Effect of some insect growth regulators on certain biological, biochemical and histopathological aspects of the cotton leafworm,Spodoptera Littoralis (BOISD.)(Lepidoptera: Noctuidae)
Abstract: The effects of the three insect growth regulators (IGRs) chlorfluazuron, flufenoxuron and pyriproxyfen on certain biological, biochemical and histopathological aspects of late 6th instars of S. littoralis treated as newly moulted 4th instars with the LC50 values of these compounds were studied.
The two chitin synthesis inhibitors, chlorfluazuron and flufenoxuron were the first and second most toxic IGRs, respectively for the larvae, whereas the juvenile hormone mimic, pyriproxyfen was the least toxic compound. Chlorfluazuron and flufenoxuron decreased the mean larval duration in the parental generation (the generation during which the treatment was carried out) and in both the first and second generations (the generations following the parental generation), as compared to non-treated larvae. This was slightly decrease, except for that obtained in the parental generation treated with chlorfluazuron where it was significant. This is also true for treatment with pyriproxyfen in the second generation the slightly decrease in the mean larval duration was obtained. In contrast, treatment with pyriproxyfen increased the mean larval duration in both the parental and first generations as compared to control. Nevertheless, such slight increase.
Chlorfluazuron and flufenoxuron slightlly decreased the mean pupal duration in the parental, first and second generations as compared to non-treated pupae. On the other hand, treatment with pyriproxyfen did not, approximately, affect the mean pupal duration in the three generations. The same pattern was more or less obtained for the mean pupal weight after treatment with the same three IGRs.
Both sexes of S. littoralis moths surviving 4th instars treated with the LC50 values of chlorfluazuron, flufenoxuron and pyriproxyfen lived shorter than non-treated moths in the three generations. Such decrease was significant only for the two sexes treated with chlorfluazuron in all the three generations, and for the male and female moths treated with flufenoxuron in both the parental and second generations, respectively. The percent of egg-hatch also was decreased as a result of treatment with the three tested IGRs in the three generations. However, chlorfluazuron exhibited the highest effect in suppressing the reproductive potentials of the female moths.
The two chitin synthesis inhibitors, chlorfluazuron and flufenoxuron significantly decreased the haemolymph glutamate¬oxaloacetate (GOT) and glutamate-pyruvate transaminases (GPT) activities of S. littoralis late 6th instars treated as 4th instars with the LC50 of these IGR's, as compared to non-treated larvae. However, pyriproxyfen slightlly increased and decreased GOT and GPT activities, respectively. In contrast, the three tested IGRs significantly increased the haemolymph acid and alkaline phosphatases activities of late 6th instars treated also as 4th instars, as compared to non-treated larvae. On the other hand, treatment with chlorfluazuron, flufenoxuron and pyriproxyfen decreased the haemolymph carbohydrases activity of late 6thinstarss as compared to non-treated larvae, except for an increases in invertase activity was obtained at treatment with pyriproxyfen only. The change in carbohydrases activity was significant at all treatments, except for the activity of invertase at treatment with both flufenoxuron and pyriproxyfen, and for the activity of trehalase at treatment with both chlorfluazuron and pyriproxyfen where theirs no change.
The total content of the haemolymph main nutrients (lipids, proteins and carbohydrates) of late 6'h instars showed a great variation with the different treatments. The total content of lipids was increased at treatment with both flufenoxuron and pyriproxyfen and was decreased at treatment with chlorfluazuron only. The total content of proteins was increased at treatment with both chlorfluazuron and pyriproxyfen, whereas it was decreased at treatment with flufenoxuron only. However, the total carbohydrate content was decreased at treatment with chlorfluazuron, flufenoxuron and pyriproxyfen as compared to non¬
treated larvae. This change in the main haemolymph nutrients was significant only for the total protein and carbohydrate contents at treatment with both chlorfluazuron and flufenoxuron.
The total haemocyte counts of late 6thinstars was increased due to treatment of 4th instars with the two chitin synthesis inhibitors, chlorfluazuron and flufenoxuron. The reverse was true for treatment with the juvenile hormone analogue, pyriproxyfen. The same pattern was also obtained for the viability of the haemocytes. There are five types of haemocytes in S. littoralis larvae: prohaemocytes, plasmatocytes, granulocytes, spherulocytes and oenocytoids. The most pronounced effect of treatment with the three tested IGRs was a significant increase in the number of both prohaemocytes and spherulocytes due to treatment with pyriproxyfen, and meanwhile a significant decrease and increase in the number of both granulocytes and spherulocytes respectively after treatment with flufenoxuron. Also, treatment with chlorfluazuron significantly increased the number of plasmatocytes, and meanwhile significantly decreased the number of both spherulocytes and oenocytoids, respectively.
Treatment of 4th instars of S. iittoralis with both flufenoxuron and pyriproxyfen resulted in severe histological changes in the integument, fat body and midgut of the surviving late 6th instarss. Chlorfluazuron disrupted the fonnation of endocuticle, whereas pyriproxyfen did not affect the cuticle formation, but it damaged only the hypodermis. These two IGRs caused collapsing and lysis of the fat cells with a higher magnitude in case of treatment with pyriproxyfen. The most prominent changes induced by these two compounds for the midgut was the vacuolation of the epithelial cells and disruption of the peritrophic membrane. Ultrastructural studies revealed that treatment with both chlorfluazuron and pyriproxyfen caused enhancement of lysosomal organelles in the midgut columnar epithelium, disruption of the microvilli, vacuolation of the cytoplasm of the columnar cells and fragmentation of the nuclear chromatin materials.
Publication year 2004
Availability location معهد بحوث وقاية النباتات - 7 شارع نادى الصيد - الدقى - الجيزة.
Availability number
Organization Name
Country Egypt
Publisher Name: كلية العلوم- جامعة القاهرة
Place: الجيزة
Author(s) from ARC
Agris Categories Pests of plants
AGROVOC
TERMS		 Biochemical pathways. Biological control agents. Chlorfluazuron. Developmental stages. Flufenoxuron. Insect growth regulators. Pathology. Spodoptera littoralis.
Proposed Agrovoc pyriproxyfen;
Publication Type PhD Thesis
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