Tropical and Subtropical Agroecosystems E-ISSN: 1870-0462 [email protected] Universidad Autónoma de Yucatán México Iloba, B.N.; Umoetok, S.B.A. Effects of Dinarmus basalis (rendani) on the population density of Callosobruchus maculatus (fabricius) on stored cowpea (Vigna unguiculata walp) seeds Tropical and Subtropical Agroecosystems, vol. 7, núm. 1, 2007, pp. 59-62 Universidad Autónoma de Yucatán Mérida, Yucatán, México Available in: http://www.redalyc.org/articulo.oa?id=93970108 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Tropical and Subtropical Agroecosystems, 7 (2007): 59-62 SHORT NOTE [NOTA CORTA] EFFECTS OF Dinarmus basalis (RENDANI) ON THE POPULATION Tropical and DENSITY OF Callosobruchus maculatus (FABRICIUS) ON STORED COWPEA (Vigna unguiculata WALP) SEEDS Subtropical [EFECTO DE Dinarmus basalis SOBRE LA DENSIDAD POBLACIONAL DE Callosobruchus maculatus (FABRICIUS) EN SEMILLA ALMACENADA DE Agroecosystems Vigna unguiculata WALP] B.N. Iloba1 and S.B.A. Umoetok2* 1Department of Zoology, University of Benin, Benin 2Department of Crop Science, University of Calabar. Calabar E-Mail: [email protected] *Corresponding author SUMMARY RESUMEN The control of Callosobruchus maculatus F. on Se estudio el control de Callosobruchus maculatus F. cowpea seeds was studied in the laboratory using en semillas de Vigna empleando el parasitoide Dinarmus basalis as parasitoid. Five males and Dinarmus basalis. Cinco hembras y machos adultos females adult C. maculatus were allowed to oviposit de C. maculatus fueron depositados para ovipositar en onto ten sets of cowpea seeds each set weighed 5g. 5g de semillas de vigna. Cinco machos y hembras de Five males and females D. basalis were introduced at D. basalis fueron introducidos a intervalos de tres días three days intervals (beginning from the 6th day after (iniciando el día 6 posterior a la oviposición) en las oviposition) into each of the nine sets that had been semillas infestadas con huevos de C. maculatus, se infested with eggs of C. maculatus contained in mantuvo un grupo control donde D. basalis no fue specimen bottles. No D. basalis was introduced into introducido. No se encontró diferencias (P> 0.05) en el the tenth set of cowpea seeds and this served as número de huevos ovipositados por cada hembra de C. control. No differences were observed in the number maculatus (rango 37.80 - 41.20). No se encontró of eggs laid per female C. maculatus in all the sets (P> difrencias (P > 0.05) en el número de adultos de C. 0.05) and this ranged from 37.80 - 41.20. No maculatus que emergieron cuando D. basalis fue differences were observed on adult C. maculatus that introducida en los días 6, 9 y 12 post oviposición emerged when D. basalis was introduced at the 6th, 9 th (DAO). La emergencia de C. maculatus se incrementó and 12th day after oviposition (DAO) (P> 0.05). cuando D. basalis fue inoculado a partir del día 21 Percent emergence was 0.59, 0.53 and 1.85% at 6, 9 DAO. El % de D. basalis por hembra en cada cultivo and 12th day, respectively. C. maculatus emergence fue 12.81% en día 6, 17.56% día 15 y decremento increased from 67.81% in the treatment that was significativamente (11.78%) cuando la inoculación fue inoculated on the 21st DAO to 74.48 when inoculation realizada en el día 30. La mortalidad observada en C. was done on the 30th day. The total D. basalis per maculatus incremento de 25.03% a 99.41% en los female in each culture was 12.81% on the 6th day to cultivos parasitados y fue de 25.52% en el grupo 17.56% on the 15th day and decreased significantly to control. La introducción de D. basalis durante el 11.78% when inoculation was done on the 30th day. estadío larval de C. maculatus causó una mayor The observed percentage mortality of C. maculatus mortalidad y no tuvo efecto en los adultos de C. increased from 25.03% to 99.41% on the parasitised maculatus. culture when compared to 25.52 in the control. Introduction of D. basalis during the larval stage of C. Key words: Oviposición, inoculación, mortalidad, maculatus caused higher mortality of the pest and little parasitoides. or no effect on the adult C. maculatus. Key words: Oviposition, inoculation, mortality, parasitoid. INTRODUCTION with ample distribution in tropical and subtropical regions where this crop represents one of the main The bruchid Callosobruchus maculatus is an important sources of protein in human diet (Singh et al., 2005). pest of stored cowpea (Vigna unguiculata L. Walp) It is reported to be the principal storage pest of cowpea 59 Iloba and Umoetok, 2007 grain in sub-Saharan Africa (Taylor, 1981). Infestation Five grams of the disinfested cowpea seeds were of C. maculatus starts in the field and continues in weighed into ten different specimen bottles (labelled storage (Messina, 1984). The insect infests cowpea A-J) with fine nylon net lids of about 1x1 mm mesh before harvest and causes quantitative and qualitative size and these were replicated four times. Cowpea losses to seeds in storage facilities (Shade et al., 1990). seeds in each of the bottles were infested with five Caswell (1984) and Murdock et al. (1997) reported pairs (females and males) of the newly emerged C. that during traditional post harvest storage in Nigeria, maculatus (0-3 days old) and were allowed to oviposit cowpea grain stored in pods for 8 months had 50% of for three days. the grain damaged by bruchids but when stored as grain, 82% had one or more holes. Female C. Introduction of D. basalis to cowpea infested with maculatus oviposits on the pods and larval eggs of C. maculatus. development is entirely within the seeds (Messina, 1984, Stoll, 2000). Each of the nine bottles containing the infested cowpea except the control was now infested with five The Hymenoptera Dinarmus basalis is an pairs (males and females) of D. basalis at three days ectoparasitoid larvophagous species, which is also intervals and labeled A-I. No D. basalis was present in the graineries and represents 80-90% of the introduced into the tenth bottle (labeled J) and this bruchid larvophagous parasitoids in the cowpea fields served as the control. Treatments were replicated four and the stores (Ouedraogo et al., 1996). According to times and set-aside on a laboratory bench arranged in Dugravot et al. (2002), D. basalis is an efficient completely randomised block design. natural enemy, which could be used for biological control. The larva of C. maculatus is parasitised inside Data collection the seeds by D. basalis (Dugravot et al., 2002, Gauthier et al., 2002). The objective of this study was The number of eggs laid by C. maculatus per female to manage the population density of C. maculatus by was recorded. Emergence of C. maculatus and D. introducing D. basalis at the time the pest is basalis per female were recorded. The total number of susceptible to the parasitoid. D. basalis in each culture was used for analysis. The percentage mortality and emergence (%) was MATERIALS AND METHODS calculated based on the mean number of adult C. maculatus per female that emerged relative to the total Cowpea seeds that were collected from cowpea store number of eggs laid per female. Data were taken in Uselu market, Benin City were placed in a beaker in cumulatively from 20 – 38 DAO and the means were an oven at 60o C for one hour to disinfest them used for analysis of variance. The Fisher’s least (Murdock and Shade, 1991). The experiment was significant difference (Wahua, 1999) was used to carried out in the University of Benin laboratory under separate the means where applicable. a temperature of 28 ± 2 oC and 70 ± 10 % RH. Cowpea seeds (200g) were infested with five males and RESULTS AND DISCUSSION females (0-3 days old). The sexes of C. maculatus were determined by examining the elytral pattern Emergence of C. maculatus was observed from the (Southgate et al., 1957). Females are usually dark 20th DAO until 38th day when no emergence was coloured and possess four elytral spots, while males observed. D. basalis emergence was observed from the are pale brown and less distinctly spotted. 12th DAO. Results (Table 1) indicated no significant Furthermore, males have comparatively shorter differences (P> 0.05) in the mean number of eggs laid abdomen and the dorsal side of the terminal segment is per female C. maculatus. Significant differences (P < sharply curved downwards and inwards. In contrast, 0.05) occurred in adult C. maculatus that emerged females have comparatively longer abdomen and the after inoculation of the parasitoid. The first six days dorsal side of the terminal segment is only slightly after inoculation, significantly lower C. maculatus bent downwards (Bandara and Saxena, 1995). The emerged compared with the cultures that were disinfested cowpea seeds were put in five jars with net inoculated later. The highest emergence of C. mesh lids. The seeds in each jar were re-infested with maculatus was observed with the 27th DAO, although C. maculatus. The C. maculatus were allowed to there were no significant differences in emergence oviposit for three days before they were removed. between the 27th, 30th and the control. Percent mortality was significantly higher in the cultures that Cultures of D. basalis were reared from the stock were inoculated earlier at the 6th to 18th DAO (i.e. the collected from parasitised cowpea purchased at the larval stages) compared with the control or cultures Uselu market, Benin City.