Vegetational response to herbicide treatment for brush control in Tanzania

Abstract

Dense stands of small trees restrict understory production and provide suitable habitat for tsetse-fly in many areas in Tanzania. Three methods (ring barking, cut stump and frilling) of applying a mixture of esters of 2,4-D (2,4-dichlorophenoxy acetic acid) and 2,4,5-T (2,4,5-trichlorophenoxy acetic acid) for tree control were compared. There were no significant differences in mortality (P<0.10) of Combretum species among the application methods. Mortalities for all species ranged from 37 to 48%. Applications in June had pronounced effects on Combretum molle and Combretum ternifolium on the reddish-brown soil and black soils sites, respectively. Combretum binderanum on the reddish-brown soil site tended to respond differently in June and December to cut stump and ring barking treatments. Overall, Combretum molle and Combretum ternifolium were more susceptible to the herbicide treatments than was Combretum binderanum. Total herbage standing crop in the reddish-brown soil site was not affected by method or the season of herbicide application (P>0.10). On the black soil site Andropogon gayanus and forbs produced more herbage standing crop under the ring barking treatment in June compared to the control. Percent composition of Panicum infestum on the reddish-brown soil site was higher in the June herbicide applications than that in December applications. On the black soil site, composition of Andropogon gayanus was significantly lower in the December ring barking treatment than in the control, whereas forb composition was significantly higher (P<0.10) in the June ring barking treatment compared to the control. The frilling treatment applied in June appeared to give the most positive response for management objectives.