IN-VITRO EVALUATION OF METARHIZIUM ANISOPLIAE AS BIOPESTICIDE FOR RED-STRIPED SOFT SCALE INSECT (PULVINARIA TENUIVALVATA) IN SUGARCANE
Authors: Josie Buletin and Nyle Pardillo
Josie Buletin: State University of Northern Negros, Philippines.
Nyle Pardillo: State University of Northern Negros, Philippines.
ABSTRACT
Sugarcane (Saccharum officinarum L.) production in Negros Occidental, Philippines, has experienced reduced yield productivity due to pest infestations. Recently, the red-striped soft scale insect (Pulvinaria tenuivalvata) has emerged as a significant threat, causing leaf yellowing, reduced photosynthesis, decreased sugar content, and lower yields. To address P. tenuivalvata infestations, this study evaluated the in vitro efficacy of the entomopathogenic fungus Metarhizium anisopliae as a biological control agent. A completely randomized design (CRD) was used to expose insect nymphs to varying spore concentrations (1 × 10⁶ to 1 × 10⁹ spores/ml), with comparisons to a chemical insecticide control (thiamethoxam + lambda-cyhalothrin) and sterile water. Mortality rates of P. tenuivalvata and pathogenicity of M. anisopliae were observed over 15 days. Probit analysis determined the lethal concentration (LC₅₀) and lethal time (LT₅₀). Application of 1 × 10⁸ and 1 × 10⁹ spores/ml of M. anisopliae resulted in 90–91% mortality of P. tenuivalvata at 15 days, comparable to the chemical insecticide. The LC₅₀ decreased from 2.3 × 10⁶ spores/ml at 5 days to 1.2 × 10³ spores/ml at 15 days, while the LT₅₀ decreased from approximately 7 days to 4 days with increasing spore concentration, indicating faster mortality at higher doses. Post-infection, behavioral and morphological changes in P. tenuivalvata were consistent with fungal infection. These results indicate that M. anisopliae is an effective and environmentally sustainable biological control agent against P. tenuivalvata, producing higher mortality at increased concentrations. The optimal concentration for rapid and efficient pest suppression was identified as 1 × 10⁸ spores/ml. This study provides a scientific basis for integrated pest management strategies in sugarcane and supports further greenhouse and field applications.
Keywords: Sugarcane, Red-striped soft scale insect, Metarhizium anisopliae, entomopathogenic fungus, biological control, integrated pest management, LC₅₀, LT₅₀, in vitro evaluation, sustainable pest management