Abstract
Background
The pink bollworm (Pectinophora gossypiella) is a major pest of cotton, causing economic losses by damaging seeds and fiber. Cotton growers typically use systemic and broad-spectrum insecticides for its management, which pose risks to human health and the environment. Consequently, there is a need for eco-friendly alternatives. This study evaluates the bio-efficacy of the entomopathogenic fungus Metarhizium anisopliae strain TMBMA1 against pink bollworm and assesses its compatibility with major insecticides. Additionally, to comprehend the dynamics of colonization and the infection processes of EPF, scanning electron microscopy (SEM) of infected larvae was carried out.
Result
We challenged second instar PBW larvae to eight different concentrations (1×10³ to 1×10¹⁰ conidia ml-1) of M. anisopliae TMBMA1. The highest mortality (100%) occurred at the highest concentrations i.e., 1×10⁹ and 1×10¹ spores ml-1, while the lowest mortality rate (46.6%) was observed at 1×10³ spores ml-1 concentration compared to control (3.33%). TMBMA1's biocontrol efficacy was validated by Probit analysis, exhibiting an exceptionally low LC50 value of 7.1 × 10⁵. The comparative evaluation revealed that M. anisopliae TMBMA1 performed par excellent with insecticide (Cypermethrin 20EC) giving 100% mortality, both being superior to a commercial product of M. anisopliae (60%). The EPF strain was profusely colonized on both the internal and external surfaces of PBW larvae, according to SEM analysis. Compatibility studies with insecticides revealed > 98% and > 96% reduction in the sporulation of M. anisopliae due to the treatment of Emamectin Benzoate 1.5% + Profenofos 35% WDG and Profenofos 50EC, respectively. In contrast, Cypermethrin 10% EC, Emamectin Benzoate 5% SG and Neem Seed Kernel Extract (NSKE 1500 PPM) treatments reported minimal reduction (11%, 13% and 21% respectively) in spore production.
Conclusion
According to the current investigations, the M. anisopliae strain TMBMA1 exhibits high virulence against PBW and offers a promising eco-friendly solution for managing this pest. It shows significant potential to proliferate on both external and internal surfaces of PBW. This strain can be integrated into PBW management programs with chemical insecticides, thereby improving pest control and lessen environmental impact.