This study provides the first genetic characterization of the soybean looper, Chrysodeixis includens (Walker, 1857), an important defoliating pest species of soybean crops in Brazil. Population genetic variability and the genetic structure of C. includens populations were evaluated by using ISSR markers with samples from the major soybean producing regions in Brazil in the growing seasons 2011/2012. Seven different primers were applied for population characterization of the molecular variability and genetic structure of 8 soybean looper populations from 8 states of Brazil. The seven ISSR loci generated 247 bands in 246 individuals of C. includens sampled. The expected heterozygosity (H E) in the populations varied between 0.093 and 0.106, while the overall H E was 0.099, indicating low genetic diversity. The analysis of molecular variance indicated that 98% of the variability was expressed among individuals within populations (F ST = 0.021, p = 0.001). The low level of polymorphism over all populations, the high levels of gene flow, and the low genetic structure are indicatives of the exchange of genetic information between the different sampled regions. Population structuring suggests the presence of two major groups which do not correlate with their geographic sampling location in Brazil. These results may indicate recent recolonization of C. includens in Brazil or migration patterns following source-sink dynamics. Furthermore, the presence of two groups within C. includens suggests that a study on development of resistance or any other genetic-based trait needs to be evaluated on both groups, and pest management in soybean fields should be aware that differences may come to the control strategies they use.

ABSTRACT. Genomic DNA extraction is crucial for molecular research, including diagnostic and genome characterization of different organisms. The aim of this study was to comparatively analyze protocols of DNA extraction based on cell lysis by sarcosyl, cetyltrimethylammonium bromide, and sodium dodecyl sulfate, and to determine the most efficient method applicable to soybean caterpillars. DNA was extracted from specimens of Chrysodeixis includens and Spodoptera eridania using the aforementioned three methods. DNA quantification was performed using spectrophotometry and high molecular weight DNA ladders. The purity of the extracted DNA was determined by calculating the A260/A280 ratio. Cost and time for each DNA extraction method were estimated and analyzed statistically. The amount of DNA extracted by these three methods was sufficient for PCR amplification. The sarcosyl method yielded DNA of higher purity, because it generated a clearer pellet without viscosity, and yielded high quality amplification products of the COI gene I. The sarcosyl method showed lower cost per extraction and did not differ from the other methods with respect to preparation times. Cell lysis by sarcosyl represents the best method for DNA extraction in terms of yield, quality, and cost effectiveness.

This note is the first report of Syntomopus parisii De Santis 1976 and Leptomeraporus sp. (Hymenoptera, Pteromalidae) simultaneously parasitizing Melanagromyza sojae Zehntner, 1900 (Diptera, Agromyzidae) in Brazil. The Pteromalidae parasitoids are natural enemies of stem miner flies, opening perspectives for biological control of soybean stem miner fly.

Stink bugs and whiteflies are major concerns for pest management in Brazilian soybean fields, causing severe economic losses to soybean growers and leading to excessive insecticide applications per crop cycle. Despite biological differences, these two sap-sucking pests often co-occur in soybean fields and can be successfully managed with the same insecticide spray, reducing operational costs to the growers. The aim of this work was to evaluate the efficacy of eleven insecticides in the control of stink bugs and whiteflies. Two insecticide sprays were made with an interval of 14 days between them. The results from ANOVA and Tukey post-hoc test (P≤0.05) revealed significant differences among treatments. Acetamiprid + bifenthrin (75 + 75 g a.i. ha-1) was the most efficient treatment for the control of stink bugs, reaching 97.8% of insect mortality. Cyantraniliprole + bifenthrin (50 + 50 g a.i. ha-1) was the most efficient treatment for the control of whiteflies, reaching 78.8% of insect mortality. This treatment also presented the highest combined control of stink bugs and whiteflies, reaching 83.5% of insect mortality