Effectiveness of biological control and socioeconomic impacts of the invasive parthenium hysterophorus in Arusha, Tanzania

Abstract

This study assessed the methods which are likely to be biologically and socio-economically effective to control the invasive species P. hysterophorus in Arusha Tanzania. A variety of methods have been found ineffective in long-term control of P. hysterophorus. Thus, an effective integrated approach needs to be identified. In addition, perception and socioeconomic

consequences about P. hysterophorus by farmers and pastoralists are still poorly understood. The study assessed the effect of a newly implemented bio-control agent, Zygogramma bicolorata, in 4 m 2 field plots. Further a novel approach of controlling P. hysterophorus was tested by using herbicidal extracts of the naturalized plants Dovyalis caffra and Cassia auriculata and compared it with 2,4-D. Finally, 123 farmers and 128 pastoralists in Mbuguni, Olasiti, Murieti and Sepeko wards were interviewed. It resulted that Z. bicolorata, particularly at highest population densities, is capable of reducing height of P. hysterophorus by 87% and biomass by 91%. There was a significant reduction (50%) in the measured parameters after application of low concentration of extracts of C. auriculata leaves and bark and D. caffra leaves and fruits (DcL and DcF). Invasion of farm fields by P. hysterophorus leads to yield reduction by half according to 21% of farmers, and 46% of farmers claimed that their income was negatively affected. Therefore, this study suggests the use of environmentally friendly bio-herbicides since it can foster P. hysterophorus control and emphasize that this method should be integrated with Z. bicolorata in the infestation areas for long-term suppression of P. hysterophorus.