Received 9 June 2016; accepted 24 July 2016; published 28 July 2016
Jatropha curcas L. (Euphorbiaceae) is a shrub native to Central America that produces inedible oil used as fuel in total or partial substitution of fossil fuels  . Jatropha curcas seeds contain 30% - 40% oil, which can be an alternative to diesel fuel  . Oil of J. curcas is a high performance biodiesel unlike other biodiesels, and can be used without mixing and without engine modifications, making the prospects offered by J. curcas incomparable to those of others in the field of diesel or alternative to conventional diesel  . Biofuels contribute to reducing the energy dependence of countries with no access to oil resources  . Nowadays, there is the valuation of the plant of J. curcas. This valuation essentially aims at diversifying agricultural production and increasing the incomes of small producers to alleviate poverty in rural areas through the development of short production chains of crude vegetable oil  . Jatropha curcas L. restores marginal soils, improves soil fertility, reforests degraded land to promote land tenure security, diversifies income generation and fights against straying animals  .
In Burkina Faso, four species of Jatropha are known: J. curcas L., J. gossypiifolia L., J. podagrica and J. inte- gerrima  . But the species J. curcas L. remains the most widespread and the most exploited. The Burkinabe government and private promoters were strongly mobilized for the production of J. curcas after the oil crisis of the 2000s  . Jatropha curcas plantations in Burkina Faso occupied an area of 86,908 ha in 2010  .
However, J. curcas is subject to the attacks of many pests and diseases that can have a significant impact on the production of this shrub, despite its toxicity and its biocidal properties for which oil is known    .
In Africa, several insect pests feed on the plant of J. curcas L. These include crickets, beetles, bugs, scale insects, etc.    .
In Burkina Faso, Calidea panaethiopica and Aphtona whitfieldi were reported as the most common insect pests observed in 60% of jatropha plantations   .
The female of C. panaethiopica usually lays its eggs on fruit and sometimes on the underside of leaves of Jatropha. Larvae and adult of C. panaethiopica feed on the flowers and fruits of J. curcas. Attacked flowers become dried and attacked fruits often have brown spots causing necrotizing malformed or empty seeds. The average grain loss of J. curcas due to C. panaethiopica was 59%  . As for A. whitfieldi, the female lays her eggs in the soil at the base of the neck of the plant. After hatching, the larvae and the adults feed on the leaves.
Despite the economic importance of these insect pests, their alternative host plants are not yet well known. However,  reported that cotton in Tanzania, sorghum and sunflower in South Africa are host plants for C. dregii, which is a cousin of C. panaethiopica. Author  indicated that C. panaethiopica was a polyphagous insect of many host plants containing toxic compounds, such as Ricinus communis, J. podagrica and Gossypium sp. This is why our focus was on species of Euphorbiaceae family. The potential host plants were cultivated in six communes of the Sissili province, South Burkina Faso: Léo, Biéha, Boura, Niabouri, Tô and Silly.
In conclusion, C. panaethiopica larvae and adults and A. withfieldi adults have been found hosts of J. gossypiifolia in addition to J. curcas their preferred host. No other host plant was found in South Burkina Faso for these insect pests. It would be necessary to extend our research to other agro ecological regions of Burkina Faso to increase the chance to find probable host plants of these insect pests.
The main objective of this study was to identify alternative wild or cultivated host plants of C. panaethiopica and A. whitfieldi in South Sudan region of Burkina Faso. This knowledge is important in the process of develop- ing efficient control methods against these insect pests.
2. Material and Methods
2.1.1. Study Sites
The study was conducted from June 3rd 2013 to November 30th 2014 in six locations, namely Léo, Biéha Boura, Niabouri, Tô and Silly in the Sissili province, South-Sudanese zone of Burkina Faso.
The plant material was composed of sorghum panicles (Sorghum bicolor), cotton capsules (Gossypium hirsutum), sunflower (Helianthus annuus), tobacco (Nicotiana tabacum), fruits and flowers of perennial or annual wild Eu- phorbiaceas for C. panaethiopica and leaves for A. whitfieldi.
2.1.3. Insect Material
The insect material was composed of adults and larvae of C. panaethiopica and adults of A. whitfieldi.
2.2.1. Sampling Methods
The search for alternative host plants for C. panaethiopica and C. A. withfieldi included both herbaceous and woody Euphorbiacea. The most important criteria were that the J. curcas’ plantation had to be closed to a fallow. In each selected J. curcas’ plantation, each four sides of the field were prospected and the vicinity fallow was also visited up to 500 m from the J. curcas’ field. The observations were done along a diagonal of the plantation. At least four fields were visited once a week in each commune. Potential host plants were identified, registered (their scientific name and their phenology were mentioned in a book) their organs (small branches, leaves, flowers etc.) were removed and brought back to the laboratory in Léo for feeding test by the two insect pests.
2.2.2. Breeding Method
The experience started as soon as the targeted plants were established in the field from June to November and the experience in the laboratory lasted for about twelve weeks. In the laboratory, adults and larvae of C. panaethiopica have been in contact with fruits and flowers of different potential host plants cultivated or wild. Four adult couples and five larvae of C. panaethiopica were put in a plastic box of 40 cm × 50 cm with a hole of 15 cm × 10 cm on each side, in the presence of fruits and flowers of each potential host plant. Four other adult couples of C. panaethiopica were also placed in a breeding box in the presence of J. curcas fruit as a control. The fruits and flowers of potential host plants were renewed once a week.
The observations in the laboratory focused on the behavior of C. panaethiopica vis-à-vis the fruits and flowers of potential alternative host plants. These observations were done twice a day, morning at 7 am and evening at 18 pm.The insects were kept in conditions closed to those of the surrounding environment (30˚C temperature, 69% RH, and a photoperiodof 12:12 [L:D] h). The laboratory was well-ventilated thanks to large windows.
Regarding A. whitfieldi, each Euphorbiaceae was put in a plastic box and was brought into contact with the in- sect pest. The observations were done twice a day.
This study was conducted during the rainy season, from June to September 2014.
The list of potential host plants wild or cultivated for A. whitfieldi and C. panaethiopica studied in South Sudan region of Burkina Faso is presented in Table 1.
The sign (+) indicates that the insect pests attack the host plant in the field and the laboratory and the (-) means they do not feed on the plant in both conditions.
C. panaethiopica (Hemiptera: Scutelleridae) feeds on the flowers and fruits of J. curcas and A. whitfieldi (Cole- optera: Chrysomelidae) consumes the leaves of J. gossypiifolia. The latter is a very common wild Euphorbiaceae of the outskirts of swampy areas and near the boxes in the Sissili province. The two insect pests were absent on all other potential host plants identified in the study area. However, the rare literature reported that C. panaethiopica met on a large host range including cultivated crops.
The results showed that larvae and adults of C. panaethiopica and adults of A. whitfieldi are pests of J. gossy- piifolia in addition to J. curcas.
The study on the alternative host plants of C. panaethiopica and A. whitfieldi included crops like sorghum, cotton, sunflower, tobacco and wild perennial or annual Euphorbiacea. The results of this study have shown that
Table 1. List of potential host plants of Calidea panaethiopica and Aphtona whitfieldi in the Sissili province, South Sudanian zone of Burkina Faso.
C. panaethiopica and A. whitfieldi are pests of J. gossypiifolia in addition to J. curcas. Surprisingly, and in con- tradiction with what is reported in the literature, both insect pests have only been found on any other plant in Southern Burkina Faso. However,  reported that C. panaethiopica was a polyphagous insect of many host plants that contain toxic compounds. These host plants include Ricinus communis, J. podagrica and Gossypium sp. Author  reported C. dregii Germar as being a cotton pest in Tanzania and sorghum and sunflower pest in South Africa. Authors  and  reported in India and West Africa, some Hemiptera such as Calidea spp., Eurystylus sp., Campylomma sp., Creontiades Rambar pallidus and Nezara viridula as major insect pests of sorghum. Author  reported that in Nigeria, C. panaethiopica was a pest of flowers and fruits of Ricinus communis. For  in Ghana, C. dregii is a common pest throughout the year, usually on the flowers and sometimes on the stems of J. podagrica.
Authors thank Mr. Yacouba Nignan, research assistant in the Fondation Fasobiocarburant for his help in the field. This project was funded by the Agence Française de Développement (AFD) through a grant of the Fonds Français pour l’Environnement (FFEM) and co-funded by the Fondation Fasobiocarburant. The implementation of the pro- ject was coordinated by l’Agence de Développement de la Coopération Internationale dans les domaines de l’Agri- culture, de l’alimentation et des espaces ruraux.