Gutierrez, Jean

Crossref

Horizon / Pleins textes

Experimental & Applied Acarology, 3 (1987) 163-168 
Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 
163 
Short Communication 
The Cassava Green Mite in Africa: One or Two 
Species? (Acari: Tetranychidae) 
/p &,a 4 9  
p 1q-p 
J. GUTIERREZ 
ORSTOM c/o I.A.M., 3191, Route de Mende, 34060 Montpellier Cedex (France) 
[ I Q  +y 
(Accepted 17 March 1987) J /2 
ABSTRACT 
Gutierrez, J., 1987. The cassava green mite in Africa: one or two species? (Acari: Tetranychidae) . 
Exp. Appl. Acarol., 3: 163-168. 
Despite a certain amount of confusion that has prevailed for several years with respect to the 
Mononychellus complex (cassava green mite = CGM; Acari: Tetranychidae) which attacks cas- 
sava plantations in Africa, strong arguments indicate that a single taxonomic unit corresponding 
to the species Mononychellus progresiuus Doreste, 1981, was introduced in 1971 from South 
America. 
INTRODUCTION 
The accidental introduction of spider mites of the genus Mcqonychellus 
Wainstein into African cassava plantations had such an econo&!$ i&pact that 
attempts were made to solve the problem by attending to the most Ürgent things 
first and by calling in several organizations, each of which has a different com- 
petence. By approaching the question in this way, some interesting reactions 
were provoked, but as the situation persisted, it also resulted in a certain con- 
fusion in several areas. 
The subject is complicated by the fact that for someone who is not an expert, 
the symptoms produced by the CGM in cassava (chlorosis of young leaves 
followed by defoliation of young shoots) can be confused in the field with those 
produced by the cassava mealybug (CM) , Phenacoccus manihoti Matile-Fer- 
rero, or by the African cassava mosaic virus ( ACMV) , At many conferences, 
there are still discussions to decide which of these calamities should be given 
priority in research. 
Several species of phytophagous mites existed beforehand in Africa. They 
attacked cassava, but only caused slight damage. Generally their color was red 
( Tetranychus spp.) or garnet-red (Oligonychus spp.) , and consequently they 
were easy to see with the naked eye. By contrast, the CGM is smaller and has 
a very mimetic green color, so that often it can only be seen with a hand lens. 
I 
0168-8162/87/$03.50 O 1987 Elsevier Science Publishers B.V. 
I 
164 
The CGM was first collected in Africa near Kampala (Uganda) in 1971 
(Lyon, 1973 ) , At that time, Mononychellus, whose name had just been changed 
(Wainstein, 1971), only contained 17 species, of which 4 had been reported on 
cassava in different South American countries: Mononychellus bondari (Pas- 
choal, 1970), M. caribbeanae (McGregor, 1950), M. planki (McGregor, 1950) 
(Paschoal, 1971) and M. tanajoa (Bondar, 1938). The specimens collected in 
Uganda were identified as Mononychellus tanajoa, which had just been redes- 
cribed by Flechtmann and Baker (1970). This designation was given to all the 
CGMs collected in Africa for several years, until the discovery in Gabon and 
Nigeria ( Flechtmann, 1982 ) of another species, Mononychellus progresiuus 
Doreste, 1981. Some trouble then arose, and authors began referring to the 
Mononychellus complex, and tried to analyze it, for example by comparing, 
without much success, the length of the dorsal setae of specimens from differ- 
ent areas. 
The situation can be clarified to some extent by examining the parallel courses 
of research in South America and Africa. 
THE COURSE OF RESEARCH IN SOUTH AMERICA 
It all started in 1938 with Bondar’s publication. Since his microscope slides 
had apparently been lost, and since the original description had been done 
quite inaccurately, based only on females, Flechtmann and Baker collected 
from Manihot sp., in the type-region of Bahia, a Mononychellus species that 
they described in 1970 (Flechtmann and Baker, 1970). They basically took 
into account the dorsum of the female (reticulation of the prodorsum, striation 
pattern of the opisthosoma, length and position of the dorsal setae), whereas 
the males remained unknown. 
In the same work, Flechtmann and Baker divided the species M. planki 
(McGregor) into two taxa, i.e. M. planki sensu stricto (McGregor) , which has 
reticulations on the prodorsum and the base of each of the opisthosomal setae, 
and M. mcgregori (Flechtmann and Baker), which has regular striations over 
the whole dorsum. Consequently, the mites collected on cassava in Brazil, and 
identified as M. plankì by Paschoal (1971), should actually have been named 
M. mcgregori, since the author himself indicated that there were fewer reticu- 
lations on these specimens. Subsequently, Urueta (1975) collected M. mcgre- 
gori on cassava in Colombia. 
In 1979, Doreste reported M. estradaì (Baker and Pritchard, 1962) on cas- 
sava in Venezuela, and then in 1981 described two new species of Monony- 
chellus collected on the same plant: M. manihoti and M. progresiuus, whose 
aedeagi were represented, as well as that of M. <unajoa. In 1982, he added’jld. 
chemosetosus (Paschoal, 1970) to the list (Doreste, 1979,1981,1982). 
Eight other Mononychellus ,were described elsewhere on other host plants, 
both in Mexico and in South Africa (Smith Meyer, 1974; Tuttle et al., 1974, 
165 
1976), so that, based on the literature, the genus Mononychellus would now 
appear to contain 27 species, 8 of which live on cassava in South America: M. 
bondari, M.  caribbeanae, M.  chemosetosus, M. estradai, M. manihoti, M. mcgre- 
gori, M.  progresivus, and M ,  tanajoa. 
In reality, however, this group should be completely revised. Examinations 
of recently collected specimens, especially from Africa (personal observations; 
H.R. Bolland, pers. commun., 1986; C.H. W. Flechtmann, pers. commun., 1986; 
I.C.I.P.E., 1986) have made it clear that in the genus Mononychellus, as for 
example in the genus Eutetrunychus Banks (Gutierrez, 1985), the length of 
the dorsal setae, which has been used for years as a criterion for distinguishing 
the species, varies considerably from one strain to another, and even between 
specimens of the same strain. 
Moreover, it is generally necessary to rely on the author's original descrip- 
tions, since the microscope slides are not available, or can only be examined 
on location in each country. These publications are often incomplete, and even 
Contain certain errors. The chaetotaxy of the legs differs from one author to 
another, e.g. that of the legs of one female is based on a specimen that is clearly 
masculinized, which is a frequent phenomenon in the Tetranychidae, or the 
number of ordinary setae is not the same in the two sexes. The shape of the 
peritremes appears to be homogeneous in this group. Other morphological 
characters (empodia, shape of the spinning eupathidium of the palpal tarsus) 
have been studied in some species, but not in others. The presence or absence 
of reticulations on the dorsum of the body is a constant specific character 
(Flechtmann andBaker, 1970), but this element is difficult to illustrate reliably. 
Curiously enough, the form of the aedeagus has only been used very recently, 
whereas the majority of the Tetranychinae species are rather easily distin- 
guished on this basis, since the work of Ewing (1913). 
Figure 1 shows the aedeagi of eight Mononychellus species that live on cas- 
sava. The discovery of the male of M. caribbeanae by Livschitz and Salinas 
Croche (1968) has gone unnoticed, or has not been taken into account by other 
authors. 
- The knob of the aedeagus of M. progresivus is small and slender, and very 
different from that of M. tanajoa, which is globular. 
- There is a striking resemblance between the aedeagus of M. estradai and that 
of M. tanajoa, and both of them are close to that of M. caribbeanae. Moreover, 
M. estradai and M. tanajoa have the same reticulation of the prodorsum and 
nine ordinary setae on the tibia I, whereas M. caribbeanae has only eight (Tut- 
tle et al., 1976; Livschitz and Salinas Croche, 1968). Consequently, I consider 
that M. estradai (Bàker and Pritchard, 1962) is a synonym of M. tanajoa 
(Bondar, 1938). 
- There is also some doubt about the validity of M. chemosetosus (Paschoal, 
1970), whose aedeagus resembles that of M.  planki sensu stricto ( McGregor, 
Examination of these aedeagi elicits several remarks: 
3 
166 
h 
Fig. 1. Aedeagi of the different Mononychellus species recorded on Manihot spp. throughout the 
world. (A) Mononychellus estradai (Baker and Pritchard, 1962); (B) M. caribbeanae (Mcgre- 
gor, 1950); (C) M. tanajoa (Bondar, 1938); (D) M. bondari (Paschoal, 1970); (E) M.progresiuus 
Doreste, 1981; (F) M. manihoti Doreste, 1981; (G) M. chemosetosus (Paschoal, 1970); (H) M. 
mcgregori (Flechtmann and Baker, 1970). 
1950) (see Flechtmann and Baker, 1970). Moreover, the two species have the 
same dorsal reticulation and nine ordinary setae on the tibia I. 
THE CASSAVA GREEN MITE IN AFRICA 
All the samples I have been able to collect or receive from Africa are related 
to M. progresiuus. They originate either from Kenya, where they were collected 
in 1985 and 1986 by W. Helle in the context of the I.C.I.P.E., or from the 
Republic of Congo, where they were collected in 1984 and 1985 (Gutierrez et 
or from the Ivory Coast (new record) where I collected them in both forest 
and savanna areas in 1985. 
Despite my requests, no one has been able to provide me with a specimen of 
M. tanajoa from Africa. 
The confusion that prevailed for several years in the designation of Mon- 
onyehellus has led certain authors to speak of a Mononychellus complex attack- 
al., 1985) and then in 1986, in different localities belonging to several biotopes, 1 
' I  
'A 
167 
ing cassava in Africa, which has added to the mystery surrounding the famous 
CGM, but I consider that only a single species was in fact introduced into 
Africa. It was named M. tanajoa for about 8 years (1973-1981), but since the 
description of M.  progresivus in 1981 it should have been designated by this 
name. The determination of the first African Mononychellus specimens was 
based only on a study of the female dorsum, but when the description of the 
two sexes became available, and when it became possible to compare the male 
aedeagi, it was clear that there was only one species, M.  progresivus. This pro- 
vides a simple explanation to the remarks of Macfarlane (1984), who rioted in 
his key to spider mites recorded on cassava in Africa that “the first records of 
Mononychellus from Africa were determined as M.  tanajoa” and that “the 
majority of records are probably M. progresivus”. 
If there is a complex, it is only an intraspecific one and not an interspecific 
complex, as was suggested. The morphological variations between strains - 
represented, for example, by the length of the dorsal setae - correspond to a 
genetic variability common to  several species of Tetranychidae. The genetic 
divergences of populations, which arise especially from the haplo-diploid nature 
of spider mites, have been extensively studied in the temperate zone in Tetran- 
ychus urticae Koch (Helle and Pieterse, 1965; Dupont, 1979; De Boer, 1980, 
1981) and in the tropics in Tetranychus neocaledonicus André (Gutierrez and 
Van Zon, 1973). In these two species, genetic variability is not expressed by 
clear morphological variations, but crosses between strains result in different 
levels of incompatibility. Crosses between strains of CGM from different Afri- 
can countries would probably lead to similar results and would show a gene 
flow between the various African morphs of Mononychellus progresivus. 
A 
) 
hr 
REFERENCES 
De Boer, R., 1980. Genetic affinities between spider mite Tetranychus urticae (Acarina: Tetran- 
De Boer, R., 1981. Genetic affinities between spider mite Tetranychus urticae populations in a 
Doreste, E., 1979. Acarologia. Univ. Central Venezuela, Maracay, Venezuela, 285 pp. 
Doreste, E., 1981. Acaro del género Mononychellus Wainstein (Acari: Tetranychidae) asociados 
con la yuca (Manihot spp.) en Venezuela. Bol. Entomol. Venez., N.S., 1: 119-130. 
Doreste, E., 1982. El complejo de Acaros tetraniquidos como plaga importante del cultivo de la 
yuca. Rev. Fac. Agron. (Maracay), 12: 249-254. 
Dupont, L.M., 1979. On gene flow between Tetranychus urticae Koch, 1836 and Tetranychus 
cinnabarinus (Boisduval) Boudreaux 1956 ( AcarLTetranychidae) : synonymy between the 
two species. Entomol. Exp. Appl., 25: 297-303. 
Ewing, H.E., 1913. The taxonomic value of characters of the male genital armature in the genus 
Tetranychus Dufour. Ann. Entomol. Soc. Am., 6: 453-460. 
Flechtmann, C.H.W., 1982. The cassava mite complex III. New distribution records mainly from 
Colombia and Africa. References to other plants. An. Esc. Sup. Agric. “Luiz de Queiroz”, 39: 
ychidae) populations in a non-agricultural area. Entomol. Exp. Appl., 2 8  22-28. 
non-agricultural area II. Entomol.Exp. Appl., 30: 63-67. 
809-813. 
168 
Flechtmann, C.H.W. and Baker, E.W., 1970. A preliminary report on the Tetranychidae (Acar- 
ina) of Brazil. Ann. Entomol. Soc. Am., 63: 156-163. 
Gutierrez, J., 1985. Systematics. In: W. Helle and M.W. Sabelis (Editors), Spider Mites, Their 
Biology, Natural Enemies and Control (World Crop Pests, Vol. 1A). Elsevier, Amsterdam, pp. 
Gutierrez, J. and Van Zon, A.Q., 1973. A comparative study of several strains of the Tetranychus 
neocaleclonicus complex and sterilization tests of males by x-rays. Entomol. Exp. Appl., 16: 
Gutierrez, J., Delobel, A. and Ganga, I., 1985. Mononychellusprogresiuus in the Republic of Congo. 
Cassava Newsletter, CIAT, Cali, Colombia, 9: 16. 
I.C.I.P.E., 1986. Africa-wide project for biologia1 control of cassava pests: 1.C.I.P.EJI.I.T.A. col- 
laborative project on Cassava Green Spider Mites (MononycheElus spp., Tetranychidae) in 
Tropical Africa. First Progress Report (Oct. 1985-Jan. 1986), Nairobi, Kenya, 70 pp. 
Helle, W. and Pieterse, A.H., 1965. Genetic affinities between adjacent populations of spider mites 
(Tetrunychus urticae Koch). Entomol. Exp. Appl., 8: 305-308. 
Livschitz, I.S. and Salinas Croche, A., 1968. Preliminares Acerca de los Acaro “Tetranicos” de 
Cuba. Centro Nac. Fitosanit., Cuba, 157 pp. 
Lyon, W.F., 1973. A plant feeding mite Mononychellus tunajoa (Bondar) new to the African 
continent threatens cassava (Manihot esculenta Crantz) in Uganda. PANS, 19: 36-73. 
Macfarlane, D., 1984. Key to spider mites (Tetranychidae) recorded on Cassava in Africa, with 
a note on slide preparations. In: A.H. Greathead, R.H. Markham, R.J. Murphy, S.T. Murphy 
and I.A.D. Robertson (Editors), Proc. Reg. Training Workshop, East Africa, 30 April-4 May 
Paschoal, A.D., 1970. Contribuição ao conhecimento da familia Tetranychidae no Brasil (Arachn- 
Paschoal, A.D., 1971. A review of the Carribbeanae group (Acarina: Tetranychidae). Rev. Per- 
Smith Meyer, M.K.P., 1974. A revision of the Tetranychidae of Africa (Acari) with a key to the 
Tuttle, D.M., Baker, E.W. and Abbatiello, M., 1974. Spider mites from North-western and North 
Tuttle, D.M., Baker, E.W. and Abbatiello, M., 1976. Spider mites of Mexico. Int. J. Acarol., 2: 
Urueta, E.J., 1975. Arañas rojas (Acarina: Tetranychidae) del departemento de Antioquia. Rev. 
Wainstein, B.A., 1971. Mononychellus, a new name for Mononychus (Acariformes, Tetranychi- 
75-90. 
123-134. 
1984. C.I.B.C.,Ascot,pp. 31-35. 
ida: Acarina). Thesis, Esc. Sup. Agric. “Luiz de Queiroz” Sa0 Paulo, Brasil, 124 pp. 
uanaEntomol., 14(1): 177-179. 
genera of the world. South Afr. Dept. Agric. Techn. Serv., Entomol. Mem., 36: 1-291. 
Central Mexico (Acarina: Tetranychidae) . Smithsonian Contrib. Zool., 171: 1-18. 
1-102. 
Colomb. Entomol., 1: 1-14. 
dae) . Zool. Zhur., 50: 589 (in Russian). 
REPRINTED FROM: 
, ELSEVIER SCIENCE PUBLISHERS, AMSTERDAM 


The cassava green mite in Africa : one or two species ? (Acari : Tetranychidae)

Abstract

Similar works

Full text

Available Versions

Crossref

Horizon / Pleins textes