1. Unit 9: Basic Weed Scouting

2. Unit 9: Basic Weed Scouting
Unit 9 Objectives:
Knowledge of basic scouting procedures
Understanding of proper scouting times
Using field weed surveys
Basic weed ID

3. Unit 9: Basic Weed Scouting
Early season weed scouting
Done within 2 wks of planting after emergence
Also can determine:
Need for hoeing
Preemergence & preplant herbicides
Need for post emergence herbicides
ID and record weed species

4. Unit 9: Basic Weed Scouting
Determine severity of weed infestation
Count number of weeds/10’ of row for heavy infestations, weeds/100’ of row for light infestations
Sample area <5 ac
Record weed height & growth stage
Also note soil conditions
Can help indicate herbicide effectiveness
Too dry, not enough moisture for chemical uptake
Too wet, herbicide may have leached through root zone

5. Unit 9: Basic Weed Scouting
Identify weeds as early as possible for most effective control
Weed mapping
Complete a detailed weed map of each field by mid-May
Will help you monitor changes in weed population throughout the year, & from year to year
Include:
Perennial weed locations

6. Unit 9: Basic Weed Scouting
Annual weed locations & infestation levels
Mark distinguishing features
Final weed survey
Timing: late July to mid-August
Add to, or complete another weed map
Don’t generalize observations from areas near waterways, poorly drained areas, next to borders
Rank species from most commonly to least commonly found

7. Unit 9: Basic Weed Scouting
Economic Threshold guidelines
Weeds and crop compete for the same resources:
Soil
Fertility
Sunlight
Water
Problems other than yield losses:
Clogging, damaging harvest equipment
Loss of cash rented ground to “neater” farmers

8. Unit 9: Basic Weed Scouting
Weed infestations the first 4-6 wks, then treatment = no economic losses
No weeds first 4-6 wks, then weed infestation = minimal yield losses, but increased weed seed production
Similar weeds typically cause economic losses in similar crops
Grass weeds to grass type crops
Corn weeds to corn type crops
Broadleaf weeds to broadleaf type crops (soybeans)

9. Unit 9: Basic Weed Scouting
Giant Foxtail
Blade is densely hairy
Ligule has fringe hairs
Found through the Midwest

10. Giant Foxtail

11. Unit 9: Basic Weed Scouting
Yellow foxtail
Sheath is flattened, smooth with split, overlapping, smooth margins
Blade is smooth with long hairs
Ligule has fringe hairs

12. Yellow Foxtail

13. Unit 9: Basic Weed Scouting
Green Foxtail
Sheath – round to slightly flat w/ split, overlapping hairy margins
Blade is smooth to rough w/ rough margins
Ligule is a fringe of hairs
Continuous hairy collar

14. Green Foxtail

15. Unit 9: Basic Weed Scouting
Fall Panicum
Sheath – slightly flat, smooth w/ split, overlapping membranous margins
Blade is smooth w/ prominent mid-vein
Ligule is a fringe of hairs
Continuous collar

16. Fall Panicum

17. Unit 9: Basic Weed Scouting
Shattercane
Sheath – rounded and smooth w/ split, overlapping thin, membranous margin
Blade – flat w/ sparsely placed hairs on upper surface
Ligule – long, membranous, rounded w/ jagged ciliated margin

18. Shattercane

19. Unit 9: Basic Weed Scouting
Johnsongrass
Very similar to shattercane

20. Johnsongrass

21. Unit 9: Basic Weed Scouting
Yellow Nutsedge
Leaves – triangular, taper to a point, greenish yellow
Very distinctive

22. Yellow Nutsedge

23. Unit 9: Basic Weed Scouting
Quackgrass
Sheath – rounded w/ sparse, short hairs, can be smooth & split, overlapping margins
Blade – flat, rough to smooth
Ligule – short, membranous, truncate in shape

24. Quackgrass

25. Unit 9: Basic Weed Scouting
Burcucumber
Hypcotyl – green & rough
Cotyledons – oblong to spoon shaped
True leaves – alternate, pentagon shaped somewhat hairy
Petioles – long & greed
Fruit – barbed, prickly bristles

26. Burcucumber

27. Unit 9: Basic Weed Scouting
Common Cocklebur
Hypcotyl – smooth, fleshy, purple tinge near soil
Cotyledons – fleshy, shiny, long and thin shaped
True leaves – opposite (first pair), alternate later
Serrated leaves
Oval in shape
Rough to hairy surface
Petioles – long, hairy, can be purple spotted

28. Common Cocklebur

29. Unit 9: Basic Weed Scouting
Jimsonweed
Hypcotyl – fleshy, purple tinged, smooth
Cotyledons – smooth, narrow, short petioles
True leaves – alternate, large, smooth, pointed apex, toothed margins
Petioles – long, pale green to purple, may have short hairs

30. Jimsonweed

31. Unit 9: Basic Weed Scouting
Common Lambquarters
Hypcotyl – purple, smooth
Cotyledons – fleshy, long, oval, dull color
True leaves – seem paired at first, become alternate
Pale green
Oval shape
Irregular toothed margins
Petioles – long, pale green

32. Common Lambsquarters

33. Unit 9: Basic Weed Scouting
Ivyleaf Morningglory
Hypcotyl – dull green to purple, crease along both sides
Cotyledons – shiny, smooth, deeply indented base
True leaves – alternate, hairy, three lobed leaves
Petioles – long, hairy, green to reddish tint

34. Ivyleaf Morningglory

35. Unit 9: Basic Weed Scouting
Pitted Morningglory
Hypcotyl – smooth, somewhat purple
Cotyledons – smooth, butterfly shaped, deeply indented lobes, pointed
True leaves – alternate, smooth, heart shaped, maybe purple margins
Petioles – long and pale green to purple

36. Pitted Morningglory

37. Unit 9: Basic Weed Scouting
Tall Morningglory
Hypcotyl – dull green to purple, smooth
Cotyledons – shiny, smooth, deeply indented base
True leaves – alternate, hairy broadly heart shaped, pointed apex
Petioles – long, hairy, dull green to reddish tint

38. Tall Morningglory

39. Unit 9: Basic Weed Scouting
Eastern Black Nightshade
Hypcotyl – reddish to purple
Cotyledons – pointed tip w/ sparse hairs
True leaves – alternate, oval, wavy tooth margins
Underside – red to purple
Petioles – red, purple, green, sparse hairs

40. Eastern Black Nightshade

41. Unit 9: Basic Weed Scouting
Smooth Pigweed
Hypcotyl – reddish purple
Cotyledons – oblong, purple tinge, rough to smooth
True leaves – alternate, oval, notched or pointed apex, pale green to reddish
Petioles – long, may be hairy
Root – long, red taproot

42. Smooth Pigweed

43. Unit 9: Basic Weed Scouting
Common Ragweed
Hypcotyl – purplish, rigid, rough
Cotyledons – club-shaped, rounded apex, smooth surface
True leaves – opposite, irregular lobed
Petioles – grooved, widen to V-shaped stem

44. Common Ragweed

45. Unit 9: Basic Weed Scouting
Giant Ragweed
Hypcotyl – smooth, shiny, can be purple blotched
Cotyledons – spatulate, rounded apex gradually narrowing to base, smooth, shiny
True leaves – opposite, oval, pointed w/ serrated margins, rough short-haired surface
Petioles – concave above, winged toward stem, rough hairy surface

46. Giant Ragweed

47. Unit 9: Basic Weed Scouting
Smartweed
Hypcotyl – smooth, tinged dark purple
Cotyledons – smooth, fleshy, elongated, shiny w/ hairy margins
True leaves – alternate and elongated, shiny, may be spotted purple, hairy margins
Petioles – short, arise from swollen joints

48. Smartweed

49. Unit 9: Basic Weed Scouting
Waterhemp
Hypcotyl – reddish purple
Cotyledons – oblong, purple tinge
True leaves – alternate, narrow oval to elongated, pale greed to reddish, smooth
Petioles - long

50. Waterhemp

51. Unit 9: Basic Weed Scouting
Velvetleaf
Hypcotyl – velvety, soft short hairs
Cotyledons – heart shaped, rounded apex, fuzzy surface
True leaves – alternate, heart shaped, rounded apex, serrated margin, velvety surface
Petioles – round, covered w/ soft hairs

52. Velvetleaf

53. Unit 9: Basic Weed Scouting
Field Bindweed (perennial)
Hypcotyl – smooth
Cotyledons – kidney shaped
True leaves – alternate, spade shaped, smooth
Petioles - smooth

54. Field Bindweed

55. Unit 9: Basic Weed Scouting
Hedge Bindweed (perennial)
Hypcotyl – smooth
Cotyledons – kidney shaped
True leaves – alternate, larger than field bindweed, arrowhead shaped
Petioles - smooth

56. Hedge Bindweed

57. Unit 9: Basic Weed Scouting
Hemp Dogbane (perennial)
Hypcotyl – red above ground
Cotyledons – elongated, smooth
True leaves – opposite, elliptic, thick, shiny, white midvein
Petioles – short, smooth, “milklike” sap

58. Hemp Dogbane

59. Unit 9: Basic Weed Scouting
Common Milkweed (perennial)
Hypcotyl – pale green to purple
Cotyledons – elliptical, thick, covered w/ short hairs
True leaves – opposite, thick, dull, velvety, elliptical, pointed
Petioles – ridged, “milklike” sap

60. Common Milkweed

61. Unit 9: Basic Weed Scouting
Honeyvine Milkweed (perennial)
Hypcotyl – green to slightly pink, smooth
Cotyledons – shiny, oblong, rounded apex, narrows into long petiole
True leaves – opposite, oblong to heart shaped, pointed apex, dull green to bluish tint
Petioles – long, sparsely hair covered

62. Honeyvine Milkweed