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Summary of bindweed responses
Following is an edited summary of the 9 responses I have received to date on
organic control of field bindweed (Convolvulus arvensis), also known as
creeping jenny or small morningglory. Authors/addresses were deleted. They
are in no particiular order. I hope I have not left anyone out. Thanks to
one and all for taking time to respond.
1. I am not sure how large the acreage is but sometimes using an organic
mulch like straw can help to smother weeds, but organic mulches must be
spread onto a clean surface and must be thick enough to cover the entire
soil surface to shade our weed seedlings. There has been research that
shows a reduction in broadleaf weed seedlings when rye is used as a cover
crop. Rye has allelopathic effects on broadleaf weed germination.
2. I can tell you it is a serious problem here too, even on ground
fumigated with methyl bromide/chloropicrin. It would seem any "top kill"
would result in carbohydrate starvation (e.g. flaming/sharpshooter) and
would eventually be effective. But how many years would it take?? Seems Dr.
Clyde Elmore at UC Davis did some work in the past on this or other
perennial weeds to determine how quickley one needed to come back to kill
new growth so that there is a net reduction in food reserves - I think it
was fairly quick as I recall..........very important for the CHO starvation
to be effective.
3.We have a few patches of bindweed on our 3 acres of organic vegetables,
both field and hedge. We have tried covering it over with black plastic
for the whole season; when we remove the plastic in the fall it comes right
back. We have tried full-season bare fallow as well as "smother" crops
like buckwheat with the same results. The stuff drives us nuts.
Apparently, the root systems can go down 30 feet or more, so it is quite
difficult to exhaust it. You can hoe it one day and it will grow back by
the next.
4. Bindweed is, *I think*, very similar to wild buckwheat which grows here.
If it is, it is
very susceptible to flaming, at least when young. Because it keels over
more easily than
many crops, it *might* be possible to flame certain emerged crops fairly
aggressively to get
the bindweed. Certainly flaming controls wild buckwheat very well (crop)
preemergent. Caution advised, tho. ;-) I use geese as weeders, but I'm
unsure whether they eat buckwheat or bindweed or not. If they do, certain
crops such as potatoes, strawberries etc. could be cleaned up that way. It
would require segregating goose tolerant crops from crops considered
palatable by the geese.
I find that mulching is not very effective in controlling buckwheat.
5. In my experience, bindweed thrives on fertility. As you improve the soil
the bindweed gets more invasive. This is why rotation is important. I have
observed strong alleopathic effects when spring barley is planted in soil
infested with bindweed. I seem to remember that it burned down the bindweed
like an herbicide. You could try a few strips of barley in your garden. This
effect takes place early in the growth stage of the barley. mybe you could
incorporate it as a green manure, and plant something else after.
6 I would want to look at the soil test with the suspicion that K might be
high in relationship with Ca. One would want first to make sure Ca is
arount 70% of the cation exchange capacity in terms of base saturation %.
They I would recommend green fallowing after deep plowing. I suggest deep
plowing because bindweed has deep rhizomes and sends up shoots which will
be severed by the horizontal slicing action of the plow. Green fallowing
may seem expensive compared to herbicides but at least is has the
additional value of improving the soil's overall fertility and quality
while combatint weeds. I suggest planting an vigorous green manure crop
with inexpensive seed cereal grains, buckwheat, etc or mixed with legume
such as vetch. When 16" to knee high disc or rototill into the top 6" of
soil along with any weeds which will be struggling along in this enormously
competitive environment. At disc down this is a good time to add compost
or manure and other fertilizers especially rock phosphate (the biological
activity associated with green manure incorporation generates lots of
organic acids which help weather rock fertilizers. As soon as initial
decomposition is well underway, one should replant another green manure
crop. A typical sequence I have used several times to eliminate perennial
weeds goes like this: Late summer or early fall - rye and vetch. Late
winter - manure on green manure crop as new growth begins Late spring -
disc down and replant to buckwheat or oats with peas. Summer - disc and
replant buchwheat. Late summer plant vetch with rye again to provide
overwinter cover - this field will be very well suited to organic vegetable
production the following spring. This will reduce annual weeds very
effectively as well and will probably eliminate soil borne crop diseases
for the several seasons to follow.
One alternative might be to turn active swine into the field in hopes
they will rid the soil of bindweed but I think the green fallow is far more
effective and beneficial for future production.
I hope this proves usefull to you, and would be interested in hearing how
things turn out......
7. I have been working on trying to control field bindweed with
vinegar. I have used two volumes, 20 gal/a and 40 gal/a of straight
vinegar (5% acetic acid). The best control with 20 gal/a was about 15% -
not too good. When I doubled the volume, control was as high as 60% and
averaged 50%. I plan to continue this work, looking at sequential
applications - perhaps two or three applications at tow to three week
intervals or to use a higher concentration of acetic acid (10% or higher).
Up to this point, I have been using regular vinegar from the grocery
store, but to increase the concentration and lower the cost, I will start
using glacial acetic acid, available at any chemical supply company.
Glacial acetic acid is what food companies buy and then dilute with water
to make vinegar. The price I heard was $6./gallon, which will make 15 or
so gallons of vinegar.
Sharpshooter or Scythe - These are two different names for the
same active ingredient - pelargonic acid. Scythe, the current name, is
made by Mycogen corporation. It is a contact herbicide, very effective
against annual weeds. I know that Mycogen is trying to get this materail
approved for use by CCOF, but I'm not sure where it currently stands. In
my comparisons of Scythe vs. vinegar, I didn't see a lot of differences,
although I did not look at Scythe for field bindweed control.
8. I am not sure how large the acreage is but sometimes using an organic
mulch like straw can help to smother weeds, but organic mulches must be
spread onto a clean surface and must be thick enough to cover the entire
soil surface to shade our weed seedlings. There has been research that
shows a reduction in broadleaf weed seedlings when rye is used as a cover
crop. Rye has allelopathic effects on broadleaf weed germination.
9. If the bindweed isn't wreaking havoc on production, I'd leave it. We found
bindweed drew some of our destructive insects away from our crops.
Dr. Laurie Hodges, Vegetable Specialist
377 Plant Sciences - University of Nebraska
Lincoln, NE 68583-0724
phone: 402-472-2854
fax: 402-472-8650
e-mail: Hort034@unlvm.unl.edu