Antioxidants proved decade ago to be promising protective additives to Baculoviruses against deleterious effect of UV in sunlight , Present semi field experiments' tests the role of nano antioxidants in providing better protection for baculoviruses. The treatments with Spodoptera littoralis nuclear polyhedrosis virus (SpliMNPV), consisted of (Nano Aluminum Oxide with or without SpliMNPV LC₉₀, and Nano Zinc Oxide with or without SpliMNPV LC₉₀) at five different concentrations.100, 200, 300, 400 and 500 ppm for different investigation periods of artificial UV source for maximum 5 then 10 hours in laboratory then 50 ml / squash plant with five replications, on which neonate larvae of Spodoptera littoralis were exposed daily. Larval mortality was recorded till the 15^th day post application. Results are based on laboratory and leaf-bioassays to test Lethal Infectivity Time to 50% (LIT₅₀) of population. The results showed that LIT₅₀ 82.759 hours and 52.500 hours for additive nano zinc oxide and nano aluminum oxide; respectively at 500 ppm concentration while it gave 14.482 with virus alone treatment and 100.788 hours with Cacao 5% as positive control, the mechanism of protection was studied through transmission electron microscope. The total antioxidants activity was determined using DPPH (2, 2-diphenyl-1-picrylhydrazyl) antioxidant assay technique as a first record to use this technique at this type of investigations. The obtained result suggested the possible capability of nano antioxidants in prolonging the virus activity on plant foliage under small scale semi-field application besides it suggests to do  DPPH antioxidant assay technique first in the future with any candidate before the bioassay due to its clear image about the antioxidants activity.