Insecticidal Efficacy of Castor and Hazelnut Oils in Stored Cowpea Against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)
Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)
is a primary pest of cowpea and other legumes worldwide, both in fields
and in stored seeds. Castor oil at 5, 6, 7, 8 and 9 mL kg-1
and Hazelnut at 2.8, 4.4, 6, 7.6 and 9.2 mL kg-1 were tested
against C. maculatus in cowpea. All bioassays were conducted at
27±1°C and 65±5% r.h and mortality was counted after
24, 48 and 72 h of exposure. After the 72 h mortality count, all adults
were removed and the vials were left at the same conditions for further
35 days to assess progeny production. The increase of dose and exposure
interval increased mortality. After 72 h of exposure, mortality received
to 80.83% on Hazelnut oil at high rate (9.2 mL kg-1). Mortality
in the case of Castor oil was higher than Hazelnut and received to 86.66%
at 9 mL kg-1. The lowest LC50 value on 72 h was
observed in the Hazelnut (6.57 mL kg-1). In contrast, the lowest
LC95 value on 72 h was observed in the Castor (l0.94 mL kg-1).
Complete suppression in progeny production was achieved on cowpea treated
with Castor oil at 9 mL kg-1 but in the all case, the percentage
of reduced progeny received up to 90%. In conclusion, treatment of grain
with vegetable oil could have important practical implications for parts
of the world where pesticides are expensive or in short supply.
Cowpea, Vigna unguiculata Walpers, is an important food legume and an
essential component of cropping systems in the drier regions and marginal areas
of the tropics and subtropics. With their high protein content cowpeas are a
natural supplement to cereal, root and tuber staples in the human diet (Cherry
et al., 2005). The beetles of the family Bruchidae are closely associated
with the plant family Leguminosae and many species are important primary insect
pests of stored legumes (Rajapakse and Van Emden, 1997).
Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) is a primary pest
of cowpea and other legumes worldwide, both in fields and in stored seeds (Singh
and Van Emden, 1979). Attack on stored grain by C. maculatus significantly
reduces the quantity and quality of seeds destined for both human consumption
and sowing purposes. The development of a single larva in a grain can lead to
weight losses of 8-22% (Credland et al., 1986).
Residual insecticides have been used routinely for many years to control insect
pests in stored grain. These insecticides are primarily organophosphorous and
pyrethroid compounds and the residues from this single application can often
prevent insects from establishing in stored grain. However, use of residual
insecticides is becoming less desirable because of the resistance in major insects,
regulatory restrictions on use of insecticides, awareness of environmental pollution,
the increasing cost of storage insecticides, erratic supplies, worker safety
and consumer desire for a pesticide-free product, has led to pest management
specialists reappraising natural products (Arthur, 1996;
Lorini and Galley, 1999). Control of C. maculatus currently relies
on the use of chemical insecticides (Jackai and Adalla, 1997).
Plant products have played an important role in the traditional methods of
protection against crop pests and disease vectors (Poswal
and Akpa, 1991). In ancient times, oils obtained from locally available
plants were used for stored grain protection against insect attack. In recent
years, attention has been given to the use of vegetable oils as post harvest
grain protectants against insects (Perieira, 1983; Don-Pedro,
1989; Bekele et al., 1995; Rajapakse
and Van Emden, 1997; Obeng-ofori et al., 2000;
Obeng-ofori and Amiteye, 2005). The mode of action of
these oils is yet to be confirmed, but most appear to cause death in the insect
egg, larvae or adult by suffocation (Don-Pedro, 1989).
The action of vegetable oils is due to suffocation, but in other cases, oils
can act as antifeedants or even act as Insect growth regulators (IRGs) by affecting
metamorphosis (Weaver and Subramanyam, 2000).
The objectives of the present study were to assess the efficacy of two
vegetable oils, Castor (Ricinus communis L.) and Hazelnut (Corylus
avellana L.) against C. maculatus on stored cowpea.
MATERIALS AND METHODS
Insect rearing: The initial stock culture of C. maculatus
was obtained from Department of Plant Protection, Agricultural Faculty,
Urmia University, Urmia, Iran. Cowpea grains of the variety Kamran cleaned
and disinfested by storing at -12°C for a week. Insect cultures were
maintained in glass jar (1 L) filled with 200 g of clean and disinfested
cowpea grains. Each jar was then infested with 200 adults of C. maculatus
of mixed sex and age and covered with nylon mesh secured with rubber
bands. Infested grains were incubated at 27±1°C and 65±5%
relative humidity (r.h.) with a natural photoperiod. After 72 h, the parental
adults were removed by sieving and the cowpea grains were kept at the
same conditions. Progeny emergence was checked daily and new adults were
kept in separation jar containing cowpea grains.
The oils: Vegetable oils (from Castor, Ricinus communis L.
and Hazelnut, Corylus avellana L.) were obtained from a local supermarket.
Bioassay: On the basis of preliminary tests, the oils were applied at
five rates in a logarithmic series (Robertson and Preisler,
1992): 2.8, 4.4, 6, 7.6 and 9.2 mL kg-1 for Hazelnut and 5, 6,
7, 8 and 9 mL kg-1 for Castor. Mortality was counted after 24, 48
and 72 h of exposure. Five lots of 0.5 kg of cowpea were prepared and placed
in separate cylindrical jars and treated with appropriate rate. All jars were
shaken manually for approximately 5 min to achieve equal distribution of the
oils in the entire grain mass. Four samples, of 50 g each, were taken from each
jar as replication. Thirty 0-24 h old adults were used for each replication.
All experiments carried out in 27±1°C and 65±5% r.h. After
the 72 h mortality count, all adults (dead and alive) were removed from the
vials and the vials were left in the incubators at the same conditions for further
35 days to assess progeny production.
Statistical analysis: The mortality counts were corrected by using Abbott′s
(1925) formula. Percentage of reduction in progeny production was determined
by the [(No. progeny in control No. progeny in treatment)/No. progeny in controlx100]
formula (Aldryhim, 1990). To equalize variances, mortality
percentage of adults and percentage of reduction in progeny production were
transformed using the square root of the arcsin. The data were analyzed using
Analysis of Variance (SAS, 2000). Means were separated
by using the Tukey Multiple Range Test at p = 0.05. The dose required to kill
50% of the insects (LC50) was estimated using probit analysis (SPSS,
Adult′s mortality: For Castor oil, all main effects as well
as all associated interaction were significant at the p<0.0001 level
(rate: df =4, 59; F = 107.82; exposure: df = 2, 59; F = 37.33; ratexexposure:
df = 8, 59; F =2.9). Although, for Hazelnut oil, all main effects as well
as all associated interaction were significant at the p<0.0001 level
(rate: df = 4, 59; F = 76.27; exposure: df = 2, 59; F = 11.18; ratexexposure:
df = 8, 59; F = 3.61). Adult′s mortality of C. maculatus on
control treatment was very low (2.83%). Mortality percentage was increased
with increase of rate and exposure interval in both oils. At the 72 h
exposure interval, the highest mortality levels for castor oil were recorded
at 9 mL kg-1, where 86.66% (Fig. 2). In contrast,
for hazelnut, the highest mortality levels were recorded at 9.2 mL kg-1,
were 80.83% (Fig. 1).
The lowest and highest LC50 values on 72 h were observed in
the Hazelnut and Castor (6.57 and 7.05 mL kg-1, respectively).
In contrast, the lowest and highest LC95 values on 72 h were
observed in the Castor and Hazelnut (l0.94 and 14.13 mL kg-1)
||Mean adult mortality (%+SE) of C. maculatus adults,
on cowpea treated with Hazelnut oils at after 24, 48 and 72 h of exposure
||Mean adult mortality (%+SE) of C. maculatus adults,
on cowpea treated with Castor oils at after 24, 48 and 72 h of exposure
||The lethal dose for 50% (LC50) of C. maculatus
adults in cowpea treated with oils on 72 h
||Mean percentage of reduction (±SE) in progeny production
(F1) of C. maculatus in cowpea treated with Castor and Hazelnut oils
|Means followed by the same letter(s) in the row are
not significantly different (Tukey Multiple Range test at p = 0.05)
Progeny production: The application of oils highly significantly
reduced progeny production in the cowpea treated with both oils and the
main effect was significant in Castor (rate: df = 4, 19; F = 6.93; p =
0.0023) and Hazelnut (rate: df = 4, 19; F = 4.43; p = 0.0045). In both
oil and all rates, the percentage of reduction in progeny production received
up to 90%, even in low rate. The highest progeny reduction observed in
the cowpea treated with Castor oil at the rate of 9 mL kg-1
(100%) (Table 2).
In this study, vegetable oils; Castor and Hazelnut applied at different
rates, caused considerable mortality of C. maculatus compared to
untreated controls but the Castor oil can provide better control
of C. maculatus. Dead insects from oil-treated grain showed signs
of rapid immobilization with their legs flexed and clinging to either
the grain or the container surface. This observation highlights the need
for screening for more plant materials for use in the management of this
Several earlier studies have demonstrated the effectiveness of different vegetable
oils in protecting grains against major stored-product insect pests (Shaaya
et al., 1976; Don Pedro, 1987, 1989;
Obeng-ofori, 1995). Singh et al.
(1978), Messina and Renwick (1983), Pandey
et al. (1983), Pereira (1983) and Don-Pedro
(1989) have shown that oil coating is effective in controlling C. maculatus
and present result are accordance with them results. Although, the mode of action
of vegetable oils is not clearly understood, it has been suggested by Don-Pedro
(1989) that insect death caused by oils is due to anoxia or interference
in normal respiration resulting in suffocation (Schoonhoven,
1978). The oils could also act as antifeedants or modify the storage micro-environment
thereby discouraging insect penetration and feeding (Obeng-ofori,
Pacheco et al. (1995) used refined soybean and
crude castor oils and these were evaluated for the control of infestations of
C. maculatus and C. phaseoli (Gyllenhal) in stored chickpea (Cicer
arietinum L.). They observed that both oils inhibited population growth
of the two insect species as compared to untreated seeds. Castor oil was more
effective than soybean oil. In our experiments, also the Castor oil was more
effective than Hazelnut because of higher mortality (86.66% in 9 mL kg-1
for Castor in contrast of 80% in 9.2 mL kg-1 for Hazelnut).
Rajapakse and Van Emden (1997) demonstrated that corn,
groundnut, sunflower and sesame oil reduced oviposition by three bruchid species:
C. maculatus, C. chinensis and C. rhodesianus by over
70% at a concentration of 10 mL kg-1 cowpea seeds. In our experiments,
the percentage of reduction in progeny production received up to 90% in both
oils even at low rates (93.85% in 2.8 mL kg-1 for Hazelnut and 98.75%
in 5 mL kg-1 for Castor) and complete reduction in progeny production
observed in cowpea treated with 9 mL kg-1 of Castor oil that received
to 100%. Credland (1992) has explained the ovicidal effect
of oils on bruchids in terms of asphyxiation by occluding a funnel which is
probably the major route of gas exchange between a thin area of the chorion
and the outside.
In conclusion, the results of this study show that Castor and Hazelnut
oils, when added to cowpea, affords good protection to the grain by killing
various life stages of C. maculatus via contact, antifeedant and
possibly stomach action. Further research into the bioactivity of these
two oils and its constituents against other stored product insects is
needed before commercial application can be considered. The application
of oils may minimize insecticide usage and hence reduce health hazards
to applicators and reduce the amount of insecticides used to protect stored
products. The mode of action of vegetable oils needs to be studied in
more detail to promote the development of more potent fractions for use
as grain protestants. Treatment of grains with vegetable oils could have
important practical applications in the parts of the world where insecticides
are expensive, in short supply or where vegetable oils are readily available.
Abbott, W.S., 1925.
A method of computing the effectiveness of an insecticide. J. Econ. Entomol., 18: 265-267.CrossRef | Direct Link |
Aldryhim, Y.N., 1990.
Efficacy of the amorphous silica dust, Dryacide against Tribolium confusum
DuV. and Sitophilus granarius
(L.) (Coleoptera: Tenebrionidae and Curculionidae). J. Stored Prod. Res., 26: 207-210.CrossRef | Direct Link |
Arthur, F.H., 1996.
Grain protectants: Current status and prospects for future. J. Stored Prod. Res., 32: 293-302.CrossRef |
Jembere, B., D. Obeng-Ofori, A. Hassanali and G.H.N. Nyamasyo, 1995.
Products derived from the leaves of Ocimum kilimandscharicum
(Labiatae) as post-harvest grain protectants against the infestation of three major stored product insect pests. Bull. Entomol. Res., 85: 361-367.CrossRef |
Cherry, A.J., P. Abalo and K. Hell, 2005.
A laboratory assessment of the potential of different strains of the entomopathogenic fungi Beauveria bassiana
(Bals.) Vuillemin and Metarhizium anisopliae
(Metsch.) Sorokin to control Callosobruchus maculatus
(F.) (Coleoptera: Bruchidae) in stored cowpea. J. Stored Prod. Res., 41: 295-309.CrossRef | Direct Link |
Credland, P.F., 1992.
The structure of bruchid eggs may explain the ovicidal effects of oils. J. Stored Prod. Res., 28: 1-9.Direct Link |
Credland, P.F., K.M. Dick and A.W. Wright, 1986.
Relationships between larval density, adult size and egg production in the cowpea seed beetle, Callosobruchus maculatus
. Ecol. Entomol., 11: 41-50.CrossRef | Direct Link |
Don-Pedro, K.N., 1989.
Mechanisms of action of some vegetable oils against Sitophilus zeamais
motsch (Coleoptera: Curculionidae) on wheat. J. Stored Prod. Res., 25: 217-223.CrossRef | Direct Link |
Don-Pedro, K.N., 1987.
Insecticidal activity of plant oils against stored product pests. Ph.D. Thesis. University of London.
Weaver, D.K. and B. Subramanyam, 2000.
Botanicals. In: Alternatives to Pesticides in Stored-Product IPM, Subramanyam, B.H. and D.W. Hagstrum (Eds.). Kluwer Academic Publishers, Dordrecht, ISBN-13: 9780792379768, pp: 303-320
Jackai, L.E.N. and C.B. Adalla, 1997.
Pest Management Practices in Cowpea: A Review. In: Advances in Cowpea Research, Singh, B.B., D.R. Mohan-Raj, K.E. Dashiell and L.E.N. Jackai (Eds.). Sayce Publishing, Devon, UK., pp: 240-258
Lorini, I. and D.J. Galley, 1999.
Deltametrin resistance in Rhyzopertha dominica
(Coleoptera: Bostrychidae) a pest of stored grain in Brazil. J. Stored Prod. Res., 35: 37-46.Direct Link |
Messina, F.J. and J.A.A. Renwick, 1983.
Effectiveness of oils in protecting stored cowpeas from the cowpea weevil (Coleoptera: Bruchidae). J. Econ. Entomol., 76: 634-636.CrossRef | Direct Link |
Obeng-Ofori, D. and S. Amiteye, 2005.
Efficacy of mixing vegetable oils mixed with pirimiphos-methyl against the maize weevil, Sitophilus zeamais
Motschulsky in stored maize. J. Stored Prod. Res., 41: 56-57.Direct Link |
Obeng-Ofori, D., B. Jembere, A. Hassanali and C. Reichmuth, 2000.
Effectiveness of plant oils and essential oil of Ocimum
plant species for protection of stored grains against damage by stored product beetles. Proceedings of the 7th International Working Conference on Stored Product Protection, October 14-19, 1998, Sichuan Publishing House and Technology, Chengdu, China, pp: 799-808
Obeng-Ofori, D., 1995.
Plant oils as grain protectants against infestations of Cryptolestes pusillus
and Rhyzopertha dominica
in stored grain. Entomol. Exp. Applicata, 77: 133-139.CrossRef | Direct Link |
Pacheco, I.A., M.F.P.P.M. de Castro, D.C. de Paula, A.L. Lourencao, S. Bolonhezi and M.K. Barbieri, 1995.
Efficacy of soybean and castor oils in the control of Callosobruchus maculatus
(F.) and Callosobruchus phaseoli
(Gyllenhal) in Stored Chick-peas (Cicer arietinum
L.) J. Stored Prod. Res., 31: 221-228.CrossRef | Direct Link |
Pandey, G.P., R.B. Doharey and B.K. Varma, 1983.
Efficacy of some vegetable oils for protecting greengram against the attack of Callosobruchus maculatus
(F.). Indian J. Agric. Sci., 51: 910-912.
Pereira, J., 1983.
The effectiveness of six vegetable oils as protectants of cowpeas and bambara groundnuts against infestation by Callosobruchus maculatus
(F.) (Coleoptera: Bruchidae). J. Stored Prod. Res., 19: 57-62.CrossRef | Direct Link |
Poswal, M.A.T. and A.D. Akpa, 1991.
Current trends in the use of traditional and organic methods for the control of crop pests and diseases in Nigeria. Int. J. Pest Manage., 37: 329-333.CrossRef | Direct Link |
Rajapakse, R. and H.F. van Emden, 1997.
Potential of four vegetable oils and ten botanical powders for reducing infestation of cowpeas by Callosobruchus maculatus
, C. chinesis
and C. rhodesianus
. J. Stored Prod. Res., 33: 59-68.CrossRef | Direct Link |
Robertson, J.L. and H.K. Preisler, 1992.
Pesticide Bioassays with Arthropods. 1st Edn., CRC Press, Boca Raton, Florida, ISBN-10: 0849364639, pp: 35-48
The SAS System for Windows. Version 7, SAS Institute, Cary, NC
Schoonhoven, A.V., 1978.
Use of vegetable oils to protect stored beans from bruchid attack. J. Econ. Entomol., 71: 254-256.CrossRef | Direct Link |
Shaaya, E., G. Grossman and R. Ikan, 1976.
The effect of straight chain fatty acids on growth of Calandra oryzae
. Israel J. Entomol., 11: 81-90.Direct Link |
Singh, S.R. and H.F. Van Emden, 1979.
Insect pests of grain legumes. Ann. Rev. Entomol., 24: 225-278.CrossRef | Direct Link |
Singh, S.R., R.A. Luse, K. Leuschner and D. Nangju, 1978.
Groundnut oil treatment for the control of Callosobruchus maculatus
(F.) during cowpea storage. J. Stored Prod. Res., 14: 77-80.CrossRef | Direct Link |
SPSS for Windows User's Guide Release 10. 1st Edn., SPSS Inc., Chicago