Proceedings of the Eighth International Workshop on Biological Control and Management of Chromolaena odorata and other Eupatorieae, Nairobi, Kenya, 1-2 November 2010. Zachariades C, Strathie LW, Day MD, Muniappan R (eds) ARC-PPRI, Pretoria (2013) pp 29-34

Abundance of Chromolaena odorata, its influence on entomofauna and implications for farmers’ activities in south-western

R.A. Adebayo

Department of Crop, Soil and Pest Management, School of Agriculture and Agricultural Technology, Federal University of Technology , , Nigeria [email protected]

Chromolaena odorata (L.) King & Robinson (Asteraceae), an invasive alien plant of terrestrial habitat in many tropical and sub-tropical regions of the world, was investigated in the South-West Ecological Zone of Nigeria. Investigations, including field observations on C. odorata and a survey of farmers’ knowledge and opinions of it and knowledge of its biological control, were conducted at the Teaching and Research Farm of the Federal University of Technology Akure (FUTA) and at Ipogun, a farmers’ community at Local Government Area of Ondo State, respectively. Field observations revealed that about 50% of undeveloped FUTA land was infested to varying degrees with C. odorata. More plant species were found on observed C. odorata–free land compared with land infested with C. odorata. The insect species collected on C. odorata were in the orders Orthoptera, Lepidoptera, Homoptera and Hymenoptera. Mottled, discoloured and distorted leaves characterized C. odorata infested with aphids. Results of the survey indicated there awareness of C. odorata by the farmers (70%) although they lack knowledge of biological control of the weed. Infestation of farms by C. odorata increases production costs substantially and when infestations are large, abandonment of farmlands occurs. Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae) was not recovered during the period of the field observation, nor were any C. odorata plants observed to be galled by the fly Cecidochares connexa Macquart (Diptera: Tephritidae). This investigation provided additional information on the effects of C. odorata on biodiversity and impacts on resource-poor farmers. Further studies on the biocontrol of C. odorata are recommended.

KEYWORDS: alien; Aphis spiraecola; Cedidochares connexa; invasive; Nigeria; Pareuchaetes pseudoinsulata

INTRODUCTION stands in disturbed areas, grasslands, fallows and forestry plantations (Holm et al. 1977). Chromolaena odorata (L.) King & Robinson Chromolaena odorata spreads rapidly due to its (Asteraceae: Eupatorieae), is a widely efficient short- and long-distance dispersal distributed neotropical shrub introduced to abilities. Since its introduction to Nigeria, C. many parts of the tropics (McFadyen 1991; odorata has become a major weed of arable and Witkowski and Wilson 2001). It probably plantation crops as well as forests and spread to Africa in 1937 through the rangelands, thus constituting a serious threat to importation of contaminated Gmelina arborea agriculture, biodiversity and ecosystems in Roxb. (Verbenaceae) seeds to Nigeria from Sri West, Central and southern Africa (Erasmus Lanka (Ivens 1974). The weed is widespread in 1988; Timbilla and Braimah 1996; Timbilla et the southern parts of Nigeria and common in al. 2003; Adebayo and Uyi 2011). More than 20 states like Abia, Akwa-Ibom, Anambra, of the 36 states of Nigeria, including those of Bayelsa, Cross River, Delta, Ebonyi, Edo, Ekiti, the South Western region, are now highly Enugu, Imo, Kogi, Kwara, Lagos, Oyo, Osun, infested with C. odorata (Uyi et al. 2008). Ogun, Ondo, Rivers, and parts of Nasarawa state in Nigeria (Uyi et al. 2008). It forms pure South-western Nigeria contributes substantially

29 Eighth International Workshop on Biological Control and Management of Chromolaena odorata and other Eupatorieae to the agricultural production of Nigeria as a To correlate the presence of C. odorata with result of its conducive climatic conditions. plant and insect species, two parallel line- Economic crops grown in the region include transects, each 100m long, lying 100m apart cacao, oil palm, maize, cocoyam and cowpea. from one another in C. odorata-infested and C. This present study investigates the presence of odorata-free areas were sampled using the C. odorata in relation to other plant species and systematic and stratified sampling method to insects and its impact on farmers’ activities in described by Hammond (1992) and Uyi et. al. South-western Nigeria. (2009). On a weekly basis over two months, four quadrats of 1m2 were randomly sampled MATERIALS AND METHODS for plants and insects along each 100m transect. Plants observed were identified and recorded This study was conducted at the Teaching and while insect species associated with C. odorata Research Farm of the Federal University of were observed, identified and recorded. The Technology Akure (FUTA) and at Ipogun, a number of mottled and non-mottled leaves was farmers’ community at Ifedore Local also counted on aphid-infested C. odorata Government Area of Ondo State, between April plants along transects. Chromolaena odorata and September 2010. Field observations on C. plants were observed for the presence of two odorata were made at the first site during the biocontrol agents, Pareuchaetes pseudoinsulata wet season and a survey of farmers’ knowledge Rego Barros (Lepidoptera: Arctiidae) and and opinions of it and knowledge of its Cecidochares connexa Macquart (Diptera: biological control was conducted at the second Tephritidae), both of which have established site. elsewhere in West Africa (Zachariades 2011).

Table 1. Plant species on C. odorata-infested and C. odorata-free land at the Teaching and Research Farm of the Federal University of Technology Akure. C. odorata- C. odorata- Plant species Family infested land free land Chromolaena odorata Asteraceae + + Achyranthes aspera Amaranthaceae + − Ageratum conyzoides Asteraceae − + Alternanthera sessilis Amaranthaceae − + Aspilia africana Asteraceae + − Asystasia gangetica Acanthaceae + + Axonopus compressus Poaceae + + Boerhavia diffusa Nyctaginaceae − + Boerhavia erecta Nyctaginaceae − + Butyrospermum parkii Sapotaceae − + Centrosema pubescens Fabaceae − + Commelina benghalensis Commelinaceae + + Dissotis erecta Melastomataceae − + Euphorbia heterophylla Euphorbiaceae − + Hypoestes cancellata Acanthaceae − + Ipomoea involucrata Convolvulaceae − + Melanthera scandens Asteraceae + − Melastomastrum capitatum Melastomataceae + − Oplismenus burmannii Poaceae + + Sida acuta Malvaceae + + Sporobolus pyramidalis Poaceae − + Talinum triangulare Portulacaceae − + Trianthema portulacastrum Aizoaceae − +

30 Adebayo: Chromolaena in south-western Nigeria

Table 2. Mean (± SE) number of Aphis spiraecola, mottled and non-mottled leaves of Chromolaena odorata plants per square metre at the Teaching and Research Farms of the Federal University of Technology Akure, over eight weeks of sampling in 2010. Month Week No. aphids Mottled Non-mottled leaves leaves May 1 93.7 ± 6.3 2.5 ± 0.3 11.2 ± 2.1 2 93.5 ± 5.6 2.3 ± 0.2 13.0 ± 1.8 3 101.2 ± 10.0 3.0 ± 0.1 11.5 ± 2.0 4 97.0 ± 4.3 2.8 ± 0.2 10.0 ± 1.3 June 5 192.5 ± 10.2 9.3 ± 1.2 9.0 ± 1.6 6 203.7 ± 25.4 12.5 ± 2.0 9.8 ± 2.4 7 177.5 ± 8.60 8.8 ± 1.3 9.6 ± 1.3 8 206.0 ± 24.8 13.8 ± 2.0 10.6 ± 2.0 Special attention was paid to the terminal shoots odorata, or 83%) were found on land free of C. to detect any signs of galling by the fly. odorata compared with land infested with the plant (10 out of the 23, including C. odorata, or Questionnaires were administered to 40 43%) (Table 1). This supports previous reports randomly selected farmers to determine their of the ability of C. odorata to suppress existing knowledge of C. odorata, methods for its vegetation and natural succession, ultimately control and its impacts on their farming reducing species richness (Timbilla and activities. Braimah 1996; Goodall and Zacharias 2002). Chromolaena odorata has also been reported to RESULTS AND DISCUSSION decrease the carrying capacity and species diversity in grassland and forests (Erasmus Field observations revealed that about 50% of 1991). FUTA’s undeveloped land was infested to varying degrees with C. odorata. More plant The insect species collected on C. odorata were species (19 out of a total of 23, including C. in the orders Orthoptera (Zonocerus variegatus

Figure 1. Additional cost of control for C. odorata per hectare of land at Ipogun, Ifedore Local Government Area of Ondo State.

31 Eighth International Workshop on Biological Control and Management of Chromolaena odorata and other Eupatorieae

a

b

Figure 2. Age groups (a) and educational status (b) of farmers interviewed during the survey at Ipogun.

L., Pyrgomorphidae), Lepidoptera, Homoptera was also similar to that reported by Uyi et al. (Aphis spiraecola Patch, Aphididae) and (2008) who also suggested potential danger to Hymenoptera (mostly Crematogaster sp., agricultural crops. Formicidae). Similar insect species have been observed in Nigeria on C. odorata by Oigiangbe Results of the survey indicated that the majority et al. (2007). of farmers (70%) are aware of the presence of C. odorata, although they lacked knowledge on The presence of A. spiraecola was characterized biological control of the weed. Among the two by mottled, discoloured and distorted leaves. names commonly used by farmers to describe During May in the rainy season, the highest C. odorata, ‘Akintola’ is mostly used (80%) mean number (± SE) of A. spiraecola per compared to ‘Awolowo’ (20%). These are the square metre recorded was 101.2 ± 10.0 while names of past leaders who have ruled in in June the highest mean observed was 206.0 ± Nigeria. In Ghana, C. odorata is locally called 24.8 (Table 2), resulting in an increase in the Acheampong, named after one the past numbers of leaves that were mottled. presidents. A majority of the farmers Populations of A. spiraecola was also observed interviewed (67%) preferred slashing and to increase substantially with steady rain but burning C. odorata to control it, compared to reduced with persistent heavy rains. This result the 33% who favoured the use of herbicides.

32 Adebayo: Chromolaena in south-western Nigeria

This may have resulted from the high cost of identified as being associated with C. odorata herbicides, their scarcity or considerations of during the study are also implicated as posing health risks. However, where heavy infestations potential pest risk to agricultural crops. The occurred, fewer than half (42.5%) of farmers impact of C. odorata on farmers is socio- preferred clearing the land, while the majority economical as it influences their activities and (57.5%) usually abandoned the infested farms. subsequently increases their cost of production. Half of the sampled farmers attributed the Farmers are aware of the pestilence of C. additional costs of production to infestation by odorata and recognise the need for control. C. odorata. Generally, an average of US$15/ha However, the currently employed methods are was the estimated additional cost of production rarely effective or are impractical, thus (Fig. 1). The age groups of farmers varied, with biological control of the weed remains a 62.5% aged between 26 to 35 years (Fig. 2a). priority. The majority of farmers (85%) are male by sex when compared to 15% female. Most of the Therefore, the following recommendations are respondents surveyed were farmers (90%), made: while a few civil servants (10%) do engage in  That biological control of C. odorata be farming activities. The educational status of considered in Nigeria. farmers varied: most (35%) had obtained  Although P. pseudoinsulata and C. connexa secondary school certificates, followed by those were not observed during the study, they with only primary school leaving certificates should be included in the agents to be (30%), while about 25% had informal education considered for the control of C. odorata. and only 10% possessed higher degrees (Fig.  Aphis spiraecola constantly caused severe 2b). The level of education of individual damage by mottling and distorting the leaves farmers correlate with their grasp of this study of C. odorata. Thus, it should be further and greatly influenced their responses. studied to know the extent of its damage on C. odorata. Pareuchaetes pseudoinsulata was not recovered during the study period, nor were any C. ACKNOWLEDGEMENTS odorata plants observed to be galled by C. connexa. This observation however, differs The author is grateful to Mr Adegoroye from the report of P. pseudoinsulata being Tumininu of the Department of Crop, Soil and recovered at Benin, Edo State, a neighbouring Pest Management, Federal University of state to Ondo State (Uyi 2011). The inability to Technology, Akure, Nigeria for his assistance in detect P. pseudoinsulata during the study might identification of the weed species. I also be due to the short study period or the time of appreciate the good gesture of all the farmers the year and should not infer that the moth does interviewed for their cooperation. CTA and not exist in Ondo State. IOBC are thanked for providing funding to attend the 8th international workshop in Kenya CONCLUSION AND where this paper was presented. RECOMMENDATIONS REFERENCES The results obtained in this study indicate that at the Teaching and Research Farm of FUTA there Adebayo RA, Uyi UO (2010) Biological control were fewer plant species in the presence of of invasive weed species: Nigerian experience. dense stands of C. odorata than where it was Int J Agric Res 5 (12):1100-1106 low in density. Given that there were no observed differences in characteristics between Erasmus DJ (1988) A review of mechanical and these two areas, it is possible that dense stands chemical control of Chromolaena odorata in of C. odorata acted to suppress other plant South Africa. In: Muniappan R (ed) species through competition and possible Proceedings of the first international workshop allelopathy. Some of the insect species on biological control of Chromolaena odorata,

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Timbilla JA, Zachariades C, Braimah H (2003) Biological control and management of the alien

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