1

Integrated weed management

Kampan Kafle

Department of Life Science, Kathmandu University

AGRS-101

Dr. Professor Roshan Subedi

Assignment due date: N/A

 2

Integrated weed management

Summary

Integrated weed management is an overall technique diversity that focuses on multiple

methods which involves all biological, chemical, mechanical, cultural as well as chemical

approaches with the sole purpose of removing the weeds in the most efficient and effective way

possible. The modern weed management system solely depends upon chemical means such as

herbicides. While IWM tries to avoid such harmful chemical measures, it does not exclude such

means. IWM supports the environment and encourages diversity as the excess use of pesticides

is replaced by other mechanical or biological measures. Resistance in weeds to herbicides can be

prevented as variation in methods doesn’t allow weeds to evolve into a resistant form. If the

government agencies, profit and non-profit organization and institutions work to address IWM

we could see farmers moving towards more sustainable agriculture in the near future.

Introduction to weed

Weeds have typically been defined as ‘plants which are a nuisance’ (Harper, 1960, as

cited in Booth,2003, p.3) or ‘a plant where we do not want it’ (Salisbury, 1961, as cited in

Booth,2003, p.3). Barbour et al. (1999, as cited in Booth,2003, p.3) defined a weed as a ‘non-

native invasive plant’ and they distinguished between ‘invasive plants’ that invade only natural

or slightly disturbed habitats, and ‘pest plants’ that interfere with agricultural or managed natural

areas. It is estimated that losses due to weeds is comparatively higher than that due to insects

and pests. (SR Reddy,1999) Weeds can introduce certain diseases and pests to the adjacent crops

but at the same time they can also harm the crops through allelopathy. Some of the weeds can

cause radical effects to the quantity and quality of crops which is mentioned below.
 3

o Alfalfa when grown in a weed free environment, 55-cm rows produced 820 kg ha-1 of seed in

the year of planting. But when it was mixed with 40 weeds then the seed yield was reduced to 45

kg ha-1 (Dawson and Rincker, 1982, in Zimdahl, 2004)

o (Dhima et al. 2000). Torner et al. (1991) did a research on Spanish barley and winter wild oats

where they compared the competitive ability of both the plants.. As the density of winter wild oat

increased, barley yield declined exponentially. Yield declined 10 percent with winter wild oat

densities of 20 to 80 panicles m-2 and yield losses were 50 percent when panicle density was

greater than 300 m-2.

o In case of Bangladesh it was estimated that weeds can cause the yield loss of 33.16% of the

food crops, 41.26% of cereal crops, 31.76% in pulses, 40.82% in oilseeds, 40.28% in rice crops

and 34.23% in fiber crops. (Karim and Rezaul, 1988)

Integrated weed management

An IWM definition from Australia has an HR weed focus: ‘‘to reduce selection pressure

for resistance to any single control agent and to manage herbicide resistant weeds within a

profitable system’’ (Sutherland, 1991, in Harker and O’Donovan,2013, p.2). Integrated weed

management is an overall technique diversity that focuses on multiple methods which involves

all biological, chemical, mechanical, cultural as well as chemical approaches with the sole

purpose of removing the weeds in the most efficient and effective way possible. When all the

biological characteristics and ecological behavior of weeds has been identified, Successful IWM
 4

techniques will be established. (Harker and O'Donovan, 2013, p.2) There are six components of

integrated weed management. They are: Prevention, hand weeding, mechanical methods,

cultural, chemical and biological components.

 Preventative methods: It involves the preventative measures like proper seed selection to

avoid weed growth.

 Chemical methods: It involves the use of herbicides in proportionate amount.

 Biological methods: It involves the use of biological means like insects and plants that

will cease the growth of weeds.

 Mechanical methods: Common methods like tillage and hand weeding are done.

 Cultural methods: It involves how sowing, cultivation and harvesting is done and when.

Objectives:

- To acquaint with the concepts of Integrated weed management and its practices.

- To learn about the benefits, limitations and applications of Integrated weed management.

Methodology:

Most of the information collected in this research are from books, research articles,

websites and videos. Online medium like google scholar and general search were used. I

considered articles published on weed biology, weed ecology, integrated weed

management, weed-crop competition as they provide information on weeds, their effects,

their reaction to environment and yield loss annually. Following queries were inserted in

google scholar to find the sources related to weed management.

 Definition of Weed
 5

 Definition of Integrated weed management

 Benefits of integrated weed management

 Limitations of Integrated weed management

 Yield loss due to weeds

Result

What is integrated weed management?

Integrated weed management refers to a comprehensive system of weed management that

includes all the traditional and modern weed management techniques. The main objective of

IWM is to collect the all the information and techniques to create a system that helps in

eradication or prevention of weed growth and to provide a medium for weed control without

disturbing the natural resources. The modern weed management system solely depends upon

chemical means such as herbicides. While IWM tries to avoid such harmful chemical measures,

it does not exclude such means. It should be noted that IWM should not be about the exclusion

of one means and application of another. Instead, it includes every possible means to avoid weed

growth. The main factors that constitute the integrated weed management are:

1.Preventative factor

• Unused and disturbed land are prone to weed infestation.

• Early identification of weed in the field can save from trouble for the future.

• Imported seeds, plants and equipment has to be properly examined if there is any weed attached

to it.
 6

2.Biological factor

•The main objective of using environmental means to control the weed is to minimize the

chemical use that may potentially harm the neighboring plants.

•Since the chemical and physical means aren’t being effective against new variants of weeds,

biological means are preferred in modern agricultural system.

•Some of the insect plays an important role in weed control. Such as:

 Bindweed mites – field bindweed

 Flea beetles – leafy spurge

 Mecinus janthiniformus – Dalmatian toadflax

 Larinus minutus Cyphocleonus achates – diffuse knapweed

(Methods of Weed Control (Natural Resources), 2021)i

For every 1% increase in yield, weed infestation should be eliminated to the extent of 3%

in barley, 2% in wheat, 0.5% in maize, 3% in tomato and 8% in apple. (SR Reddy,1999)

3. Chemical factor

 Herbicides has proven to be the most effective chemical measure for managing weeds.

 Herbicides are the dominant tool used in modern agriculture but its excessive use does

not prove effective against many weed species. Hence it is not the complete solution to

weed management. (Harker and O'Donovan, 2013)

4. Mechanical method

Some of the most common mechanical methods of weed management are:

 Hand hoeing: It is the mostly practiced methods to remove biennial and annual crops as

weed growth can be completely destroyed.

 7

 Hand pulling: It is the physical removal of weeds by using nothing but hands itself. It is

also used to remove the annual and biennial weeds from their roots.

 Digging: By digging into the deep layers of the soil the weed roots can be pulled out. It is

often followed by hand picking. Perennial weeds can be controlled by this method.

 Burning: It is used to destroy the matured and dried parts of the weeds. It also helps to

kill green weed growth when other methods are impracticable.

 Mulching: The fundamental principle of mulching is to prevent the weeds from exposure

to the sunlight. By restricting the environment that is suitable for the weeds, their growth

can be completely stopped.

 Soil solarization: High soil temperature can oppress the weed growth and their seed

germination. The heating of soil surface is called solarization. (Reddy, 1999)

5.Cultural method:

 Cultural method refers to practices that can be done for developing the resistance in

crops. It can be done through:

 Selection of big and viable seeds that will produce strong and viable plants.

 Timing of seed sowing and crop harvest in order to make plants grow faster than the alien

plants.

 Crop rotation can play a major role as crop-bound and crop-associate weeds such as

Avena futua can be removed from the field to provide a new growing environment for the

new seasonal crops.

 Reducing the space between the rows inhibits the growth or development of weeds.

 Preparatory tillage can be done to expose the weeds to the sunlight and heat that hinders

their further development.

 8

(Integrated Weed Management: Benefits of Methods Used in Complex, 2021)

Mechanical
methods

Preventative Biological
methods methods
Integrated
weed
management

Cultural Chemical
practice methods

(Bajwa, 2014)

Principal components of IWM are:

Weed identification: A successful IWM system can be created only after the proper

research and knowledge about the given specific weeds and its interaction with the environment

i.e., crops.

Weed Detection. Weed detection technology provides essential ‘‘scouting’’

information in many weed management systems. (Harker et al., 2013)

Preventative weed management: Maxwell and O’Donovan (2007) suggested that a first

principle of nonchemical weed management could be that the higher the uncertainty in a crop–

weed interaction, the more management emphasis should be placed on prevention and less on

causing weed mortality.

Benefits of integrated weed management:

 9

Since integrated weed management deals with all the practices and measures, the benefits

of every measure can be included in case of IWM:

 IWM supports the environment and encourages diversity as the excess use of pesticides is

replaced by other mechanical or biological measures.

 Resistance in weeds to herbicides can be prevented as variation in methods doesn’t allow

weeds to evolve into a resistant form.

 Crop quality and soil quality has lower chances of being mediocre because of minimum

disturbance due to weeds.

 It is applicable for both large-scale and small-scale farms and it gives a profitable return

for both of the farms.

 The high-intensity cropping system can be implemented as the crops no longer has to

compete against weeds for nutrition.

(Eagri.org, 2021)

Although integrated weed management has been able to address and solve some of the

major defects in weed management system, it still has some drawbacks which are

mentioned below.

Disadvantages of Integrated Weed Management

 The main drawback of IWM when it comes to chemical method is that it requires a

technical knowledge to properly apply herbicides in adequate dose in chosen time so that

it just doesn’t affect the surrounding crops. (INTEGRATED WEED MANAGEMENT -

ABC of Agri, 2021)

 10

 Complexion arises when we try to implement this method as not all farmers are

acquainted with the concepts of integrated weed management. Hence it is a challenge to

convince farmers to imply this system of weed management.

Conclusion

The integrated weed management seems to be more logical solution against weed

resistance and weed growth. The concept of IWM was introduced just few decades ago

but its application has brought about many profitable changes in the modern world. Many

countries have stopped prioritizing the herbicides and are adopting the strategies of IWM.

Since the new researches have confirmed the ineffectiveness of herbicides in many

common weeds, the IWM has become even more significant. The challenge that the

world is facing in actual implementation is the technical knowledge involved with the

farmers. If the government agencies, profit and non-profit organization and institutions

work to address this problem, we could see farmers moving towards more sustainable

agriculture in the near future. Therefore, Integrated weed management is the future of the

modern and sustainable agriculture.

 References
i

ABC of Agri. 2021. INTEGRATED WEED MANAGEMENT - ABC of Agri. [online] Available at:
<https://abcofagri.com/integrated-weed-management/> [Accessed 4 June 2021].

Bajwa, A., 2014. Sustainable weed management in conservation agriculture. Crop Protection, 65,
pp.105-113.

Barbour, M.G., Burks, J.H., Pitts, W.D., Gilliam, F.S. and Schwartz, M.W. (1999) Terrestrial Plant
Ecology, 3rd edn, Benjamin, Cummings, California

Dawson, J. H., and C. M. Rincker. 1982. Weeds in new seedings of alfalfa (Medicago sativa) for seed
production: Competition and control. Weed Sci. 30:20–25.

Dhima, K. V., I. G. Eleftherohorinos, and I. B. Vasilakoglou. 2000. Interference between Avena

sterilis, Phalaris minor and five barley cultivars. Weed Res. 40:549–559.

Eagri.org. 2021. [online] Available at: <http://eagri.org/eagri50/AGRO304/pdf/lec08.pdf> [Accessed 4

June 2021].

Harker, K. and O'Donovan, J., 2013. Recent Weed Control, Weed Management, and Integrated Weed
Management. Weed Technology, 27(1), pp.1-11.

Harper, J.L. (1957) Ecological aspects of weed control. Outlook on Agriculture 1, 197–205
Salisbury, E.J. (1961) Weeds and Aliens. Collins, London.

Karim, Rezaul. (1998). Relátive yields of crops and crop losses due to weed competition in bangladesh.
41. 318-324

Keeley, P. E., and R. J. Thullen. 1991a. Growth and interaction of barnyardgrass (Echinochloa
crusgalli) with cotton (Gossypium hirsutum). Weed Sci. 39:369–375.

Larimer.org. 2021. Methods of Weed Control (Natural Resources). [online] Available at:
<https://www.larimer.org/naturalresources/weeds/control> [Accessed 25 May 2021].

Pantone, D. J., J. B. Baker, and P. W. Jordan. 1992. Path analysis of red rice (Oryza sativa L.)
Competition with cultivated rice. Weed Sci. 40:313–319.

Reddy, S. (1999). Principles of Agronomy, Tirupati, India: Kalyani Publishers.

Scholes, C., S. A. Clay, and K. Brix-Davis. 1995. Velvetleaf (Abutilon theophrasti) effect on corn (Zea
mays) growth and yield in South Dakota. Weed Technol. 9:665–668.

Smith, R. J., Jr. 1983. Competition of bearded sprangletop (Leptochloa fascicularis) with rice (Oryza
sativa). Weed Sci. 31:120–123.

Sutherland, S.J.M. 1991. Developing integrated weed management systems. Pages 47–59 in R. E.
Torner, C., J. L. Gonzalez-Andujar, and C. FernandezQuintanilla. 1991. Wild oat (Avena sterilis L.)
competition with winter barley: Plant density effects. Weed Res. 31:301–308.
.