Effectiveness and Persistence of Some Synthetic Insecticides and their Nanoformulation Against Whitefly (Bemisia tabaci) and Aphids (Aphis craccivora) on Fennel Plants and Soil

Fennel Foeniculum vulgare Mill. is one of the most important herbal plants in Egypt due to its medicinal properties. Aphids and whiteflies are considered from the major pests which attack the crop, their control using synthetic pesticides caused many problems from which is the presence of pesticide residues at levels higher than Maximum residue limit (MRL) values. This study aims to compare synthetic and (non-conventional) nano form of the pesticides used for controlling these pests, to help in decreasing the persistence and resistance problems of pesticides. The LC50 values of acetamiprid, dinotefuran and their nano-form were recorded 5.085, 3.355, 0899, and 0.760 ppm against whitefly, while for aphids they were 3.566, 4.068, 0.590 and 0.705 ppm, respectively. Two field trials were conducted during 2018-2019 in a fennel farm in the Governorate of Fayoum, Egypt, to test the efficacy of four insecticides; thiamethoxam (Actara 25%WG), dinotefuran (Oshin 20%SG), acetamiprid (Mospilan 20%SP) and thiocyclam hydrogen oxalate (Evisect 75%WG) (thiocyclam hydrogen oxalate) against aphid adults and whitefly nymphs. Dinotefuran caused the highest percent reduction against whiteflies, while acetamiprid caused the highest reduction against aphids. A third season was lunched to measure the efficacy of dinotefuran, acetamiprid and their nano forms against whiteflies and aphids. Nano-mospilan was the most effective insecticide during the third season with 94.19% reduction against aphids, while nano-dinotefuran was the most effective compound against whiteflies with 99.13% reduction. Residues were determined in plant and soil using, a QuEChERS (quick, easy, cheap, effective, rugged, and safe) based protocol coupled with liquid chromatography-tandem mass spectrometry (LC–MS/MS) with a recovery percentage of 99.9 and 99.7%, for dinotefuran and acetamiprid. Comparing the initial amounts showed that acetamiprid and nano-acetamiprid were 0.95 and 0.27 mg/kg, in plant and 1.3 and 0.31 mg/kg in soil, respectively. Dinotefuran and nano-dinotefuran initial were 6.77, 0.69 mg/kg in plant and 3.9, 0.88 in soil, respectively. Tested insecticides dissipated differently and results showed that acetamiprid was not detected in 10 days, while its nano form in 5 days and dinotefuran in 15 days and for its Nano form 7 days in plant. However, in soil they were not detected 21 days for synthetic and 10 days for nano form of both pesticides.Residues were determined in plant and soil using, a QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based protocol coupled with liquid chromatography-tandem mass spectrometry (LC–MS/MS) with a recovery percentage of 99.9 and 99.7%, for dinotefuran and acetamiprid. Comparing the initial amounts showed that acetamiprid and Nano-acetamiprid were 0.95 and 0.27 mg/kg, in plant and 1.3 and 0.31 mg/kg in soil, respectively. Dinotefuran and Nano-Dinotefuran initial were 6.77, 0.69 mg/kg in plant and 3.9, 0.88 in soil, respectively. Tested insecticides dissipated differently and results showed that Acetamiprid was not detected in 10 days, while its Nano form in 5 days and dinotefuran in 15 days and for its Nano form 7 days in plant. However, in soil they were not detected 21 days for conventional and 10 days for nano form of both pesticides.