~ 1209 ~ Journal of Entomology and Zoology Studies 2018; 6(4): 1209-1219 E-ISSN: 2320-7078 P-ISSN: 2349-6800 JEZS 2018; 6(4): 1209-1219 © 2018 JEZS Received: 08-05-2018 Accepted: 10-06-2018 Mohammad Ali Tanani Department of Zoology and Entomology, Faculty of Science, Al-Azhar University, Cairo, Egypt B Nader Ali Bakr Department of Zoology and Entomology, Faculty of Science, Al-Azhar University, Cairo, Egypt Correspondence Mohammad Ali Tanani Department of Zoology and Entomology, Faculty of Science, Al-Azhar University, Cairo, Egypt Effectiveness of the chitin synthesis inhibitor, diofenolan, on survival and development of the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) Mohammad Ali Tanani and Nader Ali Bakr Abstract The objective of current investigation was to evaluate the toxicity and developmental effects of diofenolan (10.0, 1.0, 0.1, 0.01 and 0.001 ppm) on this insect pest Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) in Physiology laboratory, department of Zoology and Entomology, Faculty of Science, Al-Azhar University during 1917. LC50 values were estimated in 0.028 ppm and 0.036 ppm, after treatment of newly hatched and full grown larvae, respectively. After treatment of the newly hatched or full grown larvae with sublethal concentrations of Diofenolan, larval duration was pronouncedly prolonged and the developmental rate was drastically regressed, in a dose-dependent course. The pupation process was detrimentally prohibited, regardless the larval instar under treatment. Although diofenolan failed to exhibit a disruptive effect on the metamorphosis program (larval-pupal intermediates) after treatment of the newly hatched larvae, such program was impaired after treatment of full grown larvae, especially at the higher three concentrations. Also, the pupal morphogenesis was disturbed (pupal deformities) after treatment of larvae, irrespective of the instar under treatment. Keywords: Adult, larva, metamorphosis, morphogenesis, mortality, pupa 1. Introduction The discriminate and intensive uses of many conventionally synthetic pesticides have led to several dramatic problems, such as the environmental pollution, hazards to human and animals, destruction of the pollinators and other non-target insects as well as the natural enemies, like parasites and predators [1-7] . At present, insect growth regulators (IGRs) are considered as the possible alternative agents of the traditional insecticides for controlling insect pests [3-5] . IGRs can be grouped according to their mode of action as chitin synthesis inhibitors (CSIs) and substances that interfere with the action of insect hormone (i.e. juvenile hormone analogues, ecdysteroids) [8] . Diofenolan is a CSI used for the control of several pests, such as some lepidopterous species and scale insects [9, 10] , Papilio demoleus [11] , Musca domestica [12] , Rhynchophorus ferrugineus [13, 14] , Schistocerca gregaria [15-17] and Pectinophora gossypiella [18, 19] . Fortunately, it was found non-toxic for several beneficial parasitoids and predators of some pests, such as Chrysoperla carnea [20] . Worldwide, the pink bollworm Pectinophora gossypiella is one of the most destructive insect pests that cause terrible damage to the cotton because it is difficult to be controlled by conventional insecticides [21, 22] . Larvae damage the floral outgrowths, flowers, bolls, developing seeds within bolls and deteriorate the staple length and strength of lint. The termination of boll growth results in boll rotting and premature or partial boll opening [23] . In Egypt, this insect causes serious damage to cotton arising to one million kentar annually [24, 25] . Moreover, P. gossypiella has been reported to develop resistance against the transgenic cotton varieties in some regions of the world, such as Arizona (USA) [26] . In Egypt, also, this insect has recently developed resistance to several classes of traditional insecticides currently used in cotton fields because of its ability to detoxify these chemicals [27] . Therefore, IGRs have been initiated recently to avoid the environment hazards and to minimize the serious problems of synthetic insecticides to humans and animals, as well as to delay the resistance development in P. gossypiella [28-32] . The present study was conducted to evaluate the toxicity of Diofenolan and its disruptive effect on development and metamorphosis of P. gossypiella.