Insects Associated With Jatropha curcas Linn. (Euphorbiaceae) in West Niger

Jatropha curcas L. (physic nut) is a drought resistant shrub originated from Central America and belonging to the Euphorbiaceae family (Legendre 2008). Jatropha genus is widely distributed in tropical countries (Heller 1996). In many west and central African countries, J. curcas is used as a hedge to protect crops against wind, hydrous erosion, and animals (Henning 2008). The seeds of J. curcas are rich in oil, which is used as a Biofuel, making this plant important for renewable energies research. In Niger, plantations of J. curcas are found at research institutions and in some private farms. There is no documentation on insect associated of J. curcas in Niger. Insect pests of J. curcas have been characterized in Nicaragua by Grimm and Maes (1997); in Brazil by Foidl et al. (1996), and Grimm and Maes (1997); in India by Shanker and Dhyani (2006); in Republic of Cape Verde by Freitas (1906), Ferrão and Ferrao (1984), and Munch and Kiefer (1986); and in West Africa by Terren et al. (2012). The most frequently observed insect pest of J. curcas in Nicaragua is Pachycoris klugii (Burmeister 1835) (Heteroptera: Scutelleridae; Grimm and Maes 1997, Grimm 1999, Peredo 2002), which feeds on flower and fruit, causing malformation of the seeds, which can reduce the quality of the oil. Leptoglossus zonatus (Dallas 1852) (Heteroptera: Coreidae) has also been observed in Nicaragua. It is polyphagous, and also infests sorghum, maize, and tomato (Grimm and Maes 1997). In Senegal, Oedaleus senegalensis (Krauss 1877) (Acrididae) was observed to cause damage to seedling leaves (Grimm and Maes 1997). The larvae and adults of Calidea panaethiopica (Kirkaldy 1909) (Scutelleridae) have also been observed in Senegal by Terren et al. (2012) and in Mexico by Tepole-Garcia et al. (2012).

This study aims to investigate insects associated with J. curcas in Western Niger and to identify those that can be pests of this shrub.

Materials and Methods

Inventoried Sites

The collecting sites were selected according to ecological area. Two sites were selected for their low precipitations: Sahelian area: Saga (Sa) and Niamey (Ni), and a third: Soudano Sahelian area: Gaya (Ga).

The plantation of J. curcas at Saga (Sa) (13° 45′ N; 2° 14′ E) is located 5 km South East from Niamey. It is an irrigated site created by an NGO: SIP ‘School Instrument of Peace’. The plantation was installed in 2009 with 1-m intrarow spacing. The plantation is irrigated twice a week during the first 5 mo, except during rainfall. Precipitation in 2010 and 2011 was 545 and 441 mm, respectively, with a monthly temperature comprised between 28 and 35°C. The plantations of the two other sites Gaya and Niamey are not irrigated. The shrubs surrounding the plantation mainly include Acacia albida Del, Azadirachta indica A. Juss, and Prosopis juliflora (Sw). D.C. (Peyre and Fabregues 1970).

The second site (Niamey, Ni) consisted in a teaching field (3° 30′ N; 2° 05′ S) belonging to the Faculty of Agronomy at Abdou Moumouni University of Niamey. Two categories of plantations are present there: a small hedge of 4-yr-old plant and a second plantation of 400 m² with 1-m intrarow spacing and 2-m interrow spacing. The seeds used were obtained from International Crop Research Institute Semi-Arid Tropics (ICRISAT) and Senegal. A mixture of J. curcas varieties were planted including Baas 38; Baas 32; Katil; Bfb1; ISC14; SNES 44; Falou; GB 14; Las Pillas 11, and SENS 30. The precipitations were 442 and 341 mm in 2010 and 2011, respectively. The average temperature was comprised between 28 and 35°C. The shrubs surrounding this plantation included Acacia nilotica L., Ziziphuss mauritiana Lam., A. indica A. Juss, and P. juliflora (Sw). D.C. (Peyre and Fabregues 1970).

The third collecting site was situated at Gaya, and is located 280 km South East from Niamey. The site is a private farm of 135 ha located at 21° 23′ N and 3° 49′ E. Only 1.05 ha is occupied by J.curcas. The plantation is divided into two groups of trees according to the age and method of plantation: 250 m² planted by vegetative propagation in March 2006 with a spacing of 1 by 1 m, and 800 m² planted by direct seeding in June 2008 with 2.5 by 2.5 m spacing. The annual average rainfall in 2010 and 2011 was, respectively, 650 and 780 mm. The maximum average daily temperature was 25°C in 2010 and 34°C in 2011. The shrubs identified around the exploitation were: Combretum micranthum, Guiera senegalensis, Mangifera indica, and Citrus spp. (Peyre and Fabregues 1970).

Collection of Insects

Two methods namely plugging and trapping were used to collect a maximum number of insects.

The plugging method was applied by using an umbrella under a branch of a physic nut shrub. All trees present along an ‘M’-shaped transect were inventoried, for a total of 20 trees. The average number of branches per tree was 35–40, for 2-yr-old trees.

The branch was shacked and insects that fall into the umbrella were collected and transferred into bottles containing 70% ethanol. The operation lasts 10 min per shrub. The method is completed by visual observation and manual picking with a flexible gripper and butterfly net. Each site was visited twice per month between 8 a.m. and 4.30 p.m. on the same day because of the distance among the sites, but the traps are visited every day. Insects were collected for 5 mo, from June to October, in 2010 and 2011.

Three yellow traps containing water were also placed in each plantation, at the foliage level of the shrubs. The traps were distanced by 30 m and placed triangularly. The traps were checked at 8 a.m. and 6 p.m. every day. The traps were placed for 5 mo from June to October. This technique makes it possible to evaluate an insect’s population dynamics on the plantation. The insects collected were placed in bottles containing ethanol, along with the following information: date, trap’s number, and name of site.

The insects were identified in the laboratory. Binocular magnifying glass was used to observe and compare homologue specimens. We consulted the most recent and specialized literature. The families insect’s keys used were those of Delvare and Aberlenc (1989), Mike et al. (2004), Lecoq (1988), Launois and Launois-Luong (1989), Launois-Luong and Lecoq (1989), and Zahradnik (1984). In addition, the identification of the most collected insects was confirmed by the insect’s database of Niger in the National Institute of Agronomic research of Niger (INRAN) and the identification was confirmed by specialists from Gembloux Agro-Bio Tech (Belgium) and Museum of Paris (France).

The Diversity Index

In each study site, we have calculated the indices of diversity of Shannon Weavers and Simpson. These indices evaluate the importance of insects diversity found on J. curcas in order to make comparisons between localities and year.

The diversity index of Shannon–Weaver (1948) is based on the formula: H′ = − Σ((N_i/N) × log₂ (N_i/N)), where N_i the number of individuals of a given species, varying from 1 to S (the total number of species) and N total numbers of insects, H′ lies between 1 and 5 bits. The maximum index is attained when all the individuals are equally distributed for all species. It is accompanied by the Pielou equitability index (1966), also called the equal distribution index (Blondel 1979), which represents the report/ratio of H′ to the theoretical maximum index of the population (H_max).

The index of Simpson (1949) measures the probability that two randomly selected individuals belong to the same species: D = Σ N_i (N_i − 1)/N (N − 1), where N_i the number of individuals of a given species and N is the total number of insects. When this index has a value of 0, there is maximum diversity; when it is equal to 1, diversity is minimal, with the aim of obtaining ‘the best diversity index values’. The diversity index of Simpson is calculated by 1 − D. Maximum diversity is represented by 1, and minimal diversity by 0. This index of diversity gives greater importance to abundant species.

Statistical Analysis

Mean numbers of insects were subjected to a one-way analysis of variance ANOVA followed by Tukey’s post hoc tests (P < 0.05). The software used was MINITAB16. Values are expressed as means ± standard deviation.

Results and Discussion

In total, 25 insect species were collected from Niamey site in 2010 and 2011. These insect species belong to 16 families (Table 1). Hymenoptera were the most frequent order, representing 44% of the collected insects. Orthoptera and Coleoptera represented 30 and 11% of the total capture, respectively. Diptera, Heteroptera, and Plecoptera are 10, 4, and 1% respectively.

The locality of Gaya is significantly different from the other sites because it is not only a strongly sprinkled zone, but also the Jatropha plantations are older (Table 2).

In Niamey, there were fewer Acrididae (O. senegalensis, Oedaleus nigeriensis) in June, but their numbers increased between July and August (Fig. 1).

Fig. 1.

Three most important insect pests of J. curcas at Niamey in 2010 and 2011.

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Cetoniidae (Pachnoda interrupta) was more abundant during the period of flowering. Pentatomidae (Agonoscelis versicoloratus, Nezara viridula) were captured only during the flowering period of the plant (between July and August).

At Saga, 955 insects belonging to 34 species and 23 families were collected during the 2 yr between June and October. Orthoptera were the most numerous (36%) Hymenoptera, Coleoptera, Diptera, Heteroptera, and Plecoptera counted for 25, 15, 14, 8, and 2%, respectively (Tables 1 and ²).

Heteracris leani (Uvarov 1941) was frequently collected in Saga, because of the presence of rice plantations. Cetoniidae were captured between July and August during the flowering period of the plant (Fig. 2).

Fig. 2.

Three most important insect pests of J. curcas at Saga in 2010 and 2011.

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The species Rhabdotis sobrina (Gory and Percheron 1833) was observed only at this site. Pentatomidae were also captured during the flowering period (between July and August) of the plant.

In the Gaya site, 38 insects’ species were observed in 2010 and 2011. These species are grouping into 24 families. Hymenoptera and Heteroptera were found to be the most frequent orders with 24% for each order. Coleoptera, Orthoptera, Diptera, and Plecoptera represented 23, 20, 9, and 0%, respectively, of the total captures. The numbers of Acrididae were greater at the beginning (June and July) and end of the rainy season (September and October) (Fig. 3).

Fig. 3.

Three most important insect pests of J. curcas evolution at Gaya in 2010 and 2011.

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The presence of Acanthacris ruficornis citrina (Audinet-Serville 1838) (Acrididae) in June and July marks the uniqueness of this site. The Pentatomidae were observed during the flowering of J. curcas (between July and August).

The insects associated with J. curcas mainly belonged to Orthoptera, Coleoptera, Heteroptera, Hymenoptera, and Diptera in Niger (Table 3). The two major families of Orthoptera were Acrididae and Pyrgomorphidae. The most frequent insects species during our observations were O. senegalensis (Krauss 1877), O. nigeriensis (Uvarov 1926); Catantops stramineus (Walker 1870), Parga cyanoptera (Uvarov 1926); H. leani, A.ruficornis citrina, for Acrididae, and Poekilocerus bufonius hieroglyphicus (Klug 1832) for Pyrgomorphidae. Acrididae were observed in all the localities, whereas H. leani was specific to Niamey and Saga sites. A. ruficornis citrina (Acrididae) and P. bufonius hieroglyphicus (Pyrgomorphidae) were observed only at Gaya. O senegalensis was previously observed on J. curcas in Senegal (Grimm and Maes 1997). This Acrididae feeds on leaves and seedlings. They are also pests of cereals (millet, sorghum) in the Sahelian area, because of the damage they cause to the panicle and leaves (Boys 1978). Corynorhynchus radula (Klug 1820) and Stiphra robusta (Mello-Leitão 1939) (Orthoptera: Proscopiidae) were observed in Brazil by Saturnino et al. (2005); they destroy the leaves and the flowers of J. curcas.

The Coleoptera insects observed on J. curcas in Niger include P. interrupta (Olivier 1789), Pachnoda marginata (Herbst 1790), Pachnoda sinuata (Heinrich and McClain 1986); R. sobrina (Cetoniidae) and Decapotoma lunata (Pallas 1772) (Meloidae). They are all phytophagous, and their adults feed on flowers (Brown 1991). This explains their presence in large numbers during the flowering stage of J. curcas. Oxycetonia versicoloratus (Fabricius 1775) (Coleoptera: Cetoniidae) has been observed on J. curcas in India by Shanker and Dhyani (2006). It was found to feed on leaves and flowers of J. curcas. Bostrichus sp. (Coleoptera: Bostrichidae) has been identified on J. curcas in Republic of Cape Verde by Freitas (1906) and Munch and Kiefer (1986). This insect makes galleries in the wood of J.curcas. Aphtona dilutipes (Jacoby) (Coleoptera: Chrysomelidae) is observed in Mozambique by Gagnaux (2009). This Coleoptera feeds on leaves of J. curcas. Pantomorus femoratus (Sharp 1891) (Coleoptera: Curculionidae) and Lagocheirus undatus (Voet 1778) (Coleoptera: Cerambycidae) were observed on J. curcas by Grimm and Maes (1997) in Nicaragua. The first insect feeds on the leaves, and the second on the seedlings.

Heteroptera species observed on J. curcas in different localities of Niger included: A. versicoloratus (Dallas 1851); N. viridula (Linn 1758); Antestia lymphata (Kirkaldy 1909) (Pentatomidae), Leptoglossus membranaceus (Fabricius 1781), Cletus trigonus (Thunberg 1783), and C. panaethiopica (Kirkaldy 1909) (Scutelleridae). They feed on flowers and fruits of J. curcas. N. viridula, and L. zonatus are pests of J. curcas in Nicaragua (Grimm and Maes 1997). They feed on fruit of J. curcas.

In the lower valley of the Senegal River C. panaethiopica was observed on J. curcas by Terren et al. (2012). The adults and nymphs of C. panaethiopica attack the flowers and capsules of J. curcas and suck the sap. Another bug, Calidea stigmata, was observed in Republic of Cape Verde and Sao Tomé by Ferrão and Ferrao (1984) and Munch and Kiefer (1986). This insect feeds on fruits of J. curcas.

Several Hymenoptera species were observed on J. curcas in Niger: Apis melifera adansonii (Linn 1761) (Apidea), Thyreus delumbatus (Vochal 1903) (Anthophoridae); Tricarinodynerus guerinii (Saussure 1856) (Eumenidae); Oecophylla longinoda (Latreille 1802); Camponotus maculatus (Fabricius 1782); Lepisiota capensis (Mayr 1862) (Formicidae); Smicromyrme atropos (Smith 1855) (Mutillidae), and Stizus fuscipennis (Smith 1856) (Sphecidae). They visit the flowers of J. curcas and take part in the pollination of this plant (Table 3).

The insect pollinators species associated with J. curcas belong to a family of Apidae (Grimm and Maes 1997, Solomon Raju and Ezradanam 2002). Banjo et al. (2006) reported that honeybee species as the main insects pollinators of J. curcas flowers in north of Nigeria.

Several insects such as Camponotus compressus (Fabricius 1787), Crematogaster sp., Solenopsis geminata (F. 1804), and Pheidole spathifer (Forel 1902) belonging to the Formicidae family were observed on J. curcas flowers in India (Solomon Raju and Ezradanam 2002, Regupathy and Ayyasamy 2011). The latter authors also showed that these insect species play important role in the pollination during the season of J. curcas flowers.

In Niger, the collected insect species of Diptera from J. curcas were found to belong to the following families: Conopidae (Conops zonatus—Krober 1915); Syrphidae (Eristalis sp.) Muscidae (Stomoxys calcitrans) Tachinidae (Gonia sp.), and Tephritidae (Ceratitis sp.) (Table 2). We also observed that these species regularly visited the J. curcas’s flowers. According to Solomon Raju and Ezradanam (2002), the contribution of Diptera in the pollination of J. curcas remains weak.

Many species of Lepidoptera were observed on J. curcas flower in Niger, but in individual number. The alcol, which was used for preservation, caused color damage, making Lepidoptera identification more complicated.

In the low valley of Senegal River leaf miner Stomphastis thraustica (Meyrick 1908) (Lepidoptera: Gracillariidae) and the leaf and stem miner Pempelia morosalis (Saalmuller 1880) (Lepidoptera: Pyralidae) have been identified (Terren et al. 2012). These caterpillars are observed in many sites in Africa but not in our sites because of the young plantations.

Evaluation of Species Diversity

The numbers of insects of both trapping and plugging methods are summarized in Table 3. In 2010, 1,719 insects were collected between June and October, with 186 from Niamey, 409 at Saga, and 1,124 at Gaya. In 2011, 2,130 insects were collected at the same sites, with 171 insects from Niamey, 546 at Saga, and 1,413 at Gaya. These large differences in abundance observed between the three localities can be due to the microclimate. Niamey and Saga are located in the Sahelian area, whose isohyets lie between 500 and 600 mm of rain. The site at Gaya, with the greatest number of insects, is located in the Soudano-Sahelian area, with isohyets ranging from 700 to 800 mm.

The Shannon–Weaver diversity indexes in 2010 were 1.36, 1.36, and 1.43 for Niamey, Saga, and Gaya, respectively (Table 4). These values correspond to a low diversity of insect species in J. curcas plantations.

The sites of Niamey and Saga have a similar diversity index; they belong to the same climatic area. The Shannon–Weaver diversity indexes in 2011 were 0.99, 1.27, and 1.41 for Niamey, Saga, and Gaya, respectively. Lower indexes were observed in 2011 at Saga and Niamey because the rain fallen was more important in 2010 (442 mm in Niamey, 545 mm in Saga) than in 2011 (341 mm in Niamey and 441 mm for Saga).

The indexes of equitability (H_max) in 2010 were 0.97, 0.88, and 0.91 for Niamey, Saga, and Gaya, respectively. The indexes for 2011 were 0.76, 0.85, and 0.90 for Niamey, Saga and Gaya, respectively. Indeed, no dominant species were found in the plantations.

The 2010 Simpson indexes were 0.91, 0.92, and 0.95 for Niamey, Saga, and Gaya, respectively, the 2011 indexes were 0.79, 0.93, and 0.95 for the same sites. This index shows the low diversity of the species of insects on J. curcas in all the localities.

Jatrophacurcas, which was recently introduced into Niger, is visited by several insects belonging to different families. In Niger, the majority of insect pests associated with J. curcas belonged to the following families: Acrididae and Pyrgomorphidae that feed on leaves and seedlings; and the Cetoniidae, Pentatomidae, Coreidae, and Scutelleridae that feed on flowers and fruits of J. curcas.

As a result, all insect species associated with J. curcas in Niger were previously observed on other favorable crops such as cereal (millet, sorghum). J. curcas was found to be attacked by Acrididae in the beginning of the rain season before the plantation of cereal crops. Others insects’ species belonging to Coleoptera, Hymenoptera, and Diptera were found to be attracted by the J. curcas flowers. The species that appear specific to J. curcas are C. panaethiopica observed only at Gaya and Calidea sp. observed at Maradi.

Acknowledgments

The authors make a point of thanking Belgian Technique co-operation (CTB) for the financing this study and professor Jean Phillipe Le Grand of paris Musium and George Gorougone of ITA of Bennin which helped us in the identification of some species of insects.

References Cited

Author notes