BIOECOLOGY OF THE BLACK SCALE (OLIVIER) (HOMOPTERA:...
Transcript of BIOECOLOGY OF THE BLACK SCALE (OLIVIER) (HOMOPTERA:...
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
N -J + 40 ~
a 80
M -J 40
--e 0 a.......
if) o- 80 w (!)
(!)-c ZI- ::J 40
if) 0 >
w
< ~ a u 80 if)
a: w co rn 40 :::> 0::
0
(!) 80 z-I--if)
400 a.. >0
o
=A k he l i a+--+
.""".". =Ma Z 0 t 0 5
~"" f"'" ". 0 .•.•••., 0 0 , " 0 ........"·,,..0 : \,."", 'I' . : ; /+~f o.....··~·· " ' '' '' ' ',,_
~ ~ : "<,+ . .,................... '\l,<, ' .! .0(.... /+~+........+
"'" .~cr.::::::::-~ ! ~ ~ f ...··············· <, +/"'+ o O.~.·"·",,...,:--+O-+~+ ,{:I ........0 <, ,....."...- '''',.''''':, ,.....--=---... ~+ O:::";;;···.. __~~ ,.%.;...__.,.... ...,... ..... .....o.. ;...
. ...•.: o • o ~ ....................'1'....:. , ", ,....... \
..l -'. \ :/-+--+""" \. 0;../ '\+ \
~+\ ,\~.-'.. 1.
'..,,0..::.L ....... ..... """T" ......__'''...;;'".···O ......
I
" .. . .: , . ': +-+ , : : :
'\.. ,.... . . _~ "'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
If)
w 60 ~
<{
u If)
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 ~
I-
If)
W --l
<t: u -10 If)
-20
r II III
OJ,......----=:=-- ....,.,...-=--__r-=--=----I~
Q.I (J) u en C Q.I
-~
~
I Q.I
~Q.I a~~ ~
n,~§ ~~ ~g ~~ ~
............--....:;~'------=..-;=--_==__ ..... (J)
Q.I <1J U > C ro <1J <1J L -...JQ.I
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
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Panis, A. 1986. Non-diaspine scales in the Mediterranean re
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