ABSTRACT
Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) is one of the major lepidopteran pests defoliating soybeans (Glycine max Merrill) in Argentina. The combined use of chemical insecticides and entomopathogenic fungi is a promising pest-control option to minimize adverse chemical effects. In this work, we evaluated the interactions between five insecticides-two being considered biorational-and five fungal entomopathogenic strains under laboratory conditions in order to determine the possible usefulness of combinations of these agents against R. nu. The insecticides were tested for compatibility at four doses by in vitro bioassay and for the lethality of R. nu by inoculations at three doses. Fungal strains were applied at 1×108, 1×106, and 1×104conidia/ml. The combinations of those insecticides with Beauveria bassiana (LPSc 1067, LPSc 1082, LPSc 1098), Metarhizium anisopliae (LPSc 907), and Metarhizium robertsii (LPSc 963) caused higher R. nu-larval mortalities than any of the individual agents alone. We observed significant differences in the in vitro conidial viability, vegetative growth, and conidia production of the five strains of entomopathogenic fungi exposed to different doses of the chemical insecticides. The combination gamma-cyhalothrin-LPSc-1067 caused the highest percent mortality of R. nu larvae, with synergism occurring between the two agents at 50% and 25% of the maximum field doses.
Subject(s)
Glycine max , Insecticides , Lepidoptera , Pest Control, Biological , Animals , Argentina , Beauveria , MetarhiziumABSTRACT
Los hongos micorrícicos arbusculares (HMA) incrementan la toma de fosfatos solubles, mientras que los hongos solubilizadores de fósforo (S) promueven la solubilización de complejos insolubles de fosfato, en conjunto benefician la nutrición de las plantas. La utilización de estos organismos en combinación con minerales o rocas que aportan nutrientes es otra alternativa para mantener la productividad de los cultivos. El objetivo de este trabajo fue combinar HMA y S con materiales piroclásticos (cenizas y pumicitas) del volcán Puyehue y rocas fosfóricas (RP) del Grupo Río Chico (Chubut) y evaluar el desempeno de estas mezclas como sustratos para la producción en maceta de Lactuca sativa. Para formular los sustratos, se utilizó como base una mezcla de Terrafertil® con cenizas. Penicillium thomii fue el S y esporas del hongo Rhizophagus intraradices (AEGIS® Irriga) sirvieron de fuente del HMA. Se evaluaron diversas combinaciones de microorganismos y la adición o no de RP. Los tratamientos fueron: 1) sustrato; 2) sustrato + HMA; 3) sustrato + S; 4) sustrato + HMA + S; 5) sustrato: RP; 6) sustrato: RP + HMA; 7) sustrato: RP + S, y 8) sustrato: RP+ HMA + S. Se efectuaron 3 repeticiones por tratamiento. Los parámetros evaluados fueron el contenido de P total y asimilable en el sustrato, el P en el tejido vegetal y la biomasa seca. Todos ellos fueron significativamente mayores en las plantas que crecieron en el sustrato adicionado con RP e inoculadas con S y HMA. Este trabajo confirma que la combinación S/HMA con cenizas volcánicas del Puyehue y las RP del Grupo Río Chico formuladas con un sustrato comercial promueven el crecimiento de L. sativa. De este modo es posible incrementar el valor agregado de geomateriales de origen nacional.
Arbuscular mycorrhizal fungi (AMF) increase the uptake of soluble phosphates, while phosphorus solubilizing fungi (S) promote solubilization of insoluble phosphates complexes, favoring plant nutrition. Another alternative to maintaining crop productivity is to combine minerals and rocks that provide nutrients and other desirable properties. The aim of this work was to combine AMF and S with pyroclastic materials (ashes and pumices) from Puyehue volcano and phosphate rocks (PR) from Rio Chico Group (Chubut) - to formulate a substrate for the production of potted Lactuca sativa. A mixture of Terrafertil®:ashes was used as substrate. Penicillium thomii was the solubilizing fungus and Rhizophagus intraradices spores (AMF) was the P mobilizer (AEGIS® Irriga). The treatments were: 1) Substrate; 2) Substrate + AMF; 3) Substrate+S; 4) Substrate + AMF+ S; 5) Substrate: PR; 6) Substrate: PR + AMF; 7) Substrate: PR + S and 8) Substrate: PR + AMF + S. Three replicates were performed per treatment. All parameters evaluated (total and assimilable P content in substrate, P in plant tissue and plant dry biomass) were significantly higher in plants grown in substrate containing PR and inoculas with S and AMF. This work confirms that the combination of S/AMF with Puyehue volcanic ashes, PR from the Río Chico Group and a commercial substrate promote the growth of L. sativa, thus increasing the added value of national geomaterials.
Subject(s)
Phosphates , Phosphorus , Lactuca , Mycorrhizae , Phosphates/metabolism , Lactuca/growth & development , Glomeromycota , FungiABSTRACT
Arbuscular mycorrhizal fungi (AMF) increase the uptake of soluble phosphates, while phosphorus solubilizing fungi (S) promote solubilization of insoluble phosphates complexes, favoring plant nutrition. Another alternative to maintaining crop productivity is to combine minerals and rocks that provide nutrients and other desirable properties. The aim of this work was to combine AMF and S with pyroclastic materials (ashes and pumices) from Puyehue volcano and phosphate rocks (PR) from Rio Chico Group (Chubut) - to formulate a substrate for the production of potted Lactuca sativa. A mixture of Terrafertil®:ashes was used as substrate. Penicillium thomii was the solubilizing fungus and Rhizophagus intraradices spores (AMF) was the P mobilizer (AEGIS® Irriga). The treatments were: 1) Substrate; 2) Substrate+AMF; 3) Substrate+S; 4) Substrate+AMF+S; 5) Substrate: PR; 6) Substrate: PR+AMF; 7) Substrate: PR+S and 8) Substrate: PR+AMF+S. Three replicates were performed per treatment. All parameters evaluated (total and assimilable P content in substrate, P in plant tissue and plant dry biomass) were significantly higher in plants grown in substrate containing PR and inoculas with S and AMF. This work confirms that the combination of S/AMF with Puyehue volcanic ashes, PR from the Río Chico Group and a commercial substrate promote the growth of L. sativa, thus increasing the added value of national geomaterials.
Subject(s)
Lactuca , Mycorrhizae , Phosphates , Phosphorus , Fungi , Glomeromycota , Lactuca/growth & development , Phosphates/metabolismABSTRACT
Rock phosphate effect on English mint (Mentha piperita L.) grown on steamed perlite:vermiculite (1:1, v:v) substrate, with and without rock phosphate, was evaluated in greenhouse experiments. Five treatments were carried out by inoculation with an arbuscular mycorrhizal fungus Glomus mosseae and a phosphorus solubilizing microorganism Penicillium thomii. Plant aerial biomass, phosphorus concentration in plant tissue, and P available in the substrate, were evaluated upon two harvests. After the first harvest, plant aerial biomass did not show significant differences between treatments using rock phosphate as fertilizer, although P content in plants inoculated with P. thomii was higher. The second harvest revealed a higher biomass and plant tissue P content in treatments inoculated with G. mosseae. P. thomii increased P available in the substrate, whereas in the absence of G. mosseae, it did not enhance plant tissue P content. Mycorrhizal colonization was not affected by P. thomii. Microbial inoculation effect on English mint growth was also evaluated. The microbial effect was positive in all treatments when compared with the control without rock phosphate.
Subject(s)
Fungi/growth & development , Mentha piperita/growth & development , Mentha piperita/microbiology , Mycorrhizae/growth & development , Penicillium/growth & development , Phosphorus/metabolism , Aluminum Oxide/chemistry , Biomass , Fungi/metabolism , Mycorrhizae/metabolism , Penicillium/metabolism , Silicon Dioxide/chemistryABSTRACT
Los efectos de las prßcticas agronómicas sobre las poblaciones de hongos formadores de micorrizas arbusculares han sido poco estudiados en condiciones de campo. Las comunidades de hongos micorrízicos son específicas del lugar y pueden ser afectadas de diferentes maneras por las practicas agronómicas. Para las areas cultivables de Argentina, la información sobre este tema es escasa. Se compararon los efectos de siembra directa (SD), labranza convencional (LC) y fertilización nitrogenada sobre la colonización de endomicorrizas y la producción de esporas en monocultivo de trigo. Se obtuvieron muestras de raíces en 3 estados fenológicos del cultivo: macollaje, floración y llenado de granos. Se procedió a su tinción, calculßndose los porcentajes de colonización. La extracción de esporas del suelo se efectuó mediante tamizado en húmedo y decantación en gradiente de sacarosa. La colonización se incrementó desde el maco-llaje hasta el llenado de granos. Sólo se observaron diferencias significativas en la colonización en maco-llaje en SD, que fue superior a LC. El número de esporas en 100 gr de suelo pre-sentó diferencias según el sistema de labranza. En LC con fertilizante el número de esporas se duplicó desde el macollaje hasta la floración. En LC sin fertilizante este número fue bajo en el macollaje, incrementßndose hasta la floración y el llenado de granos. En SD, independientemente del nivel de fertilización, el número de esporas se mantuvo estable durante todo el ciclo.