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Practical identification of weeds in the Sida L. genus

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of weeds in the

Sida

L.

Researchers and professional farmers in tropical

sub-Saharan Africa are often faced with the problem

of identifying certain weeds. Complete samples,

including flowers and fruit, are required to be able

to accurately identify standard, but usually complex,

weed flora. An identification key, based on leaf traits,

is proposed for Sida L. species (Malvaceae family)

commonly found in western Africa. Species can

thus be readily identified from the first stages

of development, before flowering.

W

eed control strategies are often developed in terms of crop features when the weed flora present in the cropfield has not been f u lly c h a ra cte rize d . W eed m anagem ent should, h o w ­ ever, be based on the biological and e c o lo g ic a l c h a ra c te ris tic s o f the weed population (LE BOURGEOIS, 1993; LE BOURGEOIS & MERLIER, 1 9 9 5 ). The c r e a tio n o f s im p le practical tools for rapid identification of weeds at any development stage is t h e re fo re a m a jo r w e e d scie n c e research objective.

The present study focuses on the Sida

L. genus (M a lv a c e a e ), c o m m o n weeds of western Africa. As farmers and control operators have access to this identification key, targeted and fully adapted weed control methods could now be recommended.

N. VIAROUGE

B iology student (Université M o ntpe llier II), L'Habitarelle, 4 8 1 7 0 Châteauneuf-de-Randon,

France

P. MARNOTTE, H. MERLIER

CIRAD-CA, BP 5 0 3 5 , 3 4 0 3 2 M o ntpe llier C ede x 1, France

How the key was

developed

Data for this identification key were derived from botanical studies, most­ ly c o n d u c te d in w e s te rn A fr ic a , along w ith analysis o f h e rbarium samples.

Flora guides used

F lo r e i l l u s t r é e d u S é n é g a l

(BERHAUT, 1979) is a fully illustra­ ted flo ra guide th a t is in te re stin g because many vegetative characters are described. Flora o f West Tropical Africa (HUTCHINSON ef al., 1958) is very complete but mainly based on f lo w e r c h a r a c te r is tic s . The

H a n d b o o k o f West A fric a n Weeds

(AKOBUNDU & AGYAKWA, 1987) and the flo ra g u id e W e s t A f r i c a n Weeds (IVENS et a i , 1978) are com­ plementary works that include des­ criptions, drawings and photographs of the whole plant.

An id e n tific a tio n key has already been d ra w n up fo r the E ragrostis

W o lf genus (Poaceae family), annual weeds o f the northern Cam eroon

region, solely based on vegetative characters (LE BOURGEOIS & KAM- BA, 1991). In addition, SEMELLART (1992) published an ide n tifica tio n table for the veronicas (Veronica spp. (Tourn.) L., Scrofulariaceae family), crop weeds in France, based on leaf shape.

Table of vegetative

characters in the Sida L.

genus

Whenever possible, the descriptive elements were characterized using herbarium samples obtained from ClRAD's tropical weed science labo­ ratory and the Institut Botanique de M ontpellier (France). A table of the different vegetative characters was drawn up (Table 1 ).

The descriptions mainly concern ful­ ly-developed leaves, as the shapes of leaves under inflorescences are high­ ly v a r ia b le . The o n ly c h a ra c te rs

Sida acuta.

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Sida

L. genus

General characteristics

The Sida L. genus belongs to the M alvaceae fam ily , w h ic h can be found throu gh out the w o rld , except in very c o ld regions. It m a in ly includes herbaceous plants, w ith some bushes, but very few trees.

M a lv a c e a e leaves are alternate, ge n e ra lly stipulate, and the leaves and stems are alw a y s d o w n y . T he c o r o lla (g e n e ra lly w h ite , p in k , red o r y e llo w ) is fo rm e d by fiv e petals inserted at the base o f the cen tra l c o lu m n , w h ic h bears the stamens. The sepals, fused at the base, can be a c c o m p a n ie d b y b ra c te o le s , f o r m in g an epicalyx. The fru it is a capsule form ed by several lo c u li that c ontain the seeds. The floral diagram for the M alvaceae fa m ily is very stable for all genera.

S om e M a lv a c e a e g e n e ra are o f c o n s id e r a b le e c o n o m ic in te re s t, i.e . f o r th e pro du ction o f textile fibres extracted from the stems (Hibiscus, A b u tiló n , Urena and even Sida L.; B O U LA N G E R , 1977) o r capsules (cotton, genius Gossypium ). Some M alvaceae genera are used in ho rticultu re (Hibiscus, A b u tiló n , etc.).

The Sida genus includes weeds that can threaten crops.

Botanical features of the Sida species studied

T h e Sida L. species d e s c rib e d in th is s tu d y are g e n e r a lly a n n u a l p la n ts w h ic h som etim es lig n ify at the base and persist fo r several years. Both herbaceous and bushy plants can thus be fo u n d w ith in the same species p o p u la tio n . The density o f p u b e s c e n c e on the leaves and stems can va ry u n d e r d iffe re n t e n v iro n m e n ta l c o n d itio n s . Nevertheless, this pu bescent tra it is c o m m o n to all Sida species, and p a r tic u la r ly p ro n o u n c e d in 5. c ord it'o lia , w h ic h rem ains ve ry d o w n y th ro u g h o u t the year.

Distribution of Sida L. species

A c c o rd in g to H U T C H IN S O N (1967) qu oted by U G B O R O G H O (1983), there are 250 Sida L. species distributed throu gh out the Am ericas and warm est regions o f both hemispheres.

H U T C H IN S O N et al. (1958) id e n tifie d 11 species o f this genus in western A frica (Table 2). A m o n g these, 5. stipulata Cav. and 5. acuta Burm. f. are n o w classified as the same species; 5. scabrida W ig h t & Arn. is not m entioned in this study as it is a rare species and not considered to be a weed.

Table 2. Classification o f nine Sida L. weed species o f western A frica (from MERLIER, 1994).

V a lid name Synonyms

Sida acuta Burm. f.

Sida alba L. Sida c o rd ifo lia L. Sida garckeana Pol.

Sida lin ifo lia C. )uss. ex Cav. Sida ovata Forssk.

Sida pilosa Retz.

Sida rh o m b ifo lia L. Sida urens L.

Sida carp ign ifolia auct., non L. Sida stipula Cav.

Sida spinosa L. Sida althaeifolia Sw. Sida corym bosa R.E. Fr.

Sida g re w io ide s G u ill. & Perr. M e lo c h ia cordata Burm. f.

Sida cordata (Burm. f.) Borss. W a a lk Sida vero n ic ifo lia Lam.

Sida h u m ilis Cav. Sida riparia Hochst.

described (as simply as possible) are those th a t are c le a r ly v is ib le on plants in situ habit, stem, base and apex of the lamina, lamina margin, average size of the lamina, venation o f the lamina base, lamina pubes­ ce n ce , and the p e tio le . A m in o r exception concerns the shape of the hairs (s im p le or s te lla te ), w h ic h requires a magnifying glass or a trai­ ned eye.

The identification

key

The nine species can be d ic h o to - mously identified solely on the basis of eight leaf traits.

M ajor characters

O nly eight main characters are taken into consideration in the key (Table 3). Based on these criteria, several keys c o u ld have been d e v e lo p e d by sim ply changing the d ichotom ous order of the characters used for the identification. After investigating dif­ ferent c o m b in a tio n s , a single key was adopted for identifying species with minimum confusion. The iden­ tification begins with the plant habit, w h ic h is a very obvious character (Table 3, Figure 1 ). All other keys tes­ ted had various disadvantages. For in s ta n c e , p u b e s c e n c e c o u ld be considered in the initial identifica­ tion steps as this character is easily assessed by confirmed botanists, but it can be confusing for non-specia- lists. A key that starts with this identi­ fication criterion would therefore be unsuitable. The length of the petiole was considered as a starting point for another key. However, this measure­ ment is difficult to evaluate without comparison, and too many species have a short petiole.

Starting point: plant habit

From the key show n in Figure 1,

S. pilosa can be immediately identi­ fie d by its c re e p in g h a b it. Then

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species with a very long narrow leaf. S. ovata is identified by the rounded shape of the lamina apex. For poin­ ted apex leaves, species w ith o u t a very cordate base are separated from 5. urens, which has a clearly cordate leaf base. Then the pubescence den­ sity is considered. Very dense and f e lt - lik e d o w n y le aves in d ic a te

the p e tiole is then considered for id e n tific a t io n o f o th e r species.

S. alba is characterized by a very

long petiole. Among species w ith a short petiole, 5. garckeana is identi­ fied if the lamina margin is irregular­ ly dentated.

In the group of plants having lamina margins which are regularly dentated,

margin of S. acuta is dentate from the base, w hile that of S. rhombifolia is only dentate from the lower third.

5. r h o m b if o lia , S. acuta and 5. garckeana are m o rp h o lo g ica lly quite similar, but they can be easily differentiated on the basis o f des­ criptions given in the key.

Table 1. Table of vegetative traits of Sida L. species of western Africa.

Habit Stem General lamina shape Lamina base apex Lamina margin L* Lamina size W* R* Lamina venation Lamina pubescence Petiole

S. Pilosa Creeping Slender, roots at level of nodes Cordate Broadly cordate Acuminate Doubly dentate 5 cm ¡.25 5 Moderate Long (almost as long as the lamina) S. linifolia Upright, diffuse. Around 60 cm Woody at base, hispid Linear to lanceolate Rounded Narrowly attenuate Entire 12 cm 1.5 cm 8 3 Moderate. Simple long hairs on both surfaces Short (relative to the length of the lamina) S. ovata Upright. Around 60 cm Covered with stellate Oval elliptical Rounded slightly notched Terminated by a rounded tooth Crenellate 3 cm 2 cm 1i .50 ¡ ¡ l l l l i l f í ; Cottony, particularly on the under surface. Small stellate hairs Medium length (1/3 of the lamina). Thickened at both ends S. urens Upright. Up 0.5 to 1 m Covered hirsute simple and stellate hairs

Cordate Cordate Acuminate Dentate 5 cm 1.6 5 or 7 Considerable. Mix of simple stellate hairs Medium length (1/4 of the lamina) S. cordifolia Upright. Around 1 m Very dense pubescence of stellate hairs Oval Slightly notched, broadly rounded Obtuse truncate

Dentate 5 cm 3 cm 1.6 5 Very dense felting of stellate hairs, greater on under surface Long (about as long as the lamina). Thickened at the S. alba Upright. Up 30 to 80 cm Covered with short stellate hairs Oval Rounded or slightly notched Obtuse Finely dentate 3 cm 1.5 cm 2 ■ 5 Upper surface glabrous; stellate hairs on the under surface Long. Nearly as longas the lamina, 3 homy spurs at the base S. garckeana Upright. To 2 m Covered simple long hairs

Rhomboid Rounded Acute Irregularly dentate 14 cm 7 cm 2 5 Quite pubescent. Simple long hairs Short S. acuta Upright. To 1 m Pubescent Oval lanceolate Rounded Regularly attenuate Regularly dentate 7 cm 2 cm 3.5 3 Slightly pubescent Thickened at both ends. Much shorter than the lamina 5. rhombifolia Upright. To 2 m

Pubescent Rhomboid Truncate Obtuse Dentate on upper two thirds 5 cm 3 cm 1.6 3 Upper surface glabrous stellate hairs on the under surface Short

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Table 3. The eight characters considered in the key, in the best c h ro no log ical order for easy id en tification .

Characters Variations

H a bit creeping or uprigh t

General lam ina shape na rrow or broad

Lam ina apex shap rounded or pointed

Lamina base shape cordate o r notched, attenuated, rounded

Pubescence very dense or not

Petiole long o r short

Lamina margin regularly or irregularly dentate

Lamina margin dentate from the base or not

Species

descriptions

Sida pilosa

Retz.

S. pilosa is characterized by its cree­ ping habit, with a thin stem and roots generally emerging from the nodes. The leaves and stems are moderately pubescent. The lamina, broadly cor­ date at the base and acuminate at the apex, has a double-dentated margin. The petiole is almost as long as the lamina. The cre a m -ye llo w flowers occur singly or in pairs. This species is rarely found in dense populations or in tropical regions.

Sida linifolia

C. Juss.

Ex Cav.

S. lin ifo lia is the only species with a linear straight-margined leaf. It has an u p r ig h t and r e la tiv e ly diffuse habit. The very dark-green stem is woody at the base. Long simple hairs are clearly visible on the stem. The cen­ tral vein of the lamina is prominent.

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j p g»*.

V "

S/c/a lirtifolia.

Photo CIRAD-AMATROP

The pubescence hairs on both sides of the lamina are simple and long. The petiole is short, w ith a pair of linear filifo rm stipules arising from the base. The flowers, white with a red centre, are clustered in a terminal corymb.

BERHAUT (1979) reported finding this plant in wet regions of Senegal, g row ing in sandy soils of wooded savanna zones. It is common in fal­ lo w lands o f t r o p ic a l A fr ic a and America (LEBRUN et a i , 1991).

Sida ovata

Forssk.

S. ovata is characterized by its oval (only a slight difference in length and width) lamina and the apex is tipped with a rounded tooth. The margin is crenellate, a trait that is not found in the other Sida species (mainly denta­ te). The lamina (especially the under surface) is coated with short stellate hairs, w hich gives it a whitish, cot- ton-like appearance. The short petio­ le is thickened at both ends, with two linear stipule outgrowths. The flo ­ wers are single or paired, w ith an orange-yellowish corolla.

This species flourishes in dry regions from Senegal to Ethiopia. It is found in Egypt and as fa r a w a y as Transvaal, Saudi Arabia and India (LEBRUN et a i , 1991).

Sida urens

L.

S. urens has an upright habit. This species is easily recognized by the sharply cordate shape of its lamina.

S. p ilo s a is the o n ly other species with a similar-shaped lamina, but it has a creeping habit. S. urens has a quite pubescent lamina, with a mix­ ture of stellate and simple hairs, and a simple dentate margin. This plant is often chlorotic, i.e. the leaves turn y e llo w and o n ly the sm all veins remain green. The petiole is quite long, h ig h ly pubescent, w ith tw o linear stipule outgrowths.

The flo ra l c o ro lla is pale orange- yellow. Glomerules of 2-10 flowers g ro w at the ends of small a x illa ry branches.

This species is q u ite c o m m o n in Senegal during the rainy season, and y e a r - r o u n d in w e t reg io n s (BERHAUT, 1979).

Sida urens.

Photo CIRAD-AAAATROP

Sida cordifolia

L.

5. c o rd if o lia has a slightly notched lamina that is broadly rounded at the base, n o t c le a r ly c o rd a te lik e

S. urens. This species can be distin­ guished by its very dense pubescence on the stems, petioles and leaves. The lamina has a velvety appearance and texture because of the densely felted stellate hairs. This coat is thic­ ker on the under surface than on dar­ ker the upper surface. The petiole is long and thickened at the apex. The flowers arise singly, or in groups of 2-4, from the leaf axils. They have a ro s e -c o lo u re d or o r a n g e - y e llo w corolla.

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Sida cordifolia.

Photo CIRAD-AMATROP

This species is c o m m o n in sandy soils of Senegal, during the rainy sea­ son and im m e d ia t e ly th e re a fte r (BERHAUT, 1979). This ruderal plant is generally found in tro p ic a l and subtropical countries, and flourishes in w e t sandy soils th ro u g h o u t the Sahel (LEBRUN eta l., 1991).

Sida olbo

L.

S. alba can be identified by its petio­ le shape. The base bears three horny spurs (or sub-spiny glands), one on each side and one below. The petio­ le is very long, almost as long as the lamina. The lamina is small (relative to the other Sida species), with a very

fin e ly dentated margin. The upper surface is glabrous, w hile the under surface is covered with stellate hairs, giving it a whitish appearance. It has single whitish flowers.

This species is common in tropical regions. It grows well in quite sandy w e t s o ils and la t e r it ie s o ils in Sudano-Sahelian regions (LEBRUN

et al., 1991 ). It is quite common in Senegal (BERHAUT, 1979).

Sido gorckeono

Pol.

An irregular dentate lam ina is the main distinguishing trait of 5. garc- keana. It has a fibrous greenish stem coated with long hairs. The lamina is rhomboid (i.e. diamond-shaped) or oval lan ce o la te . The s im p le long hairs on the lamina also differentiate th is species fro m S. a c u ta and

S. r h o m b ifo lia , w hich have stellate hairs (this difference is d iffic u lt to detect w ith the naked eye). It has single yellow flowers. S. garckeana is found in cultivated fields by road­ sides and is q u ite a b u n d a n t in N igeria (A K O B U N D U & AGYAK- WA, 1987).

Sido acuta

Burm. f.

S. a c u t a is a h e rb a c e o u s (even bushy) upright species that grows up to 1 m high. It is generally has many branches arising from the base. The lamina is oval lanceolate and slightly asymmetrical. The margin is dentate from the lamina base, i.e. the main criterion for differentiating this spe­ cies from S. r h o m b if o lia . It is only slightly pubescent. There are simple (som etim es d o u b le ) hairs on the upper surface o f the lam ina, w ith small stellate hairs on the under sur­ face. The petiole is thickened at both ends and much shorter than the lami­ na. The petiole has two linear stipule outgrow ths, one longer and more leaflike than the other. It has pale- y ellow to ochre flowers growing at the apex of an axillary penduncle. Fairly dense populations of this weed grow in w etland zones of Senegal (BERHAUT, 1979). It is one of the most c o m m o n ruderal species of

western A frica . It is found almost e v e ry w h e re a lo n g roadsides and around houses. O nce established, this species is highly competitive and considered to be one of the world's worst weeds (HOLM e ta l., 1977). In A f r ic a , it is o fte n used to make brooms because of its morphological characteristics.

Sida rhom bifolia

L.

S. rh o m b ifo lia has a very rhomboid lamina, which is the main trait diffe­ rentiating it from S. acuta. In addi­ t io n , o n ly the lo w e r t h ir d o f the la m in a m a rg in is d e n ta te , thus e m p h a sizin g its rh o m b o id shape. The upper surface of the lamina is glabrous (or bears a few very scat­ tered hairs), while the under surface is coated with short stellate hairs. A pair of filiform stipules arise from the base of the short petiole. This plant sometimes has a trailing habit, and it can grow along the ground. There are generally single, pale ye llo w to ochre flowers that grow from the leaf axils. This species has been cultiva­ ted in USA as a fodder crop. It pro­ duces a finer and more brilliant texti­ le f ib r e th a n ju te ( C o r c h o r u s L. genus). However, as the stems grow o n ly h a lf as high as those o f jute plants, the overall crop yields are lower (HENRY, 1924). S. rhombifolia

grows readily in rubble and is quite common in most tropical and subtro­ pical countries and seems to prefer wet soils. It is one of the most com­ m on ru d e ra l species in w estern Africa and found almost everywhere along roadsides and around houses.

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B ibliography

This key was designed to be simple enough for anyone without botanical training to be able to quickly identify all Sida species.

A K O B U N D U I.O., AG Y AKW A C .W ., 1987. A h a n d b o o k o f West African weeds. International Institute o f T ro p ic a l A g r ic u lt u r e O y o Road, PMB 5320, Ibadan, Nigeria, 328-337.

BERHAUT J., 1967. Flore du Sénégal. Clairafrique éditeur, Dakar, Sénégal, 485 p.

BERHAUT J., 1 979. Flore illu s tré e du Sénégal. Clairafrique éditeur, Dakar, Senegal, tome 6, 636 p.

BOULANGER J., 1977. Classification des M a lv a le s fib re s j utiè re s. C o to n et Fibres Tropicales 32 (3) : 285-290.

COLLECTIF, 1984. Flore analytique du T o g o (P h a n é ro g a m e s ). G T Z . E s c h b o rn , Germany, 751 p.

H E N R Y Y., 1 9 2 4 . P la n te s à f ib re s . Elé m ent d 'a g r ic u lt u r e c o lo n ia le . A rm a n d C o lin (sectio n a g ric u ltu re ). Paris, France, 109 p.

An

aid for integrated

weed control

Abstract... Résumé...

Resumen

N. VIAROUGE, P. MARNOTTE, H. MERLIER- Praticai

identification of weeds in the Sida L. genus. Nine Sida L. species of West African crop weeds are identified according to eight vegetative system characteristics. A table of these traits, descriptions ond drawings are proposed. Together they enable easy identification of these nine weeds without r e q u ir in g w h o le s a m p le s . T h e y a re m e a n t as aids fo r profe s s io na l f a r m e rs who do not n e cessarily h a v e ony botanical training.

K e y w o rd s : W e e d , Sida L. g e n u ,s S. acuta, S. ala b a ,

S. cordifolia, S. garckeana, S. linifoHa, S. ovata, S. pilosa,

S. rbombiloiia, S. urens, v e g etative system, identification, Africa.

With this approach, interactive iden­ tific a tio n tools have been created that are of considerable interest for field technicians, e.g. the Adventrop multimedia system, including a flora guide Adventrop. Weeds o f Sudano- Sahelian A fric a (LE BOURGEOIS & MERLIER, 1995) and a CD-ROM that was d e v e lo p e d by G RARD e t al.

(1995). This system provides a com­ plete botanical description of each of development stage, w h ile focusing on vegetative characters to enable id e n t if ic a t io n s fro m in c o m p le te samples.

Finally, it w ill be possible to evaluate integrated control procedures once insight has been gained on the deve­ lopm ent cycle of these weeds, the impact of certain cropping practices on weed developm ent cycles, and the ecological and agronomic condi­ tions required for their growth. The ultimate goal is long-term manage­ ment of weed populations. Farmers could thus avoid unwanted changes in the w eed flo ra (e.g. h e rb ic id e resistance, competition, weed propa­ g a tio n in d u c e d by c r o p p in g p ra ctice s) th a t c o u ld fo rc e them to a b a n d o n t h e ir c r o p f ie ld s (LE BOURGEOIS, 1993).

W eed control, in this perspective, could help in stabilizing agricultural systems and enhance environmental management.

H O LM L. G., PLUCKNETT D., PANCHO J. V., HERBERGER J. P., 1977. The W o rld 's Worst Weeds: Distribution and Biology. East- W est Center, U n iv e rs ity Press o f H a w a ii, Honolu lu, USA, 609 p.

H U T C H IN S O N J., DALZIEL J.M., KEAY R. W.J., HEPPER F.N., 1958. Flora o f West T ro p ic a l A frica . V o l. I part 2, 2 nd ed. The Whitefriars Press, London & Tonbridge, UK, 828 p.

IVENS G .W ., M O O D Y K., EGUNJOBI J.K., 1 9 7 8. W est A f r ic a n W e e d s. O x fo rd

University Press, Ibadan, Nigeria, 225 p. LE BOURGEOIS T.,1993. Les mauvaises herbes dans la rotation cotonnière au Nord- Cameroun (Afrique). Thesis, M o n tp e llie r II, France, 249 p.

LE BOURGEOIS T., K A M G A F., 1990. Quelques critères de détermination au stade végétatif des Eragrostis annuels, adventices des c u lt u r e s au N o r d - C a m e r o u n . W e e d Research. 31 (1) : 59-62.

LEBRUN J.-P., T O U T A IN B., GASTON A., BOUDET G., 1991. Catalogue des plantes vasculaires du Burkina Faso. CIRAD-EMVT, Maisons-Alfort, France, p. 73-74.

M A R N O T T E P., 1 9 9 0 . Listes de

mauvaises herbes de Côte d 'iv o ir e . Note T e c h n i q u e n° 1 4 /9 0 S y s t-ID E S S A -D C V . Institut des savanes. Bouaké, Côte d 'ivo ire , 50 p.

MERLIER H ., 1 9 9 4 . A c t u a lis a t io n de quelques synonymies 3rcl edition. CIRAD-CA, AMATROP, Montpellier, France, 145 p.

SENELLART J., 1 992. Les v é ro n iq u e s . Phytoma La Défense des végétaux, 439 : 23- 26.

U G B O R O G H O R.E.,1983. Evolution of

Sida L. (Malvaceae) in West Africa. Bull. Mus.

nat. Hist, nat., Paris, France, 4th sér., 5, sect. B, Adansonia n° 1 : 93-102.

N. VIAROUGE, P. MARNOTTE, H. MERLIER- Détermination

pratique des mauvaise herbes du genre Sida L.

Neuf espèces du genre Sida L. (M alv a c e a e ), adventices des cultures en Afrique de l'Ouest, sont différenciées à partir de huit critères de l'appareil végétatif. Un tableau de ces caractères, une clé de détermination pratique, un texte de description et des planches sont proposés. Ces élém ents pe rm e tte n t une déterm ination aisée de ces mauvaises herbes sans disposer d 'é c h a n t illo n s c o m p le ts . Le ur a p p lic a tio n est d e s tin é e particulièrem ent aux professionnels agricoles qui n'ont pas forcément une formation de botaniste.

Mots-clés : mauvaise herbe, genre Sida L., S. acuta, S. alaba,

S. cordifolia, S. garckeana, S. iinifolia, S. ovala, S. pilosa,

S. rbombiloiia, S. urens, appareil v ég étatif, identification, Afrique.

N. VIAROUGE, P. MARNOTTE, H. MERLIER- Determinación práctica de las malezas del genero Sida L.

Nueve especies del género Sida i IMalvaceae), adventicias de los cultivos en Africa occidental, se diferencian respecto a ocho criterios del aparato vegetativo. Se proponen un cuadro de estos caracteres, una clave de determinación práctica, un texto de descripción y planchas. Estos elementos permiten determinar fácilmente las malezas sin disponer de muestras completas. Su aplicación está destinada en especial a los profesionales agricolas que no poseen forzosamente una formación de botanistas.

Palabras clave: malezas, genero Sida i , S. acuta, S. alaba,

S. cordifolia, S. garckeana, S. Iinifolia, S. ovata, S. pilosa,

S. rhombifolia, S. urens, aparato vegetativo, identificación, Africa.

Références