Studies on the role of six enzymes in the metabolism of kinetin in mustard aphid, Lipaphis erysimi (Kalt.).

The activity of catalase, glutathione peroxidase, superoxide dismutase, O-demethylase, ATPase and succinate dehydrogenase, belonging to two main classes of detoxification enzymes (i.e. hydrolases and oxido-reductases), mostly involved in metabolism and degradation of xenobiotics in insects, were assessed under the influence of kinetin, a plant growth regulator (PGR). The nymphs (48-52 hr old) of Lipaphis erysimi (Kalt.) were permitted to feed on radish plant, Raphanus sativus L. treated with kinetin (400 ppm) for 13, 25 and 37 hr. It was found that the activity of catalase, glutathione peroxidase and superoxide dismutase increased significantly when compared with the control of the same age group, which indicated that these enzymes might be playing a significant role in the metabolism of kinetin in this insect. The activity of O-demethylase showed an increase up to 25 hr of the treatment but it decreased under prolonged treatment whereas the activity of succinate dehydrogenase fluctuated insignificantly. ATPase showed a decrease in the activity with the treatment suggesting kinetin's interference in synthesis of ATPase.

Evaluation of the possible role of five enzymes in the metabolism of IBA in mustard aphid, Lipaphis erysimi (Kalt.).

The enzymatic activity of five enzymes viz. Glutathione S-transferases, Esterases, NADH dehydrogenase, NADH oxidase and Glutathione reductase were assessed under the influence of Indole butyric acid (IBA) (400 ppm) in the nymphs (48-52h old) of mustard aphid, Lipaphis erysimi fed on radish plants treated for 13, 25 and 37h. The activity of Glutathione S-transferases, Esterases and NADH dehydrogenase increased compared to that found in the control of the same age group of nymphs and it was concluded that these enzymes might be involved in the metabolism of IBA. The other two enzymes, NADH oxidase and Glutathione reductase showed no significant increase in their activity compared to that in the control of the same age group. It was hypothesized that the latter enzymes do not play any significant role in the metabolism of IBA.

Evaluation of the pesticidal potential of the congress grass, Parthenium hysterophorus Linn. on the mustard aphid, Lipaphis erysimi (Kalt.).

Petroleum ether extracts of leaves, stem and inflorescence of Parthenium hysterophorus Linn. at 500, 1000, 2000 and 5000 ppm concentrations were tested in the laboratory for their toxic effects on the mean life span and progeny production of adults of the mustard aphid, Lipaphis erysimi (Kalt.). The investigations revealed a significant decrease in life span and progeny production with treatment. Among the three plant parts tested for their efficacy, the leaf extract showed the most significant effect in causing a dose dependent decline in both the life span and progeny production.

Influence of PGRs on carbohydrate content in Lipaphis erysimi (Kalt.).

Six compounds (IBA, chlorogenic acid, cytokinine, GA3, alar B-9 and maleic hydrazide) belonging to four different categories of plant growth hormones were used to study their effect on carbohydrate content in L. erysimi. The second instar nymphs (48 hr old) were given both dipping and leaf surface treatment with 1024 ppm concentration of compounds for two time intervals i.e. 48 and 96 hr. The carbohydrate content decreased after treatment with 4 of the plant growth regulators i.e. GA3, alar B-9, IBA and chlorogenic acid with maximum suppression in GA3 treatment. Cytokinine did not induce any derogatory influence on carbohydrate content. The treatment with maleic hydrazide, on the other hand enhanced the carbohydrate content. It could be concluded that the application of these PGRs affected the carbohydrate synthesis or metabolism.