Effects of selected management practices of gutenbergia cordifolia on insect flower visitation at Mwiba area, Tanzania

Abstract

While only few studies have presented the effect of invasive plant species on insect visitors, even less is documented about how management practices against invasive plants may impact plant pollinator networks. The study assessed how natural versus chemical-based management practices against the native invasive plant Gutenbergia cordifolia affected insect flower visitation in Mwiba area by comparing the number of insect visitors, insect species diversity and richness, the number of flowers visited, flower abundance, and diversity across treatments of Desmodium uncinatum crude leaves extract (DUL), the chemical Glyphosate (GLY), and none (Control; CON). After treatments, DUL plots had about one-third higher numbers of insects visitors compared to CON and GLY plots (F2,159 = 9.521, df = 2, p = 0.009), including higher species diversity and richness of bee in DUL than in GLY and CON (F2,12 = 5.497, df = 2, p = 0.020; F2,12 = 21.810, df = 2, p < 0.001 respectively). Further, DUL plots had almost twice as many flowers visited compared to CON and GLY plots (F2,159 = 21.595, df = 2, p < 0.001). Flower abundance was higher in DUL plots compared to CON and GLY as was flower diversity (χ 2 = 7.460, df = 2, p = 0.024; F2,12 = 3.963, df = 2, p = 0.048, respectively). Generally, this study discovered that DUL treatment did not disturb insect flower visitation while GLY strongly did; instead, DUL attracted more insect flower visitors. It is hereby concluded that using the natural plant extract treatment is highly preferable to the chemical management of invasive plant G. cordifolia.