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Background The oriental fruit fly, Bactrocera dorsalis (Hendel), is the world’s most damaging (30–100%) pest infesting important fruits and vegetables. Its control is highly challenging due to its polyphagous, multivoltine nature, and unexposed developmental stages. No known fruit fly-resistant guava germplasm is reported so far worldwide. RNAi approach in guava against fruit fly can provide an attractive alternative to overcome this problem. Main body Escherichia coli-based dsRNA expression strategy was used to investigate its potential in control of B. dorsalis via targeting its two vital genes, ecr (ecdysone receptor) and rpl19 (a ribosomal protein L19). Effects of feeding E. coli, HT115 (DE3) expressing dsRNA of Bdecr and Bdrpl19 with artificial diet to maggots of B. dorsalis resulted in severe mortality and deformities in treated maggots, emerged pupae, and adults. Total mortality (including deformity) of maggots, pupae, and adult fruit flies was 86.3% and 87.9% and was highest in 700 μl (× 200 of 3.5 × 108 cells) dsRNAs of Bdecr and Bdrpl19 bacterial treatment respectively, compared to 350 and 200 μl bacterial treatments. Severe defects in terms of developmental changes like melanisation and deformities of maggots and pupae, absence of wings, underdeveloped abdomen/absence of complete abdomen, absence of legs, severely curled wings, malformed legs, and incomplete eclosion, and suppression of these target genes expression were observed in emerged adults. Short conclusion The study provides a proof of concept of feasibility to silence two potential genes by feeding bacteria expressing dsRNA in all developmental stages of B. dorsalis to step further to perform RNAi-based pest control.

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Response of sorghum Co.26 to different levels of N and various methods of application was studied in two experiments during 1998 and 1999. Application of the required N in three splits either as 25:50:25 or 50:25:25 at basal, 15 and 30 DAS was found to enhance the grain yield up to 10.08 per cent in 1998 and 8.47 per cent in 1999 over the normal recommended two splits as 50:50 per cent at basal and 30 DAS. 90 kg N ha was found to be optimum.