Studies were conducted to evaluate some new chemistry insecticide molecules as foliar application for their bioefficacy against major sucking pests and toxicity against predators of Bt transgenic
Background During field surveillance in Gujarat, India, in 2009, scientists found that pink bollworm was surviving in the first generation of Bollgard cotton, which contains a single protein. This survival was observed in four districts of Gujarat. From 2012 to 2014, surveys revealed that pink bollworm larvae had higher survival rates on Bollgard II cotton in Amreli and Bhavnagar districts. In 2016, a pink bollworm outbreak in Maharashtra caused significant losses in cotton production, leading to damage, yield losses, and increased management costs in several regions. The objective of the present study was to determine the reaction of Pectinophora gossypiella to Cry1Ac and Cry2Ab toxins. Results Neonates of P. gossypiella collected from six distinct locations in Vidarbha were subjected to seven different concentrations of Cry1Ac. The highest LC50 value was recorded in the population collection of Yavatmal (1.362 μg/ml diet) but the lowest LC50 value of 0.600 μg/ml diet in Buldana population. The highest MIC50 value was recorded in the population collected from Yavatmal (0.743 μg/ml diet) and the lowest MIC50 value of 0.413 μg/ml diet in the Buldana population (0.431 μg/ml diet). The highest IC50 value was recorded in the population collected from Yavatmal (0.303 μg/ml diet) but the lowest IC50 value of 0.127 μg/ml diet in the Buldana population. Neonates of P. gossypiella collected from six different locations in Vidarbha were exposed to seven different concentrations (9.0, 3.0, 1.0, 0.333, 0.111, 0.037 and 0.012 for Cry1Ac and 27.0, 9.0, 3.0, 1.0, 0.333, 0.111 and 0.037 μg/ml for Cry2Ab) which revealed that the Yavatmal population had the highest LC50 value of 94.294 μg/ml diet and the lowest LC50 value was recorded in the Amravati population (42.144 μg/ml diet). The highest MIC50 value of 27.258 μg/ml diet was recorded in Buldana population, but the lowest MIC50 value was recorded in the Amravati population (12.881 μg/ml diet). The highest IC50 value of 3.209 μg/ml diet was observed in Yavatmal population, and the lowest one was recorded in the Amravati population (1.574 μg/ml diet). Conclusions According to the LC50 values, all of the P. gossypiella populations in Vidarbha were extremely insensitive and had field-evolved resistance to the Bt proteins found in the transgenic cotton varieties of Bollgard II.
The laboratory experiment was conducted during 2017-2018 to study the different biological attributes of Trichogramma chilonis Ishii as influenced by host eggs of different ages. Significantly maximum percent egg parasitization was noticed on eggs of Helicoverpa armigera (Hübner) with 62.39 percent which was at par with the Corcyra cephalonica (Stainton) eggs (60.36 percent). This was followed by Earias vittella Fabricius 46.31 percent. Less parasitized eggs were recorded in Leucinodes orbonalis Guenée (10.35 percent). Age of host eggs significantly affected the parasitization by T. chilonis. The maximum parasitization (58.87 percent) was noticed in fresh eggs i.e. 24 hrs old followed by 48 hrs (44.91 percent) while 72 hrs old eggs were less preferred by T. chilonis and could parasitize only 30.56 percent. Development period for parasitoid ranged between 8.66 to 9.44 days on different host eggs. The highest adult parasitoid longevity (7.22 days) was observed from the parasitized eggs of H. armigera which was at par with C. cephalonica (7.10 days), E. vittella (6.88 days) and L. orbonalis (6.88 days). However, the different lepidopteran eggs as well as age of host eggs did not show significant differences pertaining to percent adult parasitoid emergence. Fresh host eggs of 24 hrs could produce more female progeny of T. chilonis (54.30 percent) compared to 72 hrs old eggs (42.65 percent). The sex ratio (male: female) of emerging parasitoid progeny was observed highest on 24 hrs old eggs (1:1.55) followed by 48 hrs old eggs (1:1.23) while lowest sex ratio was observed on the eggs of 72 hrs old age (1:0.95). The maximum per day fecundity of T. chilonis was noticed on the 24 hrs old eggs (6.75) followed by 48 hrs old eggs (4.80). The lowest fecundity (2.05) of T. chilonis was observed on the 72 hrs old eggs, whereas the highest male-female ratio and fecundity was noticed on eggs of E.vittella among different hosts.
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