Evaluation of the efficacy of glyphosate plus urea phosphate in the greenhouse and the field.

BACKGROUND: Glyphosate is a non-selective, foliar-applied, systemic herbicide that kills weeds by inhibiting the synthesis of 5-enolpyruvylshikimate-3-phosphate synthase. Urea phosphate (UPP), made by the reaction of urea with phosphoric acid, was applied as an adjuvant for glyphosate in this study. Experiments in the greenhouse and the field were conducted to determine the effects of UPP by comparing the efficacies of glyphosate plus UPP, glyphosate plus 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS) and Roundup. RESULTS: The optimum concentration of UPP in glyphosate solution was 2.0% when UPP was used as an adjuvant. The ED50 values for glyphosate-UPP were 291.7 and 462.4 g AI ha(-1) in the greenhouse and the field respectively, while the values for Roundup were 448.2 and 519.6 g AI ha(-1). The ED50 values at 2 weeks after treatment (WAT) and 3 WAT were lowered when UPP was used as an adjuvant in the greenhouse and field study, and the glyphosate+UPP was absorbed over a 2 week period. UPP may increase the efficacy by causing severe cuticle disruption or accelerating the initial herbicide absorption. The result also showed that UPP could reduce the binding behaviour of Ca2+ to glyphosate. CONCLUSION: The application of UPP as an adjuvant could increase the efficacy of glyphosate and make it possible to achieve effective control of weeds with glyphosate at lower dose. Moreover, UPP showed less causticity to spraying tools and presented less of a health hazard. Therefore, UPP is accepted as being a new, effective and environmentally benign adjuvant for glyphosate.

Evaluation of the developmental toxicity of formamide in New Zealand white rabbits.

Naturally mated female New Zealand White (NZW) rabbits (24/group) received formamide (35, 70, or 140 mg/kg/day) or vehicle (1 ml/kg deionized/distilled water) by gavage on gestational days (GD) 6 through 29. The study was conducted using a 2-replicate design. Maternal food consumption (absolute and relative), body weight, and clinical signs were monitored at regular intervals throughout gestation. One and four maternal deaths occurred at the low and high doses, respectively. Abortions or early deliveries were noted in 0, 2, 2, and 8 females in the 0, 35, 70, and 140-mg/kg/day dose groups, respectively. Other clinical signs associated with formamide exposure were minimal: primarily reduced or absent fecal output at the high dose (2-13 animals/day). Also at the high dose, maternal body weight was significantly depressed on GD 21, 24, and 27 (87-90% of the control value); maternal body weight gain was significantly reduced for GD 12 to 15, 18 to 21, and 21 to 24 (treated animals gained less than 1 g, or lost up to 100 g). In addition, maternal body weight gain was reduced at the middle dose for GD 18 to 21. Maternal body weight gain, corrected for gravid uterine weight, was unaffected. Relative maternal food consumption in the high-dose group was 34-59% of control intake from GD 12 through GD 24, but was comparable to controls thereafter. At termination (GD 30), confirmed-pregnant females (9-20 per group) were evaluated for clinical status, liver weights, and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal liver weight (absolute or relative to body weight) was unaffected by treatment, but gravid uterine weight at the high dose was 71% of the control value. A significantly increasing trend was noted for the percent non-live implants per litter. In addition, although not statistically significant from the control group, the values for the percent late fetal deaths per litter and percent non-live implants per litter in the 140-mg/kg/day group were higher than maximum historical values, suggesting an increase in late gestational deaths in the surviving high-dose animals. Formamide decreased the mean number of live fetuses per litter at the high dose to 66% of the control value. Mean fetal body weight per litter for males and the sexes combined was significantly decreased at the high dose; mean female fetal body weight was also decreased, although the difference did not reach statistical significance. There was no effect of treatment on the incidence of external, visceral, or skeletal malformations or variations in animals surviving to scheduled necropsy. In summary, the no-observed-adverse-effect level (NOAEL) for maternal toxicity was 70 mg/kg/day and the lowest-observed-adverse-effect level (LOAEL) was 140 mg/kg/day under the conditions of this study. Similarly, the NOAEL for developmental toxicity was 70 mg/kg/day and the LOAEL was 140 mg/kg/day.