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Soybean Fields (soybean + field)
Selected AbstractsSurvival and oviposition of a western corn rootworm variant feeding on soybeanENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003Timothy R. Mabry Abstract The role of soybean, Glycine max (L.) Merril (Fabaceae), in the circumvention of crop rotation was evaluated by observing the effects of soybean herbivory on western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) survival and oviposition. Field collected D. virgifera adults resistant to annual rotation of corn, Zea mays (L.) (Poaceae), and soybean were given the opportunity to feed on a soybean pre-treatment diet prior to diet combinations of corn, soybean, and/or water. The number of days that the adults survived after removal of the diet combinations was used as a measure of insect vigor and diet quality. Willingness to feed on a soybean foliage pre-treatment did not indicate greater ability to benefit nutritionally from soybean herbivory. Adult D. virgifera previously feeding on corn, soybean, or water survived starvation for 8.3 ± 0.15 days, 5.1 ± 0.13 days, and 3.9 ± 0.14 days, respectively. Diabrotica virgifera recover from 2 days of starvation or poor diet if subsequently given access to corn tissues for 2 days. Eggs were laid within 1 day of access to poor diet or starvation. Other D. virgifera, captured as they flew from a cornfield into a soybean field, were maintained on soybean foliage or only water until they died. Of the beetles with access to soybean foliage, 24% fed within 24 h after capture and survived 1 day longer than insects given only water. Only 20% of these D. virgifera were able to lay eggs without consuming additional corn prior to death. Few D. virgifera enter soybean fields capable of immediate oviposition. Female reproductive status and diet quality influence the likelihood of oviposition following exposure to stress. The effects of soybean herbivory may contribute to the proximate mechanism of resistance to crop rotation. [source] Landscape composition influences patterns of native and exotic lady beetle abundanceDIVERSITY AND DISTRIBUTIONS, Issue 4 2009M. M. Gardiner Abstract Aim, Coccinellid beetles are important predators that contribute to pest suppression in agricultural landscapes. Since the introduction of the exotic coccinellids Coccinella septempunctata L. and Harmonia axyridis Pallas into the USA, several studies have reported a decline of native Coccinellidae in agroecosystems. We aimed to investigate the influence of landscape composition on native and exotic coccinellid abundance within soybean fields. Location, Iowa, Michigan, Minnesota and Wisconsin. Methods, As part of a 2-year study (2005,06) on the biological control of the soybean aphid, Aphis glycines Matsumura, we examined coccinellid communities in 33 soybean fields using yellow sticky card traps. Landscape heterogeneity and composition were measured at multiple spatial scales ranging 1,3.5 km from focal soybean fields where coccinellid sampling took place. Results, Exotic species made up 90% of the total coccinellid community in Michigan soybean fields followed by Wisconsin (84%), Minnesota (66%) and Iowa (57%). Harmonia axyridis was the dominant exotic coccinellid in all states comprising 45,62% of the total coccinellid community, followed by C. septempunctata (13,30%). Two additional exotic species, Hippodamia variegata (Goeze) and Propylea quatuordecimpunctata (L.) were also found in the region. Overall, the most abundant native coccinellid was Hippodamia convergens Guerin-Meneville; however, its abundance varied across the region, comprising 0% (Michigan) to 28% (Iowa) of the total coccinellid community. Landscape structure significantly influenced the composition of coccinellid communities in soybean agroecosystems. We found that native coccinellids were most abundant in low-diversity landscapes with an abundance of grassland habitat while exotic coccinellids were associated with the abundance of forested habitats. Main conclusion, We propose that grassland dominated landscapes with low structural diversity and low amounts of forested habitat may be resistant to exotic coccinellid build-up, particularly H. axyridis and therefore represent landscape-scale refuges for native coccinellid biodiversity. [source] Aquifer Sensitivity to Pesticide Leaching: Testing a Soils and Hydrogeologic Index MethodGROUND WATER MONITORING & REMEDIATION, Issue 4 2005Edward Mehnert For years, researchers have sought index and other methods to predict aquifer sensitivity and vulnerability to nonpoint pesticide contamination. In 1995, an index method and map were developed to define aquifer sensitivity to pesticide leaching based on a combination of soil and hydrogeologic factors. The soil factor incorporated three soil properties: hydraulic conductivity, amount of organic matter within individual soil layers, and drainage class. These properties were obtained from a digital soil association map. The hydrogeologic factor was depth to uppermost aquifer material. To test this index method, a shallow ground water monitoring well network was designed, installed, and sampled in Illinois. The monitoring wells had a median depth of 7.6 m and were located adjacent to corn and soybean fields where the only known sources of pesticides were those used in normal agricultural production. From September 1998 through February 2001, 159 monitoring wells were sampled for 14 pesticides but no pesticide metabolites. Samples were collected and analyzed to assess the distribution of pesticide occurrence across three units of aquifer sensitivity. Pesticides were detected in 18% of all samples and nearly uniformly from samples from the three units of aquifer sensitivity. The new index method did not predict pesticide occurrence because occurrence was not dependent on the combined soil and hydrogeologic factors. However, pesticide occurrence was dependent on the tested hydrogeologic factor and was three times higher in areas where the depth to the uppermost aquifer was <6 m than in areas where the depth to the uppermost aquifer was 6 to <15 m. [source] Two-year oscillation cycle in abundance of soybean aphid in IndianaAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Marc Rhainds 1The present study evaluated the population dynamics of the heteroecious soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) during an 8-year period in Indiana, shortly after its detection in North America. Sampling conducted at multiple locations revealed that A. glycines exhibited a 2-year oscillation cycle that repeated itself four times between 2001 and 2008: years of low aphid abundance were consistently followed by years of high aphid abundance. 2Similar patterns of abundance of A. glycines and coccinellids (Coleoptera: Coccinellidae) in soybean fields, both within and between-years, suggest that late season predation by coccinellids plays a role in the oscillatory cycle of aphids. Insidious flower bugs Orius insidiosus (Say) (Hemiptera: Anthocoridae) were numerically more abundant than coccinellids, although the lack of synchrony between aphids and predatory bugs suggests that O. insidiosus has a limited influence on between-year variations in aphid density. 3The inverse relationship between aphid densities before and after the start of the autumn migratory period changes direction in alternate years. High aphid density on soybean in the summer is associated with a reduced number of alate migrants produced in the autumn. Conversely, years with low density aphids on soybean in the summer are characterized by high numbers of alates that migrate to the primary host in the autumn. 4From a pest management perspective, the 2-year oscillation cycle of A. glycines is a desirable attribute with respect to population dynamics because it implies that aphids cause significant economic damage only in alternate years (as opposed to every year). Cultural practices enhancing the conservation biological control of Coccinellidae may help to preserve the periodicity of aphid infestation and restrict the pest status of A. glycines. [source] Relatedness of Macrophomina phaseolina isolates from tallgrass prairie, maize, soybean and sorghumMOLECULAR ECOLOGY, Issue 1 2010A. A. SALEH Abstract Agricultural and wild ecosystems may interact through shared pathogens such as Macrophomina phaseolina, a generalist clonal fungus with more than 284 plant hosts that is likely to become more important under climate change scenarios of increased heat and drought stress. To evaluate the degree of subdivision in populations of M. phaseolina in Kansas agriculture and wildlands, we compared 143 isolates from maize fields adjacent to tallgrass prairie, nearby sorghum fields, widely dispersed soybean fields and isolates from eight plant species in tallgrass prairie. Isolate growth phenotypes were evaluated on a medium containing chlorate. Genetic characteristics were analysed based on amplified fragment length polymorphisms and the sequence of the rDNA-internal transcribed spacer (ITS) region. The average genetic similarity was 58% among isolates in the tallgrass prairie, 71% in the maize fields, 75% in the sorghum fields and 80% in the dispersed soybean fields. The isolates were divided into four clusters: one containing most of the isolates from maize and soybean, two others containing isolates from wild plants and sorghum, and a fourth containing a single isolate recovered from Solidago canadensis in the tallgrass prairie. Most of the sorghum isolates had the dense phenotype on media containing chlorate, while those from other hosts had either feathery or restricted phenotypes. These results suggest that the tallgrass prairie supports a more diverse population of M. phaseolina per area than do any of the crop species. Subpopulations show incomplete specialization by host. These results also suggest that inoculum produced in agriculture may influence tallgrass prairie communities, and conversely that different pathogen subpopulations in tallgrass prairie can interact there to generate ,hybrids' with novel genetic profiles and pathogenic capabilities. [source] | ||||||||||