Stochastic Dynamic Northern Corn Rootworm Population Model

A complete life cycle model for northern corn rootworm, Diabrotica barberi Smith and Lawrence, is developed using a published single-season model of adult population dynamics and data from field experiments. Temperature-dependent development and age-dependent advancement determine adult population dynamics and oviposition, while a simple stochastic hatch and density-dependent larval survival model determine adult emergence. Dispersal is not modeled. To evaluate the long-run performance of the model, stochastically generated daily air and soil temperatures are used for 100-year simulations for a variety of corn planting and flowering dates in Ithaca, NY, and Brookings, SD. Once the model is corrected for a bias in oviposition, model predictions for both locations are consistent with anecdotal field data. Extinctions still occur, but these may be consistent with northern corn rootworm metapopulation dynamics

BIOPHYSICAL CONSTRAINTS AND ECOLOGICAL COMPATIBILITIES OF DIVERSE AGROECOSYSTEMS

International audienceA diagnostic approach based on multi-scale integrated analysis and model simulations was employed to identify specific or common biophysical constraints, technological changes and ecological compatibilities of the diverse subsistence (SUB) and organic (ORG) agro-ecosystems in the Fertile Crescent (FC) of West Asia and the organic and conventional (CNV) agro-ecosystem in the Northern Corn Belt (NCB) and Northern Great Plains (NGP) of the U.S. For each agro-ecosystem, soil carbon, total yield, temporal yield variance and yield coefficient of variation per crop rotation were used as sustainability indicators. Thresholds of technologies necessary for the proper functioning and flow of agro-ecosystem services were identified under the most-likely IPCC-projected climate change scenarios for the next 30 years. The carbon budgets of agro-ecosystems were largely related to the choice of crops, crop sequence, and length of the crop rotation, and were influenced by external inputs, tillage system and removal of crop residues. Carbon depletion is expected to be less in organic and subsistence agro-ecosystems when nitrogen-fixing legumes are included in more diverse crop rotations and when crop residues are incorporated into the soil. Potential nutrients loss to the environment was significantly larger in conventional systems, and nutrients are expected to be depleted over time in subsistence- faster than in organically-managed soils. Optimal and sustainable agricultural intensification is feasible through agroecosystem diversification and the proper integration of genetic and natural resources management. In all agroecosystems, for more diverse rotations to be adopted at a large scale, there needs to be large and easily accessible markets for the additional product

Anatomical Characterization of Western Corn Rootworm Damage in Adventitious Roots of Maize

Corn rootworms are one of the most economically damaging insect pests of maize, yet little is known about the feeding behavior of the larvae. This study was conducted to determine which tissues of the adventitious roots of maize are damaged by western corn rootworm (Diabrotica virgifera virgifera LeConte) larval feeding. Root axes (10 cm long) were removed from the fifth node of greenhouse-grown maize plants. Root segments 2 cm long, excised 4 or 6 cm from the root tip, were infested with second or third stage larvae, respectively, (0, 1, 3, or 6 larvae per segment) for a period of 24 hours. Root segments were fixed, embedded and sectioned to a thickness of 16 μm for light microscopy. Serial sections taken at 1 mm intervals were used to measure the amount of tissue removed during insect feeding. Light micrographs revealed that larval feeding damage was restricted to the root cortex, and no damage was visible in the pith. Up to 80% of the cortex was removed during feeding within a 24-h period. The suberized and lignified secondary walls of the endodermis and exodermis appear to act as barriers that either prevent or discourage larval feeding within the pith. These results are discussed in terms of possible explanations of the characteristics of corn rootworm damage under field conditions

Diversity and Dominant Species of Ground Beetle Assemblages (Coleoptera: Carabidae) in Crop Rotation and Chemical Input Systems for the Northern Great Plains

Dominant carabid species present in crops and crop rotation sequences commonly used in the northern Great Plains were assessed as an initial step toward the management of carabids as natural control agents. Ground beetle populations were determined by pitfall trapping in 4 crop rotation treatments maintained under high, managed, and low levels of chemical fertilizer and pesticide inputs. Diversity and species richness among crops, rotations, and input levels were compared using 3 indices—the Shannon-Weaver Index, relative diversity, and the Hierarchical Richness Index (HRI). Four carabid species, Cyclotrachelus altemans (Casey), Poecilvs lucublandus Say, Harpalns pensylvanicus (DeGeer), and Bembidion quadrimaculatum L., comprising ≈80% of the total collected, were considered dominant species. When carabid abundance data were grouped by crop, C. altemans was the dominant species in corn and alfalfa and P. lucublandus was dominant in wheat. In soybean plots, C. altemans and P. lucublandus were equally abundant. The relative abundance of H. pensylvanicus was highest in the low-input plots. High values of HRI for carabid diversity and species richness in the managed plots suggested that reduced chemical inputs encouraged greater abundance and diversity of beneficial carabids than were found in the high-input plots without the loss of yield seen in the low-input plots

Diversity and Dominant Species of Ground Beetle Assemblages (Coleoptera: Carabidae) in Crop Rotation and Chemical Input Systems for the Northern Great Plains

Dominant carabid species present in crops and crop rotation sequences commonly used in the northern Great Plains were assessed as an initial step toward the management of carabids as natural control agents. Ground beetle populations were determined by pitfall trapping in 4 crop rotation treatments maintained under high, managed, and low levels of chemical fertilizer and pesticide inputs. Diversity and species richness among crops, rotations, and input levels were compared using 3 indices—the Shannon-Weaver Index, relative diversity, and the Hierarchical Richness Index (HRI). Four carabid species, Cyclotrachelus altemans (Casey), Poecilvs lucublandus Say, Harpalns pensylvanicus (DeGeer), and Bembidion quadrimaculatum L., comprising ≈80% of the total collected, were considered dominant species. When carabid abundance data were grouped by crop, C. altemans was the dominant species in corn and alfalfa and P. lucublandus was dominant in wheat. In soybean plots, C. altemans and P. lucublandus were equally abundant. The relative abundance of H. pensylvanicus was highest in the low-input plots. High values of HRI for carabid diversity and species richness in the managed plots suggested that reduced chemical inputs encouraged greater abundance and diversity of beneficial carabids than were found in the high-input plots without the loss of yield seen in the low-input plots

Investigation of Griffithsin's Interactions with Human Cells Confirms Its Outstanding Safety and Efficacy Profile as a Microbicide Candidate

Many natural product-derived lectins such as the red algal lectin griffithsin (GRFT) have potent in vitro activity against viruses that display dense clusters of oligomannose N-linked glycans (NLG) on their surface envelope glycoproteins. However, since oligomannose NLG are also found on some host proteins it is possible that treatment with antiviral lectins may trigger undesirable side effects. For other antiviral lectins such as concanavalin A, banana lectin and cyanovirin-N (CV-N), interactions between the lectin and as yet undescribed cellular moieties have been reported to induce undesirable side effects including secretion of inflammatory cytokines and activation of host T-cells. We show that GRFT, unlike CV-N, binds the surface of human epithelial and peripheral blood mononuclear cells (PBMC) through an exclusively oligosaccharide-dependent interaction. In contrast to several other antiviral lectins however, GRFT treatment induces only minimal changes in secretion of inflammatory cytokines and chemokines by epithelial cells or human PBMC, has no measureable effect on cell viability and does not significantly upregulate markers of T-cell activation. In addition, GRFT appears to retain antiviral activity once bound to the surface of PBMC. Finally, RNA microarray studies show that, while CV-N and ConA regulate expression of a multitude of cellular genes, GRFT treatment effects only minimal alterations in the gene expression profile of a human ectocervical cell line. These studies indicate that GRFT has an outstanding safety profile with little evidence of induced toxicity, T-cell activation or deleterious immunological consequence, unique attributes for a natural product-derived lectin

An ultrastructural study of chloroplasts and microbodies in seed and seedling cotyledons of Pharbitis nil

Includes bibliographical references.Includes illustrations.The cellular ultrastructure of cotyledon tissue from seeds and seedlings of Japanese morning glory (Pharbitis nil) was studied. Weight determinations of the seed and seedling cotyledons, the same age as those studied under the transmission electron microscope, indicate that the growing cotyledons of the seed and seedling increase in biomass. During this period of growth, cellular ultrastructure of the seed and seedling cotyledons undergo marked changes. Cells of the seed cotyledon 17 days after anthesis appear as highly vacuolate cells. The appearance of lipid and protein bodies in the cells of slightly older (30 days after anthesis) seed cotyledons corresponds to an increase in fresh weight and percentage dry weight of these slightly older seed cotyledons. Upon dark germination and subsequent irradiation with white light, the fresh weight of the seedling cotyledons increases steadily. Microbodies (glyoxysomes), which aid in the enzymatic breakdown of stored lipid, are present within the dark germinated seedling cotyledon cells. Irradiation of the seedling cotyledons with white light causes the de novo development of the peroxisomes. A description of the ultrastructure of the two types of microbodies, as well as semi-quantitative analysis of their characteristic associations with lipid bodies and chloroplasts is given. Chloroplasts of seed and seedling cotyledons, which undergo developmental changes when exposed to light, were also studied. The ultrastructural appearance of the chloroplasts, as well as the amount of chlorophyll present in seed and seedling cotyledons, indicate that the chloroplasts of both seed and seedling cotyledons are able to carry on the process of photosynthesis. Plastids of dark grown seedling cotyledon cells which were irradiated with continuous far red light undergo no structural transformation.M.S. (Master of Science

Stochastic Dynamic Northern Corn Rootworm Population Model

A complete life cycle model for northern corn rootworm, Diabrotica barberi Smith and Lawrence, is developed using a published single-season model of adult population dynamics and data from field experiments. Temperature-dependent development and age-dependent advancement determine adult population dynamics and oviposition, while a simple stochastic hatch and density-dependent larval survival model determine adult emergence. Dispersal is not modeled. To evaluate the long-run performance of the model, stochastically generated daily air and soil temperatures are used for 100-year simulations for a variety of corn planting and flowering dates in Ithaca, NY, and Brookings, SD. Once the model is corrected for a bias in oviposition, model predictions for both locations are consistent with anecdotal field data. Extinctions still occur, but these may be consistent with northern corn rootworm metapopulation dynamics.</p

One Plus One Equals Three: The Synergistic Effects Of Crop Rotation On Soil Fertility And Plant Nutrition

Corn grown under annual corn-soybean crop rotation has greater accumulation of certain mineral nutrients and higher yields than corn grown in monoculture. This study was conducted to determine if complex crop rotations (with legumes in the rotation as alfalfa hay as well as soybean row crops) and different levels of agriculture chemical input affect soil fertility and corn mineral nutrient composition. The effects of crop rotation [monoculture corn, corn-soybean 2-yr rotation, corn-soybean- wheat underseeded with alfalfa-alfalfa 4-yr rotation] and input level [high input (fertilizer application for 8.15 Mg ha-1 yield goal, prophylactic herbicide and insecticide application, fall moldboard plow/spring disk and cultivation operations), intermediate input (fertilizer application for 5.33 Mg ha-1 yield goal, pesticide applications based upon pest survey and IPM principles, fall chisel plow/spring disk and cultivation operations), and low input (no fertilizer, herbicide, or insecticide applications, fall chisel plow/spring disk and cultivation operations)] on soil fertility (pH, organic matter, NO3-N, P, K, and total N) and on corn shoot dry weight, mineral nutrient (N, P, Ca, Mg) concentration and accumulation at tassel stage of development were investigated at Brookings, SD. Soil samples taken at the V6 stage of corn development indicated that crop rotation treatments reduced soil pH, increased soil NO3-N level, and decreased soil P level when compared to corn monoculture. Shoots of plants grown under either 2-yr rotation intermediate input or 4-yr rotation no input treatments had greater dry weight, as well as greater P, Ca, and Mg accumulation than these same input treatments in other rotations. These results demonstrate a beneficial effect of crop rotation upon soil fertility and corn mineral nutrition. The results of this experiment are discussed in terms of nutrient synergisms whereby nutrient absorption proceeds at a faster rate than dry weight accumulation