The research was conducted during kharif seasons of 2008 and 2009. Nineteen genotypes comprising of seventeen Bt hybrids, one conventional hybrid and one variety were evaluated for their reaction to sucking insect pests, under unsprayed condition. Observations on sucking pests were recorded at weekly intervals. The highest population of leafhopper was recorded during 28 th and 32 nd standard weeks. The highest mean incidence was recorded in H-1226. Whitefly population remained below economic threshold level (ETL) during 2008 while during 2009 it crossed ETL in RCH 134 BG-II (6.00-6.23 adults/leaf). Mean highest population was recorded in IT-905 Bt and RCH-134 BG-II. Leafhopper and whitefly population were significantly and positively correlated with temperature while negatively correlated with rainfall. Among the genotypes, it was observed that there was no significant difference in population of the sucking pests.
A field study was conducted to compare the efficacy of 10 recommended insecticides against Earias spp. on okra. Three okra plots (3 × 5 m2) were subjected to each of the 10 insecticidal sprays applied twice at an interval of 10 days. On the third, seventh, and tenth day after each spray, percent shoot and fruit infestation and yield were calculated. All insecticides significantly reduced shoot and fruit infestation compared to the control. However, chlorantraniliprole 18.5%SC was the most effective across all time points and resulted in the highest yield. A second field study, to determine the time till the maximum residue limit (MRL—0.3 mg/kg) and the limit of quantification (LOQ—0.01 mg/kg) for both fruit and soil exposed to either the recommended (125 mL/ha) or a double strength dose (250 mL/ha) of chlorantraniliprole 18.5% SC was undertaken. MRL was reached on the same day following both doses. The LOQ was reached on the seventh and tenth day at recommended and a double strength dose, respectively. Chlorantraniliprole 18.5% SC provides effective control. However, Earias spp. resistance has been observed in other crops. Thus, constant monitoring in the field is needed to ensure its effectiveness.
A screening trial with 10 castor genotypes to assess their relative reaction to leafhoppers (Empoasca flavescens) was conducted at CCSHAU, Regional Research Station, Bawal during the Kharif season, 2019-20. Among the 10 genotypes, leafhopper population varied from 2.3 to 8.3. Based on leafhopper population and hopper burn score, the triple bloom genotypes Maharaja-9 and GCH-7 were found tolerant to leafhopper whereas the single bloom genotype DCH-177 was highly susceptible. The phenols content in the castor leaves had a significant negative correlation with leafhopper population and hopper burn score while total carbohydrates present in the leaves had a significant positive correlation with leafhopper population and hopper burn score. The intensity of bloom and phenols and carbohydrates content were found to play a major role in the infestation of castor leafhopper.
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