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Isoxaflutole Shifts Kochia (Kochia scoparia) Populations in Continuous Corn

Published online by Cambridge University Press:  20 January 2017

Gustavo M. Sbatella*
Affiliation:
University of Nebraska-Lincoln Panhandle Research and Extension Center, Department of Agronomy and Horticulture, Scottsbluff, NE 69361
Robert G. Wilson
Affiliation:
University of Nebraska-Lincoln Panhandle Research and Extension Center, Department of Agronomy and Horticulture, Scottsbluff, NE 69361
*
Corresponding author's E-mail: [email protected].

Abstract

Kochia control in continuous corn became increasingly difficult in experimental plots where isoxaflutole was used PRE for 8 yr. Studies were conducted to determine if poor kochia control resulted from an escape mechanism based on different germination rates or from a difference in sensitivity to isoxaflutole. Germination at constant temperatures showed that the kochia population in the experimental plot had greater seed dormancy compared with populations growing in adjacent fields. Germination at 25 C for seeds collected from the isoxaflutole-treated area was near 20% after 20 d, whereas germination for the other populations was above 80%. The optimal temperatures to release seed dormancy for seeds from the experimental plot were alternating 35/25 C day/night temperatures. The kochia biotype that predominated where isoxaflutole was applied PRE had elevated levels of seed dormancy and required higher alternating temperatures to release dormancy than untreated control kochia. These characteristics were unique and not found in populations never exposed to isoxaflutole. Chlorophyll content was measured to determine if differences in sensitivity to isoxaflutole existed among biotypes. Absorption at 660 nm by photosynthetic pigments was similar among the biotypes at increasing herbicide rates, indicating no differences in sensitivity to isoxaflutole among populations. Reduced kochia control in the experimental plot was due to delayed seed germination, which allowed isoxaflutole to degrade before seeds germinated. The rapid herbicide dissipation from soil can be attributed in part to coarse soils, soil moisture, and the low isoxaflutole rate.

El control de Kochia scoparia (L.) Schrad en maíz de siembra continua fue cada vez más difícil en parcelas experimentales donde isoxaflutole fue usado en pre emergencia por 8 años. Se llevaron al cabo estudios para determinar si el control deficiente de Kochia scoparia (L.) Schrad. fue el resultado de un mecanismo de escape basado en diferentes periodos de germinación, ó a diferencias en la sensibilidad al isoxaflutole. La germinación a temperaturas constantes demostró que las semillas de la población de Kochia scoparia (L.) Schrad provenientes de las parcelas experimentales presentaron un mayor grado de dormicion comparada con la población que se encontraban en campos adyacentes. La germinación a 25 C para semillas recolectadas del área tratada con isoxaflutole fue cerca del 20% después de 20 días, mientras que la germinación de las otras poblaciones fue superior al 80%. Las temperaturas óptimas para liberar la inactividad de las semillas de la parcela experimental fueron alternando temperaturas de 35/25 C diurnas/nocturnas. El biotipo de Kochia scoparia (L.) Schrad que predominó donde se aplicó isoxaflutole en pre emergencia mostró elevados niveles de dormicion de semilla y alternar temperaturas más altas para liberar la dormicion, en comparación con el testigo no tratado de Kochia scoparia (L.) Schrad. Estas características fueron únicas y no se observaron en poblaciones nunca expuestas al isoxaflutole. El contenido de clorofila fue medido para determinar si existian diferencias en la sensibilidad al isoxaflutole existían entre los biotipos. La absorción a 660 nm por pigmentos fotosintéticos fue similar entre biotipos al incremental la dosis, lo que sugiere que no existe diferencias en la sensibilidad al isoxaflutole entre poblaciones. La reduccion en el control de Kochia scoparia (L.) Schrad en la parcela experimental se debió a la germinación tardía, la que permitió la degradacion del isoxaflutole antes que las semillas germinaran. La rápida disipación del herbicida en el suelo puede atribuirse en parte a la textura y contenido de humedad del suelo y a la baja dosis de isoxaflutole.

Type
Weed Biology and Competition
Copyright
Copyright © Weed Science Society of America 

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