Investigation of insect-weed interactions in the rice agroecosystem

Interactions between graminaceous weed and insect pests of rice and between management practices for these pests were investigated. Studies were conducted to examine preference and performance of rice water weevil, Lissorhoptrus oryzophilus Kuschel, on several weeds commonly found in rice fields. Several weeds were more preferred than rice, and larvae were present on several dicotyledonous weeds, suggesting the host range of L. oryzophilus is broader than previously thought. Effects of the presence of barnyardgrass, (Echinochloa crus-galli Beauv.), on rice stink bugs, Oebalus pugnax F., and L. oryzophilus populations in rice fields were investigated. Presence of barnyardgrass and the synchrony of barnyardgrass seed heads and rice panicles influenced O. pugnax densities on rice. Barnyardgrass served as a trap crop or as a source of infestation of O. pugnax depending on the developmental stage of barnyardgrass relative that of rice. Presence of barnyardgrass had little impact on L. oryzophilus . Similar studies conducted with borers and Amazon sprangletop, Leptochloa panicoides (Presl.) Hitchc. revealed that injury to rice was greater in weedy plots of rice than in pure plots of rice. Studies were conducted to determine how density of weeds affected O. pugnax populations and how weeds and O. pugnax combined to reduce grain yield and quality. Numbers of O. pugnax and percentages of filled seeds, pecky rice, and broken kernels increased as weed density increased. Increases were less severe in insecticide-treated than non-treated plots. However, yield losses from weeds and insects were not significantly greater than from weeds alone. Preference and performance of L. oryzophilus on herbicide-treated and non-treated glufosinate-tolerant rice were investigated. Glufosinate applications on glufosinate-tolerant rice reduced weevil oviposition by 30% and reduced larval densities by 20% compared to non-treated glufosinate-tolerant rice. Glufosinate was not toxic to L. oryzophilus at rates used in these experiments, and feeding was not deterred by glufosinate, suggesting that glufosinate application induced resistance. Larval densities on glufosinate-treated and non-treated glufosinate-tolerant rice in field experiments did not differ; however, delayed floods reduced numbers of larvae on rice compared to those on early flooded rice

An Evolutionary Upgrade of Cognitive Load Theory: Using the Human Motor System and Collaboration to Support the Learning of Complex Cognitive Tasks

Cognitive load theory is intended to provide instructional strategies derived from experimental, cognitive load effects. Each effect is based on our knowledge of human cognitive architecture, primarily the limited capacity and duration of a human working memory. These limitations are ameliorated by changes in long-term memory associated with learning. Initially, cognitive load theory's view of human cognitive architecture was assumed to apply to all categories of information. Based on Geary's (Educational Psychologist 43, 179-195 2008; 2011) evolutionary account of educational psychology, this interpretation of human cognitive architecture requires amendment. Working memory limitations may be critical only when acquiring novel information based on culturally important knowledge that we have not specifically evolved to acquire. Cultural knowledge is known as biologically secondary information. Working memory limitations may have reduced significance when acquiring novel

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Plant-mediated interactions between the rice water weevil and fall armyworm in rice

Greenhouse studies were conducted to investigate plant-mediated interactions between an above-ground and a below-ground herbivore when sharing a common host plant, rice (Oryza sativa L). Two common pests of rice were used: the rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, as the root herbivore, and the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) as the foliage-feeding herbivore. Rice water weevil larval performance was assessed by measuring larval density and average weight in response to different levels of defoliation by FAW larvae. The reciprocal experiment was done to evaluate FAW performance (growth rate) in response to RWW feeding. Severe defoliation by FAW decreased RWW densities by 32% and reduced larval weights by 48% compared to larvae on roots of non-defoliated plants. Effects in the converse experiments were not as strong. FAW growth rates were reduced 9-37% when feeding on rice leaves from plants damaged by RWW compared to larvae feed leaves from the no damage treatment. These reciprocal negative effects show that RWW and FAW are potential competitors when sharing a rice plant. Because RWW and FAW did not interact directly, competition was plant-mediated

Effect of depth of flooding on the rice water weevil, lissorhoptrus oryzophilus, and yield of rice

The rice water weevil, Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is a semi-aquatic pest of rice and is the most destructive insect pest of rice in the United States. Adults oviposit after floods are established, and greenhouse studies have shown that plants exposed to deep floods have more eggs oviposited in leaf sheaths than plants exposed to a shallow flood. Experiments were conducted in three mid-southern states in the USA to determine if the depth of flooding would impact numbers of L. oryzophilus on rice plants under field conditions. Rice was flooded at depths of approximately 5 or 10 cm in Arkansas in 2007 and 2008 and Louisiana in 2008, and at depths between 0-20 cm in Missouri in 2008. Plants were sampled three and four weeks after floods were established in all locations, and also two weeks after flood in Missouri. On all sampling dates in four experiments over two years and at three field sites, fewer L. oryzophilus larvae were collected from rice in shallow-flooded plots than from deep-flooded plots. The number of L. oryzophilus was reduced by as much as 27% in shallow-flooded plots. However, the reduction in insect numbers did not translate to a significant increase in rice yield. We discuss how shallow floods could be used as a component of an integrated pest management program for L. oryzophilus