Economic Injury Levels for Bt-resistant Helicoverpa zea (Lepidoptera: Noctuidae) in Cotton

Thresholds for Helicoverpa zea (Boddie) in cotton Gossypium hirsutum L. have been understudied since the widespread adoption of Bt cotton in the United States. Our study was possible due to the widespread presence of H. zea populations with Cry-toxin resistance. We initiated progressive spray timing experiments using three Bt cotton brands (Deltapine, Stoneville, and Phytogen) widely planted across the U.S. Cotton Belt expressing pyramided toxins in the Cry1A, Cry2, and Vip3Aa19 families. We timed foliar insecticide treatments based on week of bloom to manipulate H. zea populations in tandem with crop development during 2017 and 2018. We hypothesized that non-Bt cotton, cotton expressing Cry toxins alone, and cotton expressing Cry and Vip3Aa19 toxins would respond differently to H. zea feeding. We calculated economic injury levels to support the development of economic thresholds from significant responses. Pressure from H. zea was high during both years. Squares and bolls damaged by H. zea had the strongest negative yield associations, followed by larval number on squares. There were fewer yield associations with larval number on bolls and with number of H. zea eggs on the plant. Larval population levels were very low on varieties expressing Vip3Aa19. Yield response varied across experiments and varieties, suggesting that it is difficult to pinpoint precise economic injury levels. Nonetheless, our results generally suggest that current economic thresholds for H. zea in cotton are too high. Economic injury levels from comparisons between non-Bt varieties and those expressing only Cry toxins could inform future thresholds once H. zea evolves resistance to Vip3Aa19.

Toxicity of the Bt Protein Cry1Ac Expressed in Leaves of the Event of Transgenic Soybean Released in Paraguay Against Spodoptera cosmioides

Spodoptera cosmioides Walk (Lepidoptera: Noctuidae) is a polyphagous species, considered a secondary pest in soybean crop. The Intacta soybean (Bt soybean) event was released in Paraguay with Bt proteins which are supposed to be toxic for caterpillars. However, the effects of these proteins in the Spodoptera cosmioides biology still uncertainty. This study evaluated the biological activity of Bt soybean in S. cosmioides that were fed on Bt and non-Bt soybean leaves under laboratory conditions. The experiment was carried out at the Laboratory of Entomology; temperature 26±2 ºC; relative humidity: 60±10%; photoperiod: 14:00 h where 150 neonate larvae were used per treatment. The period and viability of each stage, the mortality of larval, number of eggs and neonate per couple, and the period of larvae to adult were the assessed variables. Higher mortality was observed in larvae fed with intact soybeans, but without statistical differences with non-Bt soybeans. For larval survival, period, number and total period, no statistical differences were verified. Higher percentage of fertility was observed in soybeans non-Bt but no statistical differences.

Comparing Selected Life-History Traits of Black Soldier Fly (Diptera: Stratiomyidae) Larvae Produced in Industrial and Bench-Top-Sized Containers

As global food demand is increasing along with human population growth, there is a greater need for alternative protein sources. Insect protein, especially the larvae of the black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), has become a key approach for solving this issue in part due to its ability to convert organic waste into insect biomass with minimal resource (e.g., land, water) requirements. However, most information utilized to develop industrial production of this species is reliant on data generated from laboratory-scaled studies. Unfortunately, scaling these data to an industrial level potentially is not linear resulting in over, or under, estimating production. In this study, we compared selected life-history traits of larval black soldier fly produced at benchtop (e.g., 1 liter container with 614 larvae) and industrial scales (e.g., 29.5 liter container inoculated with 10,000 larvae). Larvae were provided a single feeding (2 g/larva) in each treatment. Significant differences in the mean larval weight (24.7%), survivorship (−28.2%), and biomass conversion (−2.7%) were determined between benchtop and industrial treatments. These results indicate larval number and the associated container size are important factors to consider when designing a black soldier fly factory. Furthermore, caution should be taken when applying data from laboratory studies to industrial scale production systems as the values potentially are not linear.

Influence of parasite load on the diagnosis and occurrence of eosinophilia in alcoholic patients infected withStrongyloides stercoralis

Alcoholic patients are more susceptible toStrongyloides stercoralisinfection. The chronic use of alcohol raises the levels of endogenous corticosteroids, which regulates the development of larvae and stimulates the differentiation of rhabditiform into infective filariform larvae, thus inducing internal autoinfection. Therefore, early diagnosis is important to prevent severe strongyloidiasis. The aim of this study was to evaluate the efficacy of parasitological methods, according to the parasite load and the number of stool samples, for diagnosis ofS. stercoralisinfection, as well the peripheral blood eosinophil count in alcoholic patients. A total of 330 patients were included in this study. The diagnosis was established using three parasitological methods: agar plate culture, Baermann–Moraes method and spontaneous sedimentation. Peripheral eosinophilia was considered when the level was >600 eosinophils/mm3. The agar plate culture (APC) had the highest sensitivity (97.3%). However, the analysis of multiple samples increased the sensitivity of all parasitological methods. The sensitivities of the methods were influenced by the parasite load. When the larval number was above 10, the sensitivity of APC was 100%, while in spontaneous sedimentation the sensitivity reached 100% when the larval number was above 50. In the present study, 15.4% of alcoholic patients infected withS. stercoralis(12/78) had increased peripheral blood eosinophil count (above 600 eosinophils/mm3). For an efficient parasitological diagnosis ofS. stercoralisinfection in alcoholic patients, repeated examination by two parasitological methods must be recommended, including agar plate culture due to its higher sensitivity. Moreover,S. stercoralisinfection was associated with eosinophilia, mostly in patients excreting up to 10 larvae/g faeces.

Composition, seasonality and distribution of the Ichthyoplankton in the Lower Swan Estuary, South-western Australia

Paired conical nets (0.5 mm mesh) were used to sample ichthyoplankton at three sites in the lower Swan Estuary in each month between May 1986 and April 1987. In all, 3948 fish larvae were caught, representing 32 families and 60 species, of which 29 could be assigned species names. The Clupeidae (20.2%), Engraulididae (10.4%), Callionymidae (8.7%) and Nemipteridae (6.8%) made the greatest contributions to the total larval number, followed by the Pinguepididae (5.8%), Gobiidae (5.8%), Terapontidae (5.7%) and Monacanthidae (5.4%). The most numerous of the identified species were Engraulis australis (10.4%), Hyperlophus vittatus (8.9%), Callionymus goodladi (8.7%) and Sardinella lemuru (7.4%). The 11 most abundant of the identified species included 2 that spawn in the estuary (E. australis and Parablennius tasmanianus) and 2 that spawn at sea but are abundant as juveniles in the estuary (Pelates sexlineatus and H. vittatus). The remaining 7 species are not common as either juveniles or adults in any region of the Swan Estuary. The larvae of marine species collected just inside the estuary mouth were very similar in size to those collected a further 7.2 km upstream, indicating that they are transported rapidly through the lower estuary, presumably through tidal action. The concentrations of both eggs and larvae of all fish collectively, and the concentrations of larvae of most of the abundant identified species, peaked between late spring and midsummer (November- January).

EFFECT OF PHORATE ON SOIL ARTHROPODS AND SOYBEAN PRODUCTIVITY IN A NORTH CAROLINA COASTAL PLAIN CROPPING SYSTEM

Soil arthropods were sampled from untreated and phorate-treated conventionally tilled soybean (Forrest cv) systems at the Tidewater Research Station, Plymouth, NC. Arthropods larger than 420 microns (U.S. Std. 40 mesh) were collected in 10-cm diameter by 15-cm depth soil cores and extracted through an elutriation process. Microarthropods larger than 149 microns (U.S. Std. 100 mesh) were collected in 5-cm diameter by 5 cm-depth soil cores and extracted using a salt flotation technique. Soybean root weight, root damage, nodulation, and yield were also quantified. Coleopteran larval number in early-planted soybean was positively correlated with root weight (r = 0.404, P < 0.01) and nodulation, yet soybean yields were higher (P < 0.05) in phorate-treated than in untreated plots. Adult Ataenius spp. number was higher (P < 0.05) in phorate-treated than in untreated plots in 1984 and 1985, suggesting higher arthropod decomposer activity in phorate- than in untreated soil. Predaceous centipede number was positively correlated with the number of Chrysomelidae larvae (r = 0.478, P < 0.001) and other Coleoptera larvae (r = 0.357, P < 0.01) in late-planted soybean. Similar nodulation levels between phorate-treated and untreated plants suggests compensatory or possibly stimulatory growth in response to low levels of soil arthropod feeding.

Simultaneous selection for two correlated traits in Tribolium

SUMMARYSimultaneous selection by independent culling levels of two correlated traits in all four combinations of directions was investigated with Tribolium in a replicated experiment extending over nine generations. In addition to the two primary traits, 13-day larval weight and pupal weight, four secondary traits (pupation time, adult emergence time, adult weight and larval number) were observed.The observed responses for both selected and unselected traits agreed with theoretical expectations after the latter were adjusted for changes which occurred in genetic and phenotypic parameters. Phenotypio variances for the selected traits were correlated positively with population means, yet genetic variances and heritabilities declined in all selected populations. No change was detected in the genetic correlation between selected traits even though the divergent two-trait selection was designed especially to ‘break’ the positive correlation of + 0·55 ± 0·12 present in the base population.Striking changes in growth and developmental patterns resulting from the divergent selection were discussed in terms of metamorphic limits and ‘stabilizing’ genetic correlations.

A GENETIC STUDY OF BIOMASS IN TRIBOLIUM. I. PATH COEFFICIENT ANALYSIS OF BASE POPULATIONS

Biomass, an aggregate trait combining the metric trait 13-day larval weight with the reproductive fitness trait number of larvae per mating, was investigated in two unrelated base populations of Tribolium castaneum, black and pearl.The black population was characterized by smaller 13-day larvae, more larvae per mating due to a higher rate of fecundity, and a smaller biomass than was observed for the pearl population. Both genetic and phenotypic variances were higher in black than in pearl. Heritability estimates for larval weight approached 0.20 in both populations while those for the fitness traits were smaller and seldom exceeded 10%. Non-additive genetic effects as well as maternal influences were observed in both populations. Positive estimates for the genetic correlations between larval weight and number of larvae per mating were observed for both populations (0.47 for black and 0.17 for pearl).Path coefficient analyses revealed that larval number in both populations had greater genetic and phenotypic influences on biomass than did larval weight. In turn, egg number had a greater influence on number of larvae than did larval viability.