Efficiency of some new insecticides on physiological, histological and molecular level of cotton leafworm.

Document Type : Original Article


Plant protection research inistitute, A.R.C., Dokki-Giza, Egypt


Efficiency of indoxacarb, spinetoram and methoxyfenozide
on cotton leaf worm (Spodoptera littoralis) was determined through
exposure of second and fourth instar larvae to dipped castor bean leaves. LC50
estimates of second instar larvae ranged from 0.004 to 0.006 ppm of indoxacarb,
0.022 to 0.033ppm of spinetoram and 0.006 to 0.011ppm of methoxyfenozide. LC50
estimates of fourth instar larvae ranged from 0.36 to 0.54 ppm of indoxacarb, 1.78
to 2.64ppm of spinetoram and 1.36 to 1.69 ppm of methoxyfenozide. Also, the
ovicidal activity of these compounds was studied. Three day old eggs are more
affected than that of one or two days old in case of indoxacarb and spinetoram
while the reverse was in the case of methoxyfenozide. In nutritional assays,
all tested compounds reduce food intake and affected growth rate (GR) where
indoxacarb caused the highest rate of efficiency and followed by
methoxyfenozide and spinetoram  against 4th
larval instar fed for two days on castor leaves treated with LC50s
of the previous coumpounds. The histological examinations of 6th
larval instar cuticle (after treatment of fourth larval instar by LC50
of methoxyfenozide) showed destruction in the cuticle layers, fissures in the
endocuticle and irregular distribution of the hypodermal cells. While
indoxacarb and spinetoram treatments showed slight effect in the cuticle layers
as compared to methoxyfenozide.             In addition, the deteriorative
potentialities of aldehyde oxidase and α -
glycerophosphate dehydrogenase pattern of S.
were screened.