Synergistic biocontrol of Parthenium hysterophorus: the role of Curvularia specifera and Zygogramma bicolorata.

Parthenium hysterophorus L. is one of the most aggressive invasive weeds that threaten biodiversity as well as agricultural productivity. The current research was to determine the integrated biocontrol potential of Curvularia specifera (Ph-2) and Zygogramma bicolorata against P. hysterophorus under laboratory conditions. Inoculation with C. specifera (Ph-2) profoundly decreased seed germination by 53.81% and seedling shoot growth by 24.10% relative to the untreated control. C. specifera (Ph-2) and Z. bicolorata worked synergistically to reduce chlorophyll content, strongly inhibited photosynthetic efficiency and reduced plant vigor up to 65.8% compared to control. Feed-based incorporation of fungal spores improved beetle activity, with oviposition increasing by 31.23%, food consumption boosted 43.89% and mortality rate of beetles (adults) reduced by 47.34% compared to controls. Oxidative stress was predominantly an inhibitory mechanism, with an increase in reactive oxygen species (ROS) generation (64.52%), and antioxidant enzyme activities; catalase (58.46%), ascorbic oxidase (62.33%), and peroxidase (55.71%), together with an increase in antioxidant of the DPPH radical scavenging activity (79.35%), confirming oxidative stress occurs in treated plants. These results indicate that C. specifera (Ph-2) and Z. bicolorata have a synergistic effect to suppress P. hysterophorus via physiological and biochemical mechanisms, which can be used as an example of a sustainable and environment friendly alternative to chemical herbicides in integrated weed management.