Stewardship/Management of Stewardship/Management of Transgenic ProductsTransgenic Products

Micheal D. K. OwenMicheal D. K. OwenIowa State UniversityIowa State UniversityAmes, IA 50011 USAAmes, IA 50011 USAmdowen@iastate.edumdowen@iastate.edu

www.weeds.iastate.eduwww.weeds.iastate.edu

IntroductionIntroduction

Stewardship reflects management Stewardship reflects management decisions that will enhance and preserve a decisions that will enhance and preserve a particular crop trait particular crop trait andand are economically are economically rewarding rewarding

Some traits impart selection pressure Some traits impart selection pressure upon the pest complex for which they are upon the pest complex for which they are designed (i.e. BT)designed (i.e. BT)

Traits for herbicide resistance in crops are Traits for herbicide resistance in crops are “benign” and do not exert selection “benign” and do not exert selection pressure – the pressure – the herbicideherbicide exerts the exerts the selection pressure selection pressure

IntroductionIntroduction

The “stewardship” efforts initiated by The “stewardship” efforts initiated by the Weed Science group and the Weed Science group and supported by the Iowa Grain Quality supported by the Iowa Grain Quality Initiative represent two areas:Initiative represent two areas:• Evaluation and monitoring of weeds with Evaluation and monitoring of weeds with

variable responses to glyphosatevariable responses to glyphosate• Development of weed management Development of weed management

strategies for specific output traits or strategies for specific output traits or specialty traitsspecialty traits

Glyphosate stewardshipGlyphosate stewardship Clean fields do not necessarily equate to good weed Clean fields do not necessarily equate to good weed

managementmanagement• The objective of weed management is to The objective of weed management is to

protect crop yield potentialprotect crop yield potential Diversified weed management tactics provide Diversified weed management tactics provide

significant benefits to glyphosate-based systemssignificant benefits to glyphosate-based systems• Residual herbicides applied EPP or PRE are Residual herbicides applied EPP or PRE are

important components of a weed management important components of a weed management programprogram

• Mechanical weed control tactics should be includedMechanical weed control tactics should be included Timely application of tactics is critical for all weed Timely application of tactics is critical for all weed

management programsmanagement programs

Stewardship and Grower AttitudesStewardship and Grower Attitudes

Considerable effort in providing Considerable effort in providing information about the evolution of information about the evolution of herbicide resistanceherbicide resistance

These efforts have been marginally These efforts have been marginally effective (e.g. ALS resistance)effective (e.g. ALS resistance)

66% of Indiana growers expressed only a 66% of Indiana growers expressed only a low to moderate concern about glyphosate low to moderate concern about glyphosate resistanceresistance

Only 38% recognized the role of repeat Only 38% recognized the role of repeat MOAs on selection pressureMOAs on selection pressure

Adoption of glyphosate-resistant crops Adoption of glyphosate-resistant crops continues to risecontinues to rise

The Glyphosate DecadeThe Glyphosate Decade

Source: University & USDA reports

2000: Horseweed in DE, MD, NJ

1998: Rigid ryegrass in CA

2001: Horseweed in TN, KY

2002: Horseweed in IN, OH

2002: “Variably tolerant” waterhemp in IA, IL, MO

2003: Horseweed in AR, MS, NC

2004: Common ragweed in MO

2005: Horseweed in CA

2004: Italian ryegrass in OR2005: Palmer pigweed

suspected in NC2005: Palmer pigweed in GA and TN

2005: Common waterhemp in MO

2006: Horseweed in NE

Weeds to watch in IowaWeeds to watch in Iowa

Common lambsquartersCommon lambsquarters Giant ragweedGiant ragweed Common waterhempCommon waterhemp Asiatic dayflowerAsiatic dayflower MarestailMarestail Others?Others?

Even at low population (10 plants/m2) Asiatic dayflower reduces soybean yield (Mishra et al 2002)

Figure 2. Percentage of Asiatic dayflower control

0

5

10

15

20

25

30

35

2-4 4-8 8-10 10-12 12-16

growth stage (number of leaves)

% c

ontro

lControl

6 oz/acre

12 oz/acre

24 oz/acre

48 oz/acre

96 oz/acre

Specialty grains/high value cropsSpecialty grains/high value crops

Several field experiments have been Several field experiments have been conducted on inbreds, cultivars, and conducted on inbreds, cultivars, and output trait cropsoutput trait crops

Experiments focus on evaluating the Experiments focus on evaluating the potential for existing and new herbicides potential for existing and new herbicides to manage weeds in these cropsto manage weeds in these crops

Particular attention is given to the relative Particular attention is given to the relative tolerance of the crops to the herbicidestolerance of the crops to the herbicides

Past efforts had included considerable Past efforts had included considerable experimentation with popcorn varietiesexperimentation with popcorn varieties

2006 efforts2006 efforts

Experiments with 8 low lin soybean Experiments with 8 low lin soybean varietiesvarieties

Experiments with 3 white corn Experiments with 3 white corn varieties, 1 high oil and 1 waxy varieties, 1 high oil and 1 waxy varietyvariety

Experiments on 7 sensitive and very Experiments on 7 sensitive and very sensitive inbredssensitive inbreds

2006 efforts2006 efforts

Registered and experimental Registered and experimental herbicides were included in the herbicides were included in the experimentsexperiments

Application timing, herbicide Application timing, herbicide combinations and rates were combinations and rates were includedincluded

Results available at Results available at www.weeds.iastate.eduwww.weeds.iastate.edu

Questions?