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The influence of soil moisture and variable rate fungicide application on management of pod rot of peanut
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Pod
rot of peanut in west Texas
is usually caused by Pythium spp. or Rhizoctonia
solani.
These
fungi are best managed by applying different fungicides
to the soil at 60 and/or 85 days after planting.
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Applications
for pod rot
are expensive, particularly those for Pythium
which cost approximately $40/acre.
The pod rot damage is often not uniform across the field,
and may be worse in low areas.
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Soil
moisture is an important factor determining
the severity of pod rot. By monitoring soil moisture, it
may be possible to determine which areas of the field are
more prone to pod rot problems.
A variable rate fungicide applicator could be programmed
to apply product to the areas more likely to have pod rot,
which should save on the overall cost of management. However,
it is important to determine the association between pod
rot and soil moisture, before development of variable rate
fungicide application.
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The project had three goals in its first year:
·Measure soil moisture at a peanut field.
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Determine if there was more pod rot in the wetter areas of the field.
·Develop a variable rate fungicide applicator.
Major Accomplishments
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All three project goals were accomplished during the 2000
growing season, though the test field did not have much
pod rot (caused by Pythium spp.). However, the results are
sufficient to allow testing of variable rate Ridomil applications
to control Pythium pod rot in 2001.
· After the variable rate applications are tested
at several fields, and pod rot mapped in the fields, it
may be possible for producers to minimize the acreage treated
for pod rot. Because pod rot fungicides like Ridomil and
Quadris cost >$35/acre, for each application, treating fewer
acres could result in substantial savings.
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Principal Investigator:
Terry Wheeler
Plant Pathologist,
Texas Agricultural Experiment Station Lubbock
Cooperators:
Lubbock: D. Porter,
H. Kaufman and
C. Crumley
College Station: S. Searcy
Next phase:
The plans
for the 2001 are to test the use of variable rate applications of
Ridomil in the test field, and in one producer's field if available.
Pythium spp. are often very sensitive to soil moisture, and need
near saturated conditions to cause maximum damage. However, R. solani
may cause pod rot under a wider range of soil moisture conditions.
It will be important to identify producer's fields that have R.
solani pod rot and test the relationship between pod rot and soil
moisture.
The worse case scenario is to not apply fungicide on part of a field
and get hurt with pod rot. Until both of these fungi have been examined
for the relationship between pod rot and soil moisture, variable
rate application of fungicides should not be used.
For more information about this project, contact:
Terry A. Wheeler, PhD
Plant Pathologist
Texas Agric. Experiment Station
Rt. 3, Box 219, Lubbock, TX 79403
(806-746-4014)
FAX: (806-746-6528)
Email: ta-wheeler@tamu.edu
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