Fungicides to control green muscardine fungus, a disease of zigzag leafhopper in rearing cages

R. M. Agudu, D. B. Centina, E. A. Heinrichs, and V, A, Dyck, Entomology Department, IRRI

Zigzag leafhopper (ZLH) Recilia dorsalis (Motschulsky) frequently becomes infected with green muscardine fungus Metarrhizium anisopliae in rearing cages during the wet season. We evaluated fungicides for M. anisopliae control. The fungus was cultured on YpSs Emerson agar. Spores were mixed with the fungicides in sterile water containing 0.05% detergent as an emulsifier. The suspension was vortexed and the spores were spread on YpSs agar culture medium in a petri dish. Fungicides tested were benomyl, mancozeb, thiophanate-methyl, and mebenil at 0.5, 1.6, 0.7, and 0.75 kg ai/ha, respectively, based on the area of the petri dish. Percent germination of 300 conidia counted randomly on each plate was determined after 24 h incubation at 25°C.

Benomyl, mancozeb, and thiophanate-methyl did not allow fungus germination and development. Mebenil was less toxic, allowing 11% germination (see table). Five-day-old cultures of M. anisopliae on media treated with fungicide are shown in the figure. Initial tests for direct toxicity of the fungicides to ZLH indicated no effect on the insect. Cages and rice plants used as food should be sprayed with either benomyl, mancozeb, or thiophanate-methyl to increase ZLH survival during mass rearing.

Growth of green muscardine fungus on media treated with fungicide. Growth is complete on control and partial on mebenil.

Germination of M. anisopliae spores on culturemedia treated with four fungicides, IRRI.

Spore germinationFungicide at 24 h (%) a/

Benomyl 0 cMancozeb 0 cThiophanate-methyl 0 cMebenil 11 bUntreated 99 aa/ Means followed by a common letter are notsignificantly different at 5% level.

Aguda, R.M., D.B. Centina, E.A. Heinrichs and V.A. Dyck. 1984. Fungicides to control green muscardine fungus, a disease of zigzag leafhopper in rearing cages. Int. Rice Res. Newsl. 9(3):14-15.