Parthenium hysterophorus

Afaq, Uzma, Kumar, Gyanendra & Siddiqui, Arshi, 2024, Zygogramma bicolorata (Coleoptera: Chrysomelidae): an exotic biocontrol agent of the noxious weed, Parthenium hysterophorus (Asteraceae), The Canadian Entomologist (e 4) 156, pp. 1-23 : 12

Efficacy against Parthenium hysterophorus

Research conducted by Sushilkumar and Ray (2011) and Kanagwa et al. (2020) on the biocontrol efficacy of Z. bicolorata demonstrates that the beetle is a satisfactory potential candidate to reduce P. hysterophorus density in field conditions. In particular, Sushilkumar and Ray (2011) verify that the beetle is capable of defoliating approximately 85% of the weed plant and reducing plant density in Indian agro climatic conditions. The beetle-caused defoliation significantly reduced P. hysterophorus leaf and flower production, plant density, weed biomass, plant height, and seed production. To accomplish successful biological control of the weed, a satisfactory population build-up of Z. bicolorata is essential, this can be achieved by timely releases of the beetle in the target fields. Several such augmentative releases may be necessary to ensure the beetle’ s early establishment, but once the beetle becomes established, the population will sustain itself. The damage inflicted on P. hysterophorus by the beetle was more prominent when the biological control agent was released in higher densities and at Parthenium ’s early growth stages (Shabbir et al. 2016). The developmental stage of the beetle at the time of release has also been shown to play a key role during field releases, but the weed’ s defoliation and injuries also depend on geographic location ( McFadyen and McClay 1981). Nonetheless, Z. bicolorata larvae are known to be more effective defoliators than adults are, but adults build up effective populations and propagate new colonies in less time, which results in quick and effective control of Parthenium weed ( Hasan et al. 2020a).