A Dissertation Submitted in Partial Fulfillment of the Requirement for the Degree of Master’s in Life Sciences of the Nelson Mandela African Institution of Science and Technology
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.