Giant ragweed (Ambrosia trifida) seedling
emergence
projections for 2006
by
Brian Schutte, Emilie Regnier, Kent Harrison
OSU
Department of Horticulture & Crop Science
Weed
Ecology Laboratory
Introduction
In
Ohio agricultural fields, giant ragweed seedling emergence
starts in early spring and continues through the growing
season into July. Giant ragweed seedlings emerge
in a predictable way each year based on temperature
and rainfall. We have developed a method to predict
giant ragweed seedling emergence using meteorological
data.
2006
giant ragweed seedling emergence model results
As of July 10, seedling
emergence for 2006 is nearly complete. Few seedlings
(less than 2% of total) are expected to emerge in the
remaining growing season.
Our
predictive model was produced with information collected
at the OARDC Western Agricultural Research Station in
South Charleston, OH, so it should be representative
of giant ragweed populations in west-central Ohio agricultural
fields. This information is meant to supplement
local knowledge and observations of giant ragweed emergence
so that growers can target their weed control practices
more effectively.
Utility
of emergence model
Seedling
emergence models are necessary for well-timed and efficient
weed control. Knowledge of the giant ragweed seedling
emergence progression can be useful in both conventional
and organic crop production systems.
Conventional
farming
An
example for how this seedling emergence model can assist
in deciding when to apply post-emergent herbicides is
provided in the C.O.R.N. Newsletter article available
at the following link: Issue
2006-08
Organic
farming
In
a site where severe yield reductions result from heavy
ragweed infestations, the seedling emergence model can
assist with planting date decisions. For a field
of this sort, it is wise to delay planting until seedling
emergence is nearly complete. Allowing more seedlings
to emerge prior to planting will reduce the need for
control after planting. For example, consider
giant ragweed seedling emergence in 2005:
By
June 5, 85% of giant ragweed had emerged. Planting
on June 5 would mean that 15% of the giant ragweed would
have escaped pre-plant control measures. If planting
was delayed by two weeks, 95% of the giant ragweed would
have been eliminated by pre-plant management.
Delayed planting until
ragweed emergence is nearly complete is especially important
where giant ragweed control is difficult after crops
have emerged. However, frequent pre-plant weed
control measures will be needed to prevent emerged ragweed
plants from becoming too large. Over time, delayed
planting will diminish the giant ragweed population
since fewer and fewer plants are allowed to mature and
produce seeds.
Acknowledgements
-
Frank Forcella and Kurt Spokas of the USDA ARS
North Central Soil Conservation Research Lab at Morris,
MN provided expertise in seedling emergence modeling
and soil environment modeling.
- Jerron
Schmoll monitored giant ragweed seedling emergence
and maintained research plots from 2000 to 2004.
- Funding
for this project was provided by the Wittmeyer Knox
Scholarship.
Questions
can be sent to schutte.23@osu.edu |
