Population Growth of Soybean Aphid, Aphis glycines, Under Varying Levels of Predator Exclusion

Although soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has caused economic damage in several Midwestern states, growers in Missouri have experienced relatively minor damage. To evaluate whether existing predatory insect populations are capable of suppressing or preventing soybean aphid population growth or establishment in Missouri, a predator exclusion study was conducted to gauge the efficacy of predator populations. Three levels of predator exclusion were used; one that excluded all insects (small mesh), one that excluded insects larger than thrips (medium mesh), and one that excluded insects larger than Orius insidiosus (Say) (Hemiptera: Anthocoridae), a principal predator (large mesh). Along with manipulating predator exposure, timing of aphid arrival (infestation) was manipulated. Three infestation times were studied; vegetative (V5), beginning bloom (R1), and beginning pod set (R3). Timing of aphid and predator arrival in a soybean field may affect the soybean aphid's ability to establish and begin reproducing. Cages infested at V5 and with complete predator exclusion reached economic threshold within two weeks, while cages with predators reached economic threshold in four and a half weeks. Cages infested at R1 with complete predator exclusion reached economic threshold within five weeks; cages with predators reached economic threshold within six weeks. Cages infested at R3 never reached threshold (with or without predators). The predator population in Missouri seems robust, capable of depressing the growth of soybean aphid populations once established, and even preventing establishment when the aphid arrived late in the field

Optimizing Egg Recovery From Wild Northern Corn Rootworm Beetles (Coleoptera: Chrysomelidae)

The northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), is one of the most important insect pests in the U.S. Corn Belt. Efforts to obtain eggs from wild northern corn rootworm populations using techniques developed for other rootworm species have been unsuccessful due to lack of oviposition. In 2016, we evaluated four oviposition media in choice tests within each of three female densities in 30.5 × 30.5 × 30.5 cm BugDorm cages. The number of eggs laid per female was significantly affected by female density and the interaction of female density × oviposition media, but oviposition was relatively poor in all oviposition media (1.2 eggs per female when averaging the three female densities and all oviposition media). Single females were also evaluated in nonchoice assays in 6 cm × 6 cm × 8 cm clear plastic boxes and averaged up to 108 eggs per female depending on the oviposition media. In 2017, the cumulative number of eggs laid per female in boxes with one female was not significantly different from the number of eggs laid per female in boxes with 3 females. In 2018, the cumulative number of eggs laid per female was not significantly different between female densities of 1, 3, 5, or 10 females per box. Total egg production per box therefore increased as female density increased. More than 27,000 wild northern corn rootworm eggs were collected from just 190 females when collected relatively early in the field season. We now have an efficient and robust system for obtaining eggs from wild northern corn rootworm females

Relations between and among contaminant concentrations and biomarkers in black bass (\u3ci\u3eMicropterus\u3c/i\u3e spp.) and common carp (\u3ci\u3eCyprinus carpio\u3c/i\u3e) from large U.S. rivers, 1995–2004

Environmental contaminant and biomarker monitoring data from major U.S. river basins were summarized for black bass (Micropterus spp.) and common carp (Cyprinus carpio) sampled over a nine year period. Cumulative frequency distributions revealed taxon differences for many organochlorine residue concentrations, elemental contaminant concentrations, and biomarkers, but few gender differences were evident for chemical concentrations. Concentrations of dacthal, pentachloroanisole, p,p\u27-DDE, endosulfan sulfate, barium, cadmium, copper, manganese, lead, selenium, vanadium, and zinc were greater in carp than bass, but concentrations of mercury and magnesium were greater in bass. Gender differences were evident in bass for mercury and in carp for zinc, but the differences were small compared to taxon differences. Greater vitellogenin concentrations, 17B-estradiol concentrations, 17B-estradiol/11-ketotestosterone ratios, and percent oocyte atresia in female carp compared to female bass may be related to the sequential spawning of carp. Regression analyses indicated that as much as 78% of biomarker variation was explained by chemical contaminant concentrations. Sites grouped consistently by river basin in the chemical contaminant principal components analysis (PCA) models and were driven by mercury, magnesium, barium, mirex, and oxychlordane. PCA models for the biomarkers did not group the sites by basin for either bass or carp. Statistical analyses and data interpretation were limited by the study design. The implications of these limitations are discussed. Recommendations to be considered during the planning of future monitoring studies include the exclusion of gender- and species-specific sampling for certain chemical contaminants considering analytical methods with appropriate sensitivities; and allowing for the addition of new chemical and biological variables as methods and information needs evolve

Development of Monozygotic Twin Mouse Embryos from the Time of Blastomere Separation at the Two-Cell Stage to Blastocyst1

The development of blastomeres separated from two-cell stage murine embryos has been compared. Blastomeres were removed from the zona pellucida (ZP) and cultured individually; the twin embryos were compared during their progression to blastocyst in terms of development rate, cell number, morphology, conformation at the four-cell stage, and CDX2 and POU5F1 (also known as OCT4) expression. In general, twin embryos, whether obtained from superovulated or normally bred dams, displayed comparable cell numbers as they advanced. They formed morulae and blastocysts more or less synchronously with each other and with control embryos, although possessing about half of the latter's cell number. Despite this apparent synchrony, the majority of twin blastocysts differed in terms of their relative complements of POU5F1+/CDX2− cells, which represent inner cell mass (ICM), and POU5F1+/CDX2+ cells, which identify trophectoderm (TE). Many, but not all, exhibited a disproportionately small ICM. By contrast, demiembryos retained within their ZP and created by randomly damaging one of the two blastomeres in two-cell stage embryos exhibited a more normal ratio of ICM to TE cells at blastocyst and significantly less variance in ICM cell number. One possible explanation is that ZP-free demiembryos only infrequently adopt the same conformation as their partners, including the favorable tetrahedral form, at the four-cell stage, suggesting that such embryos exhibit a high degree of plasticity with regard to the orientation of their first two cleavage planes and that a significant number likely deviate from paths that provide an optimal geometric progression to blastocyst. These data could explain the difficulty of creating monozygotic twins from two-cell stage embryos

Optimizing Egg Recovery From Wild Northern Corn Rootworm Beetles (Coleoptera: Chrysomelidae)

The northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), is one of the most important insect pests in the U.S. Corn Belt. Efforts to obtain eggs from wild northern corn rootworm populations using techniques developed for other rootworm species have been unsuccessful due to lack of oviposition. In 2016, we evaluated four oviposition media in choice tests within each of three female densities in 30.5 × 30.5 × 30.5 cm BugDorm cages. The number of eggs laid per female was significantly affected by female density and the interaction of female density × oviposition media, but oviposition was relatively poor in all oviposition media (1.2 eggs per female when averaging the three female densities and all oviposition media). Single females were also evaluated in nonchoice assays in 6 cm × 6 cm × 8 cm clear plastic boxes and averaged up to 108 eggs per female depending on the oviposition media. In 2017, the cumulative number of eggs laid per female in boxes with one female was not significantly different from the number of eggs laid per female in boxes with 3 females. In 2018, the cumulative number of eggs laid per female was not significantly different between female densities of 1, 3, 5, or 10 females per box. Total egg production per box therefore increased as female density increased. More than 27,000 wild northern corn rootworm eggs were collected from just 190 females when collected relatively early in the field season. We now have an efficient and robust system for obtaining eggs from wild northern corn rootworm females

Comparison of Ribotyping and Repetitive Extragenic Palindromic-PCR for Identification of Fecal Escherichia coli from Humans and Animals

This report compares the performances of two popular genotypic methods used for tracking the sources of fecal pollution in water, ribotyping and repetitive extragenic palindromic-PCR (rep-PCR). The rep-PCR was more accurate, reproducible, and efficient in associating DNA fingerprints of fecal Escherichia coli with human and animal hosts of origin