism rates ranged from 50% to 80% in areas where these HIPVs were deployed, compared to only 10% in untreated control areas. The egg parasitoid Telenomus podisi demonstrated an adept ability in recognising between HIPVs in soybean blends, even in the presence of significant quantitative differences. The results from the field experiment showed the potential of HIPVs in attracting natural enemies to specific target areas within fields. (E,E)-α-Farnesene showed an improved action during the later stages of soybean growth, notably at R6. In addition, this volatile attracted other families of natural enemies. © 2024 Society of Chemical Industry.

Insecticide Susceptibilities and Enzyme Activities of Four Stink Bug Populations in Mississippi, USA.

In Mississippi, the Pentatomidae complex infesting soybean is primarily composed of Euschistus servus, Nezara viridula, Chinavia hilaris, and Piezodorus guildinii. This study employed spray bioassays to evaluate the susceptibilities of these stink bugs to seven commonly used formulated insecticides: oxamyl, acephate, bifenthrin, λ-cyhalothrin, imidacloprid, thiamethoxam, and sulfoxaflor. Stinks bugs were collected from soybeans in Leland, MS, USA during 2022 and 2023, as well as from wild host plants in Clarksdale, MS. There was no significant difference in the susceptibility of C. hilaris to seven insecticides between two years, whereas P. guildinii showed slightly increased susceptibility to neonicotinoids in 2023. Among all four stink bug species, susceptibility in 2022 was ranked as P. guildinii ≤ C. hilaris ≈ N. viridula, while in 2023, it was ranked as P. guildinii ≤ C. hilaris ≤ E. Servus. Additionally, populations of E. servus and P. guildinii collected from Clarksdale exhibited high tolerance to pyrethroids and neonicotinoids. Moreover, populations of E. servus and P. guildinii from SIMRU-2022 and Clarksdale-2023 showed elevated esterase and cytochrome P450 activity, respectively. These findings from spray bioassays and enzyme activity analyses provide a baseline for monitoring insecticide resistance in Pentatomidae and can guide insecticide resistance management strategies for Mississippi soybean.

The first extensive analysis of species composition and abundance of stink bugs (Hemiptera: Pentatomidae) on soybean crops in Brazil.

Soybean is the third-greatest global commodity crop with respect to grain production, Brazil is the largest soybean producer in the world. We performed the first extensive survey including all the five main soybean cultivation regions in Brazil over three seasons (2018/2019, 2019/2020, and 2020/2021). A total of 2386 localities were sampled, corresponding to 145 municipalities in 11 states. Sampling was carried out between the R1 and R8 soybean growth stages, using a beating sheet. Fifteen species were recorded, with five species accounting for more than 99% of the sampled insects. The Neotropical brown stink bug, Euschistus heros (F.), was the most abundant species (82.4% of the adults and 84.1% of the nymphs overall), with differences in the mean abundance between soybean macroregions. The melacanthus green belly stink bug, Diceraeus melacanthus Dallas was the second most abundant species overall, followed by the brown winged stink bug, Edessa meditabunda (F.), the furcatus green belly stink bug, Diceraeus furcatus (F.) and the red-banded green stink bug, Piezodorus guildinii (Westwood). The relative abundance of each species differed between soybean macroregions. The mean abundance of nymphs and adults of Euschistus heros at different soybean reproductive stages showed an increase from early reproductive stages to the beginning of the late reproductive stages (R5 or R6). This large-scale assessment of stink bugs provides a basis for outlining integrated pest management programs and drives the development of monitoring and control strategies, as well as future studies investigating population dynamics over time and space in soybean fields. © 2024 Society of Chemical Industry.

Optimizing the Release Pattern of Telenomus podisi for Effective Biological Control of Euschistus heros in Soybean.

An augmentative biological control program using the egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Platygastridae) is a promising tool for the management of the brown stink bug, Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) in soybeans. The T. podisi are released as adults or pupae within lab-reared E. heros eggs. Because of the small size of the parasitoid and potentially limited dispersal ability, determining the optimal release pattern is critical for biological control of the target pest. This study used sentinel E. heros eggs to investigate T. podisi dispersal within soybean crops during two distinct phenological stages: the beginning of flowering (Vn-R1) and the grain-filling phase (R5-R6). Data were analyzed using semi-variograms and kriging maps. The results indicate significant differences in parasitism rates between the two plant growth stages and among different matrices. The maximum dispersal range for T. podisi was calculated at 39.0 m in the Vn-R1 stage with a maximum parasitism rate of 42%, while in the R5-R6 stage, the maximum dispersal range was calculated to be 30.9 m with a maximum parasitism of 73%. Therefore, it is recommended that release points for T. podisi be spaced no further than 30 m apart. These results provide valuable insights for future research and applications in biological control strategies, including adjustment of the logistics and release technique depending upon the crop phenological stage.

A lightweight and enhanced model for detecting the Neotropical brown stink bug, Euschistus heros (Hemiptera: Pentatomidae) based on YOLOv8 for soybean fields

Insect pest detection and monitoring are vital in an agricultural crop to help prevent losses and be more precise and sustainable regarding the consequent actions to be taken. Deep learning (DL) approaches have attracted attention, showing triumphant performance in many image-based applications. In the adult stage, this research considers detecting a vital insect pest in soybean crops, the Neotropical brown stink bug (Euschistus heros), from field images acquired by drones and cellphones. We develop and test an improved YOLO-model convolutional neural network (CNN) with fewer parameters than other state-of-the-art models and demonstrate its superior generalization and average precision on public image datasets and the new field data provided here. Considering the proposal's precision and time of response, the possibility of deploying this technology for automatic monitoring and pest management in the near future is promising. We provide open code and data for all the experiments performed.

Biological Characteristics and Thermal Requirements of Telenomus podisi and Trissolcus basalis (Hymenoptera: Scelionidae) in Fresh and Cryopreserved Eggs of Euschistus heros and Nezara viridula (Hemiptera: Pentatomidae)

Brazil is one of the largest producers of pulses globally, and soybean ranks highly in terms of production. However, pests increase crop production costs and affect oilseed production and quality. Pests are primarily controlled by chemicals, leading to changes in insect pest populations. For example, secondary pests can become primary pests because of the selection of resistant insects and the elimination of natural enemies. Farmers have widely accepted biological control because of its high control efficacy and low environmental contamination risk. Two successful biological control programs in soybean used Telenomus podisi Ashmead (Hymenoptera: Platygastridae) to manage the Neotropical brown stink bug, Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), and Trissolcus basalis (Wollaston, 1858) (Hymenoptera: Scelionidae) to manage the southern green stink bug, Nezara viridula (Linnaeus) (Hemiptera: Pentatomidae), when these pests were the most abundant in soybean-producing regions. To release parasitoids, rearing protocols must be developed in order to optimize production. This study evaluated the effect of temperature on the biological characteristics of T. podisi and T. basalis when fresh or frozen E. heros eggs were provided. Fifty fresh or previously frozen eggs were placed with parasitoids for 24 h in a climate chamber (25 ± 1 °C, 70 ± 10% RH, and 14-h photophase). At the end of this period, the eggs were transferred to other chambers and maintained at different temperatures (19, 22, 25, 28, 31, and 34 ± 1 °C, 70 ± 10% RH, with a 14-h photoperiod). The number of emerging adults from eggs parasitized by T. basalis was lower than that from eggs parasitized by T. podisi. Differences in T. basalis and T. podisi parasitism were observed depending on whether the E. heros eggs were frozen or fresh, but neither development nor emergence were affected. The duration of egg–adult development and the longevity of the two parasitoids were inversely proportional to the temperature increase. The sex ratio of T. basalis and T. podisi progeny was not affected by different temperatures or by the use of frozen or fresh eggs. The estimated number of both parasitoids’ generations corresponded with temperature, reaching 14–15 generations/cycle of soybean for Rio Verde, GO, and 12–14 generations/cycle for Barreiras, BA. Given these characteristics, we conclude that a biological control program using T. podisi can benefit large areas of soybean production by controlling the eggs of phytophagous bugs in soybean crops.

Ovicidal activity of selected insecticides against the brown stink bug, Euschistus heros, and their toxicity to its egg parasitoid, Telenomus podisi, 2023

Ovicidal activity of selected insecticides against the brown stink bug, <i>Euschistus heros</i>, and their toxicity to its egg parasitoid, <i>Telenomus podisi</i>, 2023

Electropenetrography study of Euschistus heros (F.) (Heteroptera: Pentatomidae) nymphs feeding at different sites of the soybean pod.

This study aimed to characterize and correlate the stylet penetration behaviors of nymphs of the Neotropical brown stink bug, Euschistus heros (F.), on immature soybean pods. Waveforms were obtained using electropenetrography (EPG). The findings revealed that the nymphs exploited the xylem vessels and the seed tegument or endosperm. Primarily 4 phases were characterized: nonfeeding, pathway, salivation, and ingestion. The waveforms of each phase were similar in appearance across instars. The biological meanings of waveforms were based on visual observations, comparison with waveforms of adults, and histological studies. Np represents the insect resting or walking on soybean pod surface. Eh1 represents the first contact between the mouthparts (stylets) and plant tissue. Eh2 represents xylem sap ingestion, and Eh3 represents seed activities (including tegument and endosperm). The number of waveform events did not differ among instars for all waveforms. However, for Eh3, fifth instars performed more activities than other instars. The second instars had the smallest value, and third and fourth instars had intermediate values. For total duration, all waveforms differed among instars. Np duration was shorter for third compared with second and fourth instars and intermediate for fifth instar. For Eh1, second and third instars had the longest duration (1.5× to 2× greater) compared with fourth and fifth instars. For Eh2 and Eh3, the second-instar showed the longest (~2× greater) and shortest durations, respectively. Overall, this study provides important insights into the feeding behavior of E. heros nymphs so that effective pest management programs can be developed to contain this pest.

Habitat and vertical stratification affect capture of stink bugs (Hemiptera: Pentatomidae) and biological control of the invasive brown marmorated stink bug.

Spatiotemporal distribution of stink bugs (Hemiptera: Pentatomidae) and their natural enemies across farmscapes has been studied in more detail recently. However, the impact of plant height on vertical stratification of stink bugs and their natural enemies is rarely addressed across these diverse habitats. In this study, we examined capture of native stink bugs, the invasive brown marmorated stink bug, Halyomorpha halys (Stål)(Hemiptera:Pentatomidae), and a predaceous wasp, Astata occidentalis Cresson (Hymenoptera: Sphecidae) in pheromone-baited traps, in 2 habitats, woodlands of mostly deciduous trees mixed with some conifers and pecan orchards, in addition to their vertical stratification (0-13.7 m) at increasing heights. Furthermore, the effects of canopy height and habitat on H. halys egg mass predation and parasitism were evaluated. Adult H. halys were abundant in both habitats, but more nymphs were captured in pecan orchards. The same pattern was found for adult Euschistus servus (Say) (Hemiptera:Pentatomidae), Thyanta custator McAtee (Hemiptera:Pentatomidae), and A. occidentalis. In contrast, adult E. tristigmus (Say) (Hemiptera:Pentatomidae) and Chinavia hilaris (Say) (Hemiptera:Pentatomidae) were more abundant in woodlands. More nymphal H. halys and adults of E. servus, T. custator, and A. occidentalis were captured in ground traps than canopy traps in pecan. More adult and nymphal H. halys were captured at varying heights in the woodland canopy compared to near the ground as were adult E. tristigmus and C. hilaris. Both parasitism and predation occurred in woodland and pecan canopies. However, in one test we found that parasitism of H. halys egg masses occurred more often in the upper tree canopy, and more parasitism was detected in woodland than orchard habitat. In 2 tests, predation was higher in woodlands than pecan orchards. These results will aid in optimizing conservation biological control tactics in these habitats.

Ecological zoning of Euschistus heros in Brazil based on the net reproductive rate at different temperatures and relative-humidity levels.

The Neotropical brown stink bug, Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae), is one of the major insect pests in soybean crops, causing severe damage; however, some aspects of its biology that are essential for management remain unknown. To aid in the management of E. heros, the present study investigated the fertility life table of this species at 7 temperatures (18, 20, 22, 25, 28, 30, and 32 ± 1 °C) and 4 relative-humidity levels (30, 50, 70, and 90 ± 10%). Based on the net reproductive rate, R0, we developed an ecological zoning for this pest in Brazil, to identify climatically favorable areas for population growth. Our results indicated that the most favorable range is between 25 and 28 °C and above 70% RH. The ecological zoning indicated that farmers should be more concerned in the northern and Midwest regions, which include the state of Mato Grosso, the largest soybean and corn producer in Brazil. These results provide valuable information, indicating the hotspots most likely to be attacked by the Neotropical brown stink bug.

Effect of Insect Growth Regulator Insecticides Novaluron, Teflubenzuron and Lufenuron on the Morphology and Physiology of Euschistus heros

The Neotropical brown stink bug, Euschistus heros (F.) (Heteroptera: Pentatomidae), is an important pest that damages soybean, especially in the central-west region of Brazil. The effect of insect growth regulator insecticides on fourth-instar nymphs and adults of the neotropical brown stink bug was evaluated under laboratory and greenhouse conditions, respectively. In the laboratory, the insecticides (doses in g a.i. ha-1) novaluron (20.0 and 40.0), teflubenzuron (26.2 and 52.5), and lufenuron (20.0 and 40.0), in addition to the control (water), were tested on fourth-instar nymphs of E. heros and their development were followed to adulthood. Mortality, number of adults with and without deformities, and fecundity were determined. In a greenhouse, the effects of the same insecticides on the adult of the stink bug were evaluated by determining the fecundity and viability of the eggs laid. The fourth-instar nymphs of E. heros, when exposed to either dose of the tested insecticides presented mortality and insects with deformations, as well as reduced fecundity of females that reached adulthood. In the trial with adult E. heros, all tested insecticides reduced stink bug fecundity. In the same way, the viability of the produced eggs was reduced in all the chemical treatments, except for novaluron at the lowest dose tested, in which egg viability did not differ from the control treatment. Based on the obtained results, one can infer that the growth-regulator insecticides evaluated, although usually more suitable for the control of caterpillars, can interfere negatively in the development and reproduction of the neotropical brown stink bug, thus constituting a complementary alternative for the management of this pest.

Within-field spatial patterns of Euschistus servus and Nezara viridula (Hemiptera: Pentatomidae) in field corn.

A complex of stink bugs, primarily the brown stink bug, Euschistus servus (Say) (Hemiptera: Pentatomidae) , and the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae) , are the most damaging insect pests of field corn, Zea mays L., in the southeastern United States. Characterizing the spatial patterns of these highly mobile, polyphagous pests is critical for developing efficient and effective sampling plans. In 2021 and 2022, stink bugs and their injury were assessed biweekly from emergence through R2 in 20 corn fields. The spatial analysis by distance indices (SADIE) showed that aggregation patterns were identified primarily in adult populations of both E. servus and N. viridula, and in nymphal populations of both species to a lesser extent. Aggregation patterns were also identified in early vegetative injury, but not in ear injury assessed at R2. The spatial association of stink bugs and their injury varied with corn phenological stage. A lack of spatial association between stink bug populations early in the season and vegetative injury suggests a need for intensive sampling, particularly in fields with increased residue from cover crops. Results of this study illustrate the variability in spatial patterns of stink bugs in corn, which can help to improve sampling plans for decision-making in IPM programs.

Trade-Offs between Temperature and Fitness in Euschistus heros (Fabricius) (Hemiptera: Pentatomidae): Implications for Mass Rearing and Field Management

The brown stink bug, Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae), is one of the most abundant soybean stink bug pests in Brazil. Temperature is a key factor that affects its development and reproduction, and fluctuating temperatures may impact the development and reproduction of E. heros differently from those under constant temperatures. The objective of this study was to evaluate the influence of constant and fluctuating temperature on the biological characteristics of E. heros in three successive generations. Treatments consisted of six constant temperatures (19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C) and four fluctuating temperatures (25:21 °C, 28:24 °C, 31:27 °C, and 34:30 °C) evaluated for three successive generations. Second-stage nymphs were evaluated daily, and after they reached the adult stage, they were separated by sex, and the individual weight (mg) and pronotum size (mm) were recorded. After pair formation, eggs were collected to evaluate the pre-oviposition period, total number of eggs, and egg viability. The duration of the nymphal stage was reduced with an increase in both constant and fluctuating temperatures; however, at constant temperatures of 19 °C, 31 °C and 34 °C and fluctuating temperatures of 28:24 °C, there was no reproduction in adults. The base temperature and total degree day requirement for nymphal development were 15.5 °C and 197.4 dd, respectively. Pre-oviposition period (d), number of eggs per female, and viability of eggs (%) were affected by temperature across the generations. The multiple decrement life table analysis revealed that mortality was highest during the molting of the second-stage nymphs. These findings have important implications for E. heros' laboratory mass-rearing programs and for its management in fields.

Host preference and survivorship ofEuschistus herosstrains on cotton and soybean

AbstractThe Neotropical brown stink bug,Euschistus heros(Fabricius) (Hemiptera: Pentatomidae), is a key pest of soybean,Glycine max(L.) Merrill (Fabaceae), and recently became an economically important pest of cotton,Gossypium hirsutumL. (Malvaceae), in Brazil. This stink bug has two allopatric strains, one prevalent in southern Brazil (SS), and another in the north (NS). The two strains hybridize in central Brazil. Knowledge of host preferences and host suitability of these strains may clarify the contribution of the various gene pools to contemporary adaptive features such as the ability to harm cotton crops. We tested the attraction of theE. herosstrains and reciprocal hybrids – ♀N × ♂S (HNS) and ♀S × ♂N (HSN) – to soybean and cotton leaves and reproductive structures, and evaluated the nymph development and survivorship of the two strains and reciprocal hybrids fed on soybean or cotton. We conducted host‐choice experiments with fourth instars and adult females and evaluated the survival of immatures on soybean and cotton plants under laboratory conditions. The SS strain preferred soybean over cotton. Hybrid and NS strains chose randomly between soybean and cotton plants. All strains developed on soybean, with similar survival rates. On cotton, pure strains did not reach adulthood; however, hybrids developed on cotton but with a survival rate of &lt;1%. Our results showed that the SS strain ofE. heroswas more attracted to soybeans, and NS and hybrid strains had a polyphagous choice behavior, suggesting that current host selection has been mediated by historical and, mainly, contemporary relationships ofE. herosstrains with these hosts.

Multistate model in the behavioral study of the parasitoid Telenomus podisi for biological soybean control

Biological pest control through the use of wasps are sustainable ways of protecting plants and, consequently, agricultural production. In this context, an entomological experiment is motivated, in which the forraging and reproductive behaviors of the parasitoid Telenomus podisi were qualified over time, considering non parasitized (sp0) and parasitized (sp1) of the brown stink bug, Euschistus heros. The experiment features a longitudinal study of continuous time with variable nominal qualitative response, grouped into four mutually exclusive categories (flying-walking, drumming, oviposition and marking). Continuous time transition models, also known as multistate models, are a viable alternative for analyzing data with these characteristics. Therefore, this class of models was considered in this work to study the behavior of the parasitoid, through the average length of stay in each of the response categories, as well as their preference probabilities. As a result, there was a significant effect of the treatment of host eggs (non parasitized or previously parasitized). When having contact with previously parasitized eggs, the female parasitoid T. podisi has preference for the categories of movement which are flying-walking and drumming. In contrast, when in contact with non parasitized eggs, the female T. podisi has a preference for ovipositionand marking. The applied methodology proved to be adequate for this typical experimental situation in entomological studies associated with the description of the behavior of a parasitoid.

Insect Growth Disruptors Cause Mouthpart Malformations, Inhibition of Feeding, and Mortality in the Neotropical Brown Stink Bug Euschistus heros (Hemiptera: Pentatomidae)

The Neotropical brown stink bug, Euschistus heros, is the most important sucking pest of soybean crops, quantitatively and qualitatively affecting grain and seed. This study aimed to determine mouthpart deformities, feeding inhibition, and E. heros nymphs&amp;rsquo; mortality when in contact with insect growth disruptors (IGDs). The effects of two insecticides of the chitin biosynthesis inhibitor group (CBIs), lufenuron and diflubenzuron, and the juvenile hormone analog pyriproxyfen were tested in the laboratory. CBI application promoted mouthpart deformities, feeding inhibition, alteration of metamorphosis, and mortality of E. heros nymphs. Although pyriproxyfen did not cause mouthpart deformation, it caused certain mortality for nymphs, possibly due to physiological disorders. Lufenuron caused feed inhibition and mortality in less time when compared with diflubenzuron and pyriproxyfen. It was also more toxic to 4th instar nymphs. The insecticides, when used in higher concentrations, increased nymph&amp;rsquo;s mortality in less time. Nymphs with deformed mouthparts were unable to feed and died. All IGDs in the tested concentrations caused 100% mortality and prevented adult formation.