Toxicity of new molecules of insecticides and Bacillus thuringiensis strains to tomato pinworm Tuta absoluta Meyrick lepidoptera gelechiidae

Abstract

newlineABSTRACT newlineTOXICITY OF NEW MOLECULES OF INSECTICIDES AND Bacillus Thuringiensis STRAINS TO TOMATO PINWORM, Tuta absoluta (MEYRICK) (LEPIDOPTERA: GELECHIIDAE) newlineby newlineSANDEEP KUMAR JALAPATHI newlineDegree : DOCTOR OF PHILOSOPHY IN ENTOMOLOGY newlineChairman : Dr. J. JAYARAJ newlineProfessor (Agricultural Entomology) newlineDepartment of Agricultural Entomology newlineAgricultural College and Research Institute newlineTamil Nadu Agricultural University newlineMadurai 625 104 newline2020 newlineThe tomato pinworm, Tuta absoluta (Meyrick), is an invasive and notorious pest on tomato. It has become a serious threat to world wide tomato production with crop losses estimated from 80 to 100 per cent. Management mainly relies on insecticides because of their high infestation levels on all stages of the crop. This pest has developed resistance to several pesticides due to overuse, resulting in control failures in the field. Use of biological insecticides like Bacillus thuringiensis with insecticidal proteins, will be the best alternative to chemical insecticides for suppression of the pest. newlineDifferent populations of tomato pinworm from Theni, Dindigul, Madurai, Coimbatore and Krishnagiri in Tamil Nadu were collected and maintained at Horticultural College and Research Institute, Periyakulam. Baseline studies revealed that the LC50 ranging from 0.27 to 2.0 ppm for chlorantraniliprole, 1.01 to 2.25 ppm for flubendiamide, 0.32 to 0.90 ppm for spinosad, 0.98 to 6.52 ppm for imidacloprid, 0.82 to 6.38 ppm for indoxacarb and 967.32 to 1911.98 ppm for chlorpyriphos. Resistance ratios for six populations ranged from 1.1 to 7.7-folds in all cases. The laboratory experimental results showed that chlorantraniliprole and spinosad were the most toxic insecticides when compared to other chemicals and showed homogenous response to all populations. newlineLaboratory bioassay of susceptible population revealed LC50 values for chlorantraniliprole on 2nd, 3rd and 4th larval instars were 0.32 ppm, 0.49 ppm and 0.61 ppm respectively, for flubendiamide (1.56 ppm, 1.78 ppm and 2.48 ppm), for spinosad (0.37