Understanding Pesticide Resistance Fred Fishel and J.A. Ferrell, UF/IFAS Dept. of Agronomy P.G. Koehler and J.L. Castner, UF/IFAS Doc. SP121

Understanding Pesticide Understanding Pesticide ResistanceResistance

Fred Fishel and J.A. Ferrell, Fred Fishel and J.A. Ferrell, UF/IFAS Dept. of AgronomyUF/IFAS Dept. of Agronomy

P.G. Koehler and J.L. Castner, UF/IFAS Doc. SP121

When Pesticides Don’t Work

• Improper pest identification

• Incorrect pesticide dosage

• Improper application timing

• Pesticide doesn’t reach target pest

• Unfavorable environmental conditions

• State of poor pesticide conditions

• Pesticide resistance

F.A. Johnson, D.E. Short, and J.L. Castner, UF/IFAS Doc. SP93

When Pesticides Don’t WorkImproper pest identification

F.M. Fishel, UF/IFAS Pesticide Information Office

Crabgrass Bermudagrass

When Pesticides Don’t WorkImproper pest identification


When Pesticides Don’t WorkIncorrect pesticide dosage


When Pesticides Don’t WorkImproper application timing

CDMS

When Pesticides Don’t Work• Pesticide doesn’t reach target pest


When Pesticides Don’t Work• Unfavorable environmental conditions

CDMS

When Pesticides Don’t Work• State of poor pesticide conditions


Pesticide Resistance


Definitions: Resistance

An inheritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species.


Definitions: Tolerance

The inherent ability of a species to survive following a pesticide treatment.


Definitions: Cross vs. Multiple Resistance

Cross resistance: resistance to 2 or more pesticides that share the same mode of action.

Multiple resistance: resistance to 2 or more pesticides with different modes of action.


Resistance in General

• Kills susceptible pests, leaves resistant members of the population

• Resistant populations are usually resistant to all members of a chemical family

• Favored by continual use of a pesticide

D.E. Short and J.L. Castner, UF/IFAS Doc. SP 126

Resistance in General

C.R. Rainbolt et.al., UF/IFAS Doc. SS-AGR-243

http://edis.ifas.ufl.edu/EDISImagePage?imageID=1069094576&dlNumber=AG239&tag=FIGURE%201&credits=





“The Pesticide Treadmill”

1. Pest population rises2. Apply pesticides3. Pests become resistant4. Apply more pesticides5. Resistance becomes more prevalent6. Switch to new pesticide

Resistance Action Committees

• IRAC– http://www.irac-online.org/

• FRAC– http://www.frac.info/frac/index.htm

• HRAC– http://hracglobal.com/

http://www.irac-online.org/

http://www.frac.info/frac/index.htm

http://hracglobal.com/

Resistance: History

Insecticides


Insecticide Resistance is Costly

• Colorado potato beetle

• Budworm/bollworm complex

R.L. Jacques and T.R. Fasulo, UF/IFAS Doc. EENY146

J.L. Capinera, UF/IFAS Doc. EENY219

Causes of Insecticide Resistance

• Natural detoxification

• Binding site has become genetically modified

• Slower absorption by the insect

• Behavioral resistance

E.A. Buss, UF/IFAS Doc. EENY326


• Natural detoxification (metabolic resistance)

J.F. Butler, UF/IFAS Doc. EENY222


• Altered target-site resistance

Colorado Potato Beetle Larva Colorado Potato Beetle Adult

J.L. Jacques and T.R. Fasulo, UF/IFAS Doc. EENY146


• Penetration resistance

J.F. Butler, UF/IFAS Doc. EENY48


• Behavioral resistance

J.L. Castner, UF/IFAS Doc. EENY25

Practical Insecticide Resistance Management

• Consult a professional

• Select early-maturing varieties

• Select insecticides with care

S.E. Webb, UF/IFAS Doc. EENY802


• Monitor the population

• Remove crop residues



• Prevention

• IPM, IPM, IPM


Resistance: History

Fungicides


Fungicide Resistance

P.F. Harmon, UF/IFAS Doc. PP198

Fungicide Resistance Types

• Single gene

• Polygenic

• Cross- vs. multiple-resistance

P.F. Harmon, UF/IFAS Doc. PP203

Fungicide Resistance Factors

• Type of fungicide

• Frequency of use

• If used or alone or in combination

• Pathogen

• Viability of resistant biotypes

P.D. Roberts, UF/IFAS Doc. PP236

Fungicide Resistance Strategies

• Resistant varieties

• Crop rotation

• Dispose/destroy crop debris

• Soil sterilization

• Alternate fungicide groups

A.J. Gevens, UF/IFAS Doc. SP159

Resistance: History

Herbicides


Herbicide Resistance

• >300 resistant biotypes

• 183 species– 110 dicots– 73 monocots

• >270,000 field sites


I. Heap, International Survey of Herbicide Resistant Weeds

Herbicide Factors for Resistance

• Act on a single site of action

• Applied multiple times during a growing season

• Have long residual

• Used for several consecutive seasons

• Used as “stand-alones”

A.C. York, N.C. State University

Mechanism of Herbicide Resistance

• Exclusionary resistance– Differential uptake– Differential translocation– Compartmentalization– Metabolic detoxification

• Site of action resistance– Altered site


Weed Factors for Resistance

• Weed reproductive capability

• Weed seed dispersal mechanisms


Management Strategies

• Use herbicides only when necessary

• Rotate herbicides

• Use tank-mix or sequential mixtures

• Rotate crops

• Use caution if planting herbicide resistant crop varieties


Management Strategies

• Combine with mechanical control

• Where soil erosion is minimal, use primary tillage as a management component

• Scout fields regularly

• Clean equipment before moving


Glyphosate Technologies

• Glyphosate-resistant crops

• in-season glyphosate useBenefits Broad spectrum weed

control Crop safety Rotational crop flexibility Environmentally favorable

University of Wisconsin

Most Heavily Applied Pesticides - 1997• Atrazine (H): 75 – 82 million pounds• Metolachlor (H): 63 – 69• Metam sodium (F, H, I, N, Fm): 53 – 58• Methyl bromide (Fm): 38 – 45• Glyphosate (H): 34 – 38• Dichloropropene (N, Fm): 32 – 37• Acetochlor (H): 31 – 36• 2,4-D (H): 29 – 33• Pendimethalin (H): 24 – 28• Trifluralin (H): 21 - 25

Most Heavily Applied Pesticides - 1999• Atrazine (H): 74 – 80 million pounds• Glyphosate (H): 67 – 73• Metam sodium (F, H, I, N, Fm): 60 – 64• Acetochor (H): 3 – 35• Methyl bromide (Fm): 28 – 33• 2,4-D (H): 28 – 33• Malathion (I): 28 – 32• Metolachlor (H): 26 – 30• Trifluralin (H): 18 – 23• Pendimethalin (H): 17 - 22

Confirmed Glyphosate Resistant Weeds in the U.S. (2006)

Palmer AmaranthCommon WaterhempGiant RagweedHairy Fleabane


Horseweed (Marestail)Common RagweedItalian RyegrassRigid Ryegrass

Glyphosate Resistant Weeds: U.S.

0

1

2

3

4

5

6

7

8

1996 1998 2000 2002 2004 2006

No

. of

sp

ec

ies

Rigid ryegrass

Horseweed

Italian ryegrass

Common ragweed

Waterhemp

Palmer amaranth

Giant ragweed


Herbicide Costs Needed To Manage Palmer Amaranth in Georgia and North Carolina

Cotton

Soybean

Corn

Sensitive

Palmer

$18

$8

$10

Resistant

Palmer

$42

$24

$14

University of Georgia

"Stupidity is doing the same thing over and over again expecting different results"

~ A. Einstein

Resources







Photo/Diagram CreditsPhoto/Diagram Credits• University of Florida/IFAS• University of Georgia• N.C. State University• University of Tennessee• University of Wisconsin• CDMS

Fred Fishel, Ph.D.Department of AgronomyUniversity of Florida/IFASCopyright 2008 University of Florida

Mention of trade names in this presentation is solely for providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer’s label.

Documents

Understanding Pesticide Resistance Fred Fishel and J.A. Ferrell, UF/IFAS Dept. of Agronomy P.G. Koehler and J.L. Castner, UF/IFAS Doc. SP121