Weed Management in Potato C ropping S ystems

1. Weed Management in Potato Cropping Systems Pamela J.S. Hutchinson Potato Cropping Systems Weed Scientist Aberdeen Research & Extension Center

2. Weed Management in Potatoes: Lecture topics • Weed – Potato interference • Major problem weeds • Integrated weed management strategies for potatoes • Herbicide resistance management

3. Competition for light, water, nutrients Definition: A plant out of place

4. Harvest interference

5. Direct tuber damage: quackgrass rhizome

6. Weed – Potato Interference • Weeds may host other pests detrimental to potatoes such as insects, disease, nematodese.g. hairy nightshade hosts potato virus Y (PVY) and green peach aphid vector Green peach aphid (Myzuspersicae)

7. Weeds in Potato Cropping Systems • Weed life cycles • Major broadleaf and grass weeds • Competition with potatoes e.g. hairy nightshade • Weed identification • Refer to PPS Chapter 13 • Weed ecology: dormancy, seed-bank, germination/emergence relative to potatoes • Refer to PPS Chapter 13

8. Weeds in Potato Cropping Systems • Biennial • Perennial • Annual • Winter and summer

9. Weed – Life Cycle Biennial Second year First year

10. Field pennycress: Winter annual/biennial

11. Weed – Life Cycle • Perennials • Live for 3 or more years • Usually have an extensive stolon or root system

12. Canada thistle

13. Quackgrass

14. Weed – Life Cycle Summer Annual Winter Annual Fall Fall Summer Spring Early Summer Spring

15. Common Weeds in Potatoes: Annual broadleaves and grasses • Hairy nightshade – Solanum sarrachoides • Redroot pigweed – Amaranthus retroflexus • Common lambsquarters – Chenopodium album • Kochia – Kochia scoparia • Russian thistle – Salsolaiberica • Common purslane– Portulacaoleracea • Green foxtail – Seteria viridis • Barnyardgrass – Echinochloa crus-galli • Wild oat – Avena fatua

16. Redroot pigweed

17. Common lambsquarters

18. Kochia

19. Russian thistle Russian thistle

20. Common purslane

21. Green foxtail

22. Barnyardgrass barnyard grass

23. Wild oats

24. Hairy Nightshade • Recent grower survey results (IPM/Idaho Potato Conference) Hairy nightshade control is of great concern to many Idaho potato growers

25. Hairy Nightshade(Solanum sarrachoides Sendt.) • Same family as potato • Annual – 12 to 24 inches • Begins germination in early spring and continues germinating throughout the summer • Produces flowers and fruit until the end of the growing season in PNW • plants emerging as late as 6 wk before a killing frost can flower and produce berries with viable seed • light frost does not kill

26. Hairy Nightshade(Solanum sarrachoides Sendt.) • Sometimes mistaken for cutleaf nightshade cutleaf nightshade hairy nightshade • Leaf surface/ • stems haveglandularhairs • Leaves can have smooth to serrated edges

27. Hairy Nightshade • A large plant can produce 1700+ berries • 10 to 35 seeds per berry • Innate dormancy for 4+ months after maturity • Seed buried in the field developed dormancy when exposed to high temperatures • Longevity in soil:5 yrs = 90% germination 8 yrs = 2% germination Reports of germination after 39 yrs in soil

28. Hairy Nightshade Seed production example • 800 berries/plant x 10 seeds/berry = 8,000 seeds/plant! • 10 plants/sq ft in our nontreated checks • 43,560 sq ft/A • 43,560 x 10 plants x 8,000 seeds/plant = 3,484,800,000 seeds/A !!!

29. Hairy Nightshade: research trials • Competition: what hairy nightshade density does it take to reduce potato yield? • Critical interference period: what’s the period during the growing season when the presence of the weed will reduce yield?

30. Effect of season-long hairy nightshade competition at four densities on tuber yield of two potato varieties at Aberdeen, ID in 2004 and 2005. 1 hairy nightshade per meter row

31. Effect of season-long hairy nightshade competition at four densities on tuber yield of two potato varieties at Aberdeen, ID in 2004 and 2005. Hairy nightshadeTuber yield Varietydensity (per m row) U.S. No. 1 Total ----- % reduction ----- Russet1 21 * 16 * Norkotah2 26 * 20 * 3 27 * 25 * 100 48 * 37 * Russet 1 6 5 Burbank2 10 * 9 * 3 11 * 9 * 100 21 * 19 * *significantly different than weed-free control

32. Hairy nightshade critical interference period in potatoes • Weed-free for 0, 10, 20, 30, or 40 days after emergence (DAE) • Transplanted at emergence and then every 10 days • Weedy for 0, 10, 20, 30, or 40 DAE • Transplanted at emergence and then removed every 10 days • Maintained weed-free after removal

33. Effect of hairy nightshade planting and time of removal on U.S. No. 1 tuber yields

34. Effect of hairy nightshade planting and time of removal on U.S. No. 1 tuber yields 5% reduction = 218.5 cwt/A Must be weed free for at least 21 DAE Hairy nightshade present season-long caused 29% U.S. No. 1 loss 230 cwt/A 164 cwt/A

35. Effect of hairy nightshade planting and time of removal on U.S. No. 1 tuber yields 236 cwt/A 5% reduction = 224 cwt/A Cannot be weedy longer than 7 DAE 177 cwt/A

36. Effect of hairy nightshade planting and time of removal on U.S. No. 1 tuber yields 5% reduction if SOLSA present between 7 and 21 DAE

37. Integrated Weed Management in Potato Cropping Systems • Makes use of all tools available: • Biological • Cultural • Chemical

38. Brassica green manure fall incorporation

39. Effect of Fall-incorporated Green Manures on Hairy nightshade Biomass in Potatoes the Following Growing-season Green manures planted and incorporated fall 2006, Potatoes planted spring 2007, hairy nightshade biomass collected July 13, 2007 Potatoes were 18 to 20 inches and hairy nightshade was 14 to 20 inches tall at sampling time dry wt g/ 0.25 sq m No Green manure Oilseed radish Mustard mix: 25% Oriental 75% white 50% oilseed radish 50% Oriental mustard

40. Integrated Weed Management in Potato Cropping Systems • Weed identification • Keep field histories • Map weed infestations • Simple drawings…GPS • Can conduct site specific action depending on infestation/density

41. Integrated Weed ManagementWeed infestation/density mapping Canada thistle Wild oat Weeds throughout the field Redroot pigweed – moderate Common Lambsquarters – moderate Hairy nightshade – light except where noted Wild Oat– light except in NE section HNS

42. Integrated Weed Management in Potato Cropping Systems • Manage weeds throughout crop rotation • Coordinated plan w/ other crops • Important for perennial weed control • Few herbicide options available in potatoes • Minimize herbicide carryover • Reduce selection for resistant weeds • Plant competitive crops in the rotation • winter wheat, winter canola, barley, alfalfa

43. Integrated Weed Management in Potato Cropping Systems • Irrigate after harvest of short season crops like small grains or canola • Promote weed seed germination/emergence • Control seedlings with tillage • Control volunteer grain • Plant competitive potato varieties • Russet Burbank larger plant canopy, indeterminate growth >Russet Norkotah smaller stature, doesn’t always close over rows, less shading • Plant certified seed – maintain vigorous crop growth

44. Integrated Weed Management in Potato Cropping Systems • Current practices in potatoes include • Cultivation • Herbicides • NOTE: Combination often more effective than either alone

45. Integrated Weed Management in Potato Cropping Systems • Cultivation +’s • Less expensive than herbicides • No chemical residues • Wind not an issue • Cultivation –’s • Soil compaction, root pruning-crop injury • Heavy infestations = Multiple cultivations • Wet soil interferes with timeliness • In-row weed control difficult • Disease-spread (important in seed areas)

46. Ideal weed stage to take out with cultivator – 2-leaf

47. Can still take out with cultivator:3-4-leaf

48. Cultivation:Potato size 4-5” o.k. >8-10” = root pruning

49. Weeds left on the side-hills by cultivator

50. Clean cultivation