Start Date

29-11-2007 12:00 AM

Description

Corn rootworms have been, and in many cases still can be, managed with crop rotations. However, some populations of both northern and western corn rootworms (CRWs) have adapted to the corn-soybean rotation. Regular, annual rotations between corn and soybeans have selected for a variant of the northern CRW that has a two-year life cycle, referred to as extended diapause. Female northern CRWs deposit eggs in the soil within cornfields. When the field is rotated to soybean the next year, most eggs hatch and the larvae starve. However, a portion of the eggs remain dormant in the soil for a second winter and do not hatch until the following spring when corn is planted back into the field resulting in damage to the rotated corn. Extended-diapause northern CRWs originally caused severe injury to rotated corn in NW Iowa, SW Minnesota, SE South Dakota, and NE Nebraska during the late 1980s. Since then their range has expanded until it is now found throughout most of Iowa. South Dakota has estimated that nearly 50% of their northern CRWs are the extended-diapause variant. Data from the 2005 & 2006 monitoring program has concluded that extended diapause is present throughout eastern Iowa. This information, in combination with previous surveys, confirms that extended diapause is present at some level in all parts of that state. Although its presence has been confirmed throughout the state, its relative abundance may be changing.

DOI

https://doi.org/10.31274/icm-180809-897

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Nov 29th, 12:00 AM

Rotation Resistant Rootworms 2007

Corn rootworms have been, and in many cases still can be, managed with crop rotations. However, some populations of both northern and western corn rootworms (CRWs) have adapted to the corn-soybean rotation. Regular, annual rotations between corn and soybeans have selected for a variant of the northern CRW that has a two-year life cycle, referred to as extended diapause. Female northern CRWs deposit eggs in the soil within cornfields. When the field is rotated to soybean the next year, most eggs hatch and the larvae starve. However, a portion of the eggs remain dormant in the soil for a second winter and do not hatch until the following spring when corn is planted back into the field resulting in damage to the rotated corn. Extended-diapause northern CRWs originally caused severe injury to rotated corn in NW Iowa, SW Minnesota, SE South Dakota, and NE Nebraska during the late 1980s. Since then their range has expanded until it is now found throughout most of Iowa. South Dakota has estimated that nearly 50% of their northern CRWs are the extended-diapause variant. Data from the 2005 & 2006 monitoring program has concluded that extended diapause is present throughout eastern Iowa. This information, in combination with previous surveys, confirms that extended diapause is present at some level in all parts of that state. Although its presence has been confirmed throughout the state, its relative abundance may be changing.

 

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