Matran and Scythe organic herbicides showed potential for reducing weed pressure and labor costs in broccoli and onion crops when applied at early growth stages. For broccoli, low rates could be used safely as a directed spray but caused injury when applied over the top. Onions required even more selectivity due to no opportunity for directed spraying. Timely applications at the 1st true leaf provided best control. These herbicides may also have uses in hooded spray operations or robotic weeding to reduce hand weeding which is difficult, tedious and expensive. While more refinement is needed, organic herbicides show promise as a tool for organic vegetable producers.

1. Selectivity of Organic
Herbicides in Broccoli and
Onions
Richard Smith
Vegetable Crop and Weed Science Farm Advisor,
Monterey County

2. Comparison of Organic vs Conventional
Broccoli and Onion Production Costs
Production
System
Weeding
Costs/A
Organic1
$270
Conventional.2
$161
1 – Tourte and Smith, 2004; 2 – Smith et al. 2004
Hand weeding
costs for onions
can be extreme
due to lack of
cultivation and
dense stands

3. The waxy cuticle on cole crops and
onions protects them to some degree
from fertilizers and contact herbicides

4. Conventional Materials Commonly
Sprayed on Broccoli and Onions
• Liquid fertilizers
– AN20, NpHuric, Sulfuric Acid, Acid based
fertilizers
• Contact herbicides
– Goal 2XL, Goal Tender, Buctril (onions)
• These postemergence applications greatly
reduce production costs
• It seemed logical that postemergence
applications of organic herbicides could
be used in the same way

5. Eco-Exempt
2-Phenethyl Propionate..................21.4.%
Eugenol (Clove Oil)..........................21.4%
Matran 2
[Matran EC]
Clove Oil (46%)
Other Ingredients (54%) (Water and Lecithin)
[Clove Oil (50%) Other Ingredients* (50%)
(Wintergreen Oil, Butyl Lactate, and Lecithin) ]
AllDown
Citric Acid 5%
Acetic Acid, yucca extracts, and water 94.8%
Garlic oil 0.2%
Burnout II
Clove Oil ...... 12%
Sodium Laurel Sulphate ... 8%
Other Ingredients: Vinegar, Lecithin, Water, Citric
Acid, Mineral Oil 80%
Weed Zap
Clove Oil 30%
Inerts including vinegar 70%
[Clove Oil 45% Cinnamon Oil 45%]
Weed-A-Tak
eugenol (clove oil), 2-phenethyl propionate (peanuts),
castor oil, thyme oil and wintergreen oil.
Scythe*
Pelargonic acid
4.2 lbs ae/gal
40% inert ingredients
* To be reviewed by NOP in 2007
Adapted from Cheryl Wilen, 2006

6. Other important considerations:
Timing, weed species, weed size (< 2 true leaves)

7. Postemergence Trials on Broccoli

8. Number of Weeds in Broccoli
2006 Trial No. 1
140
120
100
80
60
40
20
0
Untreated
Transplants, 1 vs 2 passes
10.80%
Matran Rate
5.40%

9. Hours Per Acre to Weed Broccoli
2006 Trial No. 1
35
30
25
20
15
10
5
0
Untreated
10.80%
Matran Rate
5.40%

10. Number of Weeds in Broccoli
2006 Trial No. 2
140
120
100
80
60
40
20
0
Untreated
5.00%
Matran Rate
2.50%

11. Hours Per Acre to Weed Broccoli
2006 Trial No. 2
70
60
50
40
30
20
10
0
Untreated
5.00%
Matran Rate
2.50%

12. Phytotoxicity Ratings
2006 Trial No. 3
6
5
4
3
2
1
0
Untreated
Matran 5% Matran 2.5% Scythe 3% Scythe 1.5%
Direct seeded, plants a bit old
Treatments

13. Yield – Number of Heads/Plot
2006 Trial No. 3
35
a
30
ab
ab
ab
b
25
20
15
10
5
0
Untreated
Matran 5% Matran 2.5% Scythe 3% Scythe 1.5%
Treatments

15. Scythe @ 1.0%
Over the Top
Directed
Sept 18

16. Scythe @ 1.5%
Over the Top
Directed
Sept 18

17. Scythe @ 2.0%
Over the Top
Directed
Sept 18

18. Scythe
Over the Top
1.5%
2.0%
Sept 18

19. Scythe @ 1.0%
Over the Top
Directed
Sept 26

20. Scythe @ 1.5%
Over the Top
Directed
Sept 26

21. Scythe @ 2.0%
Over the Top
Directed
Sept 26

22. Broccoli Summary
• The organic herbicides examined in these
studies are not safe for over-the-top use on
broccoli
• Low rates of these herbicides can be used on
broccoli if they are applied as a directed spray
to the base of the plant
• If too much of the material gets up onto the
foliage it can cause significant phytotoxicity
• If however, the material is successfully applied
acceptable yields can be achieved.

23. Onion Studies
• Onions are different in that there is little
opportunity for the spray material to be
directed to the base of the plants
• As a result, there is greater need for
selectivity and careful selection of
appropriate rates

24. Untreated
Matran @ 20%

25. Matran EC @ 20%

26. Matran EC @ 20%

27. weed burn down and regrowth
if weed is too big at time of application

28. 2005 Dry Bulb Onion Evaluation
Treatment
Weed
Control
Percent
Phyto
Rating
Weed
Time
hrs/A
Untreated
----
0.0
20.7
Yield
1000
Bulbs/A
139.8
Matran EC
@ 20%
38.8
0.5
14.3
134.6
Goal
Tender @
0.125 lb*
82.5
2.3
5.4
139.3
* First true leaf

29. Green Onion Trial

30. 1st true leaf
2nd true leaf

31. Shepherds Purse
1st true leaf
2nd true leaf

32. Goal 2XL @ 1st true leaf
untreated

33. Matran @ 20%

34. Scythe @ 5%

35. 2005 Green Onion Trial
Weed Control Ratings
9
8
7
6
5
4
3
2
1
0
Untreated
Matran
20% 1st
Matran
20% 2nd
Scythe 5% Scythe 5%
1st
2nd
Treatments

36. 2005 Green Onion Trial
Phyto Ratings
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Untreated
Matran
20% 1st
Matran
20% 2nd
Scythe 5% Scythe 5%
1st
2nd
Treatments

37. 2005 Green Onion Trial
Yield – T/A
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Untreated
Matran
20% 1st
Matran
20% 2nd
Scythe 5% Scythe 5%
1st
2nd
Treatments

38. Size of weeds
By 2nd true leaf
39 days after planting
2 days after
3% Scythe
2006 Dry Bulb Onion Trial

40. Onion Summary
• More effective weed control can be
achieved if the organic herbicides can be
applied at the first true leaf stage
• However, we observed greater
phytotoxicity on the crop when applied at
this earlier growth stage
• If applications go on too late and the
weeds are too big, the low rates of organic
herbicides will not be adequate to
effectively control weeds.

41. Other Applications for Organic Herbicides
(Crazy ideas???)

42. Mechanical Harvest

43. Difficult, Tedious and Expensive to Hand Weed

45. There may be opportunities to use organic
Herbicides applications that are precision guided
And that are hooded to take out some of the
Weeds in this type of a situation

47. The robotic system uses
microjets
These would lend
themselves to organic
materials

48. Conclusions
• Postemergence use of organic herbicides
on broccoli and onions is a bit dicey.
• Directed sprays on broccoli are very
helpful to maintain safety
• These trials indicate that there is hope for
onions, but skill and good timing will be
necessary to make this system work

49. Conclusions
• These organic herbicides may have a role
in other ways in organic & conventional
systems
• They may feature in hooded spray
operations and possibly in robotic
weeding

50. Acknowledgements
• Cooperating growers
– Chris Drew, Sea Mist Farms
– Bob Martin, Rio Farms
– Bill Peixoto, Dick Peixoto Farms
– Jerry Rava, Rava Farms
• Research assistants
– Tiffany Bensen
– Pat Headley
– Dave Miltz.