EFFICACY ENHANCEMENT OF FOUR BIO-CONTROL AGENTS AGAINST Spodoptera littoralis (Boisd.) BY FLUORESCENT BRIGHTENER

Abstract

Efficacy enhancement of four biocontrol agents; Spintor 24% SC (Spinosad), Neemix 4.5% EC (Azadirachtin), Protecto 10% WP (Bacillus thuringiensis) and S. littoralis nucleopolyhedrovirus (SpliNPV) against S. littoralis larvae using Fluorescent Brightener-28 (FB) was investigated. These biocontrol agents were arranged according to LC 50 values in the following descending order; Spintor 24% SC (0.097 µg/cm 2 ), Neemix 4.5% EC (0.119 µg/cm 2 ), Protecto 10% WP (0.262µg/ cm 2 ) and SpliNPV (1469.388 PIB's/mm 2 ). There was no enhancement in the efficacy of Spintor 24% SC or Protecto 10% WP at LC 10 and LC 25 levels when FB was added at 0.01, 0.1 and 1.0%. On the contrary, Neemix 4.5% EC and SpliNPV were enhanced by combination with of FB concentrations. The highest enhancement effect tested was found with SpliNPV at LC 25 value with 1.0% FB, where the co-toxicity factor reached 348.8, 650 and 129.9 5, 6 and 7 days after application, respectively. The results indicated that there was a positive correlation between activity enhancement of Neemix 4.5% EC & SpliNPV and rate of increasing FB concentration. The estimated LT 50 value of tested larvae decreased from 7.01 days in the virus alone to 6.91, 6.30 and 5.70 days when FB at 0.01, 0.1 and 1.0% was added to the virus, representing percentage reductions in time which reached 1.4, 10.1 and 18.7%, respectively. Generally, the addition of FB reduced the LC 10 and LC 25 values of Neemix or SpliNPV and hastened the death of S. littoralis larvae. Also, it was found that the addition of 1% FB to SpliNPV at LC 10 caused a decrease in larval weight of S. littoralis reached by 44.1%.