Biological characterization and mating compatibility of Helicoverpa gelotopoeon (D.) (Lepidoptera: Noctuidae) populations from different regions in Argentina

Differences in morphology, mitochondrial genomes, and reproductive compatibility between two clades of parasitic wasps Aphelinus mali (Hymenoptera: Aphelindae) in China

Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) in China is comprised of two clades (termed, the Shandong and Liaoning clades). In order to clarify the genetic relationship between these two clades, we compared and analyzed the morphological characteristics and the mitochondrial genome of each, and performed a hybridization experiment. Morphological results showed that both males and females of the Liaoning clade were larger than Shandong clade, in terms of whole body, abdominal, wing and antennal lengths, however, there were no significant differences between clades for total length of the middle or hind leg of females. The length of the mitochondrial genome of the Shandong clade was 14415 bp and, for the Liaoning clade, it was 14804 bp. Each contained 31 genes, including 13 protein-encoded genes, 16 tRNA genes, and 2 rRNA genes. The highest AT level among the 13 protein-coding genes for the two clades were the same gene (ATP8) (Shandong clade, 91.52%; Liaoning clade, 90.91%). By hybridization and backcrossing, we found that there was no cross incompatibility between these two clades of A. mali. Our results indicate that the historic geographical isolation between these clades has not yet caused reproductive isolation of these populations, and they belong to the same species.

Fitness and mating compatibility of Chrysodeixis includens (W.) (Lepidoptera: Noctuidae) populations collected in different provinces and crops in Argentina

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.

Fertility Life Table, Population Parameters and Biotic Potential of Helicoverpa gelotopoeon (Dyar) (Lepidoptera: Noctuidae)

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.

Defoliation of Soybean Expressing Cry1Ac by Lepidopteran Pests

Lepidoptera, stink bugs, and weevils are important pests in soybean. For lepidopteran control, insecticides and seed treatments are used. As an alternative, Bt soybean was developed to control primary pests of Lepidoptera such as Rachiplusia nu (Guenée) (Noctuidae), Chrysodeixisincludens (Walker) (Noctuidae), Anticarsia gemmatalis Hübner (Erebidae), Helicoverpa gelotopoeon (Dyar) (Noctuidae), and Crocidosema aporema (Walsingham) (Tortricidae). However, the use of transgenic plants, and the resulting reduction of insecticide against target pests, may allow other pest species to become more prevalent in agricultural environments. Soybean expressing Cry1Ac against different lepidopteran nontarget and target insect pests was evaluated, and its performance was compared with non-Bt soybean with seed treatment. The treatments were Bt soybean, non-Bt soybean with seed treatment (Fortenza® diamide insecticide, Syngenta, Buenos Aires, Argentina), and non-Bt soybean without seed treatment. Larvae of H. gelotopoeon, Spodoptera albula (Walker) (Noctuidae), Spodoptera cosmiodes (Walker) (Noctuidae), Spodoptera eridania (Stoll) (Noctuidae), and Spodoptera frugiperda (J. E. Smith) (Lep.: Noctuidae) were used. The plants of each treatment were infested with larvae of each species, and the percentage of leaf damage produced by each species was recorded. The results showed that Bt soybean provided control of H. gelotopoeon and had a suppressive effect on S. frugiperda and S. albula. However, S. eridania and S. cosmiodes were not susceptible to the Cry1Ac protein in MON 87701 × MON 89788 soybean when evaluated by greenhouse infestation. Considering the performance of each species using non-Bt soybean without seed treatment, S. eridania would represent a potential risk in soybean crops.