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Host plants and species diversity of Mussidia (Lepidoptera: Pyralidae) in Kenya

Host plants and species diversity of Mussidia (Lepidoptera: Pyralidae) in Kenya International Journal of Biodiversity Science & Management Vol. 5, No. 1, March 2009, 35–40 RESEARCH NOTE a,b a b Benjamin Kimwele Muli *, Fritz Schulthess and Johnnie van den Berg a b International Center of Insect Physiology and Ecology, P.O. Box 30772-00100, GPO, Nairobi, Kenya; School of Environmental Sciences and Development, North West University, Potchefstroom, South Africa Mussidia nigrivenella (Lepidoptera: Pyralidae), an important pest of maize, cotton and Phaseolus bean in western Africa, has never been described as a crop pest from Eastern and southern Africa (ESA), although it was reported in the wild. Generally, little is known about the host plant range and the diversity of Mussidia spp. in ESA. Thus, surveys were carried out in Kenya between 2005 and 2007 to assess the species diversity and host plants of Mussidia. Eight plant species were found to host two Mussidia spp. and six morphospecies, which occur sympatrically in the coastal region. Only one Mussidia sp. was found attacking one host plant in the mid-altitudes. The spatial distribution of M. nr. nigrivenella, M. ‘madagascariensis’ and M. fiorii was studied. M. nr. nigrivenella and M. ‘madagascariensis’ larvae were aggregated on Canavalia cathartica and Strychnos madagascariensis, respectively, while the distribution of M. fiorii adults on Kigelia africana was regular. Sampling plans were developed for three Mussidia spp. on their respective host plants, allowing estimation of pest densities. The occurrence of M. nigrivenella in ESA could not be determined with absolute certainty. Keywords: Mussidia spp. diversity; Pyralidae; host plant range; spatial distribution; sampling plans Introduction Materials and methods The ear-borer, Mussidia nigrivenella Ragonot (Lepidoptera: Surveys for Mussidia spp. and their associated host plants Pyralidae), is one of the most important pests of maize in were undertaken in the coastal lowlands and mid-altitude West Africa (Moyal and Tran 1991; Setamou et al. 2000a). (up to 1850 m asl) regions of Kenya. These zones corre- In the field, yield losses vary from 5% to 25% (Moyal and spond to the ecoregions where M. nigrivenella occurs in Tran 1991; Setamou et al. 2000a). In addition, infestation by western Africa. In 11 surveys carried out from May 2005 to M. nigrivenella predisposes maize to attack by pre- and November 2007, mature fruits or pods from plant species in post-harvest storage beetles Carpophilus spp. (Coleoptera: families reported as hosts of M. nigrivenella in West Africa Nitidulidae) and Sitophilus zeamais Motschulsky (Setamou, Schulthess, Gounou, et al. 2000) and from others in different families with fruits at the right stage for attack (Coleoptera: Curculionidae), leading to further yield losses of up to 15%. by Mussidia spp. at the time of sampling were collected. A Surveys in West Africa revealed 20 host plant species tree, shrub or vine was considered a sampling site and was of M. nigrivenella including cultivated crops such as selected from afar based on whether it had fruits. At close maize, cotton and Phaseolus bean (Setamou, Schulthess, range, it was examined for mature fruits. Fruit samples were Gounou, et al. 2000). It was collected from maize from the randomly selected from the accessible parts (Setamou et al. 2000b). Fruits were collected from the lower, middle and lowland tropics up to mid-altitudes (up to 1200 m asl) (Oigiangbe et al. 1997; Setamou, Schulthess, Gounou, upper canopy. The plant was roughly divided into four et al. 2000; Setamou et al. 2000a; Ndemah, Schulthess, quadrants and fruits were randomly collected from each Korie, et al. 2001). By contrast, M. nigrivenella has never quadrant. At times, ripe fallen fruits were collected from been reported as a pest of crops from Eastern and southern the ground. Since fruit density varied with plant species, the number of fruits collected from each plant also varied. Fruits Africa (ESA), where, however, it is reported to occur on wild host plants (Janse 1941; LePelley 1959). It was were handpicked and, if necessary harvested using a 7-m hypothesized that, in ESA, M. nigrivenella was either telescoping pole. For trees with fruits .10 cm in diameter, under natural control on wild hosts or the locally occurring at most, 10 fruits were collected, while for trees with fruits geographic race did not attack maize (Ndemah, ,10 cm in diameter, as many as 20 fruits were collected per tree. Where many trees of the same species were found in Schulthess, Poehling, Borgemeister, Goergen 2001; the same locality, a distance of at-least 2 km was covered Setamou et al. 2002). Thus, in a first step, following pre- liminary surveys during 2001 (F. Schulthess, unpubl. before the next sampling site was selected. Due to the data), this research note presents an assessment of the differences in fruiting phenologies, fruits were collected during both the wet and dry seasons. In some cases, some diversity of Mussidia spp. and their host plant range in sites were sampled more than once depending on the lowland and mid-altitude areas in Kenya. *Corresponding author. Email: bmuli@icipe.org ISSN 1745-1590 print/ISSN 1745-1604 online # 2009 Taylor & Francis DOI: 10.1080/17451590902771300 http://www.informaworld.com 36 B.K. Muli et al. availability of fruits. Each sample was labelled according to from each plant also varied: for K. africana,at most 10fruits location using a geographic positioning system (GPS) were collected per tree, while for S. madagascariensis, (Garmin – Geko 201), plant species and date of collection. between 10 and 20 fruits were examined. For C. cathartica, When fruits were collected from an unknown plant, a depending on availability of mature dry pods, between 10 sample of leaves and/or flowers, if available, were pre- and 50 pods were examined. Similar to the host plant sur- served in a plant press for identification at the Kenya veys, sampling was done during both the wet and dry seasons Forestry Research Institute (KEFRI) or by Mr. Mathenge, and, subject to the availability of fruit, some sites were University of Nairobi. Only plants whose fruits yielded sampled more than once. Fruits of S. madagascariensis and C. cathartica were dissected and inspected for the presence adult Mussidia spp. were considered as host plants; accord- of larvae, which were reared on an artificial diet until adult- ing to Wiklund (1974), the presence of an egg or larva does hood to confirm the identity of the species. For K. africana not necessarily indicate suitability of the host for comple- fruits, which are difficult to dissect, the distribution pattern tion of the lifecycle of an insect. All fruits or pods were taken to the laboratory of the was based on densities of emerging adults. International Centre of Insect Physiology and Ecology, in Taylor’s (1961) power law was used to describe the Nairobi, in 2–l plastic containers, whose lids were well distribution of Mussidia sp. larvae on C. cathartica and ventilated to prevent excess humidity build-up. Containers S. madagascariensis and, adults on K. africana. This law were kept at 25–30 C for up to 8 weeks to ensure that all postulates a consistent relationship for a species between specimens emerged as adults. From the emerged adults, variance (s ) and mean (m): specimens having the characteristics of Mussidia spp. 2 b (Moyal 1988) were used to start laboratory colonies on an s ¼ am (1) artificial diet as described by Onyango and Ochieng-Odero (1994), while some were exposed to ethyl acetate in a kill- where b indicates the distribution of the species, with b . 1 ing jar, mounted and sent for identification by M. Nuss at indicating an aggregated, b = 1 random, and b , 1 regular the Museum fu¨r Tierkunde, Dresden, Germany, where vou- distribution, while a is considered a scalar factor without cher specimens are kept. biological meaning. These coefficients were computed by Adults were offered rough tissue paper for oviposition regressing the natural logarithm of the within-plant variance (Setamou et al. 1999). The eggs were incubated, and (lns ) against the natural logarithm of mean density (lnm) emerged neonates were put on an artificial diet. In subse- for each plant. In our case, m is the mean number of quent surveys, fruits were first visually examined for eggs individuals from fruits collected per plant. A t-test was or first-instar larvae suspected to be Mussidia spp. used to determine if b was significantly different from 1. (Preliminary observations showed that 24-h-old Mussidia To obtain optimal enumerative sample size curves, spp. eggs and first instar larvae were red in colour). The Wilson and Room (1983) incorporated the estimated var- larvae were put on an artificial diet while the eggs were iance (s ) from Taylor’s (1961) power law into the general incubated in a transparent vial until larval emergence. distribution formula by Karandinos (1976): Emerging larvae were reared on an artificial diet until adult- hood to ascertain the species. 2 2 n ¼ Z =D s =m (2) =2 In addition, two herbaceous legumes, the perennial Canavalia enseiformes L. DC (Fabaceae) and the annual resulting in Mucuna pruriens DC (Fabaceae), which commonly harbour M. nigrivenella in West Africa (Setamou, Schulthess, b2 n ¼ Z =D am (3) =2 Gounou, et al. 2000), were planted under irrigation at the Kenyan coast during 2006–2007 to trap Mussidia spp. where n is the number of samples to be taken, Z is the /2 standard normal deviate (Z = 1.96 for n, 30) and D is the /2 Spatial distribution of Mussidia spp. and development of reliability level for a fixed proportion of the mean; two sampling plans reliability levels (D = 0.2 or 0.3), were chosen depending on the accuracy of the density estimate required. Sufficient numbers of infested fruits for assessment of the spatial distribution of Mussidia spp. were available for three host plants only, namely Kigelia africana (Lam.) Benth. Results (Bignoniaceae), Canavalia cathartica Thouars. (Fabaceae) Host plants and Mussidia spp. diversity and Strychnos madagascariensis Poir. (Loganiaceae), which had been shown to harbour Mussidia spp. in a pre- Mussidia species were obtained from eight plant species, all vious study on host plant range. Mature fruits of each host found along the Kenyan coast (Table 1, Figure 1). A few of plant were randomly handpicked or harvested using a 7-m these species were also found in the mid-altitudes but only telescoping pole from the accessible parts of trees/vines. For one of them, K. africana, was found to host a Mussidia K. africana and S. madagascariensis, at times, ripe fallen species (Figure 1). The survey found seven plant species, fruits were collected from the ground. Since fruit density from four families reported as hosts of M. nigrivenella in varied with plant species, the number of fruits collected West Africa, but only two were found harbouring Mussidia International Journal of Biodiversity Science & Management 37 Table 1. List of plant species sampled, those sampled and also reported as host plants of Mussidia nigrivenella in West Africa and those harbouring Mussidia spp. in Kenya during 2005–2007. Reported as hosts of Mussidia Mussidia Family Scientific name Common name nigrivenella in West Africa spp. host Anacardiaceae Sclerocarya birrea (A. Rich) Hochst. Anacardium occidentale L. Cashew nut Bignoniaceae Kigelia africana (Lam.) Benth. African sausage tree Jacaranda mimosifolia D. Don. Bombacaceae Adansonia digitata L. Baobab x Caesalpiniaceae Erythrophloeum suaveolens Guill. & Perr. Piliostigma thorningii (Schum.) Milne-Redh. x Combretaceae Terminalia brownii Fres. Euphorbiaceae Croton megalocarpus Hutch. Fabaceae Afzelia quanzensis Welw. Pod mahogany Tamarindus indica L. Tamarind x Senna bicapsularis L. Butterfly bush Delonix regia (Bojer) Flamboyant tree Cajanus cajan L. Pigeon pea Canavalia cathartica Thouars. Maunaloa vine Canavalia enseiformes L. DC. Jack bean x Dolichos lablab L. Hyacinth bean Acacia nilotica L. Acacia stuhlmannii Taub. Gliricidia sepium (Jacq.) Walp. Mucuna pruriens (L.) DC Velvet bean x Mucuna gigantea (Willd.) DC. Senna spectabilis DC Senna singueana (Delile) Lock Parkia filicoidea Welw. ex Oliver Vigna unguiculata L. Walpers Cowpea x Loganiaceae Strychnos madagascariensis Poir. Black monkey orange Strychnos spinosa Lam. Green monkey orange Meliaceae Melia volkensii Gu¨rke Mimosaceae Albizia anthelmintica Brongn. Moraceae Ficus benjamina L. Weeping fig Ficus sycomorus L. Fig tree Moringaceae Moringa oleifera Lam. Papilionoideae Erythrina abbyssinica (A. Rich) Poaceae Zea mays L. Maize x Rhamnaceae Ziziphus mauritiana Lam. Chinese apple Rubiaceae Vangueria infausta Burch. Wild pear Solanaceae Solanum incanum L. Sodom apple Sterculiaceae Dombeya rotundifolia Hotchst. Sterculia appendiculata K. Schum. Notes: x indicates that a plant species is reported as host of M. nigrivenella in West Africa. indicates that the plant species was found harbouring Mussidia spp. species (Table 1). Nearly 80% of the total plant species Fifty percent of the host plant species, from which sampled did not yield Mussidia spp. (Table 1). Two Mussidia spp. were reared, belonged to the family Mussidia species and six putative Mussidia morphospecies, Fabaceae (Table 1). Mussidia spp. eggs were found on the which occurred sympatrically, were obtained from the dif- surface of the mature fruits or pods, mostly laid in batches; ferent host plants in the coastal area. However, due to in many cases, more than one egg batch was found per fruit. nomenclatural problems, only one species (M. fiorii Except for M. fiorii attacking K. africana, whose mature Cecconi and de Joannis) obtained from K. africana was fruits have a high-moisture content, Mussidia spp. eggs identified with certainty, while another from Canavalia were collected on drying or dry fruits. Eggs were also cathartica Thouars. was close to the West African M. nigri- found on fruits harbouring larvae or pupae, or that had venella (pers. comm., M. Nuss, Museum fu¨r Tierkunde, exit holes. Mussidia larvae were found feeding on seeds, Dresden, Germany). Henceforth, the latter species will be producing copious amounts of silk and pelleted frass, espe- referred to as Mussidia nr. nigrivenella while the other cially the species feeding on Afzelia quanzensis Welw. morphospecies will be identified by the species name of (Fabaceae), Strychnos spinosa Lam. (Loganiaceae), the host plant from which they were collected; e.g. Mussidia S. madagascariensis, A. digitata and C. cathartica. Mussidia collected from Adansonia digitata L. (Bombacaceae) ‘quanzensis’ larvae were found feeding on the seed aril becomes Mussidia ‘digitata’. before they moved to the rest of the seed. Dissection of 38 B.K. Muli et al. Figure 1. Distribution of host plants attacked by Mussidia spp. along the Kenyan coast and the mid-altitude regions during 2005–2007. The left section of the figure shows a section of the Kenyan coast at a different scale. K. africana fruits, from which M. fiorii adults emerged, Spatial distributions and sampling plans revealed that their larvae also fed on the seeds. Except for Mean densities of M. fiorii adults, M. ‘madagascariensis’ and M. fiorii, whose cocoons were found singly near individual M.nr. nigrivenella larvae were 55.9  7.6, 3.93  0.64 and exit windows, at least three pupae were found near an exit 0.73  0.14, respectively. The Taylor’s (1961) power law window with their cocoons joined. However, for M. ‘quan- regressions yielded slopes b greater than 1 for M. nr. nigri- zensis’, although pupae were found in groups, exit windows venella and M. ‘madagascariensis’ larvae on C. cathartica were rare and most of the emerging adults were thought to and S. madagascariensis, respectively, indicating aggregated escape through the open suture of the dry pod. The host distribution. In contrast, Mussidia fiorii adults on K. africana plant species attacked by the different Mussidia spp. had yielded a slope less than 1, indicating regular distribution different fruiting phenologies, hence, fruits suitable (Table 2). Student’s t-test (Sokal and Rohlf 1995) showed for attack were available at different times of the year that all slopes were significantly different from unity (P , (Figure 2). 0.001 for M. nr. nigrivenella, P = 0.002 for M. ‘madagascar- iensis’ and P , 0.001 for M. fiorii)(Table 2). The optimal sample size curves (i.e. the optimal number of samples to be taken to estimate a given density for a given Kigelia africana Adansonia digitata Adansonia digitata precision level) for the different Mussidia spp. are shown in Tamarindus indica Figure 3. Mussidia nr. nigrivenella required the highest Afzelia quanzensis Afzelia quanzensis number of samples to estimate a mean density, followed Canavalia cathartica Strychnos madagascariensis by M. ‘madagascariensis’ and M. fiorii. Strychnos spinosa JF M A M J JA S O N D Discussion Figure 2. Periods when suitable fruits of different host plants There are fewer host plants for Mussidia spp. in Kenya than were available for attack by Mussidia spp. at the Kenyan coast for M. nigrivenella in West Africa, where Setamou, during 2005–2007. The rainy season months are shaded. International Journal of Biodiversity Science & Management 39 Table 2. Taylor’s a and b coefficients and r for three Mussidia species each on their main host plants. N is the number of plants from which infested fruits were collected. Taylor’s parameters Species Host plant ab t-value r P- value N Mussidia nr. nigrivenella Canavalia cathartica 0.9125 1.58 13.68 0.89 ,0.001 24 Mussidia ‘madagascariensis’ Strychnos madagascariensis 0.8792 1.16 4.064 0.62 0.002 12 Mussidia fiorii Kigelia africana 1.4347 0.94 4.29 0.47 ,0.001 23 the year. However, it was not clear how the other species (a) survive periods of non-availability of suitable fruiting structures. Various studies have shown the dispersion of M. nigri- venella larvae to be aggregated on maize (Schulthess et al. 1991; Setamou et al. 2000b; Ndemah, Schulthess, Poehling, Borgemeister 2001) and on wild host plants (Setamou et al. 2000b). An aggregated distribution was also found for M. nr. nigrivenella larvae on C. cathartica and for Mussidia ‘madagascariensis’ larvae on S. madagascariensis. This might be attributed to the oviposition behaviour of the (b) adults as suggested by Cole (1946) and Setamou et al. (2000b), whereby eggs are laid in batches, which favours aggregation of larvae in the fruits. By contrast, M. fiorii adults showed a regular distribution on K. africana. Unlike the other Mussidia species, whose pupal cases were found aggregated around the exit windows, only one pupal case was found per exit window on K. africana fruits. This indicates fierce intraspecific competition by M. fiorii larvae, probably induced by the high per fruit densities, explaining the regular distribution of adults and, thus, pupae. Setamou (c) et al. (2000b) suggested that because of the exceedingly cryptic larval feeding behaviour of Mussidia spp., emphasis should be given to finding egg and pupal parasitoids. An aggregation of pupae around exit holes should also improve host finding and parasitism efficiency of pupal parasitoids. The current study indicates that several Mussidia spp. exist in Kenya. However, whether M. nigrivenella occurs in ESA could not be determined in the present study with absolute certainty; molecular tools might be required to Mean density of borers per fruit separate the different morphospecies into species. Figure 3. Optimal number of samples to be taken to estimate mean densities of (a) M. fiorii (b) Mussidia ‘madagascariensis’ and (c) Mussidia nr. nigrivenella with reliability levels of D = 0.2 and D Acknowledgements = 0.3. The authors are grateful to Gerphas Okuku, Julius Obonyo and John Obala for technical assistance, Eric Muchugu for geostatis- tical analysis, Dr. Matthias Nuss for identification of the Schulthess, Gounou, et al. (2000) identified 20 plant species Lepidoptera, Mr. Mathenge and KEFRI staff (Gede) for plant species identification and two anonymous reviewers for reviewing from 11 families hosting the pest. In contrast to West Africa, a previous version of the manuscript. This study was supported by Mussidia spp. was never obtained from maize in Kenya the Federal Ministry for Economic Cooperation and Development (Zhou et al. 2003 and the present study). As also found by (BMZ), Germany. Setamou, Schulthess, Gounou, et al. (2000) in West Africa, the highest number of host plant species was in the Fabaceae. All these species are of economic importance References and, except C. enseiformes, are not cultivated (Beentje Beentje HJ. 1994. Kenya trees, shrubs and lianas. Nairobi (Kenya): 1994; Mureithi et al. 1998). The continuous availability of National Museums of Kenya. suitable fruiting structures guarantees the propagation of Cole LC. 1946. A theory for analyzing contagiously distributed Mussidia spp. on K. africana and C. cathartica throughout populations. Ecology. 27:329–341. Number of samples to be taken 40 B.K. Muli et al. Janse AJT. 1941. Contribution to the study of the Phycitine Schulthess F, Bosque-Perez NN, Gounou S. 1991. Sampling lepi- (Pyralidae: Lepidoptera) part 1. J Entomol Soc South Afr. dopterous pests on maize in West Africa. Bull Entomol Res. 4:134–166. 81:297–301. Karandinos MG. 1976. Optimum sample size and comments on Se tamou M, Schulthess F, Bosque-Perez NA, Poehling HM, some published formulae. Bull Entomol Soc Am. 22:417–421. Borgemeister C. 1999. Bionomics of Mussidia nigrivenella LePelley RH. 1959. Agricultural insects of East Africa. Nairobi (Lepidoptera: Pyralidae) on three host plants. Bull Entomol (Kenya): East Africa High Commission. 307 p. Res. 89:465–471. Moyal P. 1988. Les foreurs du maı¨s en zone des savanes en Coˆte Se tamou M, Schulthess F, Goergen G, Poehling HM, d’Ivoire [Collection Etudes et The`ses]. [Paris (France)]: Borgemeister C. 2002. Natural enemies of the maize ear- ORSTOM. borer, Mussidia nigrivenella (Lepidoptera: Pyralidae) in Moyal P, Tran M. 1991. Ear-borer Mussidia nigrivenella Benin, West Africa. Bull Entomol Res. 92:343–349. (Lepidoptera: Pyralidae) of maize in Ivory Coast. I. morpho- Se tamou M, Schulthess F, Gounou S, Poehling HM, Borgemeister logical and biological data. Insect Sci Appl. 12:209–214. C. 2000. Host plants and population dynamics of the ear-borer Mureithi JG, Gachene CKK, Saha HM, Dyck E. 1998. Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae) in Incorporation of green manure legumes into smallholder farm- Benin. Environ Entomol. 29:516–524. ing systems in Kenya: achievements and current activities of Se tamou M, Schulthess F, Poehling HM, Borgemeister C. 2000a. legume screening network. Presented in an international work- Monitoring and modeling of field infestation and damage by shop on Agrobiological Management of Soils and Cropping the maize ear borer Mussidia nigrivenella Ragonot Systems; Madagascar. (Lepidoptera: Pyralidae) in Benin, West Africa. J Econ Ndemah R, Schulthess F, Korie S, Borgemeister C, Cardwell KF. Entomol. 93:650–657. 2001. Distribution, relative importance and effect of lepidop- Se tamou M, Schulthess F, Poehling HM, Borgemeister C. 2000b. terous borers on maize yields in the forest zone and mid- Spatial distribution and sampling plans for Mussidia nigrive- altitude region of Cameroon. J Econ Entomol. 94:1434–1444. nella (Lepidoptera: Pyralidae) on cultivated and wild host Ndemah R, Schulthess F, Poehling M, Borgemeister C. 2001. plants in Benin. Environ Entomol. 29:1216–1225. Spatial dynamics of lepidopterous pests on Zea mays (L.) Sokal RR, Rohlf FJ. 1995. Biometry, the principles and practice of and Pennisetum purpureum (Moench) in the forest zone of statistics in biological research. San Francisco (CA): WH Cameroon and their implications for sampling schemes. Freeman. J Appl Entomol. 125:507–514. Taylor LR. 1961. Aggregation, variance, and the mean. Nature. Ndemah R, Schulthess F, Poehling M, Borgemeister C, Goergen 189:732–735. G. 2001. Natural enemies of lepidopterous borers on maize Wiklund C. 1974. Oviposition preferences in Papilio machaon in and elephant grass in the forest zone of Cameroon. Bull relation to the host plants of the larvae. Entomol Exp Appl. Entomol Res. 91:207–212. 17:189–198. Oigiangbe ON, Ivbijaro MF, Ewete FK, Mutsaers HJW. 1997. Wilson LT, Room PM. 1983. Clumping patterns of fruit and Incidence and damage caused by maize stemborers on arthropods in cotton, with implications for binomial sampling. farmers’ fields in south western Nigeria. Afr Crop Sci Environ Entomol. 12:50–54. J. 5:295–302. Zhou G, Overholt WA, Kimani-Njogu SW. 2003. Species rich- Onyango FO, Ochieng-Odero JPR. 1994. Continuous rearing of ness and parasitism in an assemblage of parasitoids attacking the maize stemborer Busseola fusca on artificial diet. Entomol maize stemborers in coastal Kenya. Ecol Entomol. Exp Appl. 73:139–144. 28:109–118. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Biodiversity Science & Management Taylor & Francis

Host plants and species diversity of Mussidia (Lepidoptera: Pyralidae) in Kenya

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Abstract

International Journal of Biodiversity Science & Management Vol. 5, No. 1, March 2009, 35–40 RESEARCH NOTE a,b a b Benjamin Kimwele Muli *, Fritz Schulthess and Johnnie van den Berg a b International Center of Insect Physiology and Ecology, P.O. Box 30772-00100, GPO, Nairobi, Kenya; School of Environmental Sciences and Development, North West University, Potchefstroom, South Africa Mussidia nigrivenella (Lepidoptera: Pyralidae), an important pest of maize, cotton and Phaseolus bean in western Africa, has never been described as a crop pest from Eastern and southern Africa (ESA), although it was reported in the wild. Generally, little is known about the host plant range and the diversity of Mussidia spp. in ESA. Thus, surveys were carried out in Kenya between 2005 and 2007 to assess the species diversity and host plants of Mussidia. Eight plant species were found to host two Mussidia spp. and six morphospecies, which occur sympatrically in the coastal region. Only one Mussidia sp. was found attacking one host plant in the mid-altitudes. The spatial distribution of M. nr. nigrivenella, M. ‘madagascariensis’ and M. fiorii was studied. M. nr. nigrivenella and M. ‘madagascariensis’ larvae were aggregated on Canavalia cathartica and Strychnos madagascariensis, respectively, while the distribution of M. fiorii adults on Kigelia africana was regular. Sampling plans were developed for three Mussidia spp. on their respective host plants, allowing estimation of pest densities. The occurrence of M. nigrivenella in ESA could not be determined with absolute certainty. Keywords: Mussidia spp. diversity; Pyralidae; host plant range; spatial distribution; sampling plans Introduction Materials and methods The ear-borer, Mussidia nigrivenella Ragonot (Lepidoptera: Surveys for Mussidia spp. and their associated host plants Pyralidae), is one of the most important pests of maize in were undertaken in the coastal lowlands and mid-altitude West Africa (Moyal and Tran 1991; Setamou et al. 2000a). (up to 1850 m asl) regions of Kenya. These zones corre- In the field, yield losses vary from 5% to 25% (Moyal and spond to the ecoregions where M. nigrivenella occurs in Tran 1991; Setamou et al. 2000a). In addition, infestation by western Africa. In 11 surveys carried out from May 2005 to M. nigrivenella predisposes maize to attack by pre- and November 2007, mature fruits or pods from plant species in post-harvest storage beetles Carpophilus spp. (Coleoptera: families reported as hosts of M. nigrivenella in West Africa Nitidulidae) and Sitophilus zeamais Motschulsky (Setamou, Schulthess, Gounou, et al. 2000) and from others in different families with fruits at the right stage for attack (Coleoptera: Curculionidae), leading to further yield losses of up to 15%. by Mussidia spp. at the time of sampling were collected. A Surveys in West Africa revealed 20 host plant species tree, shrub or vine was considered a sampling site and was of M. nigrivenella including cultivated crops such as selected from afar based on whether it had fruits. At close maize, cotton and Phaseolus bean (Setamou, Schulthess, range, it was examined for mature fruits. Fruit samples were Gounou, et al. 2000). It was collected from maize from the randomly selected from the accessible parts (Setamou et al. 2000b). Fruits were collected from the lower, middle and lowland tropics up to mid-altitudes (up to 1200 m asl) (Oigiangbe et al. 1997; Setamou, Schulthess, Gounou, upper canopy. The plant was roughly divided into four et al. 2000; Setamou et al. 2000a; Ndemah, Schulthess, quadrants and fruits were randomly collected from each Korie, et al. 2001). By contrast, M. nigrivenella has never quadrant. At times, ripe fallen fruits were collected from been reported as a pest of crops from Eastern and southern the ground. Since fruit density varied with plant species, the number of fruits collected from each plant also varied. Fruits Africa (ESA), where, however, it is reported to occur on wild host plants (Janse 1941; LePelley 1959). It was were handpicked and, if necessary harvested using a 7-m hypothesized that, in ESA, M. nigrivenella was either telescoping pole. For trees with fruits .10 cm in diameter, under natural control on wild hosts or the locally occurring at most, 10 fruits were collected, while for trees with fruits geographic race did not attack maize (Ndemah, ,10 cm in diameter, as many as 20 fruits were collected per tree. Where many trees of the same species were found in Schulthess, Poehling, Borgemeister, Goergen 2001; the same locality, a distance of at-least 2 km was covered Setamou et al. 2002). Thus, in a first step, following pre- liminary surveys during 2001 (F. Schulthess, unpubl. before the next sampling site was selected. Due to the data), this research note presents an assessment of the differences in fruiting phenologies, fruits were collected during both the wet and dry seasons. In some cases, some diversity of Mussidia spp. and their host plant range in sites were sampled more than once depending on the lowland and mid-altitude areas in Kenya. *Corresponding author. Email: bmuli@icipe.org ISSN 1745-1590 print/ISSN 1745-1604 online # 2009 Taylor & Francis DOI: 10.1080/17451590902771300 http://www.informaworld.com 36 B.K. Muli et al. availability of fruits. Each sample was labelled according to from each plant also varied: for K. africana,at most 10fruits location using a geographic positioning system (GPS) were collected per tree, while for S. madagascariensis, (Garmin – Geko 201), plant species and date of collection. between 10 and 20 fruits were examined. For C. cathartica, When fruits were collected from an unknown plant, a depending on availability of mature dry pods, between 10 sample of leaves and/or flowers, if available, were pre- and 50 pods were examined. Similar to the host plant sur- served in a plant press for identification at the Kenya veys, sampling was done during both the wet and dry seasons Forestry Research Institute (KEFRI) or by Mr. Mathenge, and, subject to the availability of fruit, some sites were University of Nairobi. Only plants whose fruits yielded sampled more than once. Fruits of S. madagascariensis and C. cathartica were dissected and inspected for the presence adult Mussidia spp. were considered as host plants; accord- of larvae, which were reared on an artificial diet until adult- ing to Wiklund (1974), the presence of an egg or larva does hood to confirm the identity of the species. For K. africana not necessarily indicate suitability of the host for comple- fruits, which are difficult to dissect, the distribution pattern tion of the lifecycle of an insect. All fruits or pods were taken to the laboratory of the was based on densities of emerging adults. International Centre of Insect Physiology and Ecology, in Taylor’s (1961) power law was used to describe the Nairobi, in 2–l plastic containers, whose lids were well distribution of Mussidia sp. larvae on C. cathartica and ventilated to prevent excess humidity build-up. Containers S. madagascariensis and, adults on K. africana. This law were kept at 25–30 C for up to 8 weeks to ensure that all postulates a consistent relationship for a species between specimens emerged as adults. From the emerged adults, variance (s ) and mean (m): specimens having the characteristics of Mussidia spp. 2 b (Moyal 1988) were used to start laboratory colonies on an s ¼ am (1) artificial diet as described by Onyango and Ochieng-Odero (1994), while some were exposed to ethyl acetate in a kill- where b indicates the distribution of the species, with b . 1 ing jar, mounted and sent for identification by M. Nuss at indicating an aggregated, b = 1 random, and b , 1 regular the Museum fu¨r Tierkunde, Dresden, Germany, where vou- distribution, while a is considered a scalar factor without cher specimens are kept. biological meaning. These coefficients were computed by Adults were offered rough tissue paper for oviposition regressing the natural logarithm of the within-plant variance (Setamou et al. 1999). The eggs were incubated, and (lns ) against the natural logarithm of mean density (lnm) emerged neonates were put on an artificial diet. In subse- for each plant. In our case, m is the mean number of quent surveys, fruits were first visually examined for eggs individuals from fruits collected per plant. A t-test was or first-instar larvae suspected to be Mussidia spp. used to determine if b was significantly different from 1. (Preliminary observations showed that 24-h-old Mussidia To obtain optimal enumerative sample size curves, spp. eggs and first instar larvae were red in colour). The Wilson and Room (1983) incorporated the estimated var- larvae were put on an artificial diet while the eggs were iance (s ) from Taylor’s (1961) power law into the general incubated in a transparent vial until larval emergence. distribution formula by Karandinos (1976): Emerging larvae were reared on an artificial diet until adult- hood to ascertain the species. 2 2 n ¼ Z =D s =m (2) =2 In addition, two herbaceous legumes, the perennial Canavalia enseiformes L. DC (Fabaceae) and the annual resulting in Mucuna pruriens DC (Fabaceae), which commonly harbour M. nigrivenella in West Africa (Setamou, Schulthess, b2 n ¼ Z =D am (3) =2 Gounou, et al. 2000), were planted under irrigation at the Kenyan coast during 2006–2007 to trap Mussidia spp. where n is the number of samples to be taken, Z is the /2 standard normal deviate (Z = 1.96 for n, 30) and D is the /2 Spatial distribution of Mussidia spp. and development of reliability level for a fixed proportion of the mean; two sampling plans reliability levels (D = 0.2 or 0.3), were chosen depending on the accuracy of the density estimate required. Sufficient numbers of infested fruits for assessment of the spatial distribution of Mussidia spp. were available for three host plants only, namely Kigelia africana (Lam.) Benth. Results (Bignoniaceae), Canavalia cathartica Thouars. (Fabaceae) Host plants and Mussidia spp. diversity and Strychnos madagascariensis Poir. (Loganiaceae), which had been shown to harbour Mussidia spp. in a pre- Mussidia species were obtained from eight plant species, all vious study on host plant range. Mature fruits of each host found along the Kenyan coast (Table 1, Figure 1). A few of plant were randomly handpicked or harvested using a 7-m these species were also found in the mid-altitudes but only telescoping pole from the accessible parts of trees/vines. For one of them, K. africana, was found to host a Mussidia K. africana and S. madagascariensis, at times, ripe fallen species (Figure 1). The survey found seven plant species, fruits were collected from the ground. Since fruit density from four families reported as hosts of M. nigrivenella in varied with plant species, the number of fruits collected West Africa, but only two were found harbouring Mussidia International Journal of Biodiversity Science & Management 37 Table 1. List of plant species sampled, those sampled and also reported as host plants of Mussidia nigrivenella in West Africa and those harbouring Mussidia spp. in Kenya during 2005–2007. Reported as hosts of Mussidia Mussidia Family Scientific name Common name nigrivenella in West Africa spp. host Anacardiaceae Sclerocarya birrea (A. Rich) Hochst. Anacardium occidentale L. Cashew nut Bignoniaceae Kigelia africana (Lam.) Benth. African sausage tree Jacaranda mimosifolia D. Don. Bombacaceae Adansonia digitata L. Baobab x Caesalpiniaceae Erythrophloeum suaveolens Guill. & Perr. Piliostigma thorningii (Schum.) Milne-Redh. x Combretaceae Terminalia brownii Fres. Euphorbiaceae Croton megalocarpus Hutch. Fabaceae Afzelia quanzensis Welw. Pod mahogany Tamarindus indica L. Tamarind x Senna bicapsularis L. Butterfly bush Delonix regia (Bojer) Flamboyant tree Cajanus cajan L. Pigeon pea Canavalia cathartica Thouars. Maunaloa vine Canavalia enseiformes L. DC. Jack bean x Dolichos lablab L. Hyacinth bean Acacia nilotica L. Acacia stuhlmannii Taub. Gliricidia sepium (Jacq.) Walp. Mucuna pruriens (L.) DC Velvet bean x Mucuna gigantea (Willd.) DC. Senna spectabilis DC Senna singueana (Delile) Lock Parkia filicoidea Welw. ex Oliver Vigna unguiculata L. Walpers Cowpea x Loganiaceae Strychnos madagascariensis Poir. Black monkey orange Strychnos spinosa Lam. Green monkey orange Meliaceae Melia volkensii Gu¨rke Mimosaceae Albizia anthelmintica Brongn. Moraceae Ficus benjamina L. Weeping fig Ficus sycomorus L. Fig tree Moringaceae Moringa oleifera Lam. Papilionoideae Erythrina abbyssinica (A. Rich) Poaceae Zea mays L. Maize x Rhamnaceae Ziziphus mauritiana Lam. Chinese apple Rubiaceae Vangueria infausta Burch. Wild pear Solanaceae Solanum incanum L. Sodom apple Sterculiaceae Dombeya rotundifolia Hotchst. Sterculia appendiculata K. Schum. Notes: x indicates that a plant species is reported as host of M. nigrivenella in West Africa. indicates that the plant species was found harbouring Mussidia spp. species (Table 1). Nearly 80% of the total plant species Fifty percent of the host plant species, from which sampled did not yield Mussidia spp. (Table 1). Two Mussidia spp. were reared, belonged to the family Mussidia species and six putative Mussidia morphospecies, Fabaceae (Table 1). Mussidia spp. eggs were found on the which occurred sympatrically, were obtained from the dif- surface of the mature fruits or pods, mostly laid in batches; ferent host plants in the coastal area. However, due to in many cases, more than one egg batch was found per fruit. nomenclatural problems, only one species (M. fiorii Except for M. fiorii attacking K. africana, whose mature Cecconi and de Joannis) obtained from K. africana was fruits have a high-moisture content, Mussidia spp. eggs identified with certainty, while another from Canavalia were collected on drying or dry fruits. Eggs were also cathartica Thouars. was close to the West African M. nigri- found on fruits harbouring larvae or pupae, or that had venella (pers. comm., M. Nuss, Museum fu¨r Tierkunde, exit holes. Mussidia larvae were found feeding on seeds, Dresden, Germany). Henceforth, the latter species will be producing copious amounts of silk and pelleted frass, espe- referred to as Mussidia nr. nigrivenella while the other cially the species feeding on Afzelia quanzensis Welw. morphospecies will be identified by the species name of (Fabaceae), Strychnos spinosa Lam. (Loganiaceae), the host plant from which they were collected; e.g. Mussidia S. madagascariensis, A. digitata and C. cathartica. Mussidia collected from Adansonia digitata L. (Bombacaceae) ‘quanzensis’ larvae were found feeding on the seed aril becomes Mussidia ‘digitata’. before they moved to the rest of the seed. Dissection of 38 B.K. Muli et al. Figure 1. Distribution of host plants attacked by Mussidia spp. along the Kenyan coast and the mid-altitude regions during 2005–2007. The left section of the figure shows a section of the Kenyan coast at a different scale. K. africana fruits, from which M. fiorii adults emerged, Spatial distributions and sampling plans revealed that their larvae also fed on the seeds. Except for Mean densities of M. fiorii adults, M. ‘madagascariensis’ and M. fiorii, whose cocoons were found singly near individual M.nr. nigrivenella larvae were 55.9  7.6, 3.93  0.64 and exit windows, at least three pupae were found near an exit 0.73  0.14, respectively. The Taylor’s (1961) power law window with their cocoons joined. However, for M. ‘quan- regressions yielded slopes b greater than 1 for M. nr. nigri- zensis’, although pupae were found in groups, exit windows venella and M. ‘madagascariensis’ larvae on C. cathartica were rare and most of the emerging adults were thought to and S. madagascariensis, respectively, indicating aggregated escape through the open suture of the dry pod. The host distribution. In contrast, Mussidia fiorii adults on K. africana plant species attacked by the different Mussidia spp. had yielded a slope less than 1, indicating regular distribution different fruiting phenologies, hence, fruits suitable (Table 2). Student’s t-test (Sokal and Rohlf 1995) showed for attack were available at different times of the year that all slopes were significantly different from unity (P , (Figure 2). 0.001 for M. nr. nigrivenella, P = 0.002 for M. ‘madagascar- iensis’ and P , 0.001 for M. fiorii)(Table 2). The optimal sample size curves (i.e. the optimal number of samples to be taken to estimate a given density for a given Kigelia africana Adansonia digitata Adansonia digitata precision level) for the different Mussidia spp. are shown in Tamarindus indica Figure 3. Mussidia nr. nigrivenella required the highest Afzelia quanzensis Afzelia quanzensis number of samples to estimate a mean density, followed Canavalia cathartica Strychnos madagascariensis by M. ‘madagascariensis’ and M. fiorii. Strychnos spinosa JF M A M J JA S O N D Discussion Figure 2. Periods when suitable fruits of different host plants There are fewer host plants for Mussidia spp. in Kenya than were available for attack by Mussidia spp. at the Kenyan coast for M. nigrivenella in West Africa, where Setamou, during 2005–2007. The rainy season months are shaded. International Journal of Biodiversity Science & Management 39 Table 2. Taylor’s a and b coefficients and r for three Mussidia species each on their main host plants. N is the number of plants from which infested fruits were collected. Taylor’s parameters Species Host plant ab t-value r P- value N Mussidia nr. nigrivenella Canavalia cathartica 0.9125 1.58 13.68 0.89 ,0.001 24 Mussidia ‘madagascariensis’ Strychnos madagascariensis 0.8792 1.16 4.064 0.62 0.002 12 Mussidia fiorii Kigelia africana 1.4347 0.94 4.29 0.47 ,0.001 23 the year. However, it was not clear how the other species (a) survive periods of non-availability of suitable fruiting structures. Various studies have shown the dispersion of M. nigri- venella larvae to be aggregated on maize (Schulthess et al. 1991; Setamou et al. 2000b; Ndemah, Schulthess, Poehling, Borgemeister 2001) and on wild host plants (Setamou et al. 2000b). An aggregated distribution was also found for M. nr. nigrivenella larvae on C. cathartica and for Mussidia ‘madagascariensis’ larvae on S. madagascariensis. This might be attributed to the oviposition behaviour of the (b) adults as suggested by Cole (1946) and Setamou et al. (2000b), whereby eggs are laid in batches, which favours aggregation of larvae in the fruits. By contrast, M. fiorii adults showed a regular distribution on K. africana. Unlike the other Mussidia species, whose pupal cases were found aggregated around the exit windows, only one pupal case was found per exit window on K. africana fruits. This indicates fierce intraspecific competition by M. fiorii larvae, probably induced by the high per fruit densities, explaining the regular distribution of adults and, thus, pupae. Setamou (c) et al. (2000b) suggested that because of the exceedingly cryptic larval feeding behaviour of Mussidia spp., emphasis should be given to finding egg and pupal parasitoids. An aggregation of pupae around exit holes should also improve host finding and parasitism efficiency of pupal parasitoids. The current study indicates that several Mussidia spp. exist in Kenya. However, whether M. nigrivenella occurs in ESA could not be determined in the present study with absolute certainty; molecular tools might be required to Mean density of borers per fruit separate the different morphospecies into species. Figure 3. Optimal number of samples to be taken to estimate mean densities of (a) M. fiorii (b) Mussidia ‘madagascariensis’ and (c) Mussidia nr. nigrivenella with reliability levels of D = 0.2 and D Acknowledgements = 0.3. The authors are grateful to Gerphas Okuku, Julius Obonyo and John Obala for technical assistance, Eric Muchugu for geostatis- tical analysis, Dr. Matthias Nuss for identification of the Schulthess, Gounou, et al. (2000) identified 20 plant species Lepidoptera, Mr. Mathenge and KEFRI staff (Gede) for plant species identification and two anonymous reviewers for reviewing from 11 families hosting the pest. 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Journal

International Journal of Biodiversity Science & ManagementTaylor & Francis

Published: Apr 24, 2009

Keywords: Mussidia spp. diversity; Pyralidae; host plant range; spatial distribution; sampling plans

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