Screening of Argentine native fungal strains for biocontrol of the grasshopper Tropidacris collaris: relationship between fungal pathogenicity and chitinolytic enzyme activity.

Tropidacris collaris (Orthoptera: Romaleidae) is a large and voracious grasshopper, which, in recent years, has become a recurrent pest in increasingly extensive areas of Argentina's northern provinces. In the present work chitinase activity was measured in 59 entomopathogenic fungal isolates native to Argentina, and the relationship between enzymatic activity and fungal virulence was assessed. Isolate LPSC 1067 caused the highest mortality on T. collaris nymphs (97.7 ± 1.22%). Nine isolates caused no mortality, while the remaining 49 caused mortalities ranging from 6.6 ± 0.3% (LPSC 770) to 91.06 ± 1.51% (LPSC 906). Several isolates revealed chitinolytic capabilities on test plates, although the activities differed with respect to the ratio of the chitin-decay-halo and fungal-colony diameters. A principal component analysis indicated that isolate LPSC 1067, obtained from a long-horned grasshopper (Orthoptera: Tettigoniidae), would be a potential candidate for T. collaris biocontrol because the strain exhibited the highest mortality, a shorter median lethal time, and a high enzymatic activity and growth rate.