TECHNICAL BULLETIN 112 ISSN 0070 - 231·5

BIOECOLOGY OF THE BLACK SCALE SAISSETIA OLEAE (OLIVIER) (HOMOPTERA: COCCIDAE) IN CYPRUS

G. M. Orphanides

i R "t::=C E IV E i::> : 21 SEP 1990 \

! AG ~ ICULT.URAL . R ES E.AR C~\' \_ ___~~S1 rr~~E _ -d

AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE AND NATURAL RESOURCES

CYPRUS NICOSIA

JANUARY 1990

BIOECOLOGY OF THE BLACK SCALE SAISSETIA OLEAE (OLIVIER) (HOMOPTERA: COCCIDAE) IN CYPRUS

G.M. Orphanldes

SUMMARY

The black scale, Saissetia oleae (Olivier), has one complete and one partial generation per year on olives . The

extent of the second generation varies among locations. On citrus and oleander, only one generation per year

develops. Overwintering occurs mainly as first-, second- and third-ins tar larvae. Infestation on citrus was sig­

nificant only in one location. The within-tree distribution studies of the scale insect revealed more individuals of

the first, second and third instar on the leaves and more young, rubber-stage and ovipositing females on the

twigs. In general, more scale insects were found on the lower than on the upper leaf surface. However, more

crawlers settled on the upper leaf surface in May - June. Black scale infestation increased from the tip of a leafy

twig to about the l Sth pair of leaves towards its base. Twigs with 15 pairs of leaves or of about 20 em length

would be the most suitable size for population sampling.

nEPIAH'I'H

To AExaV\.O 'tTl; EALll;, Saissetia olese (Olivier), O\lJUtATJe<i>vE~ 1-2 YE'VI.t; 'to '1R6vo 6'tuv UVwt'tVOOE­'taL n:avw ornv EA~a. H 7tQc.irtTl YEv~a O\lJUtATlQOwE'taL OE 6>..£; 't~; n:EQLl)XE;. H bEV'tEQTI 6j.LO>;, bEV d'V<l~ n:A.~QTI; yw'tl. uovo IliQo<; rou n:A.l')9uOlJ.Oil 'tTJ'V <J\1IL3'l:A.T1Q<i1vE~. Tc a't01Ul rou n:A.T1900lJ.Ov nou ou­/-U'tA.T1QON0U'V 2 yME; El.vU~ n:EQ~oo6'tEQU O't~; 7tEQLOXt; 6n:ou or <J\I'V91lxE; y~u 't'lJV uvamu!;T1 rou E'V't6­1J.0u EI.VaL mo EU'VOUtE;. l":'tu E<Jn:EQ~OE~b~ 6n:ou TI n:QOOI3oA.1\ 1\'tuv OTJIUl'V't~x1\ uovo OE lJ.~u n:EQ~oX~,

XaL ornv uQOMCJlVll (QoOOMQlVll 1'1 mXQOMCJlVll), UVM'tVOOE'tU~ uovo IJ.LU n:A.1')QTI; yEvLa. To MOIJ.O n:OllMA.Uouil;E'tat <JU'VEXW; xu~ b~uXEL!J.cll;E~ xUQl.w; O'tU VEU¢ O'tabLU n:QOWILQJ'llC;. MElliE; 'tTl; XU­'tUV0IJ.Tt; 'tOU E'V't61J.Ou 0't0 lIEvbQO tbE~UV n:EQ~006'tEQE; 7tQOWIUPE; n:Qcb'tou. lIEmEQou XU~ 'tQI.rou O'tU­1I1.0u O'tU <piJllu Xat n:EQLoo6'tEQU 'VEaQU 9TJ).uxa Xat 9TJ).uxa 7tQw xa~ xu'ta 'tl1" wo'toxta n:avw O'toU; XA.alll.oxou;. rE'V~xcl, n:EQ~oo6'tEQU E'V'tOIJ.U ~Qt6T)xuv 0't'lJV xcl'tW n:aQU 0't'lJV n:a'VW EmqxivELu tou qn'JA.­A.ou. 0IJ.W;. 7tEQ~006'tEQE; 1tQOWlJ.qJE; EyxU'tUO'tal1T)xuv 0't'lJV n:avw E7tLqxiVELU rou <piJllou xu'ta rov MaLO - Iovvio. H n:QOol3oA.1\ uU;aVE'tUL MO tnv axQTI rou xA.uMoxou 7tQO; mv /3<iOTJ ore n:Qcb'tu 15

l;EilyTl <piJ).,).,(J)'V. lO..alll.OXot IJ.E 15 l;EilyTl qn'J).,).,(J)'V 1') lJ.t1xou; n:EQ!.n:ou 20 EX. MO'tEA.OW 'to mo xu'tillTl­1..0 !J.EyE90; y~u 1J.EA.E'tE; rou n:A.T19uolJ.oV rou E'V't6IJ.Ou.

INTRODUCTION damage, including defoliation and twig dieback in cases

of heavy infestation, is mainly caused by sooty mold fun­

The black scale, Saissetia oleae (Olivier), is consid­ gi which develop on the honeydew excreted by the scale

ered native to South Africa. In Cyprus it was first re­ insect onto the plant. This sticky material also hinders

corded by Solomides (1913) and has since existed as an harvesting, handling and processing of the fruit. Some

occasional pest of olive, quince and citru s trees (Morris, debilitation of the trees may also take pla ce when the

1936). Its pre sence wen t almost unnoticed until about quantit y of sap tapped by the insects is substantial.

1975 (Orphanides, 1985), when outbreaks of its popula­

tions started appearing in various parts of the island, seri­ O utbreaks of black scale populations have been as­

ously damaging olive tree s (Mel ifronides, 1978). The cribed to the upsetting of the natural balance in the olive

1

agroecosystem through the indiscriminate use of non­

selective insecticides for the control of the olive fruit fly,

Dacus oleae (Gmelin), and the olive moth , Prays oleae

Bern, or of other pests in neighbouring cultivations (Ar­

gyriou, 1969; Rosen et al.. 1971; Viggiani, 1978). They

have also been connected with increased rainfall and hu­

midity (Viggiani, 1978; Paraskakis et al.. 1980) and with

modifica tions of the microclimatic conditions through in­

creased fertilization and irrigation and lack of pruning

(Viggiani, 1978).

Since the black scale has never beenstudied in detail in

Cyprus, an in-depth study of the bioecology of this pest

was undertaken to determine the possible factors that

caused the recent outbreaks of its populations. The ulti­

mate objecti ve, however, is to develop an integrated con­

trol programme to cover all significant olive pests on the

island. The present report presents a detailed account of

various bioecological aspects of the black scale.

MATERIALS AND METHODS

Life history

The life history of the black scale was studied on olives

at Akhelia, Mazotos and Evrykhou during 1984-85; in

the latter area studies were also conducted on oleander

and lemons . Olive trees were regularly irrigated at Ak­

helia but very rarely at the other two locations. Lemon

trees were also irrigated regularly, whereas the oleanders

grew on a riverside, where water was available almost all

over the year. Samples of scale-infested twigs and

leaves were collected at random from all areas about

every three weeks throughout the study . The samples

were examined in the laboratory, counting and classify­

ing all scale insects until 500 live insects were recorded.

The classification adopted was that of Podoler et al.

(l979a) and comprised the following stages: E=eggs,

Cecrawlers, Ll efirst-instar larvae that had settled down,

L2=second-instar larvae, L3=third-instar larvae,

YF=young females , RF=rubber-stage females,

OF=ovipositing females. Since the scale insect reproduc­

es parthenogenetically, no males have so far been found

in Cyprus . In all stages the scale insects were classified

into live and dead. The latter were further separated into

actively and previously parasitized, and dead from un­

known factors.

The number of generations of the black scale was also

determined on potted olive and oleander plants, taken to

each of the above -mentioned areas, infested artifi cially

with the scale insect and examined about every three

weeks.

Within-tree distribution of the scale population

Ten leafy twigs, with 15 pairs of leaves each, were ex­

amined about every three weeks throughout the study to

determine the scale-insect's distribution on the tree. The

terms twig and leafy twig are used to denote a small

branch without and with leaves, respectively. Scale in­

sects were recorded separately 1) on each leaf surface,

following always the same leaf order, the first pair being

that on the tip of the twig and 2) on each twig.

The migration of scale insects from leaves to twigs was

also studied by marking branches on the tree and by

counting all the scale insects on the leaves and twigs

about every three weeks.

RESULTS AND DISCUSSION

Life history

The preferred host plants of the black scale found in the present study were olive, citrus and oleander (Orpha­

nides , unpublished data). The life history of the black

scale on olive in three areas is presented in Fig. I. The

main overwintering stages (Ll , L2, L3, and young fe­

males) gradually passed through the rubber stage, ma­

tured and started oviposition at the end of March, early

April, and late April, at Akhelia, Mazotos, and Evryk­

hou, respectively. The peakof abundance of ovipositing

females occurred in the same order, from late May to the

beginning of June. Oviposition lasted 2.5 to 3 months

and the pattern of the population curve was similar in all

three areas.

Appearance of young settled larvae of the first genera­

tion occurred two to three weeks after the onset of ovipo­

2

80

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"'" .~cr.::::::::-~ ! ~ ~ f ...··············· <, +/"'+ o O.~.·"·",,...,:--+O-+~+ ,{:I ........0 <, ,....."...- '''',.''''':, ,.....--=---... ~+ O:::";;;···.. __~~ ,.%.;...__.,.... ...,... ..... .....o.. ;...

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'\.. ,.... . . _~ "'II., ............... ...../ .. +.~-.~~+-d""+

0.... 0 ..... I

J F

Figure 1. Phenology of Saissetia oleae (Olivier) on olive~ at Akhel ia, Mazotos and Evrykho u (mean values of 1984 and 1985) ,

3

sition. At Akhelia, ovipositing females of the first gener­

ation started appearing in early August and their

populat ion reached a peak in early September. Their

abundance then dropped to low numbers that were ob­

served continually until spring of the following year

when the overwintered second-generation scale insects

matured and started oviposition again to repeat the cycle.

The second generation was partial to some extent, be­

cause a small part of the scale-insect population could

deve lop only one generation. At Mazotos the second

generation was partial to a higher degree, because few

ovipositing females started appearing from September

onwards, while at Evrykhou the second generation was

almost nonexistent In all three areas the ovipositing fe­

males of the second generation were smaller than those

of the first generation. Con sequently, the number of eggs

laid per female of the second generation was lower. Pre­

liminary laboratory experiments indicated that one of the

factors responsible for the small size of the ovipositing

females was the high summer temperature (above 25OC)

that prevailed during the scale's development.

The present results agree with the widely reported find­

ings that the black scale on olive is univoltine under dry

conditions and bivoltine under humid ones, with a range

of intermediate cases where there is one complete gener­

ation and a partial second one (Bodenheimer, 1951; Eb­

eling , 1959; Argyriou, 1963; Peleg, 1965; Rosen et al., 1971; Freitas, 1972; Blumberg et al .• 1975; Panis, 1977;

Viggiani, 1978; Bartlett, 1978; Abdelkhalek, 1985).

Various explanations were proposed for the development

of the partial second generation. Ecological conditions,

part icular ly the higher humidity and milder climate of

coastal areas, were the first to be suspected (Bodenheim­

er, 1951; Ebeling, 1959; Argyriou, 1963; Bartlett, 1978).

Freitas (1972) added the possible involvement of nitro­

gen fertilizers, whereas Peleg (1965) observed that irri­

gation enhanced the scale-insect's development rate.

Blumberg et al . (1975), in tum, considered changed cul­

tural practices, particularly the improved plant nutrition

as a responsible factor . Effects of the host plant and its

physiological state on the availability of some nutritional

essentia ls for the insect were suspected by Flanders

(1970), Ishaaya and Swirski (1976) and Bartlett (1978).

Finally, a different group of explanations concerned 1)

predominance of certain genotypes in some individuals

of a population that render them tolerant to unfavourable

temperature extremes (Panis, 1986), and 2) possible exis­

tence of sibling species (Rosen et al .. 1971) or strains

(Blumberg et al .. 1975). Observations in the present

study support the idea for the involvement of ecological

conditions, cultural practices and the host plant's physio­

logical state in the development of the second genera­

tion. However, the possible existence of different geno­

types, strains and/or sibling species is being investigated.

The seasonal life history of the black scale on olives,

oleanders and lemons was compared at Evrykhou (Fig.

2). Ovipositing females appeared on all three host plants

from the end of April onwards, and their peak of abun­

dance occurred at the end of May. Subsequently, the ov­

ipositing population on olives dropped sharply to very

low numbers in the second half of June, and disappeared

at the end of July. On oleanders and lemons, though, it

declined gradually and oviposition was completed in

September and October, respectively. Ovipositing fe­

males of a second generation appeared in very low num­

bers on olives from the second half of September until

early March of the following year. On lemons, an insig ­

nificant number of ovipositing females were found in

December, and could be interpreted to indicate an incipi­

ent second generation.

Panis (1977) reported one generation per year of the

black scale on citrus in most countries of the Mediterra­

nean Basin. In Israel, Peleg (1965) reported one genera­

tion per year on oranges and grapefruit while Rosen et al.

(1971) reported two generations per year, and Blumberg

et al (1975) observed an incipient bivoltine population.

Within-tree distribution of the scale-insect popula­tion.

Counts of 143,000 scale insects revealed the pattern of their distribution on a ca 20-cm olive twig and on its 30

leaves throughout the year (Fig. 3). From February on­

wards the scale insects found on twigs increased steadily

in numbers until May, thereafter dropping to very low

numbers in June. From February to May the scale-insect

population consisted mostly of young or older female

stages. About 62,000 live scale insects, counted from the

4

+-+ Ol i v e 80 Oleander

N

--J 0 ···..· _ ..· ·0 = Lemon

-+ 40

--J

0

80 ("I")

--J

40

e"" ~ . '-, ++ """" ~,t~...

O-....----.*-=_...··111::::'·00.-._._".-+,--. ...• .1J............ .

(j) Of- 80 UJ {!)<.!> <{z I- ~ 40 lJ') 0 : ,

>­

W

e,..,,,,, ,................ ~'"!" ......}.............~ :.---------- /'::/+ ~~, ~ \'~\'1,

+ .~ ~ \',

+ \~ \ " i .\

""\\ .... . " +~~i;.'~ ..ca

--J O-'----..,.----.----"'T"---"'T"----, <{ ! U 80 + ! (j)Q;:

W m tIl 40 :::J a::

... ~ .... ... + ... -to0 (!) 80 -z t ­-(j) j~

0 0400­ f > .

: I f

.0 . ..~~ , .............+-+-..0 • I I I I

J F M A M J J A 5

~ tt,~~~~

...~~:..... I, • .a . "~~ :

\1'.. ~ \

0_-·°............0

+-+_1''''''''''''.

. : .

~"'O ... ..... I

... .00

0 N 0 Figure 2. Phenology of Saissetia o/eae (Olivier) on olives, oleander and lemons at Evrykhou (mean values of 1984 and 1985).

5

80

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w 60 ~

<{

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40 0

0'"

+20

x

~-

0 .......•..•........•.. 0 = E v r y k h 0 u

+--+=Akhelia

•,,,,,,,,,,". =Ma Z 0 t 0 S

OT--....,--....,-----,-----,--~-_r_---:~~__.,.-__,r_-_r_-.....,.....-~

J F M A M J J A 5 o N o Figure 3. Black scale distribution on olive twigs at three locations in 1985.

study of the phenology on olives, showed that the first

three settled stages (L1+L2+L3) tend to occur on leaves,

whereas the last three (young females, rubber-stage and

ovipositing females) occur mostly on twigs (Fig. 4).

Similar results have been reported earlier (Pucci et al.,

1982; Panis and Marro, 1985). This explains the increase

of scale insects on the twigs in February - April (Fig. 3),

because during that period most of the scale insect popu­

lation consis ts of the last three stages (Fig.1). A gradual

migration of scales, of all stages except ovipos iting fe­

males , from leaves to twigs occurred from October to

May.

More scale insects were generally found on the lower

than on the upper surface of olive leaves, the difference

being more pronounced during the winter months

(Fig.5). A higher infestation on the lower leaf surface in

the winter was also found when 800 olive leaves from

Akhelia were examined and 3.4 and 1.3 scale insects per

lower and upper leaf surface were found, respectively.

The scale-insect's density on the upper leaf surface is

positively correlated with the existence of newly-born or

young stages. Additional counts of more than 32,000

6

scale insects on 1000 leaves during crawler activity in

May - June confirmed the findings shown in Fig. 5, and

revealed increased scale-insect populations on the upper

leaf surface at all locations where mean density levels

varied from 1.7 to 40 scale-insects per leaf. Consequent­

ly, more crawlers settle on the upper leaf surface, but lat­

er the insects either migrate elsewhere, or their mortality

is higher on the upper leaf surface. Panis and Marro

(1985), however, reported that colonization on the upper

leaf surface is scarce and that the lower leaf surface is

the main habitat for first- and second-instar larvae. Rele­

vant field counts and observations in 1984-1985 revealed

that migration of young stages does occur. Scale-insect mortality on both leaf surfaces varied. More dead scale

insects were found on the upper leaf surface when the

environmental conditions were dry and less favourable

to the insect's development. More sca le insec ts on lhe

lower leaf surface were also reported by Argyriou

(1963), Orfanidis and Kalmoukos (~970), Freitas (1972),

Padoler el al. (1979b), and Neuenschwander and Para­

skakis (1980). Tuncyurek (1975) (cited by Podoler et al.,

1979b), however, found more scale insects on the upper surface of citrus leaves.

[

.--.... (J) I=AkheliaQ.I

> 20ro ~ = M a z o t o sQ.I

--l I i=Evrykhou

(J)

rn 10 ~

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OJ,......----=:=-- ....,.,...-=--__r-=--=----I~

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-~

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I ­Q.I

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............--....:;~'------=..-;=--_==__ ..... (J)

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L­-<1J L- a o, -

Y .~. R .~. O.~.

SCALE STAGES

Figure 4. Distribution of the various black scale stages on olive twigs and leaves at three locations (mean values of 1984 and 1985).

100......--------------------------,

80

I­

Z 60 w u

cr 40 w a..

20

+-+=AkheLia

.""',,". =M a Z 0 t.. 0 S

0'''''' '''''''''''0 =E v r y k h 0 U r: . . +\0.............. X "'f-~-' ····0...

-" e. ,...... + " ......" ;f ..,.,..,... <...·.0··1+ / """" /.

""" i ;f -: / ! ·········.0 ,•••,+ /~/' ~.~~

.""" \, \-X ,/ ) .•c:::..:.•....j -~< ~.... 'o,," .•.•...•.... +<: ;

+........... ',/1" -~

........ ,..~.. ~, #.'" ~ b \ _------ ....c/

".-.-­O~-....,...---r--=-....,...--~-~-__r_-~-__r-___r-_r__-y___--t

J F M A M J J A 5 o N o Figure S. Black scale population distribution.on the upper leaf surface of olives at Akhelia, Mazotos and Evrykhou in 1985.

7

The scale-insect density on the leaves of olive twigs in­

creased steadily from the top leaves to the 12th or 13th

pair towards the twig 's base (Fig. 6). At Akhelia, though,

this increase continued up to the 15th pair . Consequent­

ly, a twig with 15 pairs of leaves, corresponding to about

20 em of twig length, represented a reliable sample unit

and gave the true picture of black scale population as ­

sessment. Scale-insect counts on longer twigs revealed a

decrease in density beyond the 15th leaf pair . Also, such

long twigs could not be collected at random because they

were not very abundant in some groves. Contrary to

these results, Neuenschwander ana Paraskakis (1980)

generally found no black scale infestation on the new

leaves beyond the 8th internode.

Development of pest outbreaks The existence of S. oleae as an insignificant olive pest

for abour 60 years without any chemical control, is a

strong indication that the scale-insect population was

kept at significantly low levels by effective natural con­

trol factors. Consequently its population outbreak in

c./)

~6 -c u If)

some areas of the island was caused by the disruption of

the natural balance that existed in the agroecosystem. In

fact , the significant scale-insect outbreaks that appeared

in Cyprus coincided with indiscriminate use of chemical

insecticides either on crops neighbouring to and/or

mixed with olive groves or on the olive trees themselves,

and with the introduction of new olive varieties with

higher demand in irrigation and fertilization. The in­

volvement of all these factors in the development of

black scale outbreaks was also reported in other coun­

tries (Argyriou, 1969; Rosen et al., 1971; Viggiani, 1978;

Paraskakis et al.. 1980). Efforts are being made to re­

establish a balance between the factors involved in the

agroecosystem.

ACKNOWLEDGEMENTS

Thanks are due to Messrs A. Georghiou and C. Hadjiy­

iannis and to Mmes E. Antoniou, M. Panayiotou and A.

Papasolomontos for technical assistance.

100

If)

w 80....J

<t U If)

60~ o

w 40>

.­<t....J

20 ::)z ::)

U

o

10

8

4

2

2 4 6 LEAF

8 10 12 14 PAIR

Figure 6. Black scale infestation on the lop 15 pairs of leaves on olive leafy twigs at Akhelia (A), Mazotos (M) and

Evrykhou (E) (mean values of 1984 and 1985). 8

I

REFERENCES

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black olive tree scale insect Saissetia oleae (Oliv.) (Hom.

Coccoidea) in the region of Fes. In Integrated Pest Con­

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159. A.A. Balkema, Publishers, Rotterdam.

Argyriou, L. 1963. Studies on the morphology and biology of

the black scale (Saissetia oleae (Bem.) in Greece. An­

nals Institute of Phytopathology. Benaki (N.S.) 5: 360­

386 (In Greek).

Argyriou, L. 1969. The status of biological control of Saissetia

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East. Vitgeverij Dr. W. Junk, Th! Hague, 663 pp.

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Melifronides, J. 1978. The problem of sooty mold on olive

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Morris, H.M. 1936. Injurious insects of Cyprus. Cyprus Agri­

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olive tree. Zeitschrift fur Angewandte Entomologie 90 :

366-378.

Orfanidis, P.S., and P.E. Kalmoukos. 1970. Observations sur

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respond ante de quelques facteurs biotiques). Annates In­

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Orphanides, G.M. 1985. Insect pests of olives in Cyprus. In

Integrated Pest Control in Olive Groves. Proceedings of

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A.Crovetti), pp. 343-347. A.A. Balkema, Publishers,

Rotterdam.

Panis, A. 1977. Ecologie et biocenoses de la cochenille noire

des agrumes dans les regions Mediterraneennes (Homop­

tera, Cocco idea, Ceccidae). Boletin del Servicio de De­

fensa Contra Plagas e Inspeccion Fitopatologica pp .

199-205.

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