Weed Resistance Management

1. Weed Resistance Management Gil Cook, PhD. Cook Ag Science Expertise

2. Herbicide Resistance: “Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or selection of variants produced by tissue culture or mutagenesis ."

3. Herbicide Resistance Definition The ability of a Weed to survive a Herbicide treatment to which the original population was susceptible

4. Herbicide Tolerance: "Herbicide tolerance is the inherent ability of a species to survive and reproduce after herbicide treatment. This implies that there was no selection or genetic manipulation to make the plant tolerant; it is naturally tolerant."

5. Herbicide Tolerance Definition The ability of a weed species to survive and reproduce after herbicide treatment

6. Past History: Cereals • In the 1940’s phenoxy herbicides were introduced. • Weeds primarily mustards – Miracle new herbicide. • Corn Gromwell was a museum specimen. • In early 1980’s; 2,4-D, MCPA, Maloran, Igran, Karmex, Buctril/Bronate & Banvel primary cereal herbicides.

7. Past History: Lentils & Peas • Dinitro primary lentil & pea herbicide. • Sencor replaced Dinitro. • These herbicides used at higher rates than current herbicides and were more likely to cause crop injury.

8. Current Situation • Cereals: ALS/AHAS primary herbicides used for broadleaf weed control. Very little crop injury. • Fallow: Glyphosate & 2,4-D formulations used. • Lentils & Peas: Pursuit main broadleaf weed control. • Very little crop injury

9. Current Situation • Herbicide Resistance and Herbicide Tolerance are becoming more serious problems each year in Eastern WA & Northern ID. • Each cropping rotation has a unique set of problems that need to addressed on a field by field basis by growers, fieldmen and consultants. • The most serious problems have been the selection of resistant bio-types of a number of different weeds.

10. Current Situation • ALS or AHAS resistant broadleaf weeds limit the number of tools available for broadleaf weed control. • ACC resistant grassy weeds are limited by the number of products available for good grass control. • Expanded use of glyphosate is selecting tolerant weeds. • Use of residual herbicides is effecting rotational cropping patterns.

11. World List of Herbicide-Resistance

12. Resistance: Herbicide Mode of Action

13. What has brought about the resistance problem? • Using the same mode of action herbicides over a long period with no relief. • Use of soil residual products. • Restricted number of products for each crop. • Huskie is the only new chemistry in recent years. • Changing cultural practices; less tillage reduces mechanical control.

14. Problems presented by ALS resistant weeds. • There are a limited number of compounds that will control ALS resistant weeds. • Since the introduction of Huskie, there is no new chemistry on the horizon. • Best product to control dog fennel is a soil residual compound that does not fit into a 2 year pulse crop – cereal rotation. • Weed populations are becoming increasingly more difficult to control with the current herbicides.

15. ALS & AHAS Resistant weeds • Dog fennel or Mayweed • China or Prickly Lettuce • Russian thistle • Kochia

16. Weeds that may become Resistant • Pineapple weed • Black mustard • Fanweed • Shepherdspurse • Jim Hill or tumble mustard • Many others

17. What is available for control? • Cereals: There are a number of new products but most are different combinations of available chemistry. • Use different modes of action. Do not use the same ones each cropping year. Mix & Match herbicides. • The new labels of products list the category so you can tell what the mode of action is. • ALS/AHAS is in Category B • ACCase is Category A • See handout sheets from Monte.

18. Solutions: • Do not use a single mode of action of herbicides for broadleaf weed control. • Look at the big picture. Do not plan herbicide usage or cultural practices based on a single year. Look at all crops that may be grown and develop a multiyear program. • Be careful of the program you select: Changing rotations may not be possible if soil residual herbicides are used.

19. Solutions (cont.): • Keep accurate records of herbicides use; date, amount & location. • Try not to over use similar modes of action • Sometimes the least expensive program now may be the most expensive in the long run. • Dealers and Fieldmen are very much aware of the problem and are constantly seeking new ways maintain good weed control.

20. Do Not Despair, We Can Manage Weed Control • May have to change standards of acceptable weed control. • May have to use products that can cause crop injury to gain another mode of action. • Research is continuing by Weed Scientists in Industry & Universities to develop new chemistries & cultural practices to control weeds.

21. Do Not Despair, We Can Manage Weed Control (cont.) • Local fieldmen are very much aware of the problems and are constantly working to develop the best program for each customer. • Cereal breeders are working to develop varieties that are more tolerant of various chemistries and better able to compete with weeds. • There is an on going search for new crops to grow that may compete with weeds and possibly use new chemistries.

22. Most reported ALS Resistance

23. Our serious ALS resistance

24. Thank you for coming Gil Cook, PhD. Cook Ag Science Expertise