Abstrct
In this study fumigant toxicity of castor oil on adults and larva of two stored product
insectsTriboliumconfusumand Trogonellagranarium was investigated.Three concentrations were prepared
2%,5% and10% respectively by using acetone,statistical analysis showed thathightest mortality for adults of
T.confusum were 23.333% and 26.666% at 2% and 10% of castor oil and all three concentrations significantly
caused high mortality but 10% of castor oil killed 100% of khaprabeetles.Results also showed that 5% and
10%concentrations of castor oil were the most effective on first , second and third larval instars of T.confusum,
as they caused 60% and 66.6% mortality for the first larval instar, 50% and 63.3% mortality for second larval
instar and, 33.3% and 40% for third larval instar at 5% and 10% concentration respectively compared with 0%
at control treatment,in addition the three concentrations of castor oil affected first ,second and third larval instars
of T. granarium significantly ,the percentage of mortality was 86.6%, 90.0% and 93.3% for the first laval
instar compared with 40.0% at control treatment, 70.0%,70.0% and 80.0% for second larval instars compared
with 20% at control treatment,and 40.0%, 63.3% and 80.0% for third larval instar compared with 20.0% at
control treatment, at 2%,5% and 10% concentrations respectively.In summary, results indicated that these
essential oils have good fumigant toxicity on stored-product pests.
Keywords:essentialoiles,castoroil,stored product insects.
1.Introduction
The confused flour beetles Triboliumconfusum (coleoptera:Tenebrionidae)andkhapra beetles
Trogonellagranarium(coleopteran:Bruchidae)arethe mostwidespreadand destructive stored_productpests
throught the world ,beetles and larvae feed on avery wide variety of dry vegetables substances (Rees,2004).The
application of various synthetic insecticides over the years has lead to a number of problems including the
development ofresistance in stored products are generally preffered because of their innate biodegradability and
less harmful compounds affecting non_ target organisms (Prabakar and Jabanesan,2004) ,all these caused
encouraged researchers tobenefit from natural materials as safe replacements to control stored product pests. The
bioactivity of essential oiles is directly relayed to its chemical composition (Angioni etal,2006) ,they possess
acute contact and fumigant tocxicity toinsects(Abdelgaleil etal,2009). .Ricinuscommunis (L.) (Euphorbiaceae) is
wide spraed in many parts of the world (Weiss,2000) contains ricin which one of the most toxic materials which
could be essily extracted from different parts of the plant (Ogunniyi,2006).There are many studies has been
found to experience the activity of this material on the serious insects pests .Aouintyetal(2006) have proved
hight activity of the aqueous extraction ofRicinuscommunis leaves on four species of mosquitos ,Obeng-Ofori
and Freeman (2000) found that ground leaves,water or acetone extracts and essential oil of R. communis were
acutely toxic to Sitophilusoryzae and Triboliumcastaneum.Castor oil alsoproduced hight mortality on adults of
scale insect Parlatoriablanchardion date palm (Naser etal,2008).In addition,many studies reported the
effectiveness of castor oil in protecting stored grains against different insect pests, Pierrard(1986)used oils of
groundnut , castor , coconut , palm kernel , corn cotton , babassu , mustard , olive , seasome , sunflower and rice
, in that study castor oil at 8 ml/kg provided complete control against Callosobrochus maculates,Lal and
Raj(2012) used neem oil, eucalyptus, sunflower oil and castor oil in protecting pigeon pea against the pulse
beetles and they found that castor oil was recorded in terms of reduction inweight loss of the grains , as it gave
100% control..
And because of the little studies that respect with the activity of material found inRicinuscommunis in
Iraq ,so this research have been designed to experience the activity of castor oil in controlling the larvae and
adults of confused floor and khapra beetles.
2.MaterialsAnd Methods
2.1 Insect rearing
Triboliumconfusum andTrogonellagranarium were reared in glass containers (20 cm length,12 cm width and 8
cm hight) covered by a fine mesh cloth for ventilation,containing wheat flour mixed with yeast (10:1) (w:w)
respectively.The culture were maintained in a dark incubator at 27±1?C and 65±5% relative humidity(Abbassand
Javad,2012).Four larval instars and adults were used to investigatethe effect of castor oil on these two pests.
2.2 Preparation of concentrations of castor oil
Castor oil was obtained from local markets ,three concentrations were prepared 2%,5% and 10%respectively,by
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ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online)
Vol.4, No.4, 2014
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using acetone (Fouad,2013).
2.3 Fumigant bioassay of insects
To determine fumigant toxicity of castor oil ,petridishes were used each containing 10 adults or larvae (of aech
instar).Filter paper whatman?1(9 cm diameter )were prepared by adding 2ml of each concentration then fiter
papers were fixed to the surface of petridishescover,Treated insects were transferred to untreated petridishes after
24 hr.Tree replicates were run for each concentration and for control group ,mortality was determined after 48hrs
after exposure .When no signs of leg or antennal movement were observed,insects were considered dead
(Mahmoudvand etal,2011).
2.4 Statistical analysis
The mortality counts were corrected by using Abbott formula (Abbott,1925).All data were analyzed by using
Analysis of variance (ANOVA) and Least significant differences (LSD).
3.Results
3.1 Fumigant bioassay on adult beetles
Figure( 1) and( 2) show mortality trends forT.confusum and T.granarium adults at different concentrations of
castor oil.Results indicated that all concentratios of castor oil affected adults of the two insects ,statistical
analysis showed that the hightest mortality for adults ofT.confusum were 23.333% and 26.666% at 2% and
10% of castor oil(Table 1).Table(2) showed mortality of T. granarium adults exposed to different concentrations
of castor oil,statistical analysis showed that all three concentrations significantly caused high mortality but 10%
of castor oil killed 100% of khapra beetles
Figure(2) mortality of Trogonellagranarium adults exposed to different cocentrations of castor oil
cocentrations of castor oil
0
13.3333
23.3333
26.6667
0
5
10
15
20
25
30
control 2 5 10
% of mortality
concentration%
20
83.3333 86.666
1.00E+02
0
20
40
60
80
100
120
control
% of mortality
concentration%
Figure (1) mortality of Triboliumconfusum adults exposed to different concentratios of castor oil
L.S.D(0.05)=10.738
2 5 10
L.S.D(0.05)=19.606
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3.2 Fumigant Bioassay on larval Instars
Table(1) and table(2) showed mortality of different larval instars of T.confusum and T. granarium exposed to
three concentrations of castor oil.Statistical analysis showed that 5% and 10%concentrations of castor oil were
the most effective on first , second and third larval instars of T.confusum, as they caused 60% and 66.6%
mortality for the first larval instar, 50% and 63.3% mortality for second larval instar and, 33.3% and 40% for
third larval instar at 5% and 10% concentration respectively compared with 0% at control treatment table(1).In
table(2) results showed that the threeconcentrations of castor oil affected first ,second and third larval instars of
T. granarium significantly ,the percentage of mortality was 86.6%, 90.0% and 93.3% for the first laval
instarcompared with 40.0% at control treatment, 70.0%,70.0% and 80.0% for second larval instars compared
with 20% at control treatment,and 40.0%, 63.3% and 80.0% for third larval instar compared with 20.0% at
control treatment, at 2%,5% and 10% concentrations respectively.
Table(1) Effect of different concentrations of castor oil on larval instars of Tribolium confusum
% of mortality
Larval instar
Concentration%
0 2 5 10
66.6* 60.0* 1st 0.0 23.3
63.3* 50.0* 2nd 0.0 23.3
40.0* 33.3* 3rd 0.0 23.3
33.3* 20.0 4th 0.0 13.3
LSD(0.05)FORLARVALINSTAR=8.061
LSD(0.05)FORCONCENTRATION=8.060
LSD(0.05)FOR INTERFERANCE=16.123
Table(2) Effect of different concentrations of castor oil on larval instars of Trogonella granarium
% of mortality
Larval instar Concentrations %
0 2 5 10
93.3* 90.0* 86.6* 1st 40.0
80.0* 70.0* 70.0* 2nd 20.0
63.3 80.0 * 40.0* 3rd 20.0
76.6* 50.0* 4th 0.0 16.6
LSD(0.05)FORLARVALINSTAR=7.279
LSD(0.05)FORCONCENTRATION=7.296
LSD(0.05)FORINTERFERANCE=14.559 .
4.Discussion
Natural compounds from plants could be efficient alternatives to conventional fumigants because of their low
toxicity to mammals, fast degradability properties,and regional availability (Rajendran and Sriranjini, 2008),our
results on fumigant toxicity ofcastor oil on adults and larval instars of T.confusum and T. granariumindicated
that this oil had a good toxicity on these pests by fumigation.It was found thatT. granariumadults and larval
instars were more affected with all castor oil concentrations than those ofT.confusumas the mortality of
T.confusum adults were hightest only in 10% concentration while all concentrations caused significant
mortalities in the adults of T. granarium,especially 10% which killed all the beetles ,on the other hand the
highly toxic concentrations of castor oil on T.confusum larva were 5% and 10% while all concentrations were
very toxic on larva of T. granarium,this indicated that khapra beetlesare more susceptible than confused
beetlesand low concentrations are more effective on them ,this result is similar to those ofAggarwal etal(2001)
which found thatadults of T. castaneum were the most highly tolerant to the vapor action of all the compounds
tested ,the difference in theresponse of the insect species to the essential oils has been reported for stored product
insects (Lee et al. 2003; Negahbanetal. 2007).
The high mortality in larva in this work was similar to that of Tounouetal(2011) which found high larval
mortality in Plutellaxylostella by using castor oil.Castor oil and pure compounds of R. communishave been
reported to exhibit high toxic effects in target animals (Olsnes, 2004).The insecticidal activity of plant materials
derived from R. cummunisis attributed to its major components of protein ricin and alkaloid ricinine which are
lethal at very low concentrations (Abbiw, 1990). Ali etal (2000) reported that oil of R.communis seeds contains
phenolic materials which have toxic properties on insects through direct effect on nervous system ,digestive
system and analytical enzymes.Ricin causes acute cell death by inactivation of ribosomal RNA, inhibiting
protein synthesis (Roberts & Smith,2004;Utskarpen et al., 2006; Parikh et al., 2008)
.Results of this study clearly illustrated that insects varied in their susceptibility to different essential oils, which
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Vol.4, No.4, 2014
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probably refers to the insecticidal ability of their active constituents.
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