SUGAR RESEARCH INSTITUTE

March 2015

Addresses

Contact:

The Institute Director

KALRO-Sugar Research Institute

Kisumu-Miwani Road

P. O. Box 44 – 40100 KISUMU, Kenya

Tel: 020 204 7307

0735-339912 Email: director.sri@kalro.org,

Website:www.kalro.org/sugar

Officer In Charge,

Sugarcane Breeding Centre - Mtwapa

P. O. Box 10275

Bamburi, Kenya

Tel: 020047304

Officer In Charge

Opapo Centre

P. O. Box 21

Rongo, Kenya

Tel: 0202047314

Officer In Charge

Mumias Centre

P. O. Box 113

Mumias, Kenya

Tel: 0202047312

SUGARCANE WEED

MANAGEMENT IN

KENYA’S SUGAR

INDUSTRY

The European Union Sugar Research Institute

Government of the Republic of Kenya

Weed as a problem of sugarcane productivity Weed could be defined as a plant which is considered undesirable, unattractive or troublesome, especially one growing where it is not wanted. Weeds have been perceived as unwanted intruders into agro-ecosystems that compete for limited resources. Negligence towards weed management in the industry is a big problem, under various agro-ecological situations. Due to sugarcane slow germination and initial growth, wider row spacing, slow lateral spread, and adequate supply of nutrients, moisture and long duration, sugarcane growth suffers from tremendous weed problems. When improved agricultural technologies are adopted, efficient weed management becomes even more important, otherwise weeds rather than crops benefit from costly inputs.

Generally, and depending on weather conditions, four or more hand weeding is needed to achieve good crop yield during the first 3-4 months of cane or active tillering stage. Presence of weeds at this period will greatly affect tiller growth, number and development of millable stalks and will compete with sugarcane for sunlight and nutrients.

Major weeds flora in sugarcane growing areas In Kenya, sugarcane is planted almost throughout the year, but mostly in March, April and May during long rain season and in September, November and December short rain season. These are also the seasonal months where there is heavy infestation of different types of weeds. There are two types of weeds classified as grasses and grass-like (Sedges), grouped as monocotyledons and broad-leafed grouped as dicotyledons. Nearly 150 weed species (both broad and narrow leafed) including annuals, perennials and parasitic weeds have been observed in sugarcane fields in different parts of the sugarcane growing zones in the country (Fig 1 and 2). The weed flora differs from location to location due to variation in agro-ecological conditions and management practices. The most troublesome broad leafed weeds of major economic importance are listed as follows:

Page 14

Me

tho

d

Rate

/ha

Ksh

s/U

nit

Co

st/h

a(K

sh

s)

Han

d

we

ed

ing

(Ks

hs)

Lab

ou

r co

st o

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ray

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(Ks

hs)

To

tal

co

st (K

sh

) %

of h

an

d w

ee

din

g

Ve

lpa

r 1

kg

/ha

4,3

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4,3

50

4,5

00

(15 x

30

0)

9

00

(3 x

30

0)

9,7

50

43

Rou

nd

-up

2L

/ha

1,1

00

2,2

00

4,5

00

90

0

7,6

00

34

We

ed

ing

16

md

x5

30

0

22

,50

0

22

,50

0

-

2

2,5

00

10

0

Se

nco

r 2

L/h

a

2,5

50

5,1

00

4,5

00

90

0

1

0,5

00

47

Striga hermonthica Striga asiatica

Tagetes minuta

Sesbania sesban

Cleome monophylla

Portulaca oleracea

Amaranthus hybridus

Amaranthus

graecizans

Acanthospermum

hispidum

Page 13 Page 2

Table 1: Comparison of weed control methods (Cost benefit

analysis)

Note:

1. 3md for spraying = 3 man days @ Kshs: 300 =

900

2. Each weeding = 15 man days @ ha

Page 3 Page 12

Biden pilosa

Datura stramonium Ageratum conyzoides

Sida alba

Emex australis

Polygonium

convolvulus

Leucas aspera

Commelina

benghalensis

Crotalaria pumila

Recommended Herbicides

The following recommended herbicides are in current use in

the Kenya sugar Industry:

Pre-emergence

1. Diuron alone at 3.75kg/ha for broad leafed weeds

2. Diuron at 2.5 kg/ha and Velpar at 750gm or 1kg/ha

(clay soil or sand loam soil); respectively as a cocktail

for both broad and narrow leafed weeds administered

as a pre or early post-emergence application

Post-emergence

1. Gesapax combi at 6 l/ha for both broad and narrow-

leafed weeds

2. Gesapax combi at 4 l/ha and Actril DS at 1.5 l/ha as a

cocktail for both broad and narrow leafed weeds

3. Velpar 75 DS at 1 kg/ha or 750 gm/ha on clay or sand

loam soil for both broad and narrow-leafed weeds

4. Glyphosate 480a/g at 2 l/ha for grass weeds

5. Glyphosate 480 a/g at 2 l/ha and Sencor at 2l/ha for

both broad and narrow leafed weeds

When a cost benefit analysis is done to compare hand weeding

done 5 times compared with herbicides application once and

one hand weeding it showed that it is more cost effective to

combine herbicide and compliment with hand weeding as

compared with only hand weeding alone (Table 1).

Page 11 Page 4

Corchorus olitorus

Galinsoga parviflora

Conyza stricta

Among the narrow leafed weeds of economic importance

are listed both as grasses and sedges; in order of their

importance in the sugarcane growing areas as follows:

Economic importance of weeds

Sugarcane initial slow-growing phase faces an acute

competition from weeds. Weed problems vary according to

agro-ecological regions and management practices. The losses

due to weeds comprise the following;

(i) direct yield losses resulting from competition,

(ii) indirect losses from reduced crop quality,

(iii) increased costs in harvesting,

(iv) poor land preparation, and

(v) harbouring insects’ pests and diseases.

Besides, weeds remove large amount of nutrients from soil.

Direct yield losses ranged from 11-74% or more depending

upon the nature and intensity of weed flora and period of

occurrence of weeds. It has also been report that climbing

weeds such as morning glory (Ipomoea purpurea) infests

sugarcane crop and causes 20-25% reduction in cane yield by

twining around clumps, bending canes, and damaging tops

Chemical method

The use of selective herbicides has a great scope in

eliminating crop-weed competition over a long period spell

of time and help in increasing cane yield. Generally,

application of single herbicide may not be effective in

controlling weeds in sugarcane because of a great diversity

in weed flora and a longer duration required in suppressing

the weeds which come in several flushes. Pre-emergence

application of Sencor at 2l/ha, Atrazine at 2.0 l/ha, Diuron at

3.0 kg/ha each followed by Round up (Glyphosate 480g/l) at

2 l/ha as post-emergence are effective for grasses or Velpar 75

DF at 700 gm or 1 kg at sandy or sandy clay loamy for broad-

spectrum weed control in sugarcane had been found to be

very effective.

Figure 8: Knapsack hand spray application of herbicides on cane

field infested with Couch grass (KESREF-Kibos sugar zone)

Page 5 Page 10

Figure 2: Major narrow leafed weeds (grasses and sedges) of economic

importance in the sugar industry

Digitaria scalarum

Sorghum halephense

Imperata cylendrica

Cynadon dactylon

Panicum ripens

Panicum maxumum

Setaria verticilliata

Cyperus rotundus

Cyperus esculentus

Trash mulching: Sugarcane after it had been harvested

generates lots of trash. Soon after emergence of cane,

trash covers of about 10-12 cm thickness should

ideally be spread in between cane rows. Trash cover

restricts sunlight and checks weed emergence.

Besides suppressing weeds, trash mulching also

conserves soil moisture, and provides a potential

source of organic matter (Fig 7).

Figure 7: Blanket trash mulching of harvested cane field

(Chemelil sugar zone)

Page 9 causing stalks to remain underdeveloped and interfering with

harvest operations. Johnson grass (Sorghum halepense) has been

observed as an alternate host of sugarcane stalk borer

(Chilotraea auricilia). The sedges (Cyperus esculentus and Cyperus

rotundus), Barnyard grass (Echinochloa crus-galli) and Couch

grasses (Digitaria scalarum) (Fig 3) are water loving weed

species which do cause enormous impediment to the growth

and development of sugarcane by blocking water drainage

and even complicate manual weeding of the crop (Radosevich

et al, 1997, Rono et al., 2002). These water loving grass-like

sedges, barnyard grasses and couch grasses are found mostly

in poorly drain cotton clay soils of Kibos, Miwani, Chemelil

and Muhoroni sugar zones; whereas in Mumias and South

Nyanza zones they are concentrated on lowland clay to loam

soils.

Figure 3: Young sugarcane crop infested with couch grass (Digitaria

scalarum)-Miwani sugar zone

Page 6

Intercropping: Sugarcane is planted in wider-row spacing of 1.2

to 1.5m. This provides an ideal opportunity for weeds to

emerge in a large numbers and infest sugarcane crop.

Inclusion of short duration crops like potatoes, blackgram,

greengram, cowpea, beans, maize, sorghum and other quick

growing intercrops in these row spaces can suppress weed

growth to a great extent. Inter-row crops planted in sugarcane

have been found quite effective in weed suppression and

higher cane yields (Fig 6). Additionally, this is another means

of alleviating poverty or generating some much needed

household income to him or her.

Figure 6: Beans intercropped with sugarcane (Ivakale location – West Kenya))

Page 8 Page 7

Bermuda grass (Cynodon dactylon), the alang –alang grass

(Imperata cylindrica) are known to play as alternate hosts to

ratoon stunting disease of sugarcane. Thus weeds essentially

harm young sugarcane sprouts by depriving them of moisture,

nutrients and sunlight. Poor growth of cane resulting from

weed infestation also affects quality.

Methods of Weed Control Mechanical method

Since sugarcane rows are widely spaced at 1.2 to 1.5m,

shallow-rooted weeds can be managed by hoeing with hand

tools or with intercultural operations during growing season

of crop (Fig 4). Generally, 3-4 hoeing are required after every

each operation during tillering phase of crop to check crop-

weed competition. The removal of weeds by mechanical

means is laborious and expensive, and weeds in intra-row

spaces are not killed. Besides, due to unfavorable weather like

during rainy season or water logged soil conditions,

mechanical weeding may not be a favourable option.

Figure 4: Mechanical cultivation for weed control in sugarcane

crops near Belle Glade, FL, 2004.

Cultural methods

Weeds in sugarcane could be managed to a large extent by

cultural practices such as crop rotation, intercropping,

mulching, etc.

Crop rotation: Certain weeds have an association with

sugarcane crop and hence, monocropping of sugarcane may

lead to severe crop-weed competition. Inclusions of green

manure crops or fodder crops like sorghum, sweet potatoes

(Fig 5a), ground nuts, beans not only suppress weeds but also

help in crop diversification for the small scale farmer,

especially those interested in dairy keeping in small units and

by so doing they are alleviating poverty and generating some

much needed household income to him or her. Alternatively,

leaving the field fallow for a period of one to two years also

reduce build up of pests and diseases associated with

sugarcane crop (Fig 5b).

Figure 5a: Sugarcane border field planted with sweet potatoes,

Ivakale, West Kenya, and (b): left fallow for one year (Chemelil zone)