Impact of Host Plants on Detoxification Enzyme Activities to Certain Compounds Efficacy against the Cotton Leafworm, Spodoptera littoralis (Boisd.)

Abstract

Bioassay and life table parameters of insect pest, Spodoptera littoralis (Boisd.) as affected with feeding on host plants of alfalfa and cabbage in comparison to feed on castor leaves. Also, the changes in detoxification enzyme activities in S. littoralis as a result of feeding on three host plants used were determined. In addition, the susceptibility of S. littoralis larvae to three compounds (Indoxacarb, Lufenuron and Uphold “Spinotorum+Methoxy fenozide”) as influenced by feeding on the aforementioned host plants was studied under laboratory conditions. The obtained results showed that: S. littoralis larvae feeding on castor leaves caused the decreasing in larval, pupal, adult durations and mortalities. However, the weights of larval and pupal were increasing comparing with rearing on alfalfa and cabbage, respectively. Life table parameters of S.littoralis affected by feeding on the host plants used. Female progeny/female (Mx), survival rate (Lx), net reproductive rate (Ro), intrinsic rate of natural increase (rm), finite rate of increase (erm) and doubling time (DT) had affected by the kind of host plant used. Detoxification enzyme activity determinations cleared that α and β esterases were the highest activities in S. littoralis larvae fed on alfalfa, followed by cabbage, then castor leaves. While acetylcholine esterase as well as carboxyl esterase activities levels were the highest in S. littoralis larvae fed on cabbage. Meanwhile, glutathion S transferase was the highest activity in S. littoralis larvae fed on castor leaves.\xa0\xa0 In comparison to larvae feeding on castor leaves with those feeding on alfalfa or cabbage, the S. littoralis 4th instar larvae susceptibility had variation in estimation. The results showed in depending on LC50, LC90; the larvae of S. littoralis feeding on alfalfa were tolerant to indoxacarb; while that feeding on cabbage tolerant to lufenuron; on the other hand, the larvae fed on castor leaves was tolerant to uphold compound. So, the susceptibility of S. littoralis differs with the kind of host plant that had the role of impact on detoxification activity enzyme changes and leads to the susceptibility of pest.