The Basics of Pesticide Resistance. Dr. Fred Fishel, Professor UF/IFAS Agronomy

Transcription

1 The Basics of Pesticide Resistance Dr. Fred Fishel, Professor UF/IFAS Agronomy

2 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

3 Terminology Resistant: Pest was originally susceptible to pesticide; over time control lost through the selection of resistant individuals. Tolerant: The inherent ability of a species to survive following a pesticide treatment was never susceptible.

4 Terminology Mode of action: describes the biochemical processes by which the pesticide poisons the pest (for example, disrupting photosynthesis). Target site of action (mechanism of action): the exact location of inhibition, such as interfering with the activity of a specific enzyme within a metabolic pathway.

5 Terminology Cross resistance: resistance to 2 or more pesticides that share the same mode of action. Dotted duckweed (Landoltia punctata) Diquat and paraquat (WSSA Group 22) Multiple resistance: resistance to 2 or more pesticides with different modes of action. Palmer amaranth (Amaranthus palmeri) Imazapic and glyphosate (WSSA Groups 2 and 9)

6 Resistance in General Biotype

7 The Pesticide Treadmill 1. Pest population rises 2. Apply pesticides 3. Pests develop resistance 4. Apply more pesticides 5. Resistance becomes more prevalent 6. Switch to new pesticide (if possible)

8 History of Resistance (Organic Pesticides) 1947 insecticides Housefly Organochlorines (DDT) Organochlorines have long since been banned for use 1960s fungicides Powdery mildew Benzimidazoles (benomyl) DuPont voluntarily canceled benomyl due to high legal costs

9 History of Resistance (Herbicides) 1957 weeds 2,4-D resistant dayflower in sugarcane field

10 Herbicide Resistance Mechanisms X X Please! Let me in! Sequestered in vacuole X X Z Help! Get me outta here! I can t do my job! X X My key won t fit! Y

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13 More than 450 resistant biotypes globally

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15 9 of the top 15 most common herbicides prone to resistance are ALS inhibitors

16 Herbicide Resistance in Florida Year Species Situation Herbicide(s) 1985 American black nightshade Tomato Paraquat 1996 Goosegrass 2001 Dotted duckweed Diquat, paraquat Aquatic 2002 Hydrilla Fluridone Palmer amaranth Cropland Imazapic, pyrithiobac-na Glyphosate Glyphosate, imazapic 2014 Ragweed parthenium Industrial Glyphosate

17 Resistance Concerns Circa mid-1990 s Because glyphosate is non-selective, Monsanto has insisted that glyphosate resistant weeds will not appear with the use of this herbicide. With the imminent release of glyphosate resistant corn and soybeans, this hypothesis will soon be tested on potentially millions of acres. Resistant weed populations have been reported already in locations outside the USA.

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19 Managing Resistance in General Rotate herbicide applications using different modes of action Use tank- or pre-mixes of different MOAs Avoid unneeded applications Follow label rates Use non-herbicidal alternatives if possible Monitor changes in weed control results

20 Playing by the Numbers

21 Spraying by the Numbers Weed Science Society of America herbicide classification system Approximately 30 herbicide modes of action identified

22 Spraying by the Numbers Aquatic Herbicide Mode of Action Group Numbers According to the WSSA WSSA group number Common name Mechanism of action 2 Bispyribac-sodium, Imazapyr, Imazamox, Penoxsulam Enzyme inhibitor (ALS) 4 2,4-D, Triclopyr Growth regulator (organo-auxin) 9 Glyphosate Enzyme inhibitor (EPSPS) 12 Fluridone 14 Carfentrazone, Flumioxazin Photosynthesis inhibitor (pigment synthesis PDS) Enzyme inhibitor (PPO) 22 Diquat Photosynthesis inhibitor 27 Topramezone NC Endothall, Hydrogen peroxide, Copper Photosynthesis inhibitor (pigment synthesis HPPD) Photosynthesis inhibitor (and other effects)

23 Spraying by the Numbers

24 Thank you for your attention!