Glyphosate Resistant Waterhemmp
• We do have glyphosate resistant
waterhemp in the area
• We also have PPO resistant (Phoenix,
Blazer, Reflex, etc.) in the area, and this is
much more prevalent than the glyphosate
resistant waterhemp population
Glyphosate Resistant Waterhemp
• We do have waterhemp (in the area) resistant to
the following herbicides– ALS, PPO (post), Atrazine (post) and glyphosate
• U of I and Monsanto – cooperated in 2008 in
Brown County, for a waterhemp management
study
• Use of pre emergent herbicide necessary,
regardless of post emergent herbicide program
Brown County
• Field history- many years of RR soybeans
• 2007 “problems”- multiple applications of
glyphosate failed to control waterhemp
populations
• Aaron Hager, U of I cooperating with
Monsanto in field experiments
• Dicamba resistant soybean were utilized
Brown County Summary*
• Very pleased with tolerance of soybean to
dicamba- perhaps rating a “1” or maybe “2”
• “Data collected to date suggest this particular
field contains biotypes of waterhemp resistant to
ALS, triazines (post), glyphosate and PPO.
We’re not certain we have yet found the one
plant that contains the four-way resistance, but
these four resistances do occur in this field”
Aaron Hager, 2008
• Soil applied herbicides have to be a component
*Aaron Hager, U of I Weed Science, fall 2008
U of I Recommendations For
Management of Glyphosate
Resistant Waterhemp
• Apply full labeled rate of soil residual (with
waterhemp activity) 7 days pre to 3 days post
plant
– Full rates at planting extend control
• Initial post application of glyphosate alone at 3-5
inch waterhemp (.75-1.0 ae)
– Limited data on tank mixes of gly/PPO
– Maximum labeled rate (1.5 ae) on confirmed resistant
waterhemp did not increase control
– Previous research shown waterhemp <5” very
sensitive
U of I Recommendations, cont.
• Fields must be scouted 7 days after initial
glyphosate application
– Research shown resistant plants continue to grow at
normal rates after gly treatment
• If waterhemp control inadequate and
retreatment necessary, consider using PPO at
full labeled rate as soon as possible
– Optimal control at 5” or less
• Re-scout treated field 10-14 days after PPO
appliation
– If waterhemp plants survive????
Liberty Link Soybeans
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Available and cleared for export in 2009
Limited acres for ’09
Stine and Growmark plus others
22 oz Ignite,w/AMS, about $22 per acre,
on weeds 3-4” in height
• Stress use of preemerge
• Glufosinate not glyphosate