Entomopathogenic Fungi as Dual Control Agents against Both the Pest Myzus persicae and Phytopathogen Botrytis cinerea

Abstract

The green peach aphid (Myzus persicae), a plant pest, and gray mold disease, caused by Botrytis cinerea, affect vegetables and fruit crops all over the world. To control this aphid and mold, farmers typically rely on the use of chemical insecticides or fungicides. However, intensive use of these chemicals over many years has led to the development of resistance. To overcome this problem, there is a need to develop alternative control methods to suppress populations of this plant pest and pathogen. Recently, potential roles have been demonstrated for entomopathogenic fungi in endophytism, phytopathogen antagonism, plant growth promotion, and rhizosphere colonization. Here, the antifungal activities of selected fungi with high virulence against green peach aphids were tested to explore their potential for the dual control of B. cinerea and M. persicae. Antifungal activities against B. cinerea were evaluated by dual culture assays using both aerial conidia and cultural filtrates of entomopathogenic fungi. Two fungal isolates, Beauveria bassiana SD15 and Metarhizium anisopliae SD3, were identified as having both virulence against aphids and antifungal activity. The virulence of these isolates against aphids was further tested using cultural filtrates, blastospores, and aerial conidia. The most virulence was observed in the simultaneous treatment with blastospores and cultural filtrate. These results suggest that the two fungal isolates selected in this study could be used effectively for the dual control of green peach aphids and gray mold for crop protection.

Keywords: Antifungal activity; Botrytis cinerea; Dual control; Entomopathogenic fungi; Myzus persicae.

Fig. 1. Representative antifungal activities of entomopathogenic fungi against Botrytis cinerea on potato dextrose agar plates. A, High activity of Beauveria bassiana SD15; B, Middle activity of Metarhizium anisopliae SD3; C, Low activity of Purpureocillium lilacinum SD18.

Fig. 2. Antifungal activities of fungal culture filtrates against Botrytis cinerea for 48 hr. The absorbance of each sample was measured at 595 nm using a microplate reader. The control is the conidial suspension treated with sterilized distilled water, and treatments are the conidial suspension treated with each Beauveria bassiana (SD1, SD7, SD8, SD9, SD12, SD14, and SD15), Lecanicillium attenuatum (SDMp1 and SDMp2), Metarhizium anisopliae SD3, and Purpureocillium lilacinum (SD17 and SD18). The fungal culture filtrate was diluted to 10% and 1% concentration with sterilized distilled water. The asterisk (^*) and pound (^#) represent significant data at 100% and 10% concentration, respectively (Tukey test, P < 0.05). Vertical bars correspond to standard error (SE).

Fig. 3. Fungicidal activities of fungal culture filtrate against Botrytis cinerea by treatment time. After treatment of the conidial suspension of Botrytis cinerea with fungal culture filtrate, the conidial suspension was collected at different hours and incubated on potato dextrose agar for 4 days. The control is the conidial suspension treated with sterilized distilled water.

Fig. 4. Control efficacy of green peach aphids by the fungal culture filtrates, blastospores and aerial conidia of Metarhizium anisopliae SD3 and Beauveria bassiana SD15. Control, 0.02% tween-80; FCF, fungi cultural filtrate; AC, aerial conidia; BS, blastospore. The asterisk (^*) and pound (^#) represent significant data on 3 and 5 days respectively after treatment (Tukey test, P < 0.05). Vertical bars correspond to the standard error.