Disruptive Effects of Selected Chitin Synthesis Inhibitors on Cotton Leaf Worm Spodoptera littoralis (Boisd.)

Abstract

Egyptian cotton leafworm, Spodoptera littoralis (Boisduval), is the most devastating agricultural lepidopterous pests of cotton and vegetable plants (Hatem et al., 2009). The intensive application of organophosphates, carbamates and pyrethroids insecticides has given rise to S. littoralis populations resistant to all of these groups (Abou-Taleb, 2010). Selective insecticides with modes of action differed from those insecticide groups are highly desirable in integrated pest management (IPM) programs. Among these insecticides are insect growth regulators (IGRs) and ivermectin insecticide group. IGRs were developed to mimic, block or otherwise interact with the hormonal system of insects (Oetken et al., 2004). These include the juvenile hormone analogues, the ecdysone agonists and the chitin synthesis inhibitors (CSIs) (Graf, 1993; Tunaz and Uygun, 2004). The use of insecticides may result in multiple sublethal effects on insect pests (Singh and Marwaha, 2000 and Sabri et al 2017). These sub-lethal effects as well as mortality must be considered when investigating the total effects of insecticides (Yin et al., 2008). Moreover, these sublethal doses may interfere with some biochemical process such as the related enzymes activity. One of the related enzymes to IGR's mode of action are phenoloxidases that related to critical steps of melanization reactions, which are crucial for the sclerotization of a new cuticle after ecdysis (Andersen, 2005). Therefore, the aim of the present work is to clarify toxicity and the role played by the sublethal dose LC50 of three IGRs belonging to CSIs on the 4 th instar larvae of S. littoralis in order to better understand of the action of these compounds on lepidopterous larvae through studying their effect on biochemical parameters. These parameters are attained by estimating activity of some enzyme affecting in cuticle formation. MATERIALS AND METHODS-Rearing technique of S. littoralis: S. littoralis strain used in this study is a laboratory susceptible strain reared in the Plant Protection Research Institute at Dokki, Giza Governorate according to El Defrawi et al., 1964.The culture was maintained under optimum conditions (27 0 C+2 and 70+5 RH) and reared on fresh castor bean leaves, the 2 nd & 4 th larval instar which used in this study.

Threshold Temperatures and Thermal Requirements of Cotton Leafworm, Spodoptera littoralis Hb.

“…(Lepidoptera: Noctuidae) is a native pest to Africa (Shonouda and Osman, 2000;El-Khawas and Abd El-Gawad, 2002), and distributed in many European countries (Pineda et al, 2007;EPPO, 2019), Asia Minor and the Middle East countries (El-Aswad, 2007;El-Sabrout, 2013;Azzouz et al, 2014). Economically, it is a dangerous pest of many field crops and vegetables in North Africa, Middle East countries including Egypt (Kandil et al, 2003) and glasshouses plants and flowers production in Southern Europe (Roques et al, 2008;Abdel-Mageed et al, 2018), as well as various cash and traditional food crops in Africa (Capinera, 2008;Khedr et al, 2015). In Egypt, cotton cultivation is one of the main resources for the economy and S. littoralis represents a key pest on cotton (Ibrahim and Ali, 2018).…”

Bioefficacy of Farnesol, A Common Sesquiterpene, On the Survival, Growth, Development, and Morphogenesis of Spodoptera littoralis (Lepidoptera: Noctuidae).

“…(Lepidoptera: Noctuidae) is a native pest to Africa (Shonouda and Osman, 2000;El-Khawas and Abd El-Gawad, 2002), it is distributed in many European countries (Pineda et al, 2007;Lanzoni et al, 2012;EPPO, 2019), Asia Minor (Brown and Dewhurst, 1975) and the Middle East countries (El-Aswad, 2007;El-Sabrout, 2013;Azzouz et al, 2014). Economically, S. littoralis is a dangerous pest of many field crops and vegetables in North Africa, Middle East countries including Egypt (Kandil et al, 2003) and the glasshouses plant and flower production in Southern Europe (Roques et al, 2008;Abdel-Mageed et al, 2018), as well as various cash and traditional food crops in Africa (Capinera, 2008;Khedr et al, 2015). In Egypt, cotton cultivation is one of the main resources for the economy.…”