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Comparative Biological Activity of Synzygium aromaticum (L) and Xylopia ethiopica on Rhizopetha dominica F (Coleoptera: Bostrychidae) and Sitophilus zeamais Motsch (Coleoptera: Cuculionidae) in Maize Grains
J. Asia-Pacific Entomol. 7(3): 339 - 342 (2004) www.entomology.or.kr
SHORT COMMUNICATION
Comparative Biological Activity of Synzygium aromatieum (L.) and Xy/opia efhiopiea on Rhizopefha dominiea F, (Coleoptera: Bostrychidae) and Sifophilus zeamais Motsch (Coleoptera: Cuculionidae) in Maize Grains Kemabonta Kehinde* and Okoye Angela Nigerian Stored Products Research Institute, P. M. B. 12543, Lagos, Nigeria
Abstract Powders obtained from dry ground leaves of Synzygium aromaticm (L) and Xylopia ethiopica
were treated under laboratory conditions (26.4 ± 3 °C and 70-79% r.h) for their abilities to protect grains from damage by adult Rhizopertha dominica F and Sitophilus zeamais Motsch. The adult insects were reared and tested on whole maize grains. The powders were mixed with maize grains at different dosage levels ranging from 1-5% (wt/wt). S. aromaticum caused significantly higher mortality in the two insects than xylopia ethopica. Maize grains treated with 5% concentration of S. aromaticum caused 90 and 55% mortalities of S. zeamais and R. dominica respectively after 7 days, while X ethiopica treated-grains caused 50 and 15% mortalities respectively at the same time. Five % concentration of S. aromaticum inhibited F1 progeny production and adult emergence of Sitophilus zeamais. Significantly lower number of Fl adults of R: dominica emerged from grains treated with S. aromaticum when compared to adult emergence from X ethiopica-treated grains. The powders significantly increased the developmental period of the two insects when compared to the control except in X ethiopica that had no significant effect on S. zeamais.
Key words biological activity, developmental period, mortality, Rhizopetha dominica, Sitophilus zeamais, Synzygium aromaticum, Xylopia ethiopica
Introduction It is estimated that 60-80 percents of all grains
produced in the tropics is stored at the farm level. For small farmers, the main purpose of storing grain is to ensure household food supplies. Farm storage also provides a form of savings to cover future cash *Corresponding author. E-mail: [email protected] Tel: +234-802-223-5317 (Received December 29, 2003; Accepted September 7, 2004)
needs through sale or for batter or gift exchange. Small quantities of grain are also stored for seed. Farmers who produce a surplus may also store grain for sale later to take advantage of seasonal price rises (Golob et al., 1999).
In Nigeria, insect pests cause the greatest loss during storage of cereals and other durable commodities such as cowpeas and oilseeds. Losses may be as low as 5 percent over a storage season (Tyler and Boxall, 1984) or may exceed 25 percent by weight in severe cases (Golob and Muwalo, 1984 and Golob et al., 1999). Rhizopertha dominica F and Sitophilus zeamais
Motsch are primary pests of maize in storage. Eggs of R. dominica are usually laid within the stored cereal. The eggs develop into scarabeiform larvae. The larvae eat their way into the grains and pupate there (Stoll, 1986). The development from egg to adult is completed in 30 days at 34°C (Hill and Waller, 1988) and a female lays an average of 400 eggs. Female S. zeamais lays an average of350 eggs singly in holes made in the grain with its mouthparts and plugs it with a waxy material. The eggs hatch into larvae called grubs, which feed extensively on the grain. The larval stage is the most destructive stage of the weevil. The larvae pupate inside the grain and adult emerges through a circular hole made on the outer coat of the grain. The life cycle of S. zeamais takes 5 weeks at 30°C and 70% relative humidity (Hill, 1983). For over two decades, the protection of stored agricultural commodities was accomplished through the use of synthetic insecticide (Ivbijaro, 1990; Lale and Efeovbokan, 1991). There is now a shift from the reliance on conventional insecticides towards the use of more natural, sustainable methods of protecting crops from insect damage. A lot of researches have been carried out on the use of plant products (Colley and Steele, 1976; Agbakwuru et al., 1978; Ivbijaro 1984; Singhamony et al., 1986; Lale, 1992). However, it is evident that far more researches are required to critically evaluate most of these plants as stored product protectants especially with respect to their comparative toxicities on all the primary stored product insect pests.
340 J. Asia-Pacific Entomol. Vol. 7 (2004)
The main purpose of this study is to seek an effective plant species, which can be readily available in the local environment and will be able to control many stored product insect pests. The objective of the research is to compare the biological activity of Synzygium aromaticum (L) (Cloves) andXylopia ethiopica (Uda) on two pests of maize in storage, Rhizopetha dominica F and Sitophilus zeamais Motsch.
number of adults that emerged and the developmental period of the adults were also noted.
Statistical analysis Data were subjected to 2-way analysis of variance (ANOVA) and means were separated using New Duncan's Multiple Range Test (NDMRT) at 0.05 level of significance.
Materials and Methods Results Insect rearing and maize grains used Maize grains were purchased from the Iddo market in Lagos, Nigeria. They were picked and kept in the freezer for 5 days to disinfest them. They were thereafter removed and kept in Kilner jars under laboratory conditions 26.4 ± 3°C and 70-79% R.H. S. zeamais and R. dominica used were collected from the entomology insectory of the Nigerian Stored Products Institute, Lagos, Nigeria. Unsexed adult insects (1-7 days old) were used. This was done by sieving insects from the existing cultures and leaving the cultures for seven days. The insects used, thereafter were 1-7 days old. '
Plant product used S. aromaticun (Cloves) and X ethiopica (Uda) produce spicy fruits used in soup flavoring and traditional medicine in Nigeria. They were reported as having insecticidal properties (Rehn and Espig, 1991; Sighamony et al., 1984; Javid and Poswal, 1995). They were purchased from Iddo market in Lagos, sun-dried for two weeks and pulverized using pestle and mortar and laboratory mill. The powders were sieved using a O.lmm mesh.
Toxicity tests Three concentrations 1, 3 and 5% (w/w) of the powders were used including a control that had no powders added to the grains. The Maize grains were admixed with the different concentrations of powders used. The unsexed, but mated insects (30 each) and 50g of the treated grains were confined inside a transparent plastic cup (disposable cups) and muslin cloth was used to cover the cups. The cloth was strapped to the cup using rubber bands to prevent escape of the insects. The mortality of the adult insects was recorded after 7 days and the insects were thereafter discarded. Four replications were made for each treatment including the control. The experiment was kept aside for the adults (F1) to emerge. The
There was no significant difference between the percentage mortality in the control and X ethiopica treated grains except with 5 percent grains treated with X ethiopica which was significantly higher than other treatments and control. The percentage mortality of R. dominica increased significantly as treatment with S. aromaticum increased (P > 0.05). 55% and 15% mortalities of adult R. dominica were recorded on grains treated with 5% S. aromaticum and X etiopica respectively after 7 days. On the other hand, percentage mortality of adult S. zeamais increased significantly from control (5%) to 5% treatment (50%) of S. aromaticum treated grains. Same trend was observed on the mortality of S. zeamais when the grains were treated with S. aromaticum. S. aromaticum caused significantly higher mortality on the two insects than X ethiopica-treated grains. R. dominica had a significantly longer developmental period from grains treated with X ethiopica and S. aromaticum than in the control grains (Table 1). No significant difference occurred in the developmental period of S. zeamais in maize grains treated' with X ethiopica and the control seeds. The developmental period of S. zeamais was significantly higher in grains treated with the two powders compared to the control. Significantly lower number of R. dominica (Fl) adults emerged from seeds treated with both X ethiopica and S. aromaticum when compared to the control. Number of R. dominica adults that emerged however differed from S. aromaticum and X ethiopica but not significantly. S. zeamais adults (F1)that emerged from S. aromaticum were significantly lower than the control. No S. zeamais (Fl) adults emerged from grains treated with 5 percent S. aromaticum (Table 2).
Discussion The results show that both S. aromaticum and X ethiopica controlled the infestation of S. zeamais and
Biological activity of two spices on R. dominica and S. zeamais
341
Table 1. Mortality of adult insects treated with X ethiopica and S. aromaticum and the developmental period of F I adults
Treatments I
X ethiopica
S. aromaticum
I
2
Concentration (%)
Mortality after 7 days (%)
R. dominica 2
Developmental period
S. zeamais
R. dominica
S. zeamais
5±O.9a
32.5±O.8a
26.0±2.la
20±2.1b
41.3±3.4b
34.2±1.5a
0
O±O.5a
I
5±3.la
2
5±O.7a
40± l.lc
44.0±3.7b
35.3±O.5a
5
15±2.9b
50±O.6c
45.3±2.9b
36.1±1.4a
0
O±O.3a
O±3.9a
32.3±2.1a
25.6± 1.9a
I
25±4.4b
35±5.lb
37.4±3.6b
35.3±O.5b
2
35±1.7b
45±3.6b
37.9±4.0b
35.6±O.8b
5
55±OAc
90±4.7c
39.5±2.6b
37.4±OAb
See Materials and Methods for details of preparation of plant toxicants. Means followed by the same letter in any column are not significantly different at 0.05 level of probability according to NDMRT.
Table 2. Fl adults that emerged from X ethiopica and S. aromaticum-treated maize grains
Treatments'
X ethiopica
S. aromaticum
J 2
Concentration(% )
Fl adults that emerged R. dominica 2
S. zeamais
0
22.5±3.9b
46.5±2.7b
I
5.5±2.1a
22.5±3.2a
2
4.0± l.la
15.2±4.5a
5
3.0±4.9a
18.5±2.3a
0
19.5±3.6b
44.5 ±4.4b
I
4.0±5.2a
1O.5± 1.2a
2
2.5±2.6a
11.5± l.3a
5
1.5 ±O.2a
O.O±O.la
See Materials and Methods for details of preparation of plant toxicants. Means followed by the same letter in any column are not significantly different at 0.05 level of probability according to NDMRT.
R. dominica when compared to the control. However, Synzygium aromaticum (L) was more effective in preventing the infestation of the two insects by increasing the mortalities of adult insect treated and reducing F1 adults that emerged from treated grains when compared to the X ethiopica. Five % (w/w) of S. aromaticum completely prevented the emergence of S. zeamais Fl adults. High mortality and or contact toxicity with the prevention of Fl emergence in S. aromaticum have been reported by a number of scientists on stored product pests. The insects include Callosobruchus maculatus (Javid and Poswal, 1995), S. zeamais (Ho et al., 1994), and Tribolium casternum (Ho et al., 1994). The high insect mortality of S. aromaticum was due to the biologically active agent called eugenol, a sesquiterpene and caryophylline (Schauenberg and Paris, 1977). Eugenol belongs to the terpenoids, which may disrupt major metabolic pathways and cause rapid death or modify oviposition. It may also be the cause
of the retardation of the development of the insects (Bell et al., 1990). S. aromaticum is also found to be particularly effective, often completely inhibiting both fungal growth and toxin production (Azzouz and Bullerrnan, 1982; Hitokoto et al., 1984). S. aromaticum can therefore serve as insecticidal or fungicidal protectant. Not many investigations have been done on the potentials of X ethiopica. Though X ethiopica did not cause rapid death of treated insects, it however may have prevented oviposition or the development of oviposited eggs. It also caused a significant retardation in developmental period of emerged insects. These may be due to the biological active components in the plant products. More research on X ethiopica should be carried out as; it has a great potential as a plant protectant. Powder of S. aromaticum is more effective than X ethiopica in controlling two major stored product pests. The farmers will not need to purchase organic
342
J. Asia-Pacific Entomol. Vol. 7 (2004)
solvent to extract S. aromaticum nor even be able to afford buying the solvents. S. aromaticum is used in traditional medicine and as a culinary spice in Nigeria. It can be bought in any market, even in the most remote villages. It stands as a promising protectant against stored product pests. However for it to be nationally accepted, further researches on its mammalian toxicity and the persistence or residual action over the period of storage are required. Acknowledgment The authors thank Mr. Shaba, S., Mrs. F.A Fagboun and Ms. Dupe Thomson for excellent technical assistance with the research work.
Literature Cited Agbakuru, E.O.P., I.U.W Osisiogu and E.N. Ugochukwu. 1978. Insecticides of Nigerian vegetable origin. II, Some nitroalkanes as protectants of stored cowpeas and maize against insect pests. Nig. 1. Sci. 12: 493-504. Bell, A.E. L.E Fellows and SJ. Simmonds. 1990. Natural products from plants for the control of insect pests. in Safer insecticide development and use. Eds. E. Hodgston and R.I. KUIT. Mercel Dekker, USA. Cobley L.S.and W.M. Steel. 1996. An introduction to the botany of tropical crops. 2nd ed., 371pp. Longman Group Limited, London, U.K. Golob, P., C. Moss, M. Dales, A. Fidger, J. Evans and I. Gudrups.l999. The use of spices and medicinals as bioactive protectants for grains. FAa Agric. Bull. 137. Golob, P and DJ.Webley. 1980. The use of plant and minerals as traditional protectants of stored products. Tropical products institute, G. 138. Now, post harvest pest and quality section, National Resources Institute, Chatman UK. Hill, D.S. 1983. Agricultural insect pests of the tropics and
their control. 2nd ed., 746pp. Cambridge University Press, Cambridge. Hill, D.S. and J.M.Waller. 1988. Pests and diseases of tropical crops. 432pp. John Willey and Sons Inc. NY. Hitokoto, H., S. Morozumi, S. Wauke, T. Sakai and H. Kurata. 1980. Inhibitory effects of spices on growth and toxin production of toxigenic fungi. Appl. Environ. Microbiol. 39: 818-212. Ivbijaro, M.F. 1984. Toxic effects of groundnut oil on the rice weevil, Sitophilus oryzae (L) in stored maize. Prot. Ecol. 33: 353-357. Ivbijaro, M.F. 1990. The efficacy of seed oils of Azadirachta indica A. Juss and Piper guinense Schum and Thonn on the control of Callosobruchus maculatus. Insect Sci. Appl. 11: 149-152. Lale, N.E.S. 1992. A laboratoty study of the comparative toxicity of products from three spices to the maize weevil. Post-harvest Bio!. Technol. 2: 61-64. Lale, N.E.S. and S.O. Efeovbokan. 1991. Resistance status of new cowpea cultivars to a storage insect pest, Callosobruchus maculatus. Post-harvest BioI. Techno!. I: 181-186. Rehms, Sand G. Espig. 1991 The cultivated plants of the tropics and subtropics- Verlag Josef Margrave. Weikersheim, Germany. Stoll, G. 1986. Natural crop protection in the tropics. AGRECOL. Ch- 4438. 188pp. Langenbruck, Switzerland. Schawenberg, P and F. Paris. 1977. Guide to medicinal plants. Butterworth Press, London. Singhamony, S., L. Anees, T.S. Chandrakala and Z.Osmani. 1984. Natural products as repellants for Tribolium casterneum Herbst. International Pest Control. 156-157. Singhamony, S., L. Anees, T.S. Chandrakala and Z. Osmani. 1986. Efficacy of certain indigenious plant products as grain protectantsagainst Sitophilus oryzae (L) and Rhizopertha dominica (F). J. Stored Prod. Res. 2: 21-23. Tyler, P.S and R.ABoxal. 1984. Post-harvest loss reduction programme; a decade of activities- what consequences? Trop. Stored Prod. Inform. 23: 13-28.
SHORT COMMUNICATION
Comparative Biological Activity of Synzygium aromatieum (L.) and Xy/opia efhiopiea on Rhizopefha dominiea F, (Coleoptera: Bostrychidae) and Sifophilus zeamais Motsch (Coleoptera: Cuculionidae) in Maize Grains Kemabonta Kehinde* and Okoye Angela Nigerian Stored Products Research Institute, P. M. B. 12543, Lagos, Nigeria
Abstract Powders obtained from dry ground leaves of Synzygium aromaticm (L) and Xylopia ethiopica
were treated under laboratory conditions (26.4 ± 3 °C and 70-79% r.h) for their abilities to protect grains from damage by adult Rhizopertha dominica F and Sitophilus zeamais Motsch. The adult insects were reared and tested on whole maize grains. The powders were mixed with maize grains at different dosage levels ranging from 1-5% (wt/wt). S. aromaticum caused significantly higher mortality in the two insects than xylopia ethopica. Maize grains treated with 5% concentration of S. aromaticum caused 90 and 55% mortalities of S. zeamais and R. dominica respectively after 7 days, while X ethiopica treated-grains caused 50 and 15% mortalities respectively at the same time. Five % concentration of S. aromaticum inhibited F1 progeny production and adult emergence of Sitophilus zeamais. Significantly lower number of Fl adults of R: dominica emerged from grains treated with S. aromaticum when compared to adult emergence from X ethiopica-treated grains. The powders significantly increased the developmental period of the two insects when compared to the control except in X ethiopica that had no significant effect on S. zeamais.
Key words biological activity, developmental period, mortality, Rhizopetha dominica, Sitophilus zeamais, Synzygium aromaticum, Xylopia ethiopica
Introduction It is estimated that 60-80 percents of all grains
produced in the tropics is stored at the farm level. For small farmers, the main purpose of storing grain is to ensure household food supplies. Farm storage also provides a form of savings to cover future cash *Corresponding author. E-mail: [email protected] Tel: +234-802-223-5317 (Received December 29, 2003; Accepted September 7, 2004)
needs through sale or for batter or gift exchange. Small quantities of grain are also stored for seed. Farmers who produce a surplus may also store grain for sale later to take advantage of seasonal price rises (Golob et al., 1999).
In Nigeria, insect pests cause the greatest loss during storage of cereals and other durable commodities such as cowpeas and oilseeds. Losses may be as low as 5 percent over a storage season (Tyler and Boxall, 1984) or may exceed 25 percent by weight in severe cases (Golob and Muwalo, 1984 and Golob et al., 1999). Rhizopertha dominica F and Sitophilus zeamais
Motsch are primary pests of maize in storage. Eggs of R. dominica are usually laid within the stored cereal. The eggs develop into scarabeiform larvae. The larvae eat their way into the grains and pupate there (Stoll, 1986). The development from egg to adult is completed in 30 days at 34°C (Hill and Waller, 1988) and a female lays an average of 400 eggs. Female S. zeamais lays an average of350 eggs singly in holes made in the grain with its mouthparts and plugs it with a waxy material. The eggs hatch into larvae called grubs, which feed extensively on the grain. The larval stage is the most destructive stage of the weevil. The larvae pupate inside the grain and adult emerges through a circular hole made on the outer coat of the grain. The life cycle of S. zeamais takes 5 weeks at 30°C and 70% relative humidity (Hill, 1983). For over two decades, the protection of stored agricultural commodities was accomplished through the use of synthetic insecticide (Ivbijaro, 1990; Lale and Efeovbokan, 1991). There is now a shift from the reliance on conventional insecticides towards the use of more natural, sustainable methods of protecting crops from insect damage. A lot of researches have been carried out on the use of plant products (Colley and Steele, 1976; Agbakwuru et al., 1978; Ivbijaro 1984; Singhamony et al., 1986; Lale, 1992). However, it is evident that far more researches are required to critically evaluate most of these plants as stored product protectants especially with respect to their comparative toxicities on all the primary stored product insect pests.
340 J. Asia-Pacific Entomol. Vol. 7 (2004)
The main purpose of this study is to seek an effective plant species, which can be readily available in the local environment and will be able to control many stored product insect pests. The objective of the research is to compare the biological activity of Synzygium aromaticum (L) (Cloves) andXylopia ethiopica (Uda) on two pests of maize in storage, Rhizopetha dominica F and Sitophilus zeamais Motsch.
number of adults that emerged and the developmental period of the adults were also noted.
Statistical analysis Data were subjected to 2-way analysis of variance (ANOVA) and means were separated using New Duncan's Multiple Range Test (NDMRT) at 0.05 level of significance.
Materials and Methods Results Insect rearing and maize grains used Maize grains were purchased from the Iddo market in Lagos, Nigeria. They were picked and kept in the freezer for 5 days to disinfest them. They were thereafter removed and kept in Kilner jars under laboratory conditions 26.4 ± 3°C and 70-79% R.H. S. zeamais and R. dominica used were collected from the entomology insectory of the Nigerian Stored Products Institute, Lagos, Nigeria. Unsexed adult insects (1-7 days old) were used. This was done by sieving insects from the existing cultures and leaving the cultures for seven days. The insects used, thereafter were 1-7 days old. '
Plant product used S. aromaticun (Cloves) and X ethiopica (Uda) produce spicy fruits used in soup flavoring and traditional medicine in Nigeria. They were reported as having insecticidal properties (Rehn and Espig, 1991; Sighamony et al., 1984; Javid and Poswal, 1995). They were purchased from Iddo market in Lagos, sun-dried for two weeks and pulverized using pestle and mortar and laboratory mill. The powders were sieved using a O.lmm mesh.
Toxicity tests Three concentrations 1, 3 and 5% (w/w) of the powders were used including a control that had no powders added to the grains. The Maize grains were admixed with the different concentrations of powders used. The unsexed, but mated insects (30 each) and 50g of the treated grains were confined inside a transparent plastic cup (disposable cups) and muslin cloth was used to cover the cups. The cloth was strapped to the cup using rubber bands to prevent escape of the insects. The mortality of the adult insects was recorded after 7 days and the insects were thereafter discarded. Four replications were made for each treatment including the control. The experiment was kept aside for the adults (F1) to emerge. The
There was no significant difference between the percentage mortality in the control and X ethiopica treated grains except with 5 percent grains treated with X ethiopica which was significantly higher than other treatments and control. The percentage mortality of R. dominica increased significantly as treatment with S. aromaticum increased (P > 0.05). 55% and 15% mortalities of adult R. dominica were recorded on grains treated with 5% S. aromaticum and X etiopica respectively after 7 days. On the other hand, percentage mortality of adult S. zeamais increased significantly from control (5%) to 5% treatment (50%) of S. aromaticum treated grains. Same trend was observed on the mortality of S. zeamais when the grains were treated with S. aromaticum. S. aromaticum caused significantly higher mortality on the two insects than X ethiopica-treated grains. R. dominica had a significantly longer developmental period from grains treated with X ethiopica and S. aromaticum than in the control grains (Table 1). No significant difference occurred in the developmental period of S. zeamais in maize grains treated' with X ethiopica and the control seeds. The developmental period of S. zeamais was significantly higher in grains treated with the two powders compared to the control. Significantly lower number of R. dominica (Fl) adults emerged from seeds treated with both X ethiopica and S. aromaticum when compared to the control. Number of R. dominica adults that emerged however differed from S. aromaticum and X ethiopica but not significantly. S. zeamais adults (F1)that emerged from S. aromaticum were significantly lower than the control. No S. zeamais (Fl) adults emerged from grains treated with 5 percent S. aromaticum (Table 2).
Discussion The results show that both S. aromaticum and X ethiopica controlled the infestation of S. zeamais and
Biological activity of two spices on R. dominica and S. zeamais
341
Table 1. Mortality of adult insects treated with X ethiopica and S. aromaticum and the developmental period of F I adults
Treatments I
X ethiopica
S. aromaticum
I
2
Concentration (%)
Mortality after 7 days (%)
R. dominica 2
Developmental period
S. zeamais
R. dominica
S. zeamais
5±O.9a
32.5±O.8a
26.0±2.la
20±2.1b
41.3±3.4b
34.2±1.5a
0
O±O.5a
I
5±3.la
2
5±O.7a
40± l.lc
44.0±3.7b
35.3±O.5a
5
15±2.9b
50±O.6c
45.3±2.9b
36.1±1.4a
0
O±O.3a
O±3.9a
32.3±2.1a
25.6± 1.9a
I
25±4.4b
35±5.lb
37.4±3.6b
35.3±O.5b
2
35±1.7b
45±3.6b
37.9±4.0b
35.6±O.8b
5
55±OAc
90±4.7c
39.5±2.6b
37.4±OAb
See Materials and Methods for details of preparation of plant toxicants. Means followed by the same letter in any column are not significantly different at 0.05 level of probability according to NDMRT.
Table 2. Fl adults that emerged from X ethiopica and S. aromaticum-treated maize grains
Treatments'
X ethiopica
S. aromaticum
J 2
Concentration(% )
Fl adults that emerged R. dominica 2
S. zeamais
0
22.5±3.9b
46.5±2.7b
I
5.5±2.1a
22.5±3.2a
2
4.0± l.la
15.2±4.5a
5
3.0±4.9a
18.5±2.3a
0
19.5±3.6b
44.5 ±4.4b
I
4.0±5.2a
1O.5± 1.2a
2
2.5±2.6a
11.5± l.3a
5
1.5 ±O.2a
O.O±O.la
See Materials and Methods for details of preparation of plant toxicants. Means followed by the same letter in any column are not significantly different at 0.05 level of probability according to NDMRT.
R. dominica when compared to the control. However, Synzygium aromaticum (L) was more effective in preventing the infestation of the two insects by increasing the mortalities of adult insect treated and reducing F1 adults that emerged from treated grains when compared to the X ethiopica. Five % (w/w) of S. aromaticum completely prevented the emergence of S. zeamais Fl adults. High mortality and or contact toxicity with the prevention of Fl emergence in S. aromaticum have been reported by a number of scientists on stored product pests. The insects include Callosobruchus maculatus (Javid and Poswal, 1995), S. zeamais (Ho et al., 1994), and Tribolium casternum (Ho et al., 1994). The high insect mortality of S. aromaticum was due to the biologically active agent called eugenol, a sesquiterpene and caryophylline (Schauenberg and Paris, 1977). Eugenol belongs to the terpenoids, which may disrupt major metabolic pathways and cause rapid death or modify oviposition. It may also be the cause
of the retardation of the development of the insects (Bell et al., 1990). S. aromaticum is also found to be particularly effective, often completely inhibiting both fungal growth and toxin production (Azzouz and Bullerrnan, 1982; Hitokoto et al., 1984). S. aromaticum can therefore serve as insecticidal or fungicidal protectant. Not many investigations have been done on the potentials of X ethiopica. Though X ethiopica did not cause rapid death of treated insects, it however may have prevented oviposition or the development of oviposited eggs. It also caused a significant retardation in developmental period of emerged insects. These may be due to the biological active components in the plant products. More research on X ethiopica should be carried out as; it has a great potential as a plant protectant. Powder of S. aromaticum is more effective than X ethiopica in controlling two major stored product pests. The farmers will not need to purchase organic
342
J. Asia-Pacific Entomol. Vol. 7 (2004)
solvent to extract S. aromaticum nor even be able to afford buying the solvents. S. aromaticum is used in traditional medicine and as a culinary spice in Nigeria. It can be bought in any market, even in the most remote villages. It stands as a promising protectant against stored product pests. However for it to be nationally accepted, further researches on its mammalian toxicity and the persistence or residual action over the period of storage are required. Acknowledgment The authors thank Mr. Shaba, S., Mrs. F.A Fagboun and Ms. Dupe Thomson for excellent technical assistance with the research work.
Literature Cited Agbakuru, E.O.P., I.U.W Osisiogu and E.N. Ugochukwu. 1978. Insecticides of Nigerian vegetable origin. II, Some nitroalkanes as protectants of stored cowpeas and maize against insect pests. Nig. 1. Sci. 12: 493-504. Bell, A.E. L.E Fellows and SJ. Simmonds. 1990. Natural products from plants for the control of insect pests. in Safer insecticide development and use. Eds. E. Hodgston and R.I. KUIT. Mercel Dekker, USA. Cobley L.S.and W.M. Steel. 1996. An introduction to the botany of tropical crops. 2nd ed., 371pp. Longman Group Limited, London, U.K. Golob, P., C. Moss, M. Dales, A. Fidger, J. Evans and I. Gudrups.l999. The use of spices and medicinals as bioactive protectants for grains. FAa Agric. Bull. 137. Golob, P and DJ.Webley. 1980. The use of plant and minerals as traditional protectants of stored products. Tropical products institute, G. 138. Now, post harvest pest and quality section, National Resources Institute, Chatman UK. Hill, D.S. 1983. Agricultural insect pests of the tropics and
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