Effect of Bt-cotton on chrysopids, ladybird beetles and their prey: aphids and whiteflies.

The effect of Bt-cotton, i.e. genetically modified cotton that contain genes expressing delta-endotoxin, on aphid, whitefly, chrysopid and coccinellid populations was determined with a two-year field study at a cotton farm near Marble Hall, South Africa. Although Bt-cotton is lepidopteran specific, non-lepidopteran arthropod populations may be indirectly influenced by the endotoxin. Abundance of aphid, whitefly, chrysopid and coccinellid populations and predator-prey interactions were used as measures to determine possible effects on the populations under investigation. The cultivation of Bt-cotton had no effect on aphid, whitefly, chrysopid or coccinellid abundance. Positive density dependent interactions occurred between aphids and coccinellids which were not influenced by Bt-cotton. A significant relationship between whitefly and coccinellid abundance, i.e. predator-prey reaction, occurred in the control and sprayed non-Bt cotton fields but was absent from the Bt-cotton fields.

Development of endosulfan tolerant strain of an egg parasitoid Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae).

A strain of T. chilonis, an egg parasitoid of lepidopteran pests tolerant to the most commonly used cyclodiene insecticide--endosulfan was developed in the laboratory. Tolerance to endosulfan was induced by exposing adult parasitoids sequentially from a sub-lethal concentration (0.004%) to the field recommended concentration (0.09%). The strain acquired tolerance to the insecticide after 341 generation of continuous exposure with LC50 values of 1074.96 ppm as compared to LC50 of (70.91 ppm) in susceptible strain. The genetical study showed that F1 crosses exhibited a semi-dominant response to endosulfan with degree of dominance value (D) of 0.58. The resistant factor of tolerant strain was 15.1 folds and of F1 cross were 8.53 folds over susceptible strain. Under net house conditions, the tolerant strain parasitised 56% Helicoverpa armigera eggs on potted cotton plants immediately after an insecticide spray, compared to 3% by the susceptible strain. High percentage survival of the immature stages of the tolerant strain proved their ability to withstand the insecticide load. Breakdown of insecticide tolerance in the strain occurred after four generations in absence of insecticide load. Use of the tolerant strain as a component of bio-intensive IPM in various crops where insecticide use is higher is discussed.

Effect of endosulfan on growth, alpha amylase activity and plasmids amplification in Bacillus subtilis.

Endosulfan, a chlorinated hydrocarbon insecticide of cyclodiene subgroup acts as a contact poison in a wide variety of organisms. In the present study, the effect of endosulfan on the growth, alpha amylase activity and plasmid amplification was investigated in Bacillus subtilis system. The bacteria were grown in medium, incubated with different concentrations (32, 48, 64 and 80 microg/mL) of endosulfan. The bacterial growth was gradually seen after 1st day at up to 48 microg/L endosulfan. The 48 microg/L endosulfan inhibited approximately 50% of the bacterial growth. No growth was observed at and after 64 microg/L endosulfan, for all days (1-5). Also, no alpha amylase activity was found in the supernatant of the culture medium containing 64 and 80 microg/L endosulfan, whereas slight activity was observed with 32 and 48 microg/L endosulfan concentration. The amount of plasmid increased up to 50% in the presence of 32 microg/L endosulfan. Endosulfan had no effect on the alpha amylase activity in vitro.

Histopathological changes in liver, kidney and muscles of pesticides exposed malnourished and diabetic rats.

Histopathological changes were observed in liver, kidney and muscles of normal, protein-malnourished, diabetic as well as both protein-malnourished and diabetic albino rats when exposed to a mixture of monocrotophos, hexachlorocyclohexane and endosulfan at varying intervals. The examination revealed hepatotoxic, nephrotoxic and muscular necrotic effects in pesticides exposed rats. Toxicity was aggravated in protein-malnourished and diabetic animals and more so, if the animals were both diabetic and protein-malnourished.

Modified behaviour in nucleopolyhedro virus infected field bean pod borer, Adisura atkinsoni and its impact on assessing the field efficacy of NPV.

When nucleopolyhedro virus of A. atkinsoni was applied at 250 LE/ha, there was no significant difference between the viruses treated and control plots with regard to the total number of live larvae feeding outside the pod. However, due to changes in behaviour in NPV infected A. atkinsoni by way of coming out of the pod, there was a significant difference when counts were taken with regard to total number of larvae found feeding inside the pod. Both endosulfan at (0.07%) and virus (125 LE/ha) in combination with endosulfan (0.035%) significantly reduced the larval population of A. atkinsoni and Sphaenarches anisodactylus. There was no significant difference between the virus and control plots with regard to percentage of pod damage. However, when the yield was assessed based on the seed weight, there was significant difference.

Cyclodiene insecticides-induced changes in the central depressive effect of chlorpromazine in rats.

Spontaneous motor activity (SMA), conditioned avoidance response (CAR), muscle coordination (MC) and pentobarbital sleep were tested in rats treated orally for 90 days with tolerated doses of the cyclodiene insecticides, aldrin (1 mg/kg) and endosulfan (2 mg/kg). The same tests were repeated in similarly treated animals after injecting chlorpromazine (4 mg/kg, i.p.). Both the insecticides shortened pentobarbital sleeping time indicating their microsomal enzyme inducing property. Aldrin suppressed SMA, CAR and MC, whereas endosulfan stimulated SMA, inhibited CAR and unaltered MC. However, their concurrent action with CPZ did not result in change in the central depressive effects of the latter, but its potency during the course of its action was altered. Its potency 15 min after injection was greater and 60-180 min later was lesser in these animals than that observed in control animals. This finding was interpreted to suggest that aldrin and endosulfan has quickened the biotransformation of CPZ and thereby shortened its duration of action. A temporary promotion of its potency was accounted to its active metabolites, since prior to inactivation, CPZ is known to be metabolized by the microsomal enzymes to active compounds.

Behavioural and biochemical changes produced by repeated oral administration of the insecticide endosulfan in immature rats.

In order to study the response of rats to repeated administration of the insecticide, endosulfan during the period of growth to maturity, food intake, body weight gain, Spontaneous Motor Activity (SMA) and Muscle Coordination (MC) were determined at regular intervals in male immature Wistar rats treated with a tolerated dose of (2 mg/kg/day) orally for 90 days. Twenty-four h after the termination of the treatment, organ weight and protein concentrations were determined. The convulsive action of picrotoxin (4 mg/kg, ip) was tested in another endosulfan-treated group. Food consumption and body weight gain decreased parallely. No changes occurred in the body tissues but for liver which was enlarged and its protein, glutamic oxaloacetic transminase and glutamic pyruvic transaminase concentrations increased. The MC was unaffected. A stimulation of SMA occurred several days (75-90) after commencing treatment and these animals responded greatly than control animals to the convulsive action of picrotoxin. These findings indicated that although endosulfan produced anorexia, there were no signs of undernourishment and motor impairment in these animals. Its toxic action were confined chiefly to the liver and central nervous system.

Age related toxic effects of endosulfan on certain enzymes of rat erythrocytes.

The effect of oral administration of endosulfan (12.5 mg/kg body weight), daily for 4 days was investigated on erythrocytes of female rats of 4 different age groups i.e. 15, 30, 70 and 365 days old. Erythrocyte membrane Na+, K(+)-ATPase and Mg2(+)-ATPase activities were significantly inhibited in all the age groups of rats. However, percent inhibition was maximum in the youngest animals. A significant decrease in the activity of erythrocyte glutathione reductase was observed in 30 and 70 days old rats whereas a significant increase in the activity of glucose-6-phosphate dehydrogenase (G-6-PD) was observed in these groups. The increase in G-6-PD activity may be a physiological response to compensate for decrease in the reduced glutathione level which results from decrease in the activity of glutathione reductase.

Differential effects of chronic endosulfan exposure to male rats in relation to hepatic drug metabolism and androgen biotransformation.

Chronic endosulfan exposure in rats led to considerable increase in the activities of drug metabolizing enzymes, whereas it had inhibitory effect on the activities of enzymes involved in the androgen biotransformation. Endosulfan also produced a dose- and duration-dependent increase in microsomal lipid peroxidation. The alterations produced after shorter duration showed much variation with respect to the dose levels and exposure period of endosulfan studied. The above biochemical changes were reversed after endosulfan withdrawal.