Chlorfenapyr and Methomyl Deterioration on Spinach Plants and Their Residual Effects in Vitro on Egyptian cotton Leafworm (Spodoptera littoralis)

Field trials conducted to determine the degradation of chlorfenapyr and methomyl insecticides in/on spinach leaves. Spinach plants sprayed with chlorfenapyr (Challenger Super™ 24% SC) and methomyl (Neomyl™ 90% SP) at the rates of 50 cm3/100 L water and 715 g/ ha, respectively. The QuEChERS method used for the extraction and clean-up of the samples. Residue amounts determined at 2 h, 2, 4, 6, 9, 13 and 16 days after application by UHPLC-UV. The mean of recovery percentages was 98.78 and 99.05 % for chlorfenapyr and methomyl, respectively. The initial deposits of chlorfenapyr and methomyl on/in spinach leaves, two hours after a single application of the insecticides were 23.17 and 235.37 mg/kg, respectively. The percentages of dissipation of chlorfenapyr were 37.68, 55.29, 69.45, 84.45 and 96.83% for 2, 4, 6, 9 and 16 days after application. The corresponding dissipation percentages of methomyl were 38.27, 56.01, 71.44, 84.34 and 97.81%. The rates of degradation (k values) were 0.212 and 0.223, while the corresponding half-life times (t0.5) were 3.27 and 3.11 days with chlorfenapyr and methomyl, respectively. It could be recommended that single application of chlorfenapyr on Spinach plants at the early ages followed by single application of methomyl at least 17 days before harvest.

Development of imidacloprid and indoxacarb formulations to nanoformulations and their efficacy against Spodoptera littoralis (Boisd)

Background The conventional pesticide formulations have many side effects on environmental. These effects were due to the huge quantity of pesticides used. Using of nanopesticide formulations can be reduced the quantity of pesticides used and subsequently decreased the cost of pest control and environment contamination. Results Indoxacarb and imidacloprid nanoparticles were developed. The size of nanoparticles ranged between 200 and 400 nm. The obtained results showed that the percentage of mortalities in second instar larvae of Egyptian cotton leafworm, Spodoptera littoralis were 95 and 75% in indoxacarb and imidacloprid nanoparticles, respectively. On the other hand, these percentages were 76.7 and 91.7%, respectively, with conventional formulations. In spite of one fifth of pesticide concentrations were used in nanoformulations, the LC50, s in nanoformulations were 2.9 and 15.9 ppm for indoxacarb and imidacloprid, respectively, compared to 34.3 and 66.5 in conventional formulation. The loading capacity in both indoxacarb nanoparticle and imidacloprid nanoparticle were 60.7 and 52.0%, respectively. Conclusion These results found that indoxacarb and imidacloprid nanoparticles were 12 and 4 times, respectively, more effective than indoxacarb and imidacloprid conventional formulations against the second instar larvae of S. littoralis. These results also showed that indoxacarb and imidacloprid nanoparticles can be used as effective formulations against the cotton leafworm larvae instead of the conventional formulation to reduce the environment contamination, control cost and pest population.