Reduction of Tungro Virus Transmission by Nephotettix virescens (Homoptera: Cicadellidae) Neem Cake-treated Rice Seedlings

Abstract

Rice seedlings grown in soil treated with neem, Azadirachta indica A. Juss, seed cake at rates of ≥150 kg/ha had a significantly lower incidence of infection of rice tungro bacilliform and spherical viruses transmitted by the leafhopper, Nephotettix virescens (Distant), than did untreated seedlings. Protection with neem seed cakes at 250 kg/ha was comparable with that provided by application of carbofuran 3G at 0.75 kg (AI)/ha. Electronic monitoring showed that the insect fed mainly on the phloem of untreated plants, but changed to xylem ingestion on neem-treated plants. Reduction in the incidence of phloem-specific tungro viruses in neem-treated plants was thus attributed to a shift in insect feeding from phloem to xylem vessels.