4 . .C I

“I-

- 2-16 - - 217 -

LITERATURA CITADA

1. Ainsworth, G. C. 1940. The identification of certain viruses found infecting leguminous plants in Great Britain. Ann. Appl. Biol. 27:218.

2 . C.14.1./A.A.B. 1971. Bean common mosaic virus. Description of Plant Viruses. No. 73.

. 3. C-M.I./A.A.B. 1971. Cowpea mosaic virus. 2 Descriptions of Plant Viruses. No. 43.

4 . Costa, A. P. 1975. Increase in the gopulation density of Bemisjb. tabaci, a treat of widespread virus i n f z n - o f legume crops in Brasil. Diseases of Legumes. Ed. Bird and WarGorosch.

In Tropical

p. 27-49.

5. Drijfhout, E. 1978. Genetic interaction between Phaseolus vulgaris and bean common mosaic virus with implications for strain identification and breed- ing for resistance. Ph.D. Thesis, IVT, Wageningen.

6. Drijfhout, E. M., Silbernagel, M. and D. Burke. 1978. Differentiation of strains of bean common mosaic virus. Neth. J. Pl. Path. 84:13-26.

7. Pierre, P. 1975. Observations on the golden mosaic of bean (Phaseolus vulgaris L.) in Jamaica. &I Tropical Diseases of Legumes. p- 55-59.

LES NOCTUELLES (LEPIDOPTERA MOCTUIDAE) NGISIBLGS AUX CULTURES IIJDUSTRIELLES ET VIVRIEXES EY GUYANE FRANCAISE

THE NOCTUIDS (LEPIDOPTER NOCTUIDAE) DANGEROUS TO FOOD AND INDUSTRIAL CROPS IN FRENCH GUILVA

2/ J. F. Silvain L’ and F. Thiberville -

RESUME

Une revue des principales productions agricoies guyanaises est faite en signalant les problemes que posent les Lepidop- teres noctuidae aux cultures dans cette region.

industrielles et vivrieres en Guyane francaise, ou susceptibles de la devenir, est presentee. Cette liste inclue des references provenant d’autres pays de la zone neotropicale.

Une liste äes noctuelles nuisibles aux cultures

Des donnees sont fournies sur la biclogie des principales especes ainsi que sur les methodes de lutte employees en Guyane francaise contre ces insectes.

I S“RY

l Here is a review of the principal agricultural productions in French Guiana, pointing out the problens caused on the

L crops in this region by noctuid moths.

1

i

We present a list of noctuids ham.fc1, or capable of becoming harzful, to inbustrial and food crops in French Guiana. This list includes references arising from other countries in the neotropical zone.

- 1/ Chargé de Recherches, Laboratoire d‘tntomologie, Office de la Recherche Scientifique et Technique Outre-Mer, Cayenne - Guyana Francaise Service Dgpartemental d’Agronomie de la Guyane

- - 2/

- 219 - - 218 -

The d a t a is fu rn i shed upon t h e b io logy of t h e main s p e c i e s , a s w e l l a s on t h e methods employed t o c o n t r o l t h e s e p e s t s i n French Guiana.

INTRODUCTION : GENERAL REMARKS OB AGRICULTURE I N FRENCH GUIANA

A g r i c u l t u r e i n Frezch Guiana has been profoundly changing of l a t e y e a r s . r a p i d l y be ing r ep laced by modern fa rming , which i n c e r t a i n f i e l d s , may w e l l l ead t o au to - su f f i c i ency and, i n due c o u r s e , e x p o r t .

The t r a d i t i o n a l f o r e s t c l e a r i n g methods a r e

Th i s development concerns only t h e c o s t a l s t r i p . The i n t e r i o r which is t e n s e , p r i m i t i v e f o r e s t , i s p r a c t i c a l l y un inhab i t ed .

D e f o r e s t a t i o n , t h e r e l inqu i shmen t of t r a d i t i o n a l methods, t h e i n c r e a s e i n t h e c u l t i v a , t e d su r face -a rea , t h e sp read of s ing le -c rop and pe renn ia l c u l t i v a t i o n s ( p a s t u r e s , sweet l i m e , p a s s i o n - f r u i t ) , t h e use of i n s e c t i c i d e s , a l l t h e s e t echn iques have induced sudden upheavals t h a t have d i s t u r b e d t h e ba l ance between h o s t - p l a n t s , h e l p f u l i n s e c t s , c rou u e s t s . The problems caused by the la t ter have l a t e l y - assumed c o n s i d e r a b l e p r o p o r t i o n s .

S imul taneous ly a s fa rming t echn iques improve, t h e fa rmers a r e i n c r e a s i n g l y concerned by t h e damage caused by t h e s e p e s t s .

AS a r e s u l t , tbey are beginning t o a s k f o r i n fo rma t ion and t h e means t o combat c rop damage. t h e c h e c k - l i s t of t h e p r i n c i p a l t y p e s of c rop d e v a s t a t i n g i n s e c t s , a long wi th a deepe r knowledge of t h e i r ecology, shou ld a l low us t o assist t h e f a rmers i n q u i t e a cons ide rab le way.

o u t t h e p r e s e n t s tudy of noctuid-moths which a r e harmful t o c rops produced i n French Guiana.

I n g e n e r a l , a perU5al of

It i s w i t h t h i s ve ry purpose i n mind t h a t w e have c a r r i e d

THE MAIN AGRICLITURAL PRODUCTIONS - A BRIEF ACCOUNT OF THE CROP DEVASTATOR NOCTUIDS CONNECTED WITH THESE

S i n c e 1976, c a t t l e - r e a r i n g has been r a p i d l y deve loping (+ 15 t o 20% p e r y e a r , a s p e r number of heads and fodder producing s u r f a c e s ) . I n 1982, 1 2 , 0 0 0 c a t t l e - h e a d s and 4 ,650 h e c t a i r e s of p r a i r i e - l a n d were r e g i s t e r e d . w i l l be i n a p o s i t i o n t o e x p o r t beef i n t h e ve ry nea r f u t u r e . The main problem encountered by t h e fa rmers i n t h e maintenance

French Guiana

I

I

, ! i

of t h e i r p a s t u r e s , a p a r t from weeds, i s t h e Spodoptera f rug ipe rda (J. E. SMITH) noc tu id which carr cause alarming damage du r ing c e r t a i n pe r iods of t h e yea r .

Sugar cane (grown wi th a view t o producing rum) i s a t r a d i t i o n a l c u l t i v a t i o n occupying l a r g e s u r f a c e s i n t h e Cayenne and S a i n t Laurent of Maroni b e l t s . Seve ra l Leucania are p r e s e n t i n t h e s e f i e l d s . it i s , n e v e r t h e l e s s , d i f f i c u l t t o e v a l u a t e t h e e x t e n t of damage caused by t h e s e i n s e c t s due t o a l a c k of e x t e n s i v e s tudy and p r e c i s e d a t a .

b

R i c e - c u l t i v a t i o n , be it p l u v i a l (as i n t h e Cacao, Iracoubo and S a i n t Laurent b e l t s ) o r i r r i g a t i o n a l ( a s i n t h e Mana po lde r ) i s be ing g r e a t l y expanded. -~ f r u g i p e r d a and Mocis l a t i p e s has fo rced fa rmers t o c a l l upon a e r i a l - s p r a y e r s which a r e extremely c o s t l y . necessary t o work o u t a warning system.

The presence of Spodoptera

It has become

Cassava, c u l t i v a t e d t r a d i t i o n a l l y i n f o r e s t c l e a r i n g s , It w e r e planned t h a t today forms a p a r t of t h e human d i e t .

i t should s e r v e as fodder f o r c a t t l e , t hen t h i s would induce a m u l t i p l i c a t i o n of s u r f a c e s where t h i s t ube r i s grown, a s w e l l a s a mechanization of i ts c u l t i v a t i o n and h a r v e s t .

There a r e some y e a r s when two types of noctuids-moths, Spodoptera f r u g i p e r d a and Mocis l a t i p e s can make havoc of t h e ma ize p l a n t a t i o n s where i t is grown on a b i g s c a l e . However, it is worth remembering t h a t i n French Guiana maize is c u l t i v a t e d mainly i n f o r e s t c l e a r i n g s .

Every y e a r l a r g e r and l a r g e r s u r f a c e s a r e consec ra t ed t o c i t r u s f r u i t s (oranges , g r a p e f r u i t and e s p e c i a l l y s w e e t l i m e ) . I C is impor tan t t o keep a c o n s t a n t watch on t h e o rcha rds .

Pass ion f r u i t ( p a s s i f l o r e s ) i s grown on a l a r g e s c a l e by r e fugees from South E a s t A s i a , and i s produced e x t e n s i v e l y i n t h e Javouhay and Cacao reg ions . c a r r i e d o u t by t h e IRE'A (Research I n s t i t u t e f o r F r u i t s and Agrumes) i n Nontsinery.

Truck-crops, c u l t i v a t e d t r a d i t i o n a l l y on s o i l o r under ,hydroponic c o n d i t i o n s (tomatoes, cabbages, beans , s a l a d s ,

A s f o r vege tab le s o r

Experiments a r e be ing

cucumbers) o f t e n permi t two t o f o u r h a r v e s t s p e r y e a r p e r p l o t . Th i s encourages t h e r a p i d m u l t i p l i c a t i o n of noc tu ids of Spodoptera genus and of P l u s i i n a e . l o c a l f r u i t s grown on a sma l l scale i n f o r e s t c l e a r i n g s a l l

e f f e c t s of t h e s e noc tu ids f o r want of f i e ld - s tudy and i n t e r e s t on t h e p a r t of t h e farmers.

.

a long t h e c o s t a l s t r i p , l i t t l e i s known about t h e harmful t

a

(-4

One must a l s o mention t h a t the n a t u r a l m i l i e u ( f o r e s t o r savannah) acts as a s u p p l i e r of fauna both harmful and h e l p f u l t o c r o p s , and t h i s m i l i e u is l o c a t e d , i n a l l c a s e s , w i t h i n inmedia te p r o s i n i t y (from a few meters t o a few k i l o m e t e r s ) of t h e f i e l d s .

I

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0

w Y) .. d

u 3 a Y I L .4 I " 0

- 221 -

- J

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canne i sucre

sugar cane

(Saccharum off inarum L . )

--

Rir / Rice

(Oryza sativa L.)

Sorgho / Sorghum

(Sarqhum vulearc P r r s )

SoJa I Soybean

í G l y c i n e nax (LI Men)

I I

I I

'JENI 1) I

Spodoptera r r u g l p e r d a /VEN(19), BRE(4), CH(3) i- Spodoptrra ! a t i f a % i a FL'151

I 1- Gphi ina tr.opicalls FL(15) BP(4) I I - H e l i o L h i s zea I I 1

1- !;onGdonta c l i t i i d a VEN(l1 I - Coiiodonta I ncu rva FL.CdA,PA.AmSudl¿Sl I I - (ioriadnnta arg0 !

I I * I

I 1- I Spodaptera Crbglperda BRE(4)

I

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I N N W

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.-

I I ~ a n i o c I cassava i- Spodoptera s r l d a n i a I a m 4)

I I l

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u : i l i ss ina Pahl . ) I Pa t a t e doucdSwea t pa t a to I lIpn..ea ba ta tas P o i r . ) I !

I - Spodo t e r = e r l d a n i s PAIBI, B R E I . ) ) I I - Spodoztera CruRiperda PA!2), B R E I 1 I - PA( 12) Spodoptrra s u n i a

Í - H r l i o t h i s Z F ~ PA(8) i I- Anticarsia pemmatalis PAI8, 121

I

N N cn I

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2) Coton (Abattis) /Cotton1 I I (Gesypium sp.)

I l I I I

3) Culturea exp¿rimentelel

Experirental crops i --

card I carree i I I t correa sp. 1 I

I I

Arachide / Peanut I (Arachis hyaoiaea L.) I

I - A rotis r e lets BRE(4) I I - Elophris agrotina BRE(4) I I - Pletqsenta concies CdA(28) I I - Spodoptem eridania BRE(4) I I - S odo tera doiichos BRE(4) I

I - Cfllopistr?a florldcnsia BRE(4) I

I - SiodoEtcra Frupiperda fL(15). VENli9) I I CHI31 I SUR(l01 BRE(4).

. 1- Spodoptera latifascia B R E 1 4 ) i 1- Spodo tfrs marima B R E L I ) I !- 1islm:his zen FL(151. CdA(ZR1, I

PA(.?. 12). E f i E ( 4 I . I I C l I I 11 I

I N N m I

I I I

i 1- Spodcptera dolichas BAE(41 I - Sadoptera Cruliperda 68Ec4)

1- Letis nycerins CdA(28)

I I - Mocis latipes ERE141 I 4 !

I .

I .

. . , a

I l

(Eucalyptus sp.) I I l I

i I I I

BRE(4) I I I

BRE(4) 1

I I I I I 1- Spodoptern eridania B R E ( ~ )

Eucalyptus

- -- I I _ h , Y A i : : ,..:pieta Ricin / Castor been 1

(Ricinus communis) I I I - SPOdoptera eridnnia BRE(4) 1- S odo t e m fru i erda I - Siodo!tere mar:ra:

I

1- AwOtiS repleta I I - Spodo?tera cridania GdA(281, B R E ( ~ ) 1 I I - Spodoptera Cru iperds VENl19). SUR(i01 1:

VEN(19)

I I

I I

I BRE(d) I Tabac / Tobacco I

(Nicotiana tsbacum L.) I I I 1

CH(3) I

I I I I I I I I I I I I

I I I - Spodo tcra IatPTa~cia CdA(28) I I I- SpodoEtera sunis CdA(28) l I 1- Heliothis lea GdA(28). BRE(4). I

I I

I I I I

I i I I

I I I I

I

4 ) Arbres Cruitiers I I I

_ _ Fruit tmes -

I I - Spodoptera fruniperda VEN(l9)

I I

(Psidium guajava L.) I

I

Hansuier / Nango I I l l s n ~ l f e r a indice L.) 1

l Pommes cannelles

I

I Swdoptera Cru i erda VEN(19) BRE(4)

I I I 1- Spodoptcro marf:

I I 1- Conodonta clotilda Antilles I I I -- Am.Sud(251 I

i I

I I I I I

Abbreviations : FL I

I supar apple

I (Anona sp.)

.i Floride. CdA - Grandes A n t i l l e s . PA Petites Antilles, VEN i VC~&~~~,~ SUR Surinam, a B r d s i i m ccL ColOmbiCs €0 EqUateUt', CH ii Chili, Am.Sud = AmCPïqUe d;.sud. w

I

N N .J

I

7

7

- 228 - t

?-

b

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:ATA CONCEKJING THE PRINCIPAL SPECIES HARMFUL TO CROPS

Spodoptera f r u g i p e r d a (J.E. SMITE)

T h i s ex t remely polyphagous noctuid-moth is the m o s t i m p o r t a n t s p e c i e s i n French Guiana from economic p o i n t of view. fodder ( 2 4 ) , rice and soyabean. As t h e d r y season approaches , f o d d e r , and i n p a r t i c u l a r D i g i t a r i a s w a z i l a n d e n s i s , t h e one most e x t e n s i v e l y used i n French Guiana, s u f f e r s g r e a t d e v a s t a t i o n owing t o t h i s noctuid-moth i n r e g i o n s where t h i s season o f t e n causes g r a s s - d e f i c i t s .

and s h o o t i n g , t h e r e p e a t e d a t t a c k s of Spodoptera f r u g i p e r d a on p l u v i a l and i r r i g a t e d rice o b l i g e t h e c u l t i v a t o r s t o c o n s t a n t l y carry o u t expens ive i n s e c t i c i d e t r e a t m e n t s .

It is s e e n mainly on graminaceous

During t i l l e r i n g , or between the s t a g e s of t i l l e r i n g

P u l l u l a t i o n s . o f t h e Spodoptera f r u g i p e r d a c a t e r p i l l a r s on soyabean (when experimented o r c u l t i v a t e d ) have been r e p e a t e d l y observed; t h e c a t e r p i l l a r s f e e d i n g f i r s t on a d v e n t i t i o u s g r a s s e s b e f o r e a t t a c k i n g the soyabean p l a n t s .

Spodoptera f r u g i p e r d a a l s o d e s t r o y s ma2ze and sorghwn c r o p s i n French Guiana. t r a d i t i o n a l f o r e s t c l e a r i n g s , h a s r a r e l y been c u l t i v a t e d f o r i n d u s t r i a l purposes ; and when such w a s t h e case, t h e havoc worked by the caterpillars e n t a i l e d f r e q u e n t

The former, grown most ly i n

D e s t i c i d e t r e a t m e n t s - L a s t l y , it' has come t o o u r n o t i c e q u i t e by a c c i d e n t

t h a t the Spodoptera f r u g i p e r d a c a t e r p i l l a r s are found qn tomatoes and cabbages, whereas eggs and larva i n t h e f i r s t s t a g e s have been d i s c o v e r e d on c i t r u s l e a v e s ( 2 1 ) .

The s p e c i e s i s p r e s e n t a l l t h e y e a r round i n French Guiana. It can produce up t o 1 2 s u c c e s s i v e g e n e r a t i o n s . The female can l a y as many as 1 , 7 0 0 eggs i n seven c o n s e c u t i v e n i g h t s ; t h e rate of h a t c h i n g ranginq between 65 and 93%. completed i n 23 t o 26 days under t h e climatic c o n d i t i o n s p r e v a l e n t i n French Guiana. an a v e r a g e , t he female deve lops two days sooner than t h e male. s t a g e s ( D a t a o b t a i n e d on D i g i t a r i a s w a z i l a n d e n s i s ) .

The development from egg t o a d u l t i s normally

It i s noterworthy t h a t , on

T h e c a t e r p i l l a r undergoes s i x t o seven l a r v a l

i ..

! i

I

- 229 -

I n t h e p a s t u r e s , where w e s t u d i e d t h i s s p e c i e s i n f a r g r e a t e r d e t a i l , t h e Spodoptera f r u g i p e r d a popula t ions appears t o f l u c t u a t e dur ing t h e y e a r , reaching t h e i r lowest l e v e l during o r a t t h e end of t h e main d r y season (October-November) and then r i s i n g aqa in d u r i n g t h e r a i n y season (mid-Novenber t o t h e beginning of August) when w e g e n e r a l l y witness t w o o r t h r e e abundant p e r i o d s s t r e t c h i n g over two t o f o u r months. These abundant p e r i o d s a r e follcwed by p e r i o d s when t h e popula t ions drop back t o a s p a r s e l e v e l . I n t h e p a s t u r e s , pluviometry seems t o play a very impoGtant p a r t i n t h i s sequence of abundant and s p a r s e popula t ion p e r i o d s , a s do t h e working of a c r e a t p a r a s i t i c complex and t h e v a r i o u s pathogenic agents .

I n t h e case of graminaceous fodder , as i n t h a t of r ice o r soyabean, t h e economic fapor tance of Spodoptera f r u g i p e r d a d r a s t i c a l l y v a r i e s from one y e a r t o another ( p e r s o n a l o b s e r v a t i o n and 14) de3ending upon whether o r n o t t h e r e have been popula t ion explos ions . d i scovered t h a t so f a r a s graminacebus fodder and r ice w e r e concerned, they w e r e seemincly a t t a c k e d more f r e q u e n t l y dur ing t h e f i r s t few years a f t e r t h e lanci had been c l e a r e d and c u l t i v a t i o n s t a r t e d , and t h e s e a t t a c k s would consequent ly diminish g r a d u a l l y as a new e c o l o g i c a l o r d e r e s t a b l i s h e d i t s e l f .

W e a l s o

The most comnonly used p e s t i c i d e s t o f i g h t a g a i n s t . t h i s noctuid-moth are de l tamethr ine and meth ida th ion w i t h a moistening agent added on. from t h e ground or by a i r . Other p e s t i c i d e s n o t t h a t

' f r e q u e n t l y used, are a monocrotophos-parathion methyl mixture (Azobane R.) i n p a r t i c u l a r , and when it comes t o maize, d iaz inon o r fonofos applieC t o t h e c o r n e t of t h e p l a n t ( 1 4 ) .

Treatments are a p p l i e d

I n t h e case of graminaceoos fodder , t h e absence of a r e g u l a r s u p e r v i s i o n of t h e g r a s s e s reduces t h e e f f i c i e n c y of p e s t i c i d e t rea tments . are c a r r i e d o u t much t o o l a t e when t h e c a t e r p i l l a r p o p u l a t i o n s are a l r e a d y e i t h e r i n t h e l a s t s t a g e s of t h e i r development o r i n t h e pupal one. s i t u a t i o n , entomologis ts f r o n t h e O.R.S.T.O.W. Centre i n Cayenne a r e c u r r e n t l y engage2 i n working o u t a warning system based on t h e use cf pheromone t r a p s . s t u d y of t h e p o s s i b i l i t i e s of using methods of b i o l o g i c a l counter -ac t ion i n a l s o under r a y (pa thogenic and p a r a s i t i c a g e n t s ) .

I n g e n e r a l , they

T o correct t h i 3

A

n. c

- 230 - - 231 -

Other noctuid-moths of the Spodoptera genus

In French Guiana, one meets with eight other noctuids belonging to the Spodoptera genus:

- Spodoptera - Spodoptera - Spodoptera - Spodoptera - Spodoptera - Spodoptera - Spodoptera - Spodoptera

androgea (CFAr'lER) , dolichos (FABRICIUS) , avanida (Schausl , -- - ,

eridania (CRAMER), latisfacia (WALKER) , marima (SCHAUS), sunia (GUENEE) , sp., in the course of being (___ defined.

Economically speaking, Spodoptera eridania is proviEg to be the most important species among those mentioned above, being very harmful to truck crops, and especially to tomatoes, on which it is often seen. It has also been found on cabbages. The young larvae are gregarious.

has been found on tomatos and, on rare occasions on cabbages.

Pupation occurs in the soil.

Spodoptera dolichos, another pest of truck crops,

Spodoptera latifascia and Spodoptera androgea have been gathered from tomato-plants.

Spodoptera marima is a species closely resembling Spodoptera ornithogalli (GUENEE) particularly when it comes to the genitalia. Nevertheless, it is smaller in size and does not possess, in the adult stage, the sexual dimorphism of the Spodoptera ornithogalli, and replaces this species in French Guiana and Brasil ( 2 6 ) . It has been found on tomatoes.

The truck-crop farmers generally carry out preventive pesticides treatments regularly with the help of diazinon, methidathion or deltamethrine. Since truck-crops, especially tomatoes, yield Guiana, the farmers these days seem quite willing to accept the cost incurred by these treatments.

a high profit in French

Xocis latipes and Mocis disseverans

French Guiana: Mocis latipes (GUENEE) and Kocis disseverans (WALKER) .

Two species of the Mocis genus have been noticed in

i

The former of the two is principally met with on graminaceous fodder (24) and rice, but our attention has also been drawn to its presence on maize and sova- bean. As regards soyabean, the Mocis latipes cater- pillars, like the Spodoptera fru-da ones, seem to feed on the leaves only after havinq consumed the adventitious crasses present inside-the field.

In the pastures, Mocis latipes make their appearance in periods sl?=sponding to those of the Spodoptera frugi erda, and it is not rare to find caterpillars of the :wo species pullulating at the same time. This species may cause considerable devastation, although varying a great deal from year to year. It is distinguished, ever more than Spodoptera frugiperda,by its population explosions which are difficult to explain. The Mocis latiDes caterpillars and larvae, although spared by most parasites, undergo heavy predation pressure by hymenoptera Vespidae. periods, this species can barely hold its own, the lowest populations being recorded in the dry season. The female Mocis latipes has a far lower fecundity than that of the Spodoptera fruqiperda (a maximum of 350 eggs per female). In the pastures, light trapping of adult (Mocis latipes gives us a good estimate of the abundant p m s o f caterpillars of this species.

Between two abundant

--

The second species of the Mocis genus, Mocis disseverans occurs in small n u m m i n the pastures during the rainy season.

Contrary to Mocis latipes, Mocis disseverans does not appear to producepopulation explosions; it is, therefore, of far less economic importance than the former. Mocis disseverans caterpillars may be distinguished from the others by their lighter colour.

pillars of the :.locis genus of noctuids are the same as those used f-odoptera frugiperda caterpillars.

In the absence of morpholögical criteria,

The pesticide treatments applied against cater-

~~

Plusiinae

Two noctcid-moths from the Plusiinae sub-familv. economically izportant in French Guiana, are Argyrogramma A .

verruca (FABRICIUS) and Pseudoplusia includens WALKER) . Both are pests of truck-crops in this country.

f

L *

* ? P I

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Argyrogramma verruca has frequently been found on lettuce and, on rare occasions, on cabbages. When using light trapping, the abundant periods of this species occur during the rainy season from December to August.

Pseudoplusia includens, better known as 00 Cramer, has been found on tomatoes and exceptionally, on lettuce.

The pesticide treatments used against these two noctuids are identical to those mentioned in connection with the Spodoptera family, and our remarks about those treatments hold equally good for the Plusiinae noctuids.

Leucania

Several species of Leucania have been caught by light traps in French Guiana. to. distinguish between these species in their adult stage, the genitalia providing the only due permitting such a differentiation. Several species have been included in our list of noctuids harmful to crops in French Guiana, which has only indicative value, since there are far too many synonymities and confusions within this genus. For this reason, it ought perhaps to be put to a+thorough examination based on. a study of the genitalia.

It is extremely difficult

Two species of the Leucania family are secondary pests of graminaceous fodder in French Guiana: Leucania senescens MOSCHLER and Leucania jaliscana SCHAUS. former, the commoner of the two, is more or less abundant, depending on the years. It is a familiar sight in the rainy season. The second one is rare, particularly abounding from January to March.

The

Another Leucania, the Leucania microsticha HAMPSON has been discovered on sugar-cane, but its economic influence is not yet known.

No special pesticide treatments are used for Leucania. In the pastures, the treatments applied for

+ Some preliminary work, in collaboration with an American research Scientist, Dr. ADMIS, is under way in French Guiana

' and in the French West Indies.

,

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Spodoptera frugiperda and Mocis latipes are effective in destroying Leucania as well.

Anticarsia gemmatalis

Very little data concerning the biology and the ecology of the Anticarsia gemmatalis HUBNER in French Guiana is available, since the cultivation of soyabean on an industrial scale has made its appearance only in very recent years.

PSMARKS RELATIVE TO THE USE OF PESTICIDES IN FRENCH GUIANA

Two general observations may be made concerning the use of pesticides to fight against noctuid-moths in French Guiana:

- The nain problem that arises when pesticides are applied to destroy defoliator noctuids is the real remanence that remains when we use these products in the extreme pluviometric conditions prevailing in the rainy season in French Guiana (Depending on the regions, the annual rainfall ranges between 2.5 and 4 meters). Often the pesticides treatments are rendered ineffective by the rain as it washes the leaves, particularly in the case of contact pesticide of the pyrethrenoid type.

It would hence, be necessary to proceed with experiments designed to adapt spraying techniques to the climatic conditions prevailing in this region.

- Taking into account the limited scope of the Guianese market, very few products are locally available. Efficiency, therefore, is not the only criterion and the choice is mostly made according to the availability of a product. In such a situation, several farmers buy their supplies from Surinam, where the range of available phytosanitary products is far wider. This in turn, presents problems of compliance with the French laws in force in French Guiana.

CONCLUSION

One may witness a multiplication of the problems deal- ing with crop pests running parallel to the development of agriculture in French Guiana. As far as Lepidoptera noctuids are concerned, we find that most of the species of an

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economic importance that have been check-off in the neighboring countries and generally in all the neotropical zone sxist in French Guiana.

The economic importance of each of these potenzial

.

ravagers will, therefore, depend upon the surface area covered by that or those crops favourable to their zulti- plication; and one may easily expect that the introeuction or expansion of a certain type of crop is bound to be eccompanied with the emergence of a new problem of noctuid pests. conditions in French Guiana, and especially the lonc duration of the rainy season, are propitious to the sustenance of large noctuid populations during most of the year.

Climatic

Spodoptera frugiperda is, at the moment, the most important noctuid from the economic view point, mos: of the efforts in the theoretical and applied research in French Guiana being directed towards it. It would be desirable th scientists working on this species in different Caribbean countries, as well as, in the entire neo-tropical 2x18 cooperate more closely and increase the exchange of data.

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at

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