Flash News
  • Irrigation of beetroot It has already been mentioned in previous articles that the soil must be kept moist until the seedlings emerge. Light regular water applications must be…
  • Sowing beetroot seed commercially Sowing beetroot commercially Sowing beetroot is a practice used by commercial farmers. They are not planted with seedlings. Once the seed is cleaned and salts…
  • Beetroot seed treatment Beetroot((By Downtowngal [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons)) seed treatment is mostly done by commercial seed companies. There are instances where local seed can…
  • Pigeon pea climatic requirements Pigeon pea climatic requirements The pigeon pea is susceptible to frost damage at all stages of growth.. The most favourable temperature range is between 18-29°C…
  • How to grow beetroot… Beetroot is not grown by many farmers. Mainly because the demand is not that great and commercial companies have the market share. A large portion…
Facebook Twitter Google Plus Pinterest
Green beans

How to control weeds in green beans

chemical weed control methods vegetables

There are 20 herbicides registered for controlling weeds in Phaseolus vulgaris. These are registered for Dry Beans, however, they should be applicable to green beans as well.  These herbicides differ with regard to stage and method of application and the spectrum of weeds they control.  These herbicides in combination with each other, or in certain cases alone, should provide satisfactory control. Unfortunately there are only 6 herbicides registered on green beans. They are listed last on this page.

Before deciding on a particular herbicide or combination of herbicides, producers must determine the weed spectrum that must be controlled during the growth period of the crop. The correct choice of herbicide is important as not all weeds are controlled by a single herbicide.  Growers should also consider if all weeds must be controlled chemically.  It is quite often feasible that mechanical control is more than sufficient. Once the crop has reached a certain stage there is little competition from weeds and control is just a waste of money.

Always adhere to manufacturer’s guidelines to application and handling as these chemicals can cause severe harm to humans of not handled correctly

To ensure optimum results it is essential that the producer read and understand all the information on the label of the container. All instructions should be followed implicitly so as to eliminate any damage that could be caused by herbicides due to incorrect dosages, time of application and poor calibration of spraying equipment.  If any information on the herbicide other than that specified on the label is required, or if anything i s unclear, it is advisable to contact the technical advisors of the firm’s marketing the herbicide. They have to assist. Ideally one would request a complete spray program which is the safest route to take.

Please be very careful when using herbicides.  There have been cases that I have seen where the wrong herbicide was applied and a complete pivot full of lettuce died.  Not only was there no harvest, but for the next 5 years one could not grow lettuce again.  This is especially tricky when multicropping soft vegetables with grain crops such as maize.

Some of the active ingredients of herbicides that can be used during various stages of Phaseolus vulgaris growth (A Guide to the Use of Herbicides, 2004 1)A Guide to the Use of Herbicides. 2004. 18th ed. Dept. of Agric. Republic of South Africa, Pretoria.):

Pre planting weed control

  • Annual grasses, yellow and purple nutsedge
    • EPTC

At planting

  • Annual broad-leaved weeds and yellow nutsedge
    • flumetsulam/S-metolachlor

Pre-emergence

  • Annual grasses, broad leaved weeds and sometimes yellow nutsedge
    • S-dimethenamid
    • metolachlor & S-metolachlor (not broad leaved weeds)
  • Annual grasses
    • flufenacet
    • metazachlor
    • metolachlor & S-metolachlor
    • pendimethalin
  • Annual broad leaved weeds
    • imazethapyr
    • metazachlor
    • pendimethalin

Post emergence

  • Annual broad-leaved weeds and yellow nutsedge
    • bendoxide
    • flumetsulam (use with Tiara)
  • Annual grasses
    • propaquizafop
    • quizalofop-P-ethyl
    • sethoxydim
    • trifluralin
  • Annual and perennial grasses
    • cycloxydim
    • fluazifop-P-butyl
    • haloxyfop-R methyl ester
  • Annual broad-leaved weeds (only certain dry bean varieties)
    • fomesafen
    • trifluralin (only certain broad leaved weeds)

All the chemicals that we use such as herbicides, pesticides and fungicides are in my opinion pollutants. They are not natural chemicals. To put it bluntly, they are quite the opposite, they are against nature.  For that reason growers should pursue alternative methods of control before any hard chemicals are unleashed on our sensitive environment. It has been found that soil treated with phosphinothricin can reduce natural good fungi by 20% and natural occurring bacteria by 40%.  What was concerning is that some pathogens had resistance to the herbicide. So applying herbicide not only killed friendly microbes and fungi, but pathogens developed resistance and can increase in the soil for that matter (Ahmad & Malloch, 1995 2)Ahmad, I., & Malloch, D. 1995. Interaction of soil micro flora with the bioherbicide phosphinothricin. Agriculture, Ecosystems and Environment 54: 165–174. ).

Herbicides registered for green beans are

  • Bendioxide
  • Cycloxydim
  • EPTC
  • Fluazifop-butyl
  • Fomesafen
  • Sethoxydin

Bendioxide (trade name: Basagran)

It is a selective contact herbicide for the post emergence control of certain annual broad-leaf weeds and suppression of yellow nutsedge. Basagran must be applied when the weeds are young and growing actively. Warm, humid conditions are also necessary for good weed control. As Basagran is a contact herbicide ti is essential that th weeds are thoroughly wetted. Any rain or overhead irrigation withing 8 hours of applications will was the herbicides of the leaves and reduce efficiency. Basagran must be applied in a minimum of 300 L water /ha, using a hollow cone or flat fan nozzle with minimum spray pressure of 350 kPa. Basagran may scorch the leaves of beans, but will have no effect on the final yield. In inland regions, especially under very high sun intensity, green beans must not be sprayed with more than 2 L/ha Basagran, as higher rates may cause permanent crop damage.

Cycloxydim (trade name: Focus Ultra)

This is a post emergence control herbicide of annual and perennial grasses. It must be applied at a dosage of 0.8 – 4 L/ha at a stage when the grasses are still very young and small.

EPTC (trade name: Eptam Super)

This is a soil incorporated herbicide for the control of annual grasses, nutgrass and certain broad-leaf weeds. Eptam must be thoroughly mixed into the soil (100-150 mm) before planting. It can also be injected during planting. The incorporation must be done withing minutes of application and ideally in one operation. Incorporation may be achieved by using a rotovator, tandem disk or offset disk. Eptam should be applied in 150 – 200 L of water/ha and it is important to note that the dosage depends on the soil clay percentage. It is therefor in the interest of the grower to determine the clay percentage of the soil in order to apply the correct dosage.

Fluazifop-butyl (trade name: Fusilade Super, Grassclear)

This is a selective systemic post-emergence herbicide for the control of annual and perennial grasses. It is not miscible with most other herbicides and must be applied separately with at least a 14 day interval. Warm, humid conditions increase weed control. If halo blight (Pseudomonas syringae pv. phaseolicola) is present, it is aggravated when Fusilade is sprayed. Halo blight susceptible cultivars are Wintergreen, Strike and Harvester. Fusilade can be applied at any stage of the crop and weed development. Rain or irrigation within one hour of application will require a second application.

Fomesafen (trade name: Flex)

It is a post-emergence herbicide for the control of annual broad leaf weeds. The herbicide must be applied at a dosage of only 1 L/ha between the seedling and 4 leaved stage of the weeds.

Sethoxydin (trade name: Nabu EC)

This selective herbicide has a short residual action for the post-emergence control of certain annual grasses. Nabu can be applied at any stange of the crop when the grass weeds are in the two-leaf to third tiller stage. Nabu is not miscible with other herbicides. it can be applied 4-5 days after any other post-emergence broad-leaf herbicide.  Nabu is sprayed with 300-500 L water/ha and Agripon must be added to facilitate effective grass control.

References   [ + ]

1. A Guide to the Use of Herbicides. 2004. 18th ed. Dept. of Agric. Republic of South Africa, Pretoria.
2. Ahmad, I., & Malloch, D. 1995. Interaction of soil micro flora with the bioherbicide phosphinothricin. Agriculture, Ecosystems and Environment 54: 165–174.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: