Control of <i>Calotropis procera </i>Infestation in Ruaha National Park, Tanzania

A targeted herbicide application was used in this study in Ruaha National Park to control the considerable infestation of <i>Calotropis procera</i> and minimize its adverse ecological effects on the ecosystem. A specific plants trial was set up at Msembe site using a Randomized Complete Block Design. The site had an estimate of more than 370 ha infested with <i>C. procera</i>. The site was portioned by establishing square sampling plots of 35m x 35m, within which 42 sub-plots (5m x 5m) were randomly distributed. Three replicates of each of seven herbicide treatments were administered using a specific treatment preparation to incisions made to stems and branches of calotropes. Results indicated a significant variation (p < 0.001) of calotrope mortality caused by treatments and period of herbicide application. A significant (p< 0.001) interaction was observed between treatments and herbicide application period. The main factor that contributed to the interaction was the glyphosate herbicide dilution. High content of glyphosate (50–100%) killed more than 75% of Calotrope when applied before noon while lower content (<50%), i.e. 5% and 12.5% were effective when applied in the noon and afternoon killing about 50% of the Calotrope. Irrespective of glyphosate application period, plant mortality increased with increasing glyphosate content and variation in glyphosate treatments was significant at p<0.001. Mixing of glyphosate and 2,4-D herbicides resulted in relatively lower calotrope mortality than glyphosate treatments alone. It was concluded that diluted and concentrated glyphosate herbicide solutions were most effective in controlling calotrope. However, the efficacy of diluted herbicide solutions (<50%) was high when applied in the afternoon and efficacy of concentrated herbicide solutions was high when applied before noon. Mixing of glyphosate and 2, 4-D resulted in low efficacy. It was envisaged that while diluted concentrations of herbicide are more effective, it is plausible to consider best time of effective herbicide application to control specific invasive plant species.