Solving Africa’s Weed Problem:

The Role of Herbicides

Leonard Gianessi, CropLife Foundation

Weedy Maize Field

Weeds compete with crops for space, nutrients, sunlight and moisture reducing crop yields.

Maize Yield Reduced 90%

Weed Free Period Required for Optimal Yields

Days After Planting

Cassava 84

Maize 56

Rice 42

Sorghum 35

Akobundu, 1987

In Malawi, one-third of the area planted to maize by smallholders is either left unweeded or weeded after the critical six weeks.

Orr, Mwale & Saiti, 2002

In Zimbabwe, 21% of cotton farmers abandon more than 20% of their cropped area each year as a result of weed infestations.

Mavudzi, et al, 2001

Handweeding is the Predominant Weed Control Practice in Sub-Saharan Africa

50-70% of the labor in crop production is spent weeding.

Chikoye, et al, 2007

Constraints on Timely Hand-Weeding

Women can be too tired or sick (malaria)

Fields can be muddy Competing time

demands: child care Pregnancy

African Yields (Tons/hectare)

Experimental Plots

Average Farmer

Maize

8

1-2

Rice

4

1

DeVries and Toenniessen, 2001

Tittonel, et al, 2007

In Africa, yield losses due to weeds range from 25% to total crop failure.

The majority of farmers identify weeding as the major constraint in their farming systems.

Vissoh, et al, 2004

Handweeding Permanently Deforms Women’s Spines

To weed one hectare a

woman walks 10 kilometers in

a stooped position.

African Weed Control: Current Practice

135 million hectares, 135 million women

200 hours/hectare

27 billion hours

20-100% yield loss

Benefits of fertilizer use dependent on weed control

Certain weeds absorb nutrients faster than crops

Without weed control, increased fertilizer use leads to more weeds

Farmers reluctant to increase fertilizer use Increased need for hand weeding “Labor bottleneck”

Labor not available for applying fertilizers

Herbicide Use Markets

Highly developed (>90% acres treated) US, Europe, Japan, Australia, Canada

Developing China, India

Not Developing (<5% acres treated) Sub-Saharan Africa

Herbicide Use Driver: Developed Countries

Shortages of workers to weed fields starting around the 1950s-60s

Herbicides greatly reduced the need for weeding by hand

California: Weeding Vegetable Crops 1940s ‒ 1960s

Hand Weeding

Japanese Rice Weeding: 1950s

500 Hand Weeding Hours/Ha : 1 Billion Hours Total

Japan: Weed Control in Rice

Herbicides replace the need for 1.89 million people weeding every day for 60 days in the summer all over Japan

Matsunaka, 2001

Pesticide Use Drivers: Developing Markets

Shortages of workers to hand weed fields

Need to produce more food for growing population

Hand Weeding in China

Millions of Farm Workers are Moving to Urban Areas

China Weed/Crop Status: 1980s

43 million hectares heavily infested 17.5 million tons of grain lost

Weedy maize field in China

Herbicide Use: China

Million Hectares

Rice in India

Hand weeding

India: Crop Herbicide Market

217

416

0

100

200

300

400

500

2005 2010

MillionUS$

Phillips McDougal

The Spraying of Chemical Herbicides is an Alternative to Handweeding

Weeds Killed Before Planting With Herbicides

-60 hours/hectare Handweeding+2 hours/hectare Herbicide Spray

Cotton Experiment: 4 Weeks After Herbicide Spray

Herbicide Treated

Untreated

-254 hours/hectare Handweeding

+1.5 kg/hectare of Chemical Lagoke, et al, 1992

Herbicide Experiment: Kenya

Weedy Herbicide Treated

Maize Yields +53%

Bean Yields +94%

Maize Experiment: Kenya

“Chemical weeding was one-third of the cost of two hand-weedings.”

Maina, et al, 2003

Herbicide Use: Smallholder Farms

1-5% use herbicides Lack of training of farmers Lack of training of Extension Service

workers Lack of spray services

“There are more weed scientists in the state of California than in all of Africa.”

Akobundu

What is urgently needed is graduate-level education in weed science (at the masters and doctoral degree levels) for nationals in the region. There are many U.S. funded agricultural development projects in Sub-Saharan Africa with several universities as contributing institutions. Nearly all of them have training in agricultural economics, plant breeding, and agronomy, but hardly any of the projects have included

training in weed science.

Akobundu, 1991

Herbicide Use: Lack of Interest

Weeds are seen as “women’s work” Governments don’t take seriously International development agencies are

reluctant to support pesticide strategies

Lack of knowledge is the most limiting factor in the adoption of herbicide technology. There is a need to train extension workers on herbicide technology, who would in turn train the farmer. If the smallholder farmers are given technical support, they would take advantage of herbicide technology and improve crop production.

Makanganise, et al 1999

Training in Herbicide Application is Necessary

The incorrect herbicide applied at the incorrect time and/or rate May not work to control weeds May damage the crop

Safety and application

Spray Service Provision Initiative

SSP initiative was conceived in early 2008 by CropLife Zambia & USAID

Aimed at promoting the responsible Use of Pesticides to approximately 50,000 Small Scale Farmers

SSP initiative was conceived in early 2008 by CropLife Zambia & USAID

Aimed at promoting the responsible Use of Pesticides to approximately 50,000 Small Scale Farmers

ZAMBIA

GROWING FOOD - CREATING RENEWABLES - SUPPLYING SUSTAINABLY

SSP Training in the Field

•SSPs are selected from among the farmers•Trained in all aspects of Responsible use

•SSPs are selected from among the farmers•Trained in all aspects of Responsible use

ZAMBIA

GROWING FOOD - CREATING RENEWABLES - SUPPLYING SUSTAINABLY

Spray Service Provision

Result• Sprayed for 4,800 fellow farmers

• Member companies reported increased sales in areas where the programme had been implemented.

Result• Sprayed for 4,800 fellow farmers

• Member companies reported increased sales in areas where the programme had been implemented.

ZAMBIA

GROWING FOOD - CREATING RENEWABLES - SUPPLYING SUSTAINABLY

Adoption of herbicide technology among female farmers has also brought behavioral change as most of them have vowed never again to weed their crops using hand hoes.

CARE Zambia, 2011

The increased use of herbicides also triggered the adoption of fertilizers, use of hybrid seeds and an increased practice of other restorative practices such as conservation farming.

CARE Zambia, 2011

There was consensus among Spray Service Providers (SSP’s) that it took them only one hour to apply herbicides to one hectare of crop. This means that in a season, one SSP can take care of 78 hectares. Using hand hoes, 78 hectares would require 468 family members to weed for the whole month.

CARE Zambia, 2011

Field Day – CLF/CNFA Project

Over 3000 farmers visited the plots

Maize Plot – Herbicide Treatment

Yield +26%; -150 Hours of labor/hectare; -50% Lower costs

Field Day Training in Herbicides at Agrodealer

Phil Stahlman, Kansas State University Volunteer Instructor, Malawi Weed Trials

Typical Agrodealer

Train agrodealers to provide extension and spraying services

Conclusions

Herbicide use is inevitable in African crop production

Adoption is likely to come from farmer demand

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