SOME ASPECTS OF THE BIOLOGY AND CONTROL OF CALLOSOBRUCHUS MACULATUS (F.) ON SOME STORED SOYABEAN GLYCINE MAX (L.) MERR VARIETIES

Joseph Allotey*¹and Emmanuel O. Oyewo²

 Pulses include all the legume crops that are grown for dried seeds such as soya beans. Due to their comparative high protein contents, ease of handling, transportation and storage, pulses are of great importance in their role in the diet of Africans. However, pulses are subject to attack by many groups of biodeteriorative agents, of which bruchids are the most important.  In Ghana, soya beans have recently become a very important pulse. Even though soya bean is considered to be relatively resistant to attack by bruchids, not much is known about its susceptibility to the cowpea weevil, Callosobruchus maculatus (F.), a major pest of pulses in Africa and what available non-chemical control measures to use against the pest. In the present study, some aspects of the biology: oviposition, development, survival, fecundity and damage caused by C. maculatus on six stored soya bean, Glycine max (L) Merr. varieties, and control of the weevil, using plant materials such as neem, Azadirachta indica A. Juss (Meliaceae) and sweet orange, Citrus sinensis (Linn.) Osbeck (Rutaceae) powders were studied under ambient laboratory conditions (temperature range 28 – 30⁰C and 59 – 75 % relative humidity). Developmental period of C. maculatus was found to differ with the different varieties suggesting differences in the suitability of the varieties as food source. Based on the length of the developmental period of C. maculatus, damage caused, number of eggs laid and number of emerged adults, variety TGX 1473-2^D was the most resistant. TGX 1025-8^E appeared to be equally resistant but for the shorter developmental period of C. maculatus on it. Of the remaining varieties: TGX 923 – 2^E, TGX 1150-6^D, TGX 1118 – 1^D and LM, the local variety LM was the most susceptible. TGX 923-2^E was the most preferred for oviposition. The plant materials, Azadirachta indica seed powder and Citrus sinensis peel powder were found to be effective as seed protectants over a three month period. A. indica seed powder was found to have ovicidal and larvicidal properties. It is effective for use to suppress Callosobruchus maculates for short periods.

 Key words:     Callosobruchus maculatus, developmental period, soya bean, Azadirachta indica, Citrus sinensis

 FRENCH

ASPECTS DE LA BIOLOGIE ET DU CONTROLE DU CALLOSOBRUCHUS MACULATUS (F.) SUR LA CONSERVATION DES GRAINES DE SOJA DES VARIETES GLYCINE MAX (L.) MERR

NOTE DE SYNTHESE

Les légumes à cosse comprennent toutes les légumineuses cultivées pour leurs graines sèches,  telles que les graines de soja. En raison de leur haute teneur en protéines, de leur résistance à la manutention, au transport et à la conservation, les légumes à cosse sont d’une grande importance.  En outre, ils jouent un rôle essentiel dans le régime alimentaire des africains. Toutefois, ils sont sujets à bon nombre de groupes d’agents de détérioration biologique dont les principaux sont les bruches.  Au Ghana, les graines de soja connaissent depuis peu une importance croissante. Toutefois, même si la graine de soja résiste relativement à l’attaque des bruches, très peu est connu sur sa vulnérabilité au charançon du niélé, Callosobruchus maculatus (F.), principal ravageur des légumes à cosse en Afrique.  De même,  on dispose de très peu d’informations sur les mesures de contrôle non-chimique disponibles pour lutter contre cet insecte. L’étude préliminaire a examiné certains aspects de la biologie dans des conditions ambiantes de laboratoire (température variant entre 28 – 30⁰C et humidité relative de 59 – 75%).  Elle a porté entre autres sur la ponte, le développement, la survie, la fécondité et les dégâts causés  par le C. maculatus sur six graines de soya conservées, des variétés Glycine max (L) Merr.  Elle a également analysé la lutte contre le charançon, en utilisant des substances végétales telles que le neem, Azadirachta indica A. Juss (Meliaceae) et l’orange sucrée, Citrus sinensis (Linn.) et les poudres Osbeck (Rutaceae). Il a été constaté que la période de croissance du C. maculatus était différente selon les diverses variétés de graines de soja, ce qui laisse supposer des différences dans la convenance des variétés en tant que source alimentaire. Compte tenu de la durée de croissance du C. maculatus, des dégâts causés, du nombre d’œufs pondus et du nombre de nouveaux adultes en croissance, la variété de graine de soja TGX 1473-2^D est la plus résistante. Le type TGX 1025-8^E semble également être résistant mais pendant la courte période de croissance du C. maculatus sur ce type de graine de soja . Parmi les variétés restantes, notamment  TGX 923 – 2^E, TGX 1150-6^D, TGX 1118 – 1^D et LM, la variété locale LM est la plus prédisposée à l’attaque du C. maculatus.  Ce charançon préfère le type TGX 923-2^E pour la ponte. Il a été constaté que les matières végétales, notamment la poudre pour le traitement des semences Azadirachta indica ainsi que la poudre pour la protection de la pelure Citrus sinensis sont efficaces dans la protection des graines sur une période de trois mois. Ainsi, la préférence est accordée à la poudre pour le traitement des semences A. indica, du fait qu’elle contient des propriétés qui tuent les œufs et les larves.

 Mots-clés: Callosobruchus maculatus, période de croissance, graine de soja, Azadirachta indica, Citrus sinensis

INTRODUCTION

The cowpea seed weevil Callosobruchus maculatus (F.) is widespread in all parts of the tropics and subtropics as a major pest of pulses including soya beans (Glycine max (L.) Merr.)[1]. However, soya bean is generally considered to be relatively resistant to attack by bruchids [2]. Haines [1] reported that Callosobruchus species have occasionally been recorded on this commodity but never as serious pests. Giga and Smith [3] reported C. maculatus as a pest of stored soya beans. Cornes [4] listed C. maculatus as a major pest of stored soya beans in Nigeria. He considered C. maculatus to be of primary importance compared to Lasioderma serricorne (F.), Oryzaephilus mercator (Fauv.), Tribolium castaneum (Herbst.) and Trogoderma granarium (Everts), which he also listed as major pests of stored soya beans in Nigeria. Relatively, not much is known about the status of C. maculatus with regard to infestation of soya beans in Ghana.

Some authors have suggested that the use of plant materials or insecticides from plant origin in storage ecosystems has many advantages over synthetic insecticides [5, 6]. The former has, therefore, been suggested as important approach in insect pest management [7, 8, 9]. The plants, Azadirachta indica A. Juss (Meliaceae) (common name: neem), and Citrus sinensis (Linn.) Osbeck (Rutaceae) (common name: sweet orange) were utilized in the present study. These plants have been reported to have some insecticidal properties against pests [7, 10]. For example, C. sinensis peel powder has proved potent against C. maculatus, depressing oviposition and progeny emergence on cowpea, although at high doses [10]. Abbiw [11] reported that crushed C. odorata leaves repel insects. C. odorata is one of the plants in Ghana reported to have some insecticidal properties [12]. Allotey and Dankwah [7] reported that at a dosage of 1.0 g per 40 g of bambara groundnut (Voandzeia subterranea (L.) Thou), A. indica was twice as effective as C. sinensis. Citrus peels and other plant materials have been used to control stored product insect pests [13].

 The aim of the present study was to provide information on: (1) oviposition, development, survival, fecundity of C. maculatus and damage caused on some stored soya bean varieties (TGX 923 – 2^E, TGX 1150-6^D, TGX 1118 – 1^D, TGX 1473-2^D and LM) and (2) the use of neem (Azadirachta indica) seed powder and Orange (Citrus sinensis.) peel powder as seed protectants against C. maculatus under ambient laboratory conditions.

MATERIALS AND METHODS

Rearing of C. maculatus

Cultures of C. maculatus were set-up in insect breeding cages (17.5 cm diameter x 36 cm deep) using black-eyed cowpeas (Vigna unguiculata (L.) Walp) obtained locally from the 31^st December Makola market in Accra. The weevils were initially collected from infested cowpeas in the same market.  Each culture contained 200 randomly selected adult weevils per 600 g of cowpeas per cage. All cultures and experimental set-ups were maintained at laboratory conditions (temperature range 28 – 30 ⁰C) and relative humidity range 59 – 75% with photoperiod of 12 hours (light): 12 hours (dark).

Procedures for maintaining cultures were similar to those described by Allotey and Dankwah [7]. All equipment used in handling the insects was dry-heat sterilised at 100 ⁰C for at least three hours as a routine measure to prevent disease or cross infestation [7]. Food media were placed in laboratory trays and sterilised in a Gallenkamp oven at 60 ⁰C for three hours before experimentation.

Experimentation

Five soya bean varieties donated by IITA, Ibadan and one local variety from the 31^st December Makola market in Accra were used for the experiments. The five varieties from IITA were TGX 1473-2^D, TGX 1118-1^D, TGX 923-2^E, TGX 1150-6^D, TGX 1025-8^E; while the local variety was LM (sourced at local market). The flightless forms of C. maculatus, which were predominant in the rearing cultures, were utilised.

Oviposition, adult emergence and damage caused

Newly emerged and unmated adults (less than 24 hours old) from rearing cultures were paired and introduced into glass vials (3.5 cm diameter x 10 cm deep) containing soya bean seeds at a pair (♂: ♀) per 30 seeds per vial. Each vial was covered with a muslin cloth held in place with a rubber band to allow for aeration. Ten replicates were set up for each of the six soya bean varieties including LM. The vials were placed on a bench with supports immersed in engine oil to prevent other insects crawling into them [7]. After 14 days, dead adults were removed with forceps and the eggs laid on the seeds in each vial were counted. The set-ups were left thereafter until the emergence of new adults from the eggs laid earlier by the introduced pairs. The new adults were carefully removed with the aid of an aspirator, put in separate plastic Petri-dishes and the number recorded. Damage was assessed by the presence of emergence holes or oval windows on the seeds.

Developmental period

The same procedure as outlined under oviposition, adult emergence and damage caused was followed. Weevils that died on the eighth day after introduction were removed with a pair of forceps. Otherwise there was no disturbance of the set-ups till the emergence of new adults from the eggs laid by the introduced pairs. Thus the developmental period from egg to adult was determined. The number of the newly emerged adults was also recorded. Results were subjected to analysis of variance (ANOVA) and Duncan’s [14] multiple range test (DMRT).

Control of C. maculatus using plant material

Only variety LM was used, because it was the most abundant of the six varieties of soya beans available.

Neem seed powder

Ripe neem (A. indica) fruits were plucked from trees on the campus of the University of Ghana and kept for two days until nearly rotten.  The fleshy mesocarps were removed and the seeds dried in the sun daily for nine days.  The dried seeds were ground with a hand grinding machine to a coarse powder.

Orange peel powder

Ripe orange (C. sinensis) peels were obtained from the orange vendors on the campus of the University of Ghana. The vendors regard the orange peel as a waste. The peel was dried in the sun daily for five days and milled with a blender to a fine particle size of about 212 µm diameter.

Treatment of soya beans

Lots of 0.5, 1.0, 2.0 and 3.0 g of prepared plant powders (A. indica, C. sinensis) were added separately to 30 g of soya bean seeds (variety LM) in cylindrical plastic containers, (6.9 cm diameter x 7.5 cm deep) and the containers shaken thoroughly to ensure even mixing. Five pairs of newly emerged adults (less than 24 hours old) of C. maculatus were introduced into each container using a fine brush, and the containers were then covered tightly with the lids. Four replicates of each treatment and untreated soya beans were set up. The content of each replicate was sieved (mesh size: 1.5 mm) after 24 hours to remove dead C. maculatus. This procedure was repeated till all the adults of C. maculatus were dead. The total number of eggs laid on the seeds per replicate was also recorded. The set-up was thereafter left undisturbed till emergence of new adults. The newly emerged adults were carefully removed with a pair of forceps till no more adults emerged. The duration of this experiment was three months. Data were analysed using ANOVA and the DMRT test.

RESULTS

Biology

Table 1 shows that there were significant (P<0.05) differences in oviposition of C. maculatus on the different soya bean varieties. Highest number of eggs was recorded on TGX 923-2^E while the least number of eggs was recorded on TGX 1473-2^D. There was no correlation between the number of emerged adults and the total number of eggs laid by C. maculatus per variety (Table 1). The highest number of emerged adults was recorded on LM even though comparatively more eggs were laid on TGX 1150-6^D and TGX 923-2^E. Thus TGX 923-2^E and TGX 1150-6^D appeared to be the most favourable food types for oviposition by C. maculatus.

More damage was caused to LM (21.67%) by C. maculatus as compared to the other varieties (Table 2). This was followed by TGX 923-2^E (14.58%). No damage was observed on TGX 1473-2^D and TGX 1025-8^E. Damage levels of 3.33% and 6.19% were recorded respectively on TGX 1118-1^D and TGX 1150-6^D. On the basis of the presence of emergence holes or oval windows on the soya bean varieties, it can be inferred that TGX 1025-8^E and TGX 1473-2^D were the most resistant varieties, since no damage was caused to them.

The mean developmental periods of C. maculatus on the varieties have been given in Table 3. The longest mean developmental periods were recorded on TGX 1118-1^D, TGX 1473-2^D and TGX 923-2^E.  No significant differences in developmental period were recorded among these varieties (P>0.05; DMRT). In general the order of the mean developmental period of C. maculatus on the soya bean varieties from the longest to the shortest in days was TGX 1118-1^D  (68.0) > TGX 1473-2^D (64.0) > TGX 923-2^E (62.57), TGX 1150-6^D (59.43)>LM (53.25)> TGX 1025-8^E (44.0). It was observed that with the exception of TGX 1025-8^E, generally the longer the developmental period, the fewer the number of adults that emerged from the variety (Table 3).

From Table 3 and with the exception of TGX 1025-8^E, it can be observed that based on the developmental period and the number of emerged adults, TGX 1118-1^D and TGX 1473-2^D, were the most resistant varieties and LM the least.  Even though C. maculatus developmental period on TGX 1025-8^E was the shortest, the number of emerged adults (n=1) was comparable to that of TGX 1118-1^D (n=1). As pointed out earlier from Table 2, TGX 1025-8^E and TGX 1473-2^E appear to be the most resistant varieties in terms of damage caused. Also from Table 1, TGX 1025-8^E and TGX 1473-2^D were the most resistant in terms of the number of emerged adults (x = 0, in both cases) though the number of eggs laid on TGX 1473-2^D was the least (TGX 1473-2^D, x = 24.7< TGX 1025-8^E, x = 41.3). Certainly TGX 1473-2^D was the only variety, which showed consistency in terms of factors considered to confer resistance [in that longer developmental period of C. maculatus (x = 64.0), no damage caused (x = 0), least number of eggs laid on it by C. maculatus (x = 24.7) and no adult emergence (x = 0)]. Thus of the soya bean varieties in the present study TGX 1473-2^D was the most resistant. Though TGX 1025-8^E appeared to be equally resistant, the shorter developmental period of C. maculatus on this variety makes TGX 1473-2^D a better choice for resistance.  Variety LM was the most susceptible [It has the highest number of emerged adults (x = 33; Table 3), highest percentage of damaged seeds (x = 21.67; Table 2) and the second shortest developmental period of C. maculatus was recorded on it (x = 53.25; Table 3)]. This meant variety LM had the highest number of holes on the seeds, indicating it was most damaged. Further, the shorter developmental period of C. maculatus on variety LM showed that it was the most suitable for the development of C. maculatus and hence the most susceptible variety. However TGX 923 – 2^E was the most preferred for oviposition by C. maculatus (TGX 923 – 2^E, x = 52.0 vs LM, x = 40.6).

Orange peel and neem seed treatments

The results of the treatment of the susceptible soya bean variety LM with orange peel and neem seed powders are given in Table 4.Oviposition of C. maculatus was depressed more with the admixture of C. sinensis peel powder than with A. indica peel powder (Table 4). A mean number of 116 eggs were laid by C. maculatus at dosages of 0.5 g and 1.0 g of A. indica seed powder compared to 181 eggs at a dosage of 0.0 g (control). With C. sinensis peel powder, the mean number of eggs laid at 0.5 g and 1.0 g were 72.0 and 32.25 respectively, as compared to 102.75 eggs laid by C. maculatus under control conditions (0.0 g). The results (Table 4) show that less than half of the mean number of eggs laid by C. maculatus at a dosage of 0.5 g of C. sinensis was recorded at the next higher dosage of 1.0 g. This outcome can be attributed to the toxicity of C. sinensis peel powder to adults of C. maculatus, which laid fewer number of eggs compared to C. maculatus adults on A. indica treated seeds (Table 4). Even though C. sinensis peel powder depressed oviposition, more adults emerged at dosage of 0.5 g (x = 7) compared to a mean of 2.3 recorded at a dosage of 0.5 g of A. indica seed powder.

DISCUSSION

Biology

From the results presented (Tables 1, 2 and 3), it can be said that the differences in oviposition by C. maculatus on the soyabean varieties may be due to surface odours of the seeds, which may attract or repel the beetles [15-17]. In cowpea, C. maculatus preferred smooth-coated and well filled seeds to rough and wrinkled varieties [15, 18, 19]. With soya beans, Girish et al. [20] noted that C. maculatus seemed to be guided in its oviposition on preferences by smoothness of surface of seed coat and size of grains. The sizes and smoothness of the soya bean varieties in the present study appeared to be uniform.

Susceptibility of the soya bean varieties can be based on the length of developmental period and the number of emerged adults. Longer developmental periods indicated that the food was not suitable for larval development or inability to utilise the food material.

In the present study, TGX 1473-2^D was the most resistant of the soya bean varieties while variety LM was the most susceptible. The resistance of legumes to bruchid attack has been reported to be due to the presence of certain amino acids and saponins [21]. Compared to cowpeas, soya beans are generally more resistant to C. maculatus attack. Applebaum et al. [2] reported that the developmental incompatibility of soya beans for the related bruchid Callosobruchus chinensis L. is partly attributed to the presence of soya bean saponins. The latter may be regarded as specific metabolic defence mechanisms of the soya beans, evolved against insects. Osman et al. [22] reported that in soya beans a low percentage of damage was caused by C. maculatus compared to 100% damage on Vigna radiata (L.) Wilczek after three months of storage. Girish et al. [20] noted that soya bean does not seem to be ideal for development by C. maculatus. As mentioned earlier, variety TGX 1473-2^D was found to be the most resistant of the soya bean varieties studied. It should, however, be noted that there always remains a possibility that the release of resistant varieties may cause selection for biotypes of bruchids that feed on resistant varieties [23]. Dick and Credland [24] demonstrated that this selection exists and that performance of the beetles rapidly improved in terms of survival and developmental rate.

Orange peel and neem seed treatments

In this study, the treatment of variety LM with A. indica seed powder showed a higher ovicidal and larvicidal effect than treatment with C. sinensis peel powder. The prepared A. indica seed powder contained some amount of oil, which formed a film of oil on the soya bean after admixture. This film of oil was responsible for the ovicidal and larvicidal properties of the A. indica peel powder as confirmed and demonstrated by several workers [25, 26]. Oil infiltration under the egg cover may block respiration or disrupt the water balance of eggs and developing embryos [25].

The present study shows that the plant materials, C. sinensis peel powder and A. indica seed powder were effective in reducing insect damage (for example the number of emergence holes) over three month periods. Similar outcomes to the present study have been reported. Citrus peels caused adult mortality in C. maculatus and deterred beetles from admixed cowpea [7, 10]. Taylor [10] considered the use of citrus peel powder impractical because of the high quantities required and that besides, losses of the toxic volatile essential oils occur because of high temperatures. However, Su and Horvat [27] noted that the non-volatile fraction of lemon oil extracted from fresh peels of Eureka lemon (Citrus limon L. Burm) was effective against C. maculatus. Seck et al. [28] reported that neem seed powder mixed with cowpeas at the rate of 3% (w/w) gave 85 to 90% mortality in C. maculatus after 72 hours. Neem seed powder effectively preserved cowpea against C. maculatus for eight months [29]. Saxena [30] reporting on insecticides from neem noted that derivatives have traditionally been used by farmers in Asia and Africa to ward off insect pests.

Plant materials are receiving greater attention as prophylactics against stored-product pests mainly because of their preserved safety to non-target organisms [13]. In the present study A. indica seed powder is more preferable because of its ovicidal and larvicidal effects at the minimum dosage of 0.5 g, which gave, a lower seed damage (x = 2.33, range 1 – 3; Table 4) compared to that of C. sinensis peel powder (x = 7, range 2 – 12; Table 4).

CONCLUSION

In conclusion, the present study shows that approximately 15 g of A. indica seed powder can be applied to 1 kg of the susceptible LM soya bean variety which was obtained locally from the market; to give effective seed protection over three month period. The plant materials utilised in this study are easily within the reach of the resource-poor farmers who are not supported by the kind of supervision and education that need to use chemicals properly and safely. Thus A. indica could be suggested for use to suppress populations of C. maculatus for short periods.

ACKNOWLEDGEMENT

We thank Dr. L. E. N. Jackai for the supply of the soya bean varieties from IITA, Ibadan.

Table 1

Oviposition and adult emergence of C. maculatus on six stored soya bean varieties

________________________________________________________________________

Soya bean                                Mean number of                                   Mean number of

varieties                                    eggs per female                         emerged adults

                                                   (x ± S. E.)                                            (x ± S. E.)

________________________________________________________________________

TGX 923-2^E                              52.0 ± 4.02 ^a                                        4.75 ± 0.93

                                                   (34 - 78)*                                            (3 - 9)^#

TGX 1150-6^D                          49.3 ± 4.02 ^a                                         1.86 ± 0.99

                                                   (25 - 67)                                              (1 - 3)

TGX 1025 - 8^E                        41.3 ± 4.02 ^b                                               0

LM                                          40.6 ± 4.02 ^b                                        6.60 ± 0.83

                                                   (27 - 67)                                              (1 - 11)

TGX 1118 - 1^D                        33.9 ± 4.02 ^c                                        1.0 ± 2.62

                                                   (13 - 62)                                                  1

TGX 1473 - 2^D                        24.7 ± 4.02 ^d                                               0

   (5 - 44)

n =  10

________________________________________________________________________

* Range of number of eggs laid per female, ^# Range of number of emerged adults

Means within the column followed by the same letter did not differ significantly at the 5% level by DMRT.

Table 2

Damage caused by C. maculatus infestation on six varieties of stored soya beans after three months

________________________________________________________________________

Soya bean                                Mean number of                                   Mean percentage of

varieties                                    damaged seeds*                                   damaged seeds

                                                   (x ± S. E.)                                            (x ± S. E.)

________________________________________________________________________

LM                                          6.50 ± 0.78 ^a                                        21.67 ± 2.78

TGX 923-2^E                              4.38 ± 0.89 ^a                                        14.58 ± 3.12

TGX 1150-6^D                          1.86 ± 0.95 ^b                                           6.19 ± 3.31

TGX 1118 - 1^D                        1.00 ± 2.52 ^b                                          3.33 ± 8.79

TGX 1025 - 8^E                                0                                                            0

TGX 1473 - 2^D                                0                                                            0

n =  10

________________________________________________________________________

* A pair of adults per replicate, Means within the column followed by the same letter did not differ significantly at the 5% level by DMRT.

Table 3

Mean developmental period and the number of emerged adults from paired C. maculatus (♂:♀) on six stored soya bean varieties

________________________________________________________________________

Soya bean                                Mean developmental                             Mean number of

varieties                                    period⁺ (x ± S. E.)                               emerged adults

________________________________________________________________________

TGX 1118 - 1^D                        68.00 ± 7.83 ^a                                                  1

TGX 1473 - 2^D                        64.00 ± 2.95 ^a                                                  3

                                                     (56 - 70)*

TGX 923-2^E                              62.57 ± 2.95 ^ab                                                 24

                                                (47 - 87)                                                         

TGX 1150-6^D                          59.43 ± 2.95 ^b                                                  20

                                                (40 - 65)

LM                                          53.25 ± 2.77 ^b                                                  33

                                                (40 - 65)

TGX 1025-8^E                          44.00 ± 7.83 ^c                                                  1

n = 10

________________________________________________________________________

⁺ Oviposition period to adult emergence, * developmental range,

Means within the column followed by the same letter did not differ significantly at the 5% level by DMRT.

Table 4

Mean number of eggs laid, and number of emerged adults of C. maculatus on LM stored

soya beans treated with A. indica and C. sinensis powder for 12 weeks

________________________________________________________________________________________________

Treatment powder                             Mean number of eggs⁺                           Mean percentage of                                     

A. indica powder                                                                                                                                                                    

0.0 g                                                        181.75 ± 12.72 ^a                                     10.5

                                                                                                                                (4 - 13)*

0.5 g                                                        116.00 ± 12.72 ^b                                     2.33

                                                                                                                                (1 - 3)

1.0 g                                                        116.75 ± 12.72 ^b                                        0

1.5 g                                                        95.50 ± 12.72 ^c                                       0.75

                                                                                                                                (1 - 2)

2.0 g                                                        46.50 ± 12.72 ^d                                          0

3.0 g                                                        50.75 ± 12.72 ^d                                                               0

^{________________________________________________________________________________________________________________________________________________} 

C. sinensis powder

0.0 g                                                        102.75 ± 8.07 ^a                                           8

                                                                                                                                (5 -9)

0.5 g                                                        72.00 ± 8.07 ^b                                             7

                                                                                                                                (2 - 12)

1.0 g                                                        32.25 ± 8.07 ^c                                           0.25

                                                                                                                                    (1)

1.5 g                                                        26.00 ± 8.07 ^c                                              0

2.0 g                                                        20.00 ± 8.07 ^d                                              0

3.0 g                                                          4.33 ± 9.32 ^e                                              0

n=4

_______________________________________________________________________________________________

⁺ 5 pairs of adults per replicate introduced, * Range of emerged adults

Means within the column followed by the same letter did not differ significantly at the 5% level by DMRT.

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*Corresponding author - Email: alloteyj@mopipi.ub.bw
¹Department of Biological sciences, University of Botswana, Private Bag 0022, Gaborone, Botswana.
²Department of Zoology, University of Ghana, P. O. Box 67, Legon, Ghana. Fax: (267) 3185097; Tel.: (267) 3552591.