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

Abstract

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.

VOLCANIC MATERIALS AS CARRIERS FOR THE FORMULATION OF MYCOINSECTICIDES USING THE FUNGUS Beauveria bassiana

“…Among the benefits offered by these microorganisms are their safety to human beings and animals, their relatively high specificity and the absence of the development of resistance in target organisms. Moreover, the efficiency of these microorganisms to control important pests has been proven in multiple studies (Li et al, 2010;Lacey et al, 2011;Pelizza et al, 2012;Reddy et al, 2014). A crucial step prior to its use as an insecticide is the formulation, which should assure the viability and pathogenicity of infective units during storage and after application and should improve the product form for ease of application (Jackson et al, 2010).…”

“…The choice of this strain was based on its efficacy against pest grasshopper and locust species of Argentina in the laboratory (Pelizza et al, 2012). The fungus was propagated in petri dishes containing potatodextrose agar (APG) at 25 ºC in darkness for 30 days, and conidia were harvested by scraping the surface of the cultures onto a glass petri dish with a sterile metal spatula.…”

Entomopathogenic fungi from Argentina for the control ofSchistocerca cancellata(Orthoptera: Acrididae) nymphs: fungal pathogenicity and enzyme activity

“…?W), La Rioja province, where the high temperatures and low humidity are thought to be unfavourable for fungal development (Jaronski 2010). Thus, this particular fungal isolate appears to be well adapted to living under the type of stressful conditions that would normally constitute one of the main limitations for using fungi in the biological control of locusts (Pelizza et al 2012). This is the first time that a wide variability in chitinase, protease and lipase activity as well as in locust virulence has been reported in a representative sample of different entomopathogenic fungal strains from Argentina.…”

Pyroclastic material from the Puyehue-Cordon-Caulle Volcanic Complex, Chile, as carrier of Beauveria bassiana conidia: Potential utilization in mycoinsecticide formulations

“…The choice of this strain was based on its efficacy against pest grasshopper and locust species of Argentina in the laboratory [14,15]. Conidia of the fungal strain were obtained from cultures on potato-dextroseagar medium after incubation for 10 days at 25˚C in the dark.…”

“…Fungal-conidial viability was determined as described by Lane et al [17] both before and after 18 months [14,15]. For this purpose, 1 g of the impregnated volcanic material was removed from the original stored sample and placed in test tubes containing 10 ml of 0.01% (v/v) Tween 80 (Merck).…”