A new cotton crop protection programme in Cameroon

protection

programme

in Cameroon

Note: all prices quoted in CFA francs were before the devaluation.

In 1992, 13 000 ha

of cropland was treated

by cotton producers

in Cameroon as part

of a new pesticide

protection programme

developed

by the Cameroonian

Institut de recherche

agronomique. Scientists

have tested very low

pesticide doses to address

the economically

motivated wishes of

farmers and development

agents to minimize

pesticide use.

This unique operation

in French-speaking Africa

was welcomed

by the agricultural

community: effective,

inexpensive

and environment-friendly.

S

i n c e 1 9 7 6 , t h e S o c ié t é de d é v e lo p p e m e n t du c o to n du C a m e r o u n ( S O D E C O T O N ) has been using the ultra low volume (ULV) spraying technique extensively for pesticide treatm ents at doses of 3 l/ha.

This technique, however, is relatively ineffective in c o n tr o llin g hom op te- rans (aphids and aleurodes) due to insufficient pesticide coverage in the m id d le and at the base o f sprayed c o tto n plants. These pests became a m a j o r p r o b l e m in t h e 1 9 8 0 s , prom pting further research and sub­ sequent develo pm ent of the very low v o lu m e (VLV) spraying technique at 10 l/ha, using w ater as the solvent. A p p r o x im a t e ly 2 000 ha o f co tto n c r o p l a n d w e r e t r e a t e d b y t h is technique in 1991.

Extension o f this new te chnique led to e x p e rim e n ts on a lte rn a tiv e pest c o n t r o l s tr a t e g ie s . T h e c o n t r o l J.-P. DEGUINE CIRAD-CA, IRA-CRA M a ro u a , BP 3 3 , M a ro u a , C am eroon G. EKUKOLE IRA-CRA M a roua , BP 3 3 , M a ro u a , C am eroon p r o g r a m m e s d e r i v e d f r o m t h is research are m o re c o s t - e ff e c tiv e , p ro v id e s u ffic ie n t pest p ro te c t io n , are w ell adapted to cotton cropping c o n d i t i o n s in C a m e r o o n and are environment-friendly.

Staggered-targeted

control

O f th e f iv e p ro p o s e d c o n t r o l p r o ­ grammes (inset on the next page), the best results so far, in terms of control e ffe c tiv e n e s s and t r e a tm e n t cost, have been obtained w ith "staggered- targeted c o ntrol" (Tables 1 and 2). In h ig h p e s t- p r e s s u r e s i t u a t i o n s , as occurred in the southeastern Bénoué region in 1992, staggered-targeted control provided more effective pest p r o t e c t io n th a n th e c o n v e n t i o n a l "d ose -fre qu en cy c o n tr o l" p ro g ra m ­ me. The efficiency of the staggered- targeted te c h n iq u e is e nhanced by the fact that active ingredients and dosages can be m odified according to t h e m a g n i t u d e o f th e p est outbreak.

The staggered-targeted co ntrol p ro ­ gramm e is a pp ropriate for the a gri­ cu ltu ra l e n v iro n m e n t in C am eroon and re a s s u r in g f o r s m a l l h o ld e r s . Indeed, smallholders can preschedule

cro p protection

Five pesticide control

programmes for cotton

T h e c o n v e n t i o n a l u lt r a lo w v o lu m e ( U L V ) control programme

This is a scheduled programm e. Six o r seven ULV spraying treatments are c onducted every 14 days fro m day 45 after em ergence, w ith ready-to-use fo rm u la tio n s (1-3 l/ha). T his has been the m ost w id e ly -u s e d p ro g ra m m e in C a m e ro o n o v e r the last 15 years o r so.

The dose-frequency control programme

This is a scheduled program m e that begins on day 45 after em ergence. There are 1 2 -14 V LV treat­ m ents c o n d u c te d on a 7 -d a y basis, u s in g o n e third the standard dose o f the con ven tiona l ULV programme. The active ingredient doses are redu­ ced because o f the increased spraying frequency. This program m e has been successfully extended since 1989 despite the increased labour involved, w ith an estim ated 2 5 -3 0 % savings as com pared to the con ven tiona l programme.

The staggered control programme

The staggered con tro l program m e begins on day 45 after emergence, w ith a V LV leaf ap plic a tio n every 14 days, and a total o f 6-7 treatm ents per crop season. The active ingredients are predeter­ m in ed, but the doses are set after a fie ld survey c a rrie d o u t the da y b e fore tre a tm e n t. T his was a fo r e r u n n e r to the stag ge re d -ta rg e te d c o n tro l programme.

Farmers can save 30 % by using this program m e as com pared to the con ven tiona l technique.

The staggered-targeted control programme

The schedule for this pro gra m m e is the same as that d e scribe d fo r staggered c o n tro l. H o w e v e r, both the type o f active ingredients and doses are determ ined after a field survey carried out the day b e fo re tr e a tm e n t. T h e s p ra y in g tre a tm e n ts are conducted at very lo w v olum e.

This staggered-targeted c o n tro l p ro gra m m e was tested on 2 0 0 0 ha in 1991 a n d 13 0 0 0 ha in 1992, resu lting in 5 0 % savings as c o m p a re d to the con ven tiona l con tro l programme.

The sensu stricto intervention threshold control programme

W ith this programme, the treatm ent dates, active ingredients and doses are determ ined after a pest survey in the field.

This program m e was tested on 10 ha under n o r­ m al fie ld c o n d itio n s in 1991, re s u ltin g in 6 5 % saving s as c o m p a r e d to th e U L V p r o g r a m m e . H o w e v e r, farmers and extension agents have to be f u l l y t r a i n e d o n h o w t o i m p l e m e n t th e programme. It has not yet been adapted for large- scale ap p lic a tio n s , but this w o u ld be o f interest so t h a t f a r m e r s c o u l d m a n a g e t h e i r o w n smallholdings.

T a b le 1. P esticide p r o te c tio n cost b r e a k d o w n : in c lu d in g p e s tic id e c o m p o u n d s , batteries, e q uipm en t de preciation and observer allow ances (CFA francs/ha).

Programme 1989 1990 1991

C onventional U L V * 20 870 15 800 15 800 Staggered VLV con tro l 14 540 -

-Staggered-targeted 7 950 7 180 VLV control

* Last treatment cancelled in 1990 and 1991. 1 French franc = 50 CFA francs

$1 US = 290 CFA francs

Table 2. Pesticide c o m p o u n d saving, expressed in a con ven tiona l programme.

as a percentage o f quantities used

C onditions Pyrethrinoids O rganophosphorus acaricides aphicides Staggered control (1988 test) 41 30 50 Staggered control (1989, pre-extension) 32 50 45 Staggered-targeted control (1990, test) 48 100 50 Staggered-targeted control (1990 pre-extension) 44 99 54 Staggered-targeted control (1991, test) 50 100 24 Staggered-targeted control (1991, pre-extension) 46 0 48

Test: research station plot. Pre-extension: field plot.

treatment dates and, after consulting w i t h S O D E C O T O N , d e c id e u p o n w h a t products and doses to use for the best control results against speci­ fic pests; they can therefore adjust th e ir bud ge ts a c c o r d in g to needs. W i t h th e a s s is ta n c e o f e x t e n s io n agents, field surveys are q uite easy to carry out, i.e. pest insect detection is f a c i l i t a t e d b y th e f a c t t h a t no endophagous caterpillars are present.

Finally, this method is suitable for the re la tiv e ly m ild e n v iro n m e n ts often e n c o u n t e r e d in C a m e r o o n , i.e . d a m a g e is l i m i t e d a nd th u s c r o p y i e l d s are o n e t h i r d h i g h e r th a n obtained w ith o u t treatment.

Technical

implementation

Since 1990, SO DECO TO N has been s te a d ily e x t e n d in g th e staggered- targeted control programme through some Associations villageoises auto­

gérées (AVA) — self-managed small­

h o ld e r groups — that were chosen according to several criteria:

- experience w ith VLV spraying; - the goo d re p u ta tio n o f the A V A , and farmers' receptiveness;

- the p ro fes s io na l m o t iv a t io n and dedication of the A V A coordinator in charge o f surveys and treatments.

Observation criteria and conditions

Data for 25 cotton plants are pooled for each observation c rite rio n . The quadrat infestation value is the mean for all qua­ drats. This value is then com pared to the intervention threshold (Table 3).

Carpophagous caterpillars

T he o b s e r v e r c o u n t s t h e n u m b e r o f la r v a e o n t h e c o t t o n p l a n t , w i t h a l l species pooled, i.e. Helicoverpa armigera,

Diparopsis watersi, and Earias spp.

Syllepte derogata

The observer notes the num be r o f rolled leaves infested by at least o n e S y lle p te

derogata larva on a c o tto n p la n t. N o te

th a t sc ie ntis ts are s t u d y in g o th e r s a m ­ p ling techniq ues since a diagonal sample o f 25 c o t t o n p la n ts d o e s n o t a lw a y s

provide a reliable estimate o f the infesta­ tio n levels fo r this species. T his pest is som e tim e s c lu s te re d in patches w h ic h can be overlooked in the sampling.

Spider mites

The observer, w h ile c o u n tin g a le u ro d e larvae, notes the presence (1 ) or absence (0) o f spider mites.

Aphids

T h e o b s e r v e r c o u n t s t h e n u m b e r o f le a v e s , a m o n g t h e f i v e s u b t e r m i n a l leaves on the cotton plant, infested by at least one aphid.

Aleurode larvae

O n e le af is c u t fro m the m id d le part of the cotton plant. A 6.25 c m 2 area on the

u n d e r - s u r f a c e o f t h e le a f is th e n e x a m in e d w ith a m a g n ify in g glass and aleurode larvae are counted.

Adult aleurodes

The observer shakes the cotton plant and assesses the resulting c lo u d o f w h ite flies: 0: no w h ite flies

1 : a few 2: many 3: large cloud.

Table 3. Chart to facilitate decision 25 cotton plants).

-m aking for staggered-targeted c ontrol under northern Cam eroonian field c on ditions (for

1st and 2 nd treatments 3 rd and 4th treatments 5{h treatments + Threshold Dose Threshold Dose Threshold Dose

Pyrethrinoids - Carpophagous caterpillars < 6 1/2 < 6 1/2 < 6 1/2 > 6 1 > 6 1 > 6 1 Organophosphorus acaricides - S yllepte derogata < 75 0 < 100 0 < 100 0 > 75 1/2 > 1 0 0 1/2 > 1 0 0 1/2 - Spider mites < 3 0 < 3 0 not to be considered > 3 and < 5 1/2 or not to be considered > 5 1 > 5 1/2 not to be considered

Organophosphorus aphicides

- A phids

< 19 0 < 38 0 < 38 0 > 1 9 and < 3 1 1/2 > 38 and < 63 1/2 > 38 and 63 1/2 > 3 1 1 > 6 3 12 > 6 3 1 - A le uro de larvae

not to be considered < 200 0 < 150 0 not to be considered > 200 1/2 > 150 and < 200 1/2

> 2 0 0 1 - A le uro de adults

not to be considered < 50 0 > 50 0 not to be considered > 50 1/2 > 50 1/2 Dose: 0 = no pesticide; 1/2 = half-dose; 1 = standard dose.

m

m

cro p protection

Field operations

T h e A V A c o o r d i n a t o r s and z o n e agents are trained to im plem ent the cotton block design at crop emergence. They square off the area in hectares, and then 2 500 m 2 per squared-off h e c ta re is c h o s e n r a n d o m l y ; th is sample area is supposed to be repre­ s e n ta tiv e o f a s m a llh o ld e r u n it or q u a d r a t . Each q u a d r a t is s tu d ie d throughout the crop season.

The coordinator carries out an entomo­ logical survey o f the quadrat one day before treatment. This usually takes o n e d a y , o r t w o i f t h e q u a d r a t is larger than 15 ha.

Aleurode larvae survey. Photo J.-P. Deguine

The observation results per blo ck are established by calculating the mean for all assessed quadrats. The next day (treatment day) the co ordina to r decides on w hat pesticides (pyrethri- noid or organophosphorus aphicides or a caricid es) s h o u ld be used and d ete rm ine s th e doses a c c o rd in g to

inte rv e n tio n thresholds established by th e IRA ( I n s t it u t de re c h e r c h e a g r o n o m i q u e i n C a m e r o o n ) (Table 3).

Let us take, for instance, a 4 ha block w h i c h i n c lu d e s f o u r o b s e r v a t i o n quadrats, thus 4 x 2 5 cotton plants to assess. For th e firs t tre a tm e n t, th e four carpophagous caterpillar counts are as fo llo w s : 6-5-7-8, i.e. a mean result of 6.5 for the w ho le block. This indicates that a normal pyrethrinoid d o s e s h o u ld be s p ra y e d . O n th e other hand, for the second treatment, the results of the counts are 3-2-4-1 (mean 2.5). In this case, a half-dose of pyrethrinoid w o u ld be enough to stall the infestation. This reasoning w o u l d a ls o a p p l y f o r t h e o t h e r pesticide compounds.

Successful pest

control conditions

T h e s t a g g e r e d - t a r g e t e d c o n t r o l programme offers many advantages, but tra in in g and fo llo w - u p are tw o f a c t o r s t h a t m a r k its w id e s p r e a d success. T he p o lic ie s a d o p te d by S O D E C O T O N are e x e m p l a r y in this respect.

Spray treatment o f a test block by a pest control team. PhotoJ.-P. Deguine

From survey to treatment

The c o o rd in a to r assesses 25 cotton pla nts chosen r a n d o m ly a lo ng the diagonal of the quadrat, w h ic h takes about 30 min.

O n each cotton plant, this observer looks for pests in the fo llo w in g order: a d u l t a le u r o d e s , a le u r o d e and s p i d e r m i t e l a r v a e , a p h i d s , carpophagous caterpillars and finally

Syllepte derogata caterpillars.

In fact, tr a in in g is p ro v id e d fo r all d e v e l o p m e n t a g e n ts , i n c l u d i n g supervisors, field and basic staff, and A V A c o o r d i n a t o r s in c h a r g e o f carrying out the prelim inary surveys and calculating the active ingredient doses.

The apprenticeship culm inates w ith blank tests, w h ic h are conducted just before the first cotton field treatments of less than 45 days. They focus on survey o bs e rv a tion s and tre a tm e n t conditions.

F o llo w - u p is the c o tto n p ro du c er's r e s p o n s i b i l i t y . T h is p a r a m e t e r is based on pest status observations at the study plot, and involves checking dose c a lc u latio ns and active ingre­ die nt choices and certifying that the A V A coordinato rs, w h o act as m id ­ dle m e n w it h the s m a llh o ld e rs , are fu lly aware o f the overall situation. A n e tw o rk o f s u rv e y /e a rly -w a rn in g test plots is n o w being contemplated.

Extension o f the staggered-targeted c o n tro l p ro gram m e should be suc­ cessful once these tw o conditions are c o n s o l i d a t e d , i.e . t r a i n i n g a n d fo llo w -u p . In 1993, one th ird of the area intensively cropped w ith cotton (said to be " y ie ld in g " ) was treated under this programme.

Further reading

R E N O U A ., D E G U IN E J. P., 1 9 9 2 . Ravageurs et protection de la culture co to n ­ nière au Cameroun. Coton et fibres tropicales, D o c u m e n ts , s tudies and syntheses series n° 13, Montpellier, France, CIRAD-CA.

Pesticide choice and dosage. PhotoJ.-P. Deguine

Abstract... Resumen... Résumé

J.-P. D EG U IN E , G. EKUKOLE - A new cotton crop

protection programme in Cameroon.

Protection o f cotton fro m pests and diseases in Cameroon covers th re e areas: cost reduction, conservation of the e n v ir o n m e n t an d e ffe c tiv e control o f pests. Research (IR A ) an d d e v e lo p m e n t (S 0 D E C 0 T 0 N ) institutions now pro po se v e r y low v o lu m e insecticides used w ith new p r o g r a m m e s . " S t a g g e r e d -t a rg e t e d co n tro l", th e most s u ita b le s y s te m f o r t h e C a m e r o o n c o tto n b e lt, is a scheduled in te g r a te d p r o g r a m m e . S p ra y in g dates are p ro g ra m m e d in advance at 2 -w e e k intervals f ro m day 4 5 after em ergence, but doses and active ingredients are d e term in e d according to pest num bers an d types a fte r observations in the field the da y before spraying. Since its de v e lo p m e n t in 1 9 9 1 , "S ta g g e re d -ta rg e te d control" has enabled cash savings of some 5 0 % and is al least as effective as conventional spraying pro gram m es. Finally, m ore account is ta k e n o f the en viron m en ta l conservation criterion.

Keyw ords: cotton, Gossypium hirsutum, chem ical pest control, insect pests, Cameroon.

J.-P. DEGUINE, G. EKUKOLE - Nuevo programa de

protección del algodón en Camerún.

En C a m e r ú n , la p ro tecció n fit o s a n ita r ia del a lg o d ó n ev oluc io na en tres campos: la reducción de costes, la preservación del medio am b ien te y la eficacia contra los an im ales dañinos. La investigación (IR A ) y el desarrollo ( S 0 D E C 0 T 0 N ) p r o p o n e n a c t u a l m e n t e t r a t a m i e n t o s in s e c t i c i d a s a v o l u m e n m u y b a ¡ o s e g ú n n u e v o s p r o g r a m a s . El m á s a d a p t a d o a la z o n a a lg o d o n e r a c a m e r u n e s a , la " lu c h a d i r i g i d a e s c a lo n a d a " , es un pro g ra m a razonado en función del calendario. Las fechas de las aplicaciones son fijadas por ad elan tado , cada 14 días a partir del 4 5 e dia después del brote, pero las dosis y las m aterias activas se definen según la importancia y el tipo de anim ales dañinos basándose en observaciones efectuadas en el cam po la víspera del tratam ien to . Desde su desarrollo en 1 9 9 1 , la "lucha dirigida escalonada" ha perm itido rea liza r ahorros de alred ed or del 50 % con una e f ic a c ia p o r lo m e n o s ig u a l a la d e los p r o g r a m a s tradicionales. Por último, el respeto del m edio am biente es un criterio m ejo r considerado.

P alab ra s clave : a lg o d ó n , Gossypium hirsutum , lucho química, insectos dañinos, Camerún.

J.-P. DEGUINE, G. EKUKOLE - Nouveau programme

de protection en culture cotonnière au Cameroun.

Au C am eroun , la protection ph yto san itaire du cotonnier évolue dans trois dom aines : la réduction des coûts, la pré­ s e rv a tio n de l 'e n v ir o n n e m e n t et l'e ffic a c ité co ntre les ravageurs, en particulier les insectes piqueurs suceurs. La recherche (IR A ) et le dé ve lo p p em e n t ( S 0 D E C 0 T 0 N ) pro­ posent désorm ais des tra ite m e n ts insecticides à très bas vo lum e selon de n o uveau x pro gram m es. Le plus ad ap té à la zone cotonnière camerounaise, la « lutte étagée ciblée », est un p ro g ra m m e raisonné sur calendrier. Les dates des applications sont fixées à l'avance, tous les 14 jours dès le 4 5 e jou r ap rès la le v é e . M ais les doses et les m a tiè re s actives sont définies selon l'im portance et le type de ra v a ­ geurs, à p a rtir des observations effectuées au cham p la veille du traitem en t. Depuis son développement en 1 9 9 1 , la « lutte étagée ciblée » a perm is des économies m o n é ­ taires de l'o rd re de 5 0 %, avec un e efficacité a u moins aussi b o n n e qu e les p r o g r a m m e s classiques. Enfin, le respect de l'environnement est un critère m ieux considéré. Mots-clés : cotonnier, Gossypium hirsutum, lutte chimique, insecte rav ag eur, Cameroun.