MATERIALS AND METHODS

Psyllids were collected in 12 regions in Cameroon from 1994 to 2006 (Table 1). Psyllids were captured with the help of an entomological net of 0.5 mm mesh size and with the help of a mouth aspirator. Host plants and only accessible branches (< 2 m high) were visually searched at random. Psyllids seen on the lower four feet of canopy were captured with the help of the mouth aspirator. We also used the entomological net to capture other specimens. These insects were preserved in the 70% alcohol. The collection is kept in the Laboratory of Zoology, University of Yaounde I (LZUY) and in the Naturhistorisches Museum Basle, Switzerland (NHMB). Psyllids were identified under stereomicroscope using Hollis (1984)’s keys for identification of Afrotropical Triozidae. Host plants were identified and kept in National Herbarum at Yaounde (Cameroon).

RESULTS

Two thousands one hundred and ninety six triozids of different developmental stages were captured of which 1494 belong to Trioza genus (380 males, 355 females and 759 larvae) and 702 belong to Pauropsylla genus (288 males, 353 femelles and 61 larvae). Thirty five species of triozids exist in Cameroon. Twenty-eight species were collected during this survey and 7 other species were cited by Hollis (1984) from Cameroon (Table 1). Within this fauna, 24 species are of Trioza genus and 11 species are of Pauropsylla genus. We discovered 13 undescribed species of Trioza genus and 4 undescribed species of Pauropsylla genus. Triozids feed on different host plants of 12 families: Rutaceae (1 specie), Menispermaceae (2 species), Combretaceae (1 species), Apocynaceae (3 species), Flacourtiaceae (1 species), Ebenaceae (1 species), Rubiaceae (2 species), Moraceae (9 species), Annonaceae (2 species), Rhamnaceae (1 species), Euphorbiaceae (1 species), Clusiaceae (1 species) and 6 unknown host plants.

Here is the list of the material examined.

Table 1:	List of known and unknown species of triozids (Hemiptera, Triozidae) from Cameroon with their host plants, the region where species were collected for the first time and references cited for known species

Trioza Genus

Pauropsylla genus

DISCUSSION

According to Hollis (1984), 14 species of Triozidae family (7 species of Trioza ant 7 species of Pauropsylla) were identified from Cameroon. The present study permits us to enrich the psyllid fauna of Triozidae family from Cameroon. A total of 35 species of Triozidae family was identified; 28 species were captured during this survey and 7 other species were described from Cameroon by Hollis (1984). 24 species belong to the Trioza genus and 11 species belong to the Pauropsylla genus. 17 species were undescribed of which 13 species belong to Trioza genus and 4 species belong to Pauropsylla genus. Five species of Trioza (T. erytreae, T. medleri, T. xylopia, T. anomalicornis, T. fuscivena) and 4 species of Pauropsylla (P. trichaeta, P. longipes, P. septima, P. mistura) previously knew from Cameroon (Hollis, 1984) were captured during this study and 2 species of Trioza (T. boxi, T. ghaneensis) knew elsewhere in the Afrotropical region (Hollis, 1984) were captured in Cameroon for the first time. Four species of Trioza (T. bamenda, T. bussei, T. camerounensis, T. mirificornis) and 3 species of Pauropsylla (P. eastopi, P. tatrichea, P. proxima) knew from Cameroon (Hollis, 1984) were not captured during this survey.

Host plants of triozids belong to 12 different plants families: Rutaceae, Menispermaceae, Combretaceae, Apocynaceae, Flacourtiaceae, E benaceae, Rubiaceae, Moraceae, Annonaceae, Rhamnaceae, Euphorbiaceae, Clusiaceae and 6 unknown host plants. Considering the list of host plants cited by Hollis (1984), it is important to note that Flacourtiaceae, Rubiaceae and Clusiaceae plants family are knew for the first time as triozids host plants in the Afrotropical region. The Triozidae host plants are more diversified in Cameroon than the Central European triozids species host plant (Burckhardt et al., 1991). In that region, Triozidae species developed on Herbaceous plants particularly of the families Asteraceae, Apiaceae and Rosaceae and overwinter as adults develop on conifers (Burckhardt et al., 1991).

Some of the host plants of triozids from Cameroon had various economical and pharmaceutical importances. The most important one is Citrus witch is a cultivated plant in all tropical and subtropical regions. Citrus fruits constituted the first world production of fruits and they play an important role in the human food since they are very rich in essential oils and in vitamin C (Huet 1971). The other plants are used in the African traditional medicine: Stephania abyssinica; Caloncoba welwitchii (Ake-Assi et al., 1978); Diospyros hoyleana (Bouquet et al., 1971); Xylopia sp. (Aseku and Adeniyi, 2004). The phytochemical studies permitted to isolate the active compound capable to fight efficiently against some pathogenic germs of the man: the antibacterial flavonoides isolated from Combretaceae (Martini et al., 2004); the combretastatines isolated from Combretaceae that, according to Lawrencea et al. (2004), block the cell division and would permit to limit the cellular proliferation in the case of cancer; the quinones isolated on Diospyros hoyleana for therapeutic use (Bouquet et al. 1971). The studies of Ayissi and Nyadedzor (2003) showed that the excerpts of Clausena anisata have inhibitory effects on the multiplication of the HIV 1 and HIV 2, AIDS viruses.

Triozids caused severe damages on their host plants. The sap feeding activity on host plant caused a stress to the plant; the injection of toxins to the plant tissues provokes the degeneration of leaves, buds or the whole plant; the distortion of leaves, the apparition of necrosis, pit galls or crypts on leaves and stems occurred during larval development.

Adults of T. erytreae feed and laid their eggs preferentially on youngest buds (Fig. 1). In period of higher proliferation, the number of adults per bud can be up to 30 individuals per bud (Fig. 2). The larvae develop themselves at the lower face of the leaves (Fig. 3) and during the larval development process, these larvae provoked the apparition of pit galls or crypts at the upper face of the leaves thus attacked (Fig. 4). In the nursery, the non protected young plants has their leaves puffed up, deformed and sometimes wrapped (Fig. 5). These young plants were weak and unfit for commercialisation (Tamesse and Messi, 2002). This species is a vector of bacteria causing citrus greening disease in Cameroon (Hollis, 1984; Tamesse et al., 1999).

Damages caused by Trioza sp.n.1, psyllid of Stephania abyssinica (Fig. 6), Trioza sp.n.2, psyllid of Stephania sp., Trioza sp.n.3, psyllid of Combretum sp., Trioza sp.n.4, psyllid of Funtunia elastica (Fig. 7), Trioza sp.n.8, psyllid of Ficus sp., Trioza sp.n.10, psyllid of Lasiodiscus mannii, Trioza medleri, Trioza anomalicornis and Trioza fuscivena on their host plants were usually leaves with pit galls or crypts; these leaves were wrapped, deformed and discoloured.

Trioza sp.n.5, psyllid of Caloncoba welwitchii (Fig. 8), Trioza sp.n.6, psyllid of Diospyros hoyleana, Trioza sp.n.9, psyllid of Xylopia hypolampra (Fig. 9), Trioza sp.n.7, psyllid of an unidentified Rubiaceae, Trioza sp.n.11, psyllid of Tarenna sp., Trioza ghaneensis and Trioza xylopia didn’t provoke pit galls on leaves of their host plants but these leaves were wrapped, deformed, discoloured and sometimes with necrosis.

Damages caused by Pauropsylla trichaeta (Fig. 10), P. mistura (Fig. 11), P. septima, Pauropsylla sp.n. 1, psyllid of Ficus sp.1, Pauropsylla sp.n. 2, psyllid of Ficus sp.2, Pauropsylla sp.n. 3, psyllid of Ficus sp.3 and Pauropsylla sp.n. 4, psyllid of Ficus sp.4 on their host plants are pit galls or crypts on leaves.

Fig.1 :	Adults of T. erytreae feed on young buds of Citrus sinensis

Fig. 2:	Many adults feeding and laying eggs on a single bud of Citrus sinensis

Fig. 3:	Young leaves with larvae on the lower face of the leaves

Fig.4 :	Pits galls or crypts induced by larvae of T. erytreae on the upper face of the leaves

Fig. 5:	Comparison of the development level of three young plants; two were attacked by T. erytreae and the middle one was avoid for psyllid attacks

Fig. 6:	Pits galls on Stephania abyssinica

Fig. 7:	Damages on Funtunia elastica: pits galls, discolouration and deformation of Leaves

Fig. 8:	Damages on Caloncoba welwitschii: discolouration, necrosis and drying up of leaves

Fig.9 :	Damages on Xylopia hypolampra: leaves wrapped and deformed

Fig. 10:	Damages on Ficus sur: pits galls, leaves deformed

Fig. 11:	Damages on Ficus abutilifolia: pits galls, leaves wrapped and deformed

CONCLUSIONS

In Cameroon, 35 species of psyllids of Triozidae family were recorded, of which 24 species belong to the Trioza genus and 11 species belong to the Pauropsylla genus. The present survey permitted to record in Cameroon 17 undescribed species and 2 species previously described elsewhere in the Afrotropical but unknown from Cameroon. The presence of 5 species previously described from Cameroon is confirmed. Triozids host plants had various economical and pharmaceutical importances. Damages caused by these insects on their host plants are mainly pit galls or crypts, deformation and discolouration of leaves and necrosis. Then, it is important to pursue these works notably by completing the taxonomic and biology studies of psyllids of Triozidae family in Cameroon in order to undertake an integrated pest management against species with economic and pharmaceutical interests.

ACKNOWLEDGMENTS

This work is partly funded by the Swiss National Science Foundation (Research Partnerships with Developing Countries, project number 3170A0-109221/1) to Daniel Burckhardt and Joseph Lebel Tamesse.