Weed populations and agronomic practices at wheat farms on the Hanang plains in Tanzania

Abstract

Weed species and densities of weeds present on the wheat farms at the Hanang plains in northern Tanzania were surveyed just before wheat harvest in May, 1986. The dominant weed was Setaria spp. mainly, Setaria verticillata (L.) Beauv., which occurred at an average density of 58 shoots/m². Additional weed species which occurred at average densities of greater than 1 plant/m² were Amaranthus spp., mainly Amaranthus retroflexus L., and Galinsoga parviflora Cav. The density of Setaria spp. was greatest on the farms where wheat had been grown for the longest periods of time (18 and 10 yr). The densities of the other weed species on the Hanang wheat farms were not influenced by the number of years (1–18 yr) that wheat has been grown in monoculture. Several weeds were identified that are resistant to 2,4‐D, which is currently used for broadleaf weed control, but there was no indication that these weeds were becoming a serious problem.

Keywords:

• Setaria verticillata
• Lovegrass
• Amaranthus
• Galinsoga parviflora
• Argemone Mexicans

Notes

Present address: Agriculture Canada, Lethbridge Research Station, Lethbridge, Alberta, Canada TU 4B1.