A.R. Horowitz - Dept. Entomology, ARO, Gilat Research Center ISRAEL.
A. Navon - Dept. Entomology, ARO, The Volcani Center, Bet Dagan ISRAEL
S. Levski - Dept. Entomology, ARO, The Volcani Center, Bet Dagan ISRAEL
S. Yablonski - Dept. Entomology, ARO, The Volcani Center, Bet Dagan ISRAEL
A. Niv - Cotton Board ISRAEL
Laboratory bioassays and field trials of Bttransgenic cotton (Bt-cotton) were conducted in Israel during the 1998-2000 cotton growing seasons to examine effectiveness against the main lepidopteran cotton pests. The transgenic NuCOTN 33B was compared with DP 5415 and the local Acala Sivon against Helicoverpa armigera, Earias insulana, Spodoptera littoralis and Pectinophora gossypiella (pink bollworm). In laboratory bioassays, leaves, flower buds (squares) or bolls collected periodically during the cotton season were exposed for 48h or 96h to neonates or third/fourth instars of the examined pest. In experimental small-plots with the same varieties, damage to bolls caused by E. insulana and P. gossypiella was estimated. In large-scale field trials, the efficacy of Bt-cotton was compared with the local cotton variety by weekly samplings of pest populations and cotton bolls. Leaves of Bt-cotton were collected during the early and mid season, caused high mortality (90-100%) of H. armigera and E. insulana neonates. In late season, the efficacy of the Bt-cotton leaves to H. armigera significantly declined. In flower buds, substantial bud damage was found; however, Bt-cotton decreased larval weight and penetration to bolls. Both leaves and bolls of Bt-cotton did not affect S. littoralis larvae. In all the experiments, Bt-cotton considerably protected the cotton bolls from P. gossypiella damage, as compared with the other cultivars (controls). According to field samples, there was less E. insulana damage to bolls in the Bt-cotton plots than the non-transgenic cotton, and almost no damage to cotton bolls resulted from pink bollworms. Large-scale field trials have shown that the moderate protection of Bt-cotton that had been found under laboratory conditions was sufficient in preventing economic damage to cotton fibers from H. armigera and E. insulana. The reduced level of insect pests in the Bt-transgenic cotton fields resulted in decreased applications of insecticides, supporting thereby the Israeli IRM strategy.
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