Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) is a significant agricultural pest in South America infesting several crops, including soybeans. Bacillus thuringiensis (Berliner) (Bt) soybean, expressing Cry1Ac protein, is widely planted as a control method for numerous lepidopteran pests. However, insect resistance to Bt proteins poses a threat to its sustainability. Recent field reports from Argentina, Uruguay, and Brazil have documented unexpected injury to Bt soybean caused by R. nu populations, which may indicate the development of resistance to Cry1Ac in this species. This study aimed to evaluate the biological performance, reproductive parameters, and reproductive compatibility of two R. nu strains, one susceptible (SS) and the other exhibiting reduced susceptibility to Bt toxin (RR), when reared on Bt and non-Bt soybean. Reproductive compatibility between strains was investigated through parental and hybrid crosses, evaluating fecundity, fertility, and mating success. SS larvae fed with Bt soybean failed to complete their life cycle, whereas RR larvae exhibited higher survival rates. Egg and larval stages of RR larvae were longer when reared on Bt soybean. Pupal mass was lower for Bt-fed resistant strain, although this did not reflect on fecundity and longevity. Results on parental crosses revealed that Bt-fed RR strain displayed reduced mating success, fecundity, and fertility, compared to the non-Bt treatment. Hybrid crosses showed evidence for prezygotic and postzygotic incompatibility. These results suggest a shift in susceptibility of R. nu to Cry1Ac protein and highlight the importance of implementing robust insect resistance management strategies to maintain the effectiveness of Bt crops.

Melanagromyza sojae, the soybean stem fly (Zehntner) (Diptera: Agromyzidae), is a new pest in soybean and chickpea crops in South America. The objective of this study was to determine population fluctuations of M. sojae in both crops using adults caught in yellow sticky traps and by sampling injured plants. Additionally, an update of its geographical distribution in Argentina is provided. Adults of this species were collected for multiple years and during the cycles of both soybean and chickpea crops, on volunteer soybean plants, and during periods when the crops were not present. Injuries caused by M. sojae occurred throughout the growing period of chickpea and the reproductive stages of soybean. The highest infestation level was registered in chickpea crops. Regarding the distribution of M. sojae, we have reported Medicago sativa, Vigna radiata, Mellilothus sp., Helianthus annuus, Carthamus tinctorius, Heliotropium sp., Glandularia sp., and Parthenium sp. for the first time as new host plants in Argentina. The presence of M. sojae in Chaco province (Argentina) was also reported for the first time. Finally, the highest percentage of infestation registered in chickpea crops shows that M. sojae is a pest in chickpea-growing areas in Argentina where this pest is widely distributed. It is of vital importance to develop effective control methods, to research and recommend efficient management strategies and control methods for M. sojae in chickpea.

The South American bollworm, Helicoverpa gelotopoeon (Dyar), is a member of the Heliothinae complex in Northwestern Argentina and one of the most important pests affecting soybean in the country. Currently, management of Heliothinae pest species is based on the use of insecticides and transgenic Bt crops. However, many species in the Heliothinae complex have developed resistance to these control tactics. In this regard, studies of population structure and genetic diversity studies in these agricultural insect pests are of great importance for the effective implementation of management strategies. Mitochondrial DNA is one of the types of molecular markers available for insect studies successfully employed for population genetic studies in Lepidoptera. The aim of this study was to evaluate the genetic diversity and population structure of five H. gelotopoeon populations collected from different regions and crops in Argentina using analysis of three mitochondrial DNA regions. Results of genetic variability and gene flow analyses among H. gelotopoeon populations indicated, in general, a certain genetic structure in studied populations. Possible causes for this genetic structure include differences among regions, host plants and year of sampling. Additional studies contemplating the impact of biological and ecological features are necessary in understanding the source of genetic structure in these H. gelotopoeon populations.

The Asian soybean stem borer Melanagromyza sojae (Zehntner) (Diptera: Agromyzidae) represents a threat to soybean and chickpea crops in South America. It is known that in the region its population has increased, in part, due to the difficulty in its agronomic management. This is due to the lack of knowledge regarding its biology and the environments that are favorable for its establishment. In this study, we provide a comprehensive database of records of M. sojae, as well as an updated list of its host plants from field surveys, bibliographic review, and online databases. We estimated the suitability and potential distribution of the pest considering environmental information from remote sensors and bioclimatic variables and contrasted these against land-use cover across South America. In Argentina, M. sojae was found developing on Tithonia tubaeformis (Jacq.) Cass. (Asteraceae), surviving in chickpeas and volunteer soybeans that were affected by winter frost. The most informative models and highest suitability were predicted from vegetation indices and bioclimatic variables, and coincided with sites having a high proportion of arable land. Regarding climate, the greatest suitability occurred in eastern South America, including the southern states of Brazil and Paraguay, where the final models recovered the current known distribution of the species on the continent. However, its extension may be even greater than predicted, due to the wide distribution range of its hosts. This characterization of suitability for M. sojae could be a useful resource to anticipate the regions that are most favorable for its presence and supports the need to consider the distribution of crops and host plants that could act as natural reservoirs to identify sites and streamline efforts to reduce the incidence of the pest.

Chrysodeixis includens, is an important Plusiinae pest that feeds on soybean, beans, and cotton. This species has a genetic structure determined by molecular markers in populations collected in soybean crops in Brazil and has developed resistance to insecticides. This had led to an increased interest in the genetic diversity of its populations in Argentina. This study aimed to characterize the fitness parameters and mating compatibility of geographically distant C. includens populations and on different host plants in Argentina. Intra- and inter-population crosses revealed that C. includens populations from Tucumán and Santiago del Estero provinces did not present any evidence of prezygotic and postzygotic incompatibilities, suggesting that both populations collected from soybean plants belonged to a single wide-ranging species. Prezygotic and postzygotic incompatibilities were detected between populations collected from different crops (soybean and bean). These incompatibilities may be caused by the different nutrients that each plant species renders, or the specific pest control strategies which may affect C. includens behavior. Studies of the genetic structure of C. includens populations based on mating isolation on other crops, as well as of the impact of management strategies on the specie, will increase understanding of the reproductive compatibility revealed by the present study.

Durante las últimas décadas, el cultivo de la soja a nivel mundial tuvo un crecimiento tanto en superficie como en productividad. En la Argentina sucedió de igual manera, particularmente a comienzos de este siglo, como resultante del uso de alta tecnología, convirtiendo a este cultivo y los subproductos que de él se obtienen en el pilar del sistema granario y exportador. El desarrollo del noroeste argentino (NOA) coincidió con el proceso a nivel nacional. La Estación Experimental Agroindustrial Obispo Colombres (EEAOC) de Tucumán buscó permanentemente producir cultivares adaptados a esta zona, siendo este el principal objetivo del subprograma Mejoramiento Genético del Proyecto Soja. Tarpusqa RR es una nueva variedad de soja liberada por la EEAOC, que completa su madurez fisiológica a los 117 días de la siembra (pertenece al grupo de madurez VII) con excelentes potenciales de rendimiento. Fue obtenida a través de cruzamiento y posterior avance generacional en la subestación de Monte Redondo (San Agustín, Tucumán). Tarpusqa RR fue sometida a ensayos comparativos de rendimiento (ECR) en tres diferentes sitios del área sojera tucumana durante las campañas 2008/2009 y 2009/2010, alcanzando rendimientos superiores a los testigos en la mayoría de los ensayos. Exhibe, entre otras características, baja o nula dehiscencia de vainas y un peso de 1000 semillas de 153 gramos. En cuanto a la sanidad, se destaca su resistencia a las enfermedades cancro del tallo y mancha ojo de rana, así como ante patógenos de semillas como Cercospora kikuchii y Fusarium spp.

Helicoverpa gelotopoeon (Dyar) (Lepidoptera: Noctuidae) is a polyphagous pest that has been reported causing damage in many agricultural crops such as soybean, chickpea and cotton. This species, together with Helicoverpa zea (Boddie), Helicoverpa armigera (Hübner) and Chloridea virescens (Fabricius), belongs to the Heliothinae complex of economic importance in Northwestern Argentina. Many species in the Heliothinae subfamily have developed resistance to insecticides and insecticidal proteins from Bacillus thuringiensis (Bt). Managing resistance to these control tactics in H. gelotopoeon is of high importance and dependant on knowledge of population genetics of this species. The objective of this study was to evaluate the genetic variability and structure of H. gelotopoeon populations from different host plants and geographic regions of Argentina. Towards this goal, six microsatellite loci were screened across 196 individuals. The results obtained revealed high genetic diversity and lack of clear structure among the populations of H. gelotopoeon studied. This genetic homogeneity between populations from different geographical regions and hosts could be attributed to the long‐range migratory capacity of Heliothinae and the generalist behaviour of H. gelotopoeon .

Helicoverpa armigera and H. zea (Lepidoptera Noctuidae) are genetically and physiologically closely related species that have mating compatibility under laboratory conditions. Considering the presence of H. armigera in Argentina, the lack information about its biology and evolutionary relationship with H. zea, the aim of this study was to compare biological, reproductive, population parameters and biotic potential (BP) of both species under controlled conditions. Egg and larva duration showed significant differences, being in both cases the longest duration in H. zea. Pre-oviposition, oviposition, and post-oviposition duration, and fertility presented significant differences. The only population parameter that did not differ between H. armigera (96.95) and H. zea (104.78) was the net reproductive rate (R-0). The maximum rate of population growth occurred in the day 34 and 46 for H. armigera and H. zea respectively. Biotic potential value indicated that each female of H. armigera and H. zea can produce more than 36 quintillion and 454 trillion descendants per year respectively. These analyses determined that H. armigera and H. zea have the potential to increase quickly their populations under controlled conditions. The results obtained provide additional information to plan and implement strategies for the integrated management of these species with emphasis in H. armigera in Argentina.

Helicoverpa gelotopoeon (Dyar) (Lepidoptera: Noctuidae) is a polyphagous pest that belongs to the Heliothinae complex, and has been described as feeding on numerous crops. Larvae damage mainly pods and seeds of soybean and other legumes. Adaptation to different host plants might reduce gene flow between phytophagous insect populations, which could lead to reproductive isolation. Therefore, studies on gene flow among host-associated populations are necessary to design management strategies. The objective of this study was to evaluate reproductive compatibility between 2 populations of H. gelotopoeon coming from different host plants. We collected H. gelotopoeon larvae in alfalfa and soybean crops, and studied biological and reproductive parameters, and mating compatibility. Helicoverpa gelotopoeon populations from soybean and alfalfa reared on artificial diet showed similar biological and reproductive characteristics. Intra- and inter-population crosses revealed that there are no signs of host-associated isolation, allowing gene exchange between these populations, which can be explained by the high mobility and generalist behavior of this species. This information will be useful to establish control measures for this pest.

Fil: Casmuz, Augusto Sebastian. Gobierno de Tucuman. Ministerio de Desarrollo Productivo. Estacion Experimental Agroindustrial Obispo Colombres; Argentina

Spodoptera frugiperda (J. E. Smith) is one of the major pests of maize in Argentina. The main tool for its control is the use of genetically modified maize hybrids expressing Bacillus thuringiensis (Bt) insecticidal proteins. Maize growers in Argentina initially controlled this pest with Bt maize that expressed a single Bt protein (Cry1Ab or Cry1F). Currently it is necessary to plant maize cultivars that produce two Bt proteins to achieve the satisfactory control. Recently, Cry1F field-evolved resistant populations of this species were confirmed in Argentina. The objective of this study was to evaluate the performance of S. frugiperda field-collected strains on different Bt and non-Bt maize hybrids. Strains were collected from non-Bt maize (T1), Agrisure TDMax (T2), Agrisure Viptera (T3), Agrisure Viptera 3110 (T4), Genuity VT Triple Pro (T5), and Power Core (T6). Three experiments were performed to 1) determine the survivorship and reproduction of field-collected larvae (F0) from Bt maize hybrids, 2) evaluate Cry1F resistance using an F1 screen, and 3) assess the performance of F1 strains on different maize hybrids. In the F0, the survivorship from larva to adult ranged from 0 to 63%. We obtained adults from only the T1, T2, T5, and T6 strains with no significant differences in the reproductive parameters. Continuously rearing F1 larvae on their collected hosts affected larval duration, which was significantly shorter for a known-laboratory Bt-susceptible strain than the field-collected strains. Our results support the existence of Cry1F-resistance alleles in S. frugiperda field populations in Argentina.

Fil: Vera, M. Alejandro. Provincia de Tucuman. Ministerio de Desarrollo Productivo. Estacion Experimental Agroindustrial Obispo Colombres. Seccion de Zoologia Agricola; Argentina

Fil: Casmuz, A. S.. Gobierno de Tucuman. Ministerio de Desarrollo Productivo. Estacion Experimental Agroindustrial Obispo Colombres; Argentina

Helicoverpa gelotopoeon is an endemic pest of South America that affects soybean and other important crops. Life tables are a fundamental tool used to study insect populations, resulting in crucial information for integrated pest management programs. Therefore, the aim of this study was to evaluate the biotic potential and the construction of a life table of this species under laboratory conditions. The biological parameters that showed significant differences between male and female were pupal duration, longevity and life span, which were all longer in duration for males. The net reproductive rate (R0) was 95.49, the mean generation time (T) 37.53, and the instantaneous rate of population increase "r" 0.12. The population doubling time (DT) was 5.70 days, and the daily finite rate of increase (λ) 1.13. The maximum rate of population growth occurred in the day 33. Fecundity had two peaks: at days 35 and 37. Gross and net fecundity rate, and the average number of eggs laid per female per day were 565.87, 496.07, and 18.76 respectively. The biotic potential was 2.026 x 1018 individuals/female/year. The survivorship curve showed that mortality was high during incubation period and first larval instars, then it declined until the death of last adult. These results provide important information to develop management strategies of H. gelotopoeon in South America.

Helicoverpa gelotopoeon (Dyar) (Lepidoptera: Noctuidae) es una especie polífaga que ocasiona daños en varios cultivos tanto en la etapa vegetativa como reproductiva. A pesar de ser una plaga de importancia en el noroeste argentino, no existen estudios sobre sus aspectos biológicos y reproductivos, datos fundamentales para la implementación de un programa de manejo integrado de plagas. Por ello, el objetivo del presente trabajo fue examinar los parámetros biológicos y reproductivos de una población de H. gelotopoeon recolectada en el cultivo de soja (Glycine max L.; Fabales: Fabaceae) en Tucumán. Las larvas recolectadas fueron acondicionadas y criadas en condiciones controladas (25 ± 2ºC, 70-75% HR, 14L:10O de fotoperíodo artificial). Se evaluaron los siguientes parámetros: duración de los estados de huevo, larva y pupa; peso de las pupas, longevidad de los adultos, proporción de sexos, número de espermatóforos, duración de los períodos de pre, ovi y postoviposición, fecundidad y fertilidad. En general, se encontró un período de incubación de tres días, cinco estadios larvales, un ciclo larval de 14 días, y una duración de pupa y adulto de 11 y 17 días respectivamente, completándose el ciclo de vida en 45 días. La fecundidad fue de 330 huevos por hembra con una fertilidad del 78%. Los resultados fueron comparados con aquellos obtenidos para otras especies de Helicoverpa criadas en condiciones similares. Estos estudios constituyen el primer aporte de aspectos biológicos y reproductivos de H. gelotopoeon en ambiente controlado.

Fil: Casmuz, Augusto Sebastian. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tucuman. Instituto de Tecnologia Agroindustrial del Noroeste Argentino. Provincia de Tucuman. Ministerio de Desarrollo Productivo. Estacion Experimental Agroindustrial ; Argentina

In this work, we report the effect of rainfall on Sternechus subsignatus Boheman, 1836, adult emergence after winter dormancy. This weevil is a univoltine soybean pest found in northwestern Argentina, a subtropical region with dry winters and rainy summers. Before harvest, fully grown larvae burrow into the soil where they overwinter. In the spring, they emerge as adults and recolonize the crop during its planting and early vegetative stages. Our study examines the seasonal timing of adult emergence with the aim of improving chemical control strategies and avoiding unnecessary pesticide applications. To do so, we developed a regression model to predict adult emergence onset as a function of cumulated rainfall after 1st November. The regression with the highest coefficient of determination between cumulated rainfall and adult emergence onset was Emergence onset (Julian day) = -7.98 Ln(cumulative rainfall) + 65.7. The negative relationship showed that adults emerged earlier in wet years than in dry years. Also it was observed that adults emerged from late November to mid-March, in pulses following periods of rainfall. Males were more abundant than females at first, but then the reverse was true toward the end of the period. In most cases, there was a suggestion of relationship (though not significantly) between peaks of adult emergence with peaks of rainfall 15 d before adult emergence. These results reveal that rainfall has a significant impact on the beginning and dynamics of adult emergence from the soil.

Fil: Casmuz, Augusto Sebastian. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tucuman. Instituto de Tecnologia Agroindustrial del Noroeste Argentino. Provincia de Tucuman. Ministerio de Desarrollo Productivo. Estacion Experimental Agroindustrial ; Argentina

The black soybean weevil, Rhyssomatus subtilis (Fiedler), is an important but infrequently studied insect pest of soybean, Glycine max (L.) Merrill, in South America. Severe crop damage occurs when the adult weevils attack soybean seedlings, resulting in reduced plant stands, and when weevils feed on and oviposit in seedpods. The objectives of this 3-yr study were to quantify early-season damage caused by R. subtilis to terminal buds and plant stands in soybean and evaluate insecticide seed treatments under field conditions relative to this damage. Terminal bud damage is the most consistent criteria for determining early season damage by R. subtilis to soybean. The results indicated that R. subtilis can cause as much as 36% plant stand loss in soybean. Thiamethoxam and a mixture of ethiprole + fipronil provided significant levels of control of R. subtilis damage, with the higher doses of each product tending to provide longer-lasting protection.

The Heliothinae complex in Argentina encompasses Helicoverpa gelotopoeon (Dyar), Helicoverpa zea (Boddie), Helicoverpa armigera (Hübner), and Chloridea virescens (Fabricius). In Tucumán, the native species H. gelotopoeon is one of the most voracious soybean pests and also affects cotton and chickpea, even more in soybean-chickpea succession cropping systems. Differentiation of the Heliothinae complex in the egg, larva, and pupa stages is difficult. Therefore, the observation of the adult wing pattern design and male genitalia is useful to differentiate species. The objective of this study was to identify the species of the Heliothinae complex, determine population fluctuations of the Heliothinae complex in soybean and chickpea crops using male moths collected in pheromone traps in Tucuman province, and update the geographical distribution of H. armigera in Argentina. The species found were H. gelotopoeon, H. armigera, H. zea, and C. virescens. Regardless of province, county, crop, and year, the predominant species was H. gelotopoeon Considering the population dynamics of H. gelotopoeon and H. armigera in chickpea and soybean crops, H. gelotopoeon was the most abundant species in both crops, in all years sampled, and the differences registered were significant. On the other hand, according to the Sistema Nacional Argentino de Vigilancia y Monitoreo de Plagas (SINAVIMO) database and our collections, H. armigera was recorded in eight provinces and 20 counties of Argentina, and its larvae were found on soybean, chickpea, sunflower crops and spiny plumeless thistle (Carduus acanthoides). This is the first report of H. armigera in sunflower and spiny plumeless thistle in Argentina.