No abstract

The present study explored the <i>Spilanthes acmella</i> Murr. for insecticidal principle, a plant of high value. The seed extract showed insecticidal activity against <i>Plutella xylostella</i>. Further, bioassay guided isolation of bioactive compounds resulted in insecticidal active molecule, which was identified with the help of ESI-MS and NMR. Highest activity of 95 - 100 percent was observed at low dose of 2 g/l with spilanthol, while 60 - 70 and 80 - 90 percent mortality at 5 g/l in crude seed extracts prepared in methanol and hexane after 48 hours exposure, respectively. LC₅₀ of 1.49, 5.14, 5.04, 11.75 g/l was observed with spilanthol, crude seed extract of methanol, hexane, deltamethrin, respectively. The findings indicate the potential of <i>S</i>. <i>acmella</i> with potent insecticidal toxicity for the management of <i>P. xylostella</i> and other insects of agricultural importance

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The whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) is one of the most devastating agricultural pests in many cropping systems worldwide. Growers rely on the use of insecticides to control this pest. However, some insecticides do not reduce the feeding of B. tabaci fast enough to prevent the direct and indirect damage produced by this insect. The effect of a new insecticide, cyantraniliprole 10OD (Cyazypyr™), on the feeding of B. tabaci adults, was studied under laboratory conditions. Cyantraniliprole 10OD is an insecticide that belongs to the IRAC Group 28 with a new mode of action for sucking insects, which provides rapid feeding cessation by impairing muscle function, resulting in reduced transmission of important insect vectored crop diseases. Laboratory experiments were conducted to determine the effect of cyantraniliprole along with some other commercially available insecticides on the feeding of B. tabaci adults by measuring the excretion of honeydew as an indirect assessment of insect feeding. In these experiments, cyantraniliprole resulted in significantly higher reduction of honeydew excretion (64.0%) by Q biotype B. tabaci adults during the first 30 minutes of exposure than diafenthiuron, triazophos, acetamiprid and spiromesifen, with all treatments having no adult mortality. Observations between 1 and 48 hours after exposure indicated that cyantraniliprole had numerically higher or similar reduction in honeydew production as the other insecticides, but by 48 hours (mid and high rate) and 96 hours (high rate) of exposure, cyantraniliprole had significantly higher reduction of honeydew excretion than all other insecticides tested. Low adult mortality was observed during first 24 hours of exposure in all treatments. Cyantraniliprole resulted in numerical or significantly higher adult mortality than all other treatments at the later observation intervals (72 -96 hours). The higher reduction in honeydew excretion by cyantraniliprole appeared to be related to faster feeding cessation during the initial hours of exposure by a combination of feeding cessation and direct mortality as the exposure time R. S. Rattan et al. 57increased. These findings document significant effects of cyantraniliprole on feeding cessation in Bemisia tabaci.

Lily symptomless carlavirus (LSV), the most common lily infecting virus around the world, contains 6 open reading frames (ORFs) in its genome, of which ORF5 representing coat protein (CP) is the most variable region and is used here to deduce phylogeny of the virus. CP gene of one of the LSV isolates present in the region, LSV isolate-Oh (Accession no. AJ748277) was taken as test sequence.Multiple sequence alignment of test sequence with ClustalW showed nucleotide and amino acid homology of up to 17-98% and 1-98%, respectively with other 78 carlaviral sequences from India and abroad. One conserved nucleotide motif of carlaviruses, AATAAA (Polyadenylation signal motif) was searched for, in the multiple sequence alignments but it was not found in any of the LSV isolates under study. Further, phylogenetic analysis of nucleotide sequences by DNADIST method of Neighbor-joining algorithm placed test LSV isolate most closely to its native LSV isolates from India and, LSV isolates Yunnan and Lanzou, from China. It could be interpreted that in Lily symptomless carlavirus at nucleotide level, evolution is taking place at a faster pace. Also, this virus shared its most recent common ancestry (MRCA), both with its native LSV isolates from India and as well as with LSV isolates from China, probably, indicating its origin from either of the countries. This study provides important clues about spread of the virus and to the best of our knowledge it is the fi rst detailed study of LSV coat protein gene performed at nucleotide level.