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II. Weed Flora of Upland Rice

II. Weed Flora of Upland Rice

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286



S. SANKARAN AND S. K. DE DATTA



rice were the grasses E. colona, E. indica, Paspalum conjugatum Berg., C.

dactylon, and Digitaria ciliaris (Retz.) Koel. and the broadleaf weeds Physalis

angulata L., Amaranthus spp., Cleome aspera Koen. ex. DC., and A. conyzoides.

The area planted to upland rice might be expanded if Imperata cylindrica

(L.) Beauv. could be controlled.

Philippines. De Datta (1979), Lopez et al. (1980), Tasic et al. (1980), Castin

et al. (1983a,b),and Sankaran and De Datta (1984) listed the dominant weeds

in experimental plots and in farmers’ fields in the Phillippines. Moody (1983)

named 50 species of 21 families growing in upland rice. As in other Asian

countries, monocots constituted 8045% of the weed flora, followed by a

wide variety of broadleaf weeds.

The 10 most common weed species were the monocots E. colona, C.

rotundus, E. indica, Digitaria spp., Rottboellia exaltata L. f., Dacty loctenium

aegyptium (L.) Willd., and C. benghalensis and the dicots Portulaca oleracea

L., A. spinosus, and Ipomoea triloba L.

Thailand. Earlier reports on the weed flora in upland rice in Thailand have

identified 21 families and 74 species (Kanchanomai, 1975; Schiller and

Indhaphun, 1979; Teerawatsakul, 1981). The predominant weeds were C.

benghalensis, the grasses E. colona, E. indica, C. dactylon, D. ciliaris, and R.

exaltata, and the sedges C. rotundus and F. miliacea.

Vietnam. Vuong (1973) observed that the weed flora in Vietnam is

determined by soil texture and soil moisture content. He identified E. colona,

E. indica, C. iria, C. dactylon, A. conyzoides L., Ipomoea sp., and Alternanthera

sessilis (L.) R. Br. ex. R.&S. as the important weeds.



B. WEED COMPOSITION IN UPLAND RICEIN AFRICA

The upland rice weed spectrum in Africa is less diverse than in Asia.

Shifting cultivation, the common cultural practice in several African regions,

limits weed problems and diversity (Moody, 1975). There also is little

documentation of the weed problem in the African upland rice-growing

regions.

Ivory Coast. Merlier (1974, 1983) reported more than 100 weed species in

upland rice in Ivory Coast. Six accounted for 75% of the weed biomass in rice

fields: Digitaria setigera Roth ex. R.&S., Brachiaria lata (Schumach.) C. E.

Hubb., E. indica, A. hispidum, C. benghalensis, and Trianthemaportulacastrum

L. R. exaltata is a noxious weed in the Philippines and Thailand but not a

serious problem in Ivory Coast.

Sierra Leone. Jones and Tucker (1978) found that Pennisetum subangustum (Schum.) Stapf and Hubb., Sida corymbosa R. E. Fries, Cyperus sp.,



287



WEEDS AND WEED MANAGEMENT



Chlorisfasciculata (L.) Thell, and A. conyzoides were the predominant weed

species in upland rice in Sierra Leone.

Tanzania. The weed flora recorded by Ghosh (1976) in the upland rice

fields of Tanzania varied little from that in neighbouring countries. R.

exaltata, E. crus-galli, and Oryza punctata Steud. were the predominant grass

weeds. The major broadleaf weeds were C. benghalensis, Melochia concatenata L., P. oleracea, Phyllanthus odontadenius Muel1.-Arg., and Amaranthus

spp.; Cyperus compressus L. and Cyperus diflormis L. were the common

sedges.

Nigeria. At Ibadan, Nigeria, Fagade (1976) found that Chloris pilosa

Schumach. was dominant (60%) in upland rice fields, followed by A. hispidum

(20%) and A. conyzoides (5%).

Malagasy. Falais (1978) reported that Cyperus spp., R. exaltata, and A.

conyzoides were major upland weeds in Malagasy.

The most cited upland rice weeds in Africa were the annual broadleaf

weeds A. conyzoides, C . benghalensis, P. oleracea, Ipomoea spp., Euphorbia

Table I

The Most Common Weeds in Upland Rice in Latin America"



Grasses

Cynodon dactylon (L.) Pers.

Digitarin sanguinalis (L.) Scop.

x

Echinochloa colona (L.) Link

Echinochloa crus-galli (L.) Beauv.

Eleusine indica (L.) Gaertn.

Leptochloa panicea (Retz.) Ohwi

x

Oryza satiua L. (red rice)

Rottboellia exaltata L. f.

Sedges

Cyperus ferax L.

x

Cyperus rotundus L.

Broadleaves

X

Amaranthus sp.

Amaranthus spinosus L.

X

Commelina diffusa Burm. f.

lpomoea sp.

Physalis angulata L.

Portulaca sp.

(I



x



x



x



x



X



x



x



x



x



x



x

x



x



X



x

x



x

x



X



x



x



X



x

x



x

x



x



X



X



x



X



x



x



x



x

x

x



x

x



x

x



x

x



x

x

x

x

x



x

x

x

x

x



X

X



x



x

x



x

x

x



x

x

x



x

x

x



x

x



x



x



X



X



x



x



x



x



X



x



x

x

x

X



x



X



X



X



x



x



X



x

X

X



X



X



x



X



x



Adapted from Gonzalez et al. (1983).

Other weeds in Latin America are Eclipta alba (L.) Hassk., C. odoratus, and Paspalum spp.



X



288



S. SANKARAN AND S. K. DE DATTA



hirta L., and Amaranthus spp.; the annual grasses E. indica, R. exaltata, C.

pilosa, E. colona, E. crus-galli, and Pennisetum spp.; the annual sedge Cyperus

odoratus L.; the perennial grass I. cylindrica; and the perennial sedge C.

rotundus.



c. WEED COMPOSITION IN UPLAND RICE IN LATINAMERICA

Gonzales et al. (1983) collected information on weed composition in

upland rice from 13 Latin American countries (Table I). E. colona was the

most serious grass weed.



D. DISTRIBUTION

PATTERN

OF WEEDSIN UPLAND

RICE

There are 49 families of weeds in 30 upland rice-growing countries of the

world. Asia has 248 species from 44 families, Africa 163 species from 27

families, and Latin America 65 species from 15 families.

Among the families, Poaceae (gramineae) encompasses nearly 28 % of all

weed species found in upland rice. Cyperaceae and Asteraceae each represent

10%;Amaranthaceae, Euphorbiaceae, and Papilionaceae each represent 5 %;

and Commelinaceae, Malvaceae, Rubiaceae, and Convolvulaceae each represent 3% of the total weed species present. These 10 families account for more

than 74% of all the weed species reported in upland rice.

The number of times the weed species was reported, the spread of the weed

in different countries, and the extent of yield reduction caused in upland rice

were considered to determine the order of importance of weeds for each

upland rice-growing continent. The 25 most commonly mentioned weeds in

each of the upland rices of Asia, Africa, and Latin America are listed in Tables

II-IV.

C. rotundus is the most noxious weed in upland rice regions and occurs in

almost all rain-fed rice-growing countries. Holm and Herberger (1969) and

Ronoprawiro (1975) reported that C. rotundus was a problem wherever

rain-fed rice grew. C. rotundus is formidable because it has an extensive

underground root and tuber system (Holm and Herberger, 1969) and apical

dominance (Muzik and Cruzado, 1952; Smith and Fick, 1973). It also is a

problem because it germinates and grows with upland rice (De Datta, 1974a).

E. colona is the second most serious weed in upland culture, probably

because it needs less soil moisture for growth than E. crus-galli (Noda, 1977).

In order of importance, other problem weeds are E. indica, C.dactylon, E.

crus-galli, A . conyzoides, R. exaltata, C.benghalensis, P. oleracea, and C. iria.



Table I1



A Ranking of the 25 Most Important Upland Rice Weeds in Asia"

Botanical name

Cyperus rotundus L.

Echinochloa colona (L.) Link

Eleusine indica (L.) Gaertn.

Cyperus iria L.

Cynodon dactylon (L.) Pers.

Echinochloa crus-galli (L.) Beauv.

Portulaca oleracea L.

Ageratum conyzoides L.

Amaranthus spinosus L.

Digitaria ciliaris (Retz.) Koel.

Digitaria sanguinalis (L.) Scop.

Amaranthus viridis L.

Commelina benghalensis (L.)

Rottboellia exaltata L.t

Celosia argentea L.

Dactyloctenium aegyptium (L.) Willd.

Ipomoea triloba L.

Phyllanthus niruri L.

Cyperus compressus L.

Fimbristylis miliacea (L.) Vahl

Euphorbia hirta L.

Lepthochloa chinensis (L.) Nees

Commelina diffusa Burm. f.

Eclipta alba (L.) Hassk.

Trianthema portulacastrum L.



Common nameb

Purple nutsedge

Jungle rice

Goose grass

Rice flatsedge

Bermuda grass

Barnyard grass

Common purslane

Tropic ageratum

Spiny amaranth



Life

form'



PS

AG

AG

AS

PG

AG

AB

AB

AB

AG

Large crabgrass

AB

Slender amaranth

AB

AB

Itch grass

AG

AB

Crowfoot grass

AG

3-lobe morning glory AB

Niruri

AB

AS

AS

AB

Garden spurge

AG

Spreading day flower AB

Yerba-de-tag0

AB

Horse purslane

AB



Family



Countries where reportedd



Cyperaceae

Poaceae

Poaceae

Cyperaceae

Poaceae

Poaceae

Portulacaceae

Asteraceae

Amaranthaceae

Poaceae

Poaceae

Amaranthaceae

Commelinaceae

Poaceae

Amaranthaceae

Poaceae

Convolvulaceae

Euphorbiaceae

Cyperaceae

Cyperaceae

Euphorbiaceae

Poaceae

Commelinaceae

Asteraceae

Aizoaceae



BND, IND, IDO, JPN, PHI, SLK, THI

BND, IND, IDO, SLK, VIE, PHI, THI

BND, IND, IDO, JPN, PHI, SLK, VIE

BND, IND, IDO, JPN, KOR, PHI, VIE,THI

BND, IND, IDO, PHI, SLK, VIE, THI

BND, IND, JPN, KOR, SLK, THI

IND, IDO, JPN, KOR, PHI, THI

IND, IDO, JPN, PHI, VIE, THI

BND, IND, IDO, PHI, THI

IND, IDO, JPN, KOR, THI

BND, IND, IDO, PHI

IND, IDO, JPN, THI

IND, PHI, THI

PHI, THI

BND, IND, PHI, SLK

IND, PHI, THI

BND, PHI, VIE

IND, IDO, PHI

IND, IDO, PHI, THI

IND, SLK, THI

IND, PHI, THI

JPN, PHI, THI

PHI, SLK, THI

IND, IDO, THI

IND, PHI, SLK



Number of

references

41



36

29

19

24

14

12

10

13

9

10



8

15



5

5

10

10

11



5

10

6

6

3

6

4



Based on their occurrence and/or yield reductions reported in rice.

Standard common names of weeds. -, Not available.

'AG, Annual grass; AB, annual broadleaf; AS, annual sedge; PG, perennial grass; PS, perennial sedge.

BND, Bangladesh; IND, India; IDO, Indonesia; JPN, Japan; KOR, Korea; PHI, Philippines; SLK, Sri Lanka; VIE, Vietnam; THI, Thailand.

a



Table m

N



A Ranking of the 25 Most Important Upland Rice Weeds io Africa"



B



Botanical name

Cyperus rotundus L.

Eleusine indica (L.) Gaertn.

Ageratum conyzoides L.

Rottboellia exaltata L.f.

Commelina benghalensis L.

Portulaca oleracea L.

lpomoea spp.

Cyperus odoratus L.

Chloris pilosa (L.) Schumach.

Acanthospermum hispidum DC.

Echinochloa colona (L.) Link

Euphorbia hirta L.



Common nameb

Purple nutsedge

Goose grass

Tropic ageratum

Itch grass

-



Common purslane

-



-



Bristly starbur

Jungle rice

Garden spurge



Life

form'

PS

AG



AB

AG

AB

AB

AB

AS

AG

AB

AG

AB



Family



Countries where reportedd



Cyperaceae

Poaceae

Asteraceae

Poaceae

Commelinaceae

Port ulacaceae

Convolvulaceae

Cyperaceae

Poaceae

Asteraceae

Poaceae

Euphorbiaceae



GHA, MAL, NIG, TNZ, SLE, IVO, SEG

MAL, NIG, SLE, IVO, SEG

MAL, NIG, SLE, IVO

MAL, NIG, SLE, IVO

GHA, TNZ, IVO

MAL, TNZ, IVO

NIG, IVO

NIG, IVO

NIG, IVO

NIG, IVO

IVO, GUI, SEG

MAL, SLE, IVO



Number of

references

12

7

6

6

5

4



3

3

3

3

3

3



Echinochloa crus-galli (L.) Beauv.

Digitaria spp.

Amaranthus spinosus L.

Amaranthus viridis L.

Solanum nigrum L.

Stachytarpheta spp.

Bidens pilosa L.

Aspilia spp.

Tridax procumbens L.

Pennisetum spp.

Dactylocteniurn aegyptium (L.) WillId.

Boerhavia diffusa L.

Imperata cylindrica (L.) Beauv.

a



2



Barnyard grass

Barnyard grass

Spiny amaranth

Slender amaranth

Black nightshade

Nettle leaf vervain

Hairy beggarsticks

-



Crowfoot grass

Spiderling

Cogon grass



AG

AG

AB

AB

AB

AB

AB

AB

AB

AG

AG

AB

PG



Poaceae

Poaceae

Amaran thaceae

Amaran thaceae

Solanaceae

Verbenaceae

As teraceae

Asteraceae

As teraceae

Poaceae

Poaceae

Nyctaginaceae

Poaceae



NIG, TNZ

IVO

IVO

IVO

IVO

IVO

IVO

IVO

IVO

IVO

IVO

IVO

IVO



Based on their occurrence and/or yield reduction reported in rice.

Standard names of weeds. -, Not available.

AG, Annual grass; AB, annual broadleaf; AS, annual sedge; PG, perennial grass; PS, perennial sedge.

GHA, Ghana; MAL, Malagasy; NIG, Nigeria; TNZ, Tanzania; SLE, Sierra Leone; IVO, Ivory Coast; GUI, Guinea; SEG, Senegal.



2

3

3

3

3

3

2

2

2



2

2

2

2



Table IV

A Ranking of the 25 Mast Important Upland Rice Weeds in Lath America'



W

N



Botanical name



Common nameb



Life

form'



Family



Countries where reportedd



N



Echinochloa colona (L.) Link



Jungle rice



AG



Poaceae



Cyperus rotundus L.



Purple nutsedge



PS



Cyperaceae



AS



Cyperaceae



Cyperus odoratus L.



-



Cynodon dactylon (L.) Pers



Bermuda grass



PG



Poaceae



Oryza sativa L.



Red rice



AG



Poaceae



Rottboellia exaltata L.f.

Ipomoea spp.



Itch grass

Morning glory



AG

AB



Poaceae

Convolvulaceae



Eleusine indica (L.) Gaertn.

Digitaria sanguinalis (L.) Scop.



Goose grass

Large crabgrass



AG

AG



Poaceae

Poaceae



MEX, GUA, HON, SAL, NIC, CR,

PAN, VEN, COL, ECU, BOL, BRA

MEX, GUA, HON, SAL, NIC, CR,

PAN, PER, BRA

GUA, SAL,CR, PAN,VEN,COL, ECU,

PER, BRA

GUA, HON, SAL, NIC, VEN, PER,

BOL, BRA

MEX, GUA, HON, SAL, CR, PAN,

ECU, BRA

HON, CR, PAN, VEN, COL, PER, BOL

GUA, HON, NIC, PAN, COL, PER,

BRA

SAL, NIC, ECU, PER, BOL, BRA

SAL, CR, PAN, COL, BOL, BRA



Number of

references



.Id



Leptochloa panicea (Retz.) Ohwi

Amaranthus spinosus L.

Echinochloa crus-galli (L.) Beauv.

Commelina diflusa (Burm. f.)

Portulaca sp.

Physalis angulata L.

Ischaemum rugosum Salisb.

Sorghum halepense (L.) Pers.

Eclipta alba (L.) Hassk.

Paspalum spp.

Ixophorus unisetus. (Pers.) Schlecht.

Malachra spp.

Bidens pilosa L.

Cassia tora L.

Cenchrus echinatus L.

Panicum fasciculatum Sw.



Red sprangletop

Spiny amaranth

Barnyard grass

Spreading daytlowei

Purslane

Ground cherries

-



Johnson grass

Yerba-de-tag0

-



Hairy beggarsticks

Sicklepod

Southern sandbur

Brown top panicum



AG

AB

AG

AB

AB

AB

AG

AG

AB

PG

AG

AB

AB

AB

AG

AG



Poaceae

GUA, HON, NIC, CR, PER, BOL

Amaranthaceae SAL, CR, PAN, PER, BRA

CR, ECU, PER, BRA

Poaceae

Commelinaceae MEX, CR, PAN, BRA

Portulaceae

NIC, CR, PAN, BRA

CR, PAN, PER, BOL

Solanaceae

Poaceae

PAN, COL, PER

MEX, NIC, PER

Poaceae

Asteraceae

PAN, COL, ECU

PER, BOL,BRA

Poaceae

Poaceae

SAL, NIC, CR

Malvaceae

NIC, CR, PER

Asteraceae

PAN, BRA

Caesalpiniaceae COL, PER

Poaceae

NIC, BRA

Poaceae

HON, PER



6

5

4

4

4

4

3

3

3

3

3

2



2

2

2

2



W

rD



Based on their frequency of occurrence and/or yield reductions reported in rice.

Standard common names of weeds. -, Not available.

' AG, Annual grass; AB, annual broadleaf; AS, annual sedge; PG, perennial grass; PS, perennial sedge.

MEX, Mexico; GUA, Guatemala; HON, Honduras; SAL, El Salvador; NIC, Nicaragua; CR, Costa Rica; PAN, Panama; VEN, Venezuela; COL,

Colombia; ECU, Ecuador; PER, Peru; BOL, Bolivia.



294



S. SANKARAN AND S. K. DE DATTA



111. ECOLOGY OF UPLAND RICE WEEDS

A. FACTORS

INFLUENCING THE WEED FLORA

IN UPLAND RICE FIELDS

Weed distribution in upland rice is influenced by several environmental

and management factors. Janiya et al. (1983) reported that the emergence

pattern of weed species was governed mainly by soil moisture from 0 to 15 cm

as influenced by rainfall. The type and number of weeds growing with

preceding crops, weeding treatments, and soil moisture content before and

after crop establishment (Janiya et al., 1983) determined the weed flora.

Studies in West Africa showed that weed infestation in rice grown on newly

cleared forest lands is much less than on land cultivated for several years

(Merlier, 1978). Savanna regions and short-term fallows in forest zones have

heavy weed infestations that increase risk and labor requirements beyond

economic levels (USDA/USAID, 1968; Brown, 1969; Cates, 1969; Aryeetey,

1970; Moody, 1973).

The weed flora of upland rice do not vary between climatic zones, although

rice is cultivated from forests through savannas to mid-altitudes (Akobundu

and Fagade, 1978). However, population intensity and dominant species

vary. R. exaltata may be the major weed limiting rice production in one area,

while E. colona may predominate in another area of the same climatic zone.

A. conyzoides and Tridax procumbens L. are broadleaved annuals found in

mature rice. They continue to germinate following dissipation of herbicides

or after the last hand weeding. They have little effect on yield but interfere

with harvest and harbor rodents.



B. SHIFTSIN WEED FLORA

DUETO WEED CONTROL METHODS

One study suggests that Compositae and Commelinaceae species become

dominant in fields where other weeds have been controlled with preemergence herbicides (Akobundu and Fagade, 1978). Bhandari and Moody (1981)

reported that C. rotundus populations increased in plots where

pendimethalin' was used to control R. exaftata in rain-fed, rice-based

cropping systems. A similar shift favoring C. rotundus was reported by

Navarez et al. (1983) when preemergence pendimethalin was followed by

postemergence 2,4-D in rice and when pendimethalin was applied preemergence in the succeeding mungbean [Vigna radiata (L.) Wilczek] crop to

control R. exaftata in a rice-mungbean sequence. Munroe et al. (1981)

'See Appendix for complete chemical names.



WEEDS AND WEED MANAGEMENT



295



reported that continued application of butachlor caused a shift from monocots to dicots. Sankaran and De Datta (1984) reported that C. benghalensis,

an annual broadleaf weed, became dominant in upland rice when R. exaltata

was completely controlled by preemergence applications of pendimethalin. A

shift favoring slow-growing broadleaf weeds over fast-growing annual grasses

is desirable because it significantly reduces weeding time. Unfortunately, the

shift sometimes is from a moderately easy-to-control weed to one that is

difficult to control (Mercado, 1983).



c. ADAPTATIONAND GROWTHOF WEEDS IN UPLAND RICE

Iwata and Takayanagi (1974a) reported that D. ciliaris seeds were more

adaptable to low soil moisture content (40% of field capacity) than upland

rice and other weeds such as P . oleracea, Amaranthus retro$exus L., and E.

indica. E. indica was more adaptable to high soil moisture content, even

waterlogging, than other weeds.

Iwata and Takayanagi (1974b) studied the growth rate of D. ciliaris and

upland rice sown at the same time in monoculture and mixed culture. The

optimum growth period of Digitaria was shorter, but the growth increments

during the period were larger than those of rice. In mixed cultures, Digitaria

reduced the number of tillers, the plant height, and the dry weight of rice.

In West Africa, perennial weeds of cleared, drier forest and derived savanna

zones include Cyperus spp. and I. cylindrica. Their rhizomes make them more

difficult and expensive to control than annual weeds. Infested areas are

generally allowed to lay fallow for several years before rice is planted again

(Akobundu and Fagade, 1978).



IV. WEED COMPETITION

A. THEUPLAND

RICE ECOSYSTEM

Weed competition largely governs the development of upland rice. The

usual low yield of upland rice has been attributed mainly to inadequate and

irregular moisture supply, heavy weed infestations, lack of suitable cultivars,

nutritional imbalance, and inadequate cultural practices, including inefficient

control of disease and insect pests (De Datta and Beachell, 1972). Among

these limiting factors (except poor water supply), inadequate weed control is,

perhaps, the most difficult constraint to increasing upland rice production

(De Datta, 1972; Madrid et al., 1972).



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