Distribution and Potential Impact of Feral Cotton on the Reintroduction of Cotton in the Southern Highlands, Tanzania

Abstract

Cotton (Gossypium hirsutum) production is limited by bollworms that cause declining yields and poor lint quality. Generally, farmers manage pests by employing Integrated Pest Management (IPM) strategies, which include biological, cultural, physical and chemical approaches. Pest management by quarantine and pesticide sprays reduce production area and lead to resistance build-up. The Red bollworm, Dipsaropsis castanea is an important cotton pest of significant economical importance to Tanzania. The pest invaded the Southern Highlands (SH) of Tanzania in 1960’s from southern neighbour countries causing the Government to quarantine cotton
production from 1968 as measure to limit the spread of the red bollworm. Transgenic Bt cotton with insecticidal properties presents a potential solution to the bollworm infestation in Tanzania. However, concerns associated with transgenic crops viz.; transgene flow to wild and feral relatives, increased potential for resistance evolution, need to be addressed prior to adoption of any transgenic crop. Information from national herbaria, research stations and a field survey established sparse distribution and diversity of feral cotton species G. barbadense, an exotic ornamental from Brazil though as isolated garden plants. Informal interviews revealed medicinal and fibre value of the ornamental. Diploid wild cotton relatives such as G. longicalyx and Gossypoides kirkii were also recorded but are incompatible to G. hirsutum. Field observations indicate continued red bollworm presence in the SH on feral cotton, but low in number as plants are few and isolated. Cluster analysis indicates presence of hybrid remnants of G. hirsutum and G. barbadense suggesting potential for gene flow.

Keywords: Bt cotton, bollworms, quarantine, insecticides, insect resistance, feral cotton, refuge plant