March 2013. An article on nutgrass appeared in the Los Angles Times, and sparked discussion among members. The article is given below.
A member said it was one of the most dangerous and invasive weed in Palau. It has, in my opinion, caused more abandonment of previously farmed land than any other weed. May I add under the tutelage of Dr. Joel Miles that we were successful in eliminating nutsedge in small plots using a chicken tractor, a pig tractor and by spraying urea then Round-up. I no longer recommend using Round-up since it seems to be persistent with a residual effect in our red acidic heavy clays. Also, I would avoid using urea near any sources of water.
It was with good reason that purple nutsedge, Cyperus rotundus, was given a prominent place in Holm’s book “The World’s Worst Weeds”, as it is a difficult one indeed. Yellow nutsedge, Cyperus esculentus, a species that is more at home in less tropical/more temperate climates, is almost as bad. However, if you look into its biology, there are clues on how to manage it. In Indonesia, the purple nutsedge is called “suket teki” (meaning cancer grass) or shortly “teki”, pronounced as “the key” (with a sharp “t” as in “to”).
The biology: A single “nut” (actually a tuber) sprouts and gives rise to a plant. This “nut” sends out rhizomes that form “baby nuts” every few centimeters. The original or “motherplant” keeps these “baby nuts” dormant but terminal “nuts” (= at the end of a rhizome) developed at some 10 cm or more away from the motherplant will not be kept dormant and will sprout. Dig up a complete plant with all of its rhizomes from an infected spot and you can see this for yourself: a motherplant with a number of rhizomes with tubers and the terminal tubers sprouting. Pulling the sprouts will mostly leave the “nut” intact in the ground and this will sprout again. Digging up the sprouted “nuts” only will leave the dormant “baby nuts” on the rhizome unaffected and when some of these become terminal, they will sprout. There may be quite a number of dormant “nuts” on a rhizome-string so this can continue for a considerable time. Digging up the complete rhizomes seems impossible, unless you follow the advice given: remove all topsoil to sufficient depth and cultivate your crop in the subsoil or replace the removed layer with “nut”-free soil. Mind that any “nut” remaining in the soil will be a source of reinfection. Fortunately the ability of the plant to propagate by seed is poor, but can not be completely ruled out.
The key: Break all connections of the nuts by tillering the soil, rotavating, by cutting or whatever other means available. If all connections of nuts on a rhizome are cut and each nut is single and therefore terminal, usually ALL will sprout if conditions are good for germination. Wait till you have a vigourously growing lawn?? of nutgrass and then hit it hard with a suitable herbicide that will not only kill the sprout but also kills the nuts??. As far as I know it is only glyphosate that is able to do this in a satisfactory way, but maybe other herbicides will do the job also (please let this be known on the list if you know of some!). Keep looking for new sprouts and repeat untill the weed has disappeared or untill you are satisfied with the result. Mind that if some “nuts” remain in the field, you will soon have a problem again.
I have heard some people in Indonesia roast the tubers and after removing the outer layer, use them in dishes as food. I have never had the experience of actually eating them myself but maybe this could be a way to make use of what is considered an agricultural pest by most. If you can not control it, then use it..
Another member suggested: A mulch of clear plastic for a week or so, following tillage, will induce near 100% sprouting of the tubers, and a spray of glyphosate following removal of the mulch will be translocated to the tubers and kill them. Under ideal conditions – high soil moisture and high solar radiation, the clear plastic mulch (soil solarization) may be able to give nearly 100% kill of tubers down to 15 or 20 cm.
Chickens will eat purple nutsedge. Chickens can graze between crop rows to control purple nutsedge, but only in crops that the chickens will not eat. We found them to be very effective in dryland taro, for example, and bananas. Chickens can also be rotated with vegetable crops – chickens for a couple of months to eat the nutsedge, then one rotation of vegetables. This will not get rid of the nutsedge, though; just slow it down enough to produce a crop. Sweet potato is another crop that competes well with purple nutsedge. There is no doubt that this is one of the most difficult weeds to control in vegetable crops. Holm and Plucknett in their book, “The World’s Worst Weeds” in 1977 ranked it as the world’s worst weed. The other solution is to grow tree crops; it is not very tolerant of heavy shade. It is not a problem in their agroforestry systems. It is present, but not a problem.