Weed Management

Introduction Commonly Used Herbicides Weed Management Practices Efficient use of Herbicides Calibrations Integrated Weed Management


  • Weeds are unwanted plants growing in combinations with crops.
  • They compete for the nutrients, water, space, light and other essential requirements.
  • Weed plants serve as alternate host for several pests and diseases.
  • The dominant weeds of this crop in the plains are given below.

Major weeds of Potato

Scientific name
Common name
Amaranthus viridis L Pigweed
Anagallis arvensis L Pimpemel
Avena fatua L Wild oat
Chenopodium album L Lambsquarters
Convolvulus arvensis L Field bind weed
Cyperus iria L Yellow nutsedge
Cyperus rotundus L Purple nutsedge
Melilotus alba Desr White sweet clover
Melilotus indica L All Yellow sweet clover
Phalaris minor Retz Canary grass
Pea annua L Blue grass
Setaria glauca (L) Beauv. Fox tails Carpet weed
Trianthana monogyna L Carpet weed

  • Wider spacing, frequent irrigation and liberal use of manures and fertilizers create favourable conditions for taking an early start of weeds well before the crop emerges.
  • It creates a growth margin in favour of weeds, and if unchecked, causes serious harm to the crop.
  • Early weed competition usually reduces crop yield more than late season weed growth.
  • Weed management is the process of limiting the weed infestation so that crop could be grown profitably.


Commonly used Herbicides

Basalin (Fluchloralin)

  • N-(2-Chloroethyl) - 2, 6-dinitro-N-Propyl- 4-(Trifluoromethyl) aniline.
  • It is applied before planting and mixed with the soil.
  • It is available as emulsifiable concentrate or as granules, belongs to dinitro-anilines group and is volatile.
  • It is more or less susceptible to photo-degradation and therefore be quickly incorporated into the soil before planting of potato crop.
  • It is absorbed by the root and translocated throughout the plant system.

Pendimethalin (Stomp)

  • N-(1-Ethyl Propyl)-2, 6 dinitro-3, 4- xylidine.
  • This compound also belongs to dinitro-anilines and available as an emulsifiable concentrate and as granules.
  • Under normal environmental conditions, it persists for less than a year at phyto-toxic levels in soil.
  • Pendimethalin is absorbed more rapidly by very small broad leaf weeds than by the grasses.
  • In potato, it is applied as a pre-emergence application when the weed flora has not yet germinated.

Linuron (Afalon)

  • N' - (3,4 - dichorophenyl) - N- methoxy - N - Methylurea.
  • Linuron is a substituted urea compound and selective pre-emergence herbicide for medium to heavy soils under medium rainfall conditions.
  • Linuron appears to be the best persistent of this group with no detectable residue after 4 months and hence is useful in situations where same weed germinates at later stages of crop growth viz. Poa spp.
  • Linuron at 0.5 kg/ ha gave the most effective weed control in potato at Ludhiana.
  • In potato, it controls both broad leaf and grassy weeds like Echinochloa crussgalli, Digitaria spp, Setaria spp, Amaranthus spp, Chenopoduim album, Melilotus spp. Anagallis arvensis, Vicia sativa and Funaria parviflora.


  • 2-Chloro - 4 ethylamino - 6 isopropylamino - 1,3,5 - triazine.
  • It is applied in Potato to control annual grasses and broad leaf weeds.
  • It is also absorbed through roots and translocated to other plant parts.
  • It is an effective herbicide against Digitaria spp., Echinochloa spp., Cyperus rotundus L., Chenopodium album L. and Avera fatura L. etc. Since it is more soluble than Simazine, it is best suited in areas of low rainfall.
  • It also takes less moisture to carry it into root zone or activate it.
  • It effectively controls both monocot and dicot weeds and has no residual effect on succeeding crop of wheat.


  • 2 chloro - 4, 6 - bisethylamino - 1,3,5 - trazine.
  • It is a systemic herbicide absorbed by the roots and translocated to other plant parts.
  • It does not prevent germination but kills the seedling.
  • It is primarily used to control annual grasses and broad leaf weeds in potato crop and is effective against Digitaria spp, Setaria spp, Chenopodium album, Amaranthus spp.


  • 4- amino - 6 t - butyl - 3 (methylthio) - 1,2,4 - traizin = 5 (4H).
  • Among the triazine herbicides, it is the most effective herbicide.
  • Its persistence in soil is less than the other triazine herbicides.
  • It is usually applied as pre-emergence. Sufficient moisture is required for it's effectiveness.
  • It is both root and shoot mobile herbicide with prolonged soil residual activity upto 6-12 weeks.
  • It is very effective against annual grasses and many broad leaf weeds in potato particularly Chenopodium album L., Anagallis arvensis L., Melilotus spp, Vicia sativa L., Trainthena monogyna L, Poa annua L. etc.


  • 1 , 1' - dimthyl 1- 4, 4' - bipyridylium.
  • It belongs to bi-pyridylium group and is formulated as emulsifiable concentrate.
  • Its foliar application causes wilting and rapid destruction of the weed foliage within a few hours.
  • For best results in the field, it should be sprayed in the late afternoon or mid-day rather than in the morning.
  • This allows some internal transport of herbicide during night before development of acute phyto-toxicity induced by light which could limit movement of herbicide.
  • As the high light intensifies it increases the rate of development of phyto-toxicity symptoms.
  • It has no residual activity as it is rapidly absorbed and inactivated in the soil.
  • It is the best herbicide used as directed spray for the control of annual and broad leaf weeds.
  • Paraquat may also be absorbed through skin.
  • Therefore at the time of spraying, breathing of the spray mist and prolonged skin or eye contact should be avoided.


  • N - (3, 4 - dichlorophenyl) propionamide.
  • It belongs to amide group of herbicides and is formulated as emulsifiable concentrate.
  • Propanil is a selective post-emergence herbicide and is used in potato to control several annual grasses and a limited number of annual broad leaf weeds and sedges.
  • It is effective against Cyperus rotundus L., Digitaria spp., Echinochloa spp etc.
  • The ideal time of it's spraying is at 1-3 leaf stage of the weeds.
  • As propanil is a contact spray, uniform coverage is essential.
  • It is applied as a foliar spray therefore soil type has no effect on its action.
  • Propanil is rapidly broken down in the soil thus has no residual effect on the succeeding crops.
  • It is absorbed mainly though leaves. Do not apply it when rain is expected within next 5-6 hours.Alachlor : X-chloro - 2', 6' - diethyl - N (methoxymethyl) acetanilide :
  • It belongs to amide group of herbucider and is formulated as an emulsifialite concentrate and granules.


  • It is more effective in medium textured soils than the heavy soils. It resists leaching.
  • In medium textured soils with moderate moisture, herbicidal effectiveness usually lasts for about 6-10 weeks.
  • After the application of alachlor, the early seedling and root growth are inhibited and weed seedlings do not emerge from the soil.
  • The grasses absorb the herbicide mainly through the shoots whereas broad leaf plants absorb it through the roots.


Different weed management practices in Potato may be classified

  1. Crop competition methods
  2. Physical methods
  3. Chemical methods and
  4. Integrated weed management practice.

Crop Competition Methods

Crop Weed Competition

  • One of the most favourable crop production technique consists of crowing out the weeds.
  • It directly induces healthy growth of Potato plants and indirectly maintains a crop environment that is detrimental to weeds.
  • Vigorous and fast growing potato varieties like Kufri Badshah and Kufri Jyoti are better competitors due to their adequate crop canopy to smoother weeds.
  • High competitiveness is obtained with the adoption of proper crop management practices such as

Proper crop rotations

  • Inclusion of smother crop like cow-pea and green manure crop eliminates weeds by depriving them of sunlight.
  • The weeds are also buried along with the green manure crops and destroyed.
  • It also improves the fertility status of the field on decomposition.

Hot weather cultivation

  • Some perennial weeds such as Cynodan doctylon L, Cyperus rotundus are simply reduced by ploughing the field deep during the summer months (May-June).

Good seed bed preparation

  • It gives the good start to the crop by ensuring quick emergence of potato.

Proper and timely planting

  • Planting of well sprouted tubers at sufficient soil moisture, proper depth, time and maintaining high plant densities per unit area helps in growing competitive potato crop.

Application of light irrigation

  • The crop planted in the month of September experiences high temperature.
  • The furrows formed for sowing get dry very quickly.
  • This hinders germination of Potato.
  • Therefore, application of light irrigation at short interval helps sprout the tubers rapidly.
  • It should be taken care that the water level in the furrow should rise half the furrow depth i.e. it should remain below the seed placement level of the ridge.

Placement of manures and fertilizers

  • Application of manures and fertilizers in bands near the root zone of the crop reduces the nutrient loss by weeds considerably by depriving the weeds of nutrients.
  • It also promotes the crop growth and plant vigour. This in turn smothers the weeds.

Physical methods

  • These methods are also called manual and mechanical methods of weeds control.
  • These methods do not involve chemicals but require manual energy, animal power or fuel to run implements that dig out the weeds. These methods include:

Manual weeding

  • Pulling out the weeds by hand, hand hoe, spade etc is a very common practice in Punjab and India.
  • This method is also useful for the destruction of weeds growing within the rows where they can not be controlled by cultivation.

Mechanical methods


  • Single bottom animal/tractor drawn ridger is used for earthing-up of crop while the weeds growing along the side and base of furrow are uprooted and destroyed.


  • Reduces the growth of annual weeds in potato.
  • It has a smoothering effect on weeds by excluding the light from photosynthetic portions of plant and thus helps in inhibiting the top growth.
  • It also provides an effective barrier to weed emergence.
  • In addition it helps to conserve moisture and maintain temperatures which results quick in emergence of potato.
  • Mulching can be done by the use of dry straw, grasses, other plant parts, paper, plastic and polythene films.
  • Mulch should be thick enough to prevent light penetration / transmission to suppress photosynthesis by weeds.
  • The mulch of straw in potato should be all out 5-10 cm thick.
  • Timely hoeing and weeding keeps the weed plants under check.
  • The potato crop develops crop canopy in about four weeks after crop emergence and if the weeds are controlled by this time, the crop gains a considerate competition advantages.
  • There is a need to avail full advantage of hoeing and weeding and it should by followed immediately by earthing-up.

Chemical methods of weed control

  • Weed control through chemical results in better growth of crop and often in improved yield of tubers than manual and mechanical means.
  • This is due to the elimination of mechanical damage to the plants.
  • Chemical weed control is quick, less laborious and a large area can be covered in a short time.
  • Besides, chemical weed control in seed productions program is of great practical utility for the production of healthy seed grade potato as it minimizes the spread of mechanically transmitted viruses x and s by omitting some of the cultural operations during the crop growth.
  • Several herbicides have been recommended for weed control in potato and these are used according to their availability, cost, weed flora and the cropping pattern.
  • The herbicides used in potato can be grouped in these categories.
  1. Pre-planting application
  2. Pre-emergence application
  3. Post-emergence application

Chemical weed management practices of potato

Dose per hectare
Time of Application
Stamp 30 EC (Pendimethalin) 2.5 litres Pre-emergence application after the application of first irrigation.
Tafazine 500 gm - do -
Atrataf 500 gm - do -
Sencor 1 kg - do -
Lasso / Tok E-25 5 litre - do -
Tok E- 25 / Lasso + Tafazine (2.5 litres + 250 g) Mixing of two herbicides gives better weed control than their individual applications. Apply this mixture as pre- emergence after first irrigation.
Stam F-34 2.5 litres When weeds attain the height of 5-7 cm and then do the spray.
Gramaxone 1.25 - 2.0 litres When tubers germination various from 5-10 percent and if the weed population is less than 100 plants per sq m.


  • Normally these chemicals are applied using 500 litres of water .
  • But adjust the water quantity as per the type of sprayer used to obtain equitable distribution of the spray.
  • When potato is to be followed by cucurbits (musk melons, beetle gourds), then don't use Tafazine weedicide as this group has a long persistance period and these crops could be injured if grown soon after potato.


Efficient use of Herbicides

  • Application time and method of application is very important and determines the effectiveness of the chemical applied. Therefore select the appropriate weed management practice.
  • Soil should be well prepared and brought to fine tilth before spraying.
  • Do not disturb the field after spray as the residual effect would be reduce.
  • Apply recommended dose of herbicides for effective weed kill.
  • Select the herbicides according to the weed problem.
  • Volatile herbicides should be applied to the soil before making ridges.
  • Apply contact herbicides like Gramaxone (Paraquat) only when weeds appear.
  • Select a suitable sprayer for spray.



  • The application of herbicides at rates other than the recommended levels proves either harmful or of little use.
  • Therefore calibration of the amount of herbicide, water to be applied, the speed of walking, pressure to be maintained etc. are very critical for obtaining thorough weed-kill in the crop. Calibrations can be done by using the following calculation.
  • Time Required
    Total distance travelled D metres
    Time taken for travelling the distance D m Walking speed T minutes
    (DxS)/T metres / minutes
    Swatch of spray nozzle S metre
    Area covered in time T over distance D D x S metre
    Time required to spray 1 ha (10000xT) / (D x S) minutes
    Quantity of chemical solution required
    Amount of solution discharged at the given pressure over area DxS Y litre/ min.
    Rate of discharge / m2 Y / [D x S ] litres/m2
    Amount of solution required per ha at the given pressure Y (Y x 10000) / (D x S) m2
    Since 1 ha = 10000 m2 Z litres solution required per ha

Calculation of herbicides for application

  • The herbicides are available in the market under the trade names and the recommendations are given as per active ingredient (ai) per ha.
  • Therefore it is necessary that the requirement of commercial products is worked out. The following formula is used for calculating the finally commercial product.

Weight of commercial product required

  • (Weight of chemical to be applied/ha) / (percentage of ai in commercial product) x 100
  • This is equal to X gm or litre of commercial product.
  • The X gm or litre the commercial product should be dissolved in Z likes of water required / ha.

Agitation and avoidance of drift

  • Settling of herbicides during application should be prevented especially when suspension of wettable powders is used to avoid the variation in concentration during spraying.
  • To avoid drift it is recommended to stop spraying when the wind is too strong (more than 10 km/hr).
  • For wind of 5-10 km/hr, the height of the nozzle should remain constantly downwards and near to the ground throughout spraying.


Integrated Weed Management

  • Integrated weed management approach involves the reduction of weed infestation below the economic threshold level by the judicious combination of all feasible means.
  • Growing competitive crop of potato with appropriate agronomic practices for rapid growth of potato plants, practicing proper crop rotation, summer cultivation and combination of cultural and chemical methods of weed control are some of the practices which can be integrated to reduce the weed infestation in potato crop.
  • For best results, preference should be given to the integrated weed management approach. It not only eliminates the weed flora but also counts to be cheap and provides regular workload to the farm labours.