No abstract

The toxicity of a series of organophosphorus (OP) and carbamate insecticides was measured against the midge Chironomus riparius in aquatic systems with and without sediment. Five molecular descriptors (molecular volume, Henry's law constant, n‐octanol/water partition coefficient (Kow), molecular connectivity, and linear solvation energy) were used in regression analysis as potential predictors of insecticidal activity. The regressions were conducted for each descriptor against toxicity values for the series of chemicals. Molecular volume and Henry's law constant showed no relationship with toxicity. However, log Kow was moderately successful in describing the effect of sediment on toxicity (r2 = 0.508). Prediction of toxicity was substantially improved when a linear solvation energy (LSE) or molecular connectivity (MC) model was used in regressions. In multiple regressions conducted on carbamates and OPs separately, use of MC or LSE parameters explained up to 95.8% of the variability in toxicity. Based on the results of regression analyses, sorptive interactions between these insecticides and sediment apparently dominate the processes affecting the toxicity of these compounds when sediment is present. In the absence of sediment, the regressions suggest that the molecular structure of the insecticides is more important than solubility or partitioning for determining toxicity.

Leaves harvested in 1986 from clonally propagated elm hybrids ('Pioneer', 'Homestead', '970') previously fumigated in open-top chambers with ozone at 15 parts per hundred million (pphm) or with charcoal-filtered air (CFA) were evaluated for water and nitrogen content or were fed to adult elm leaf beetles (ELB), Xanthogaleruca = (Pyrrhalta) luteola (Muller), to determine host suitability for beetle fecundity and survivorship. For all three hybrids, EL9 females fed ozone-fumigated leaves laid significantly fewer eggs than females fed CFA-fumigated leaves. Fecundity of females fed '970' leaves was higher than for females fed 'Pioneer' or 'Homestead' foliage. Fumigation treatment had no significant effect on leaf nitrogen or water content. There was a significant positive linear relationship between leaf nitrogen content and beetle fecundity for all hybrids combined. In 1988, hybrid '970' was fumigated with CFA, 15, 30, or 45 pphm ozone to determine concentration effects on EL9 fecundity, leaf consumption, and survivorship. Significantly fewer eggs were laid only at the higher concentration of ozone. Mean leaf area consumed by beetles did not vary among fumigation treatments. For both years, beetle survivorship was unaffected by hybrid or ozone concentration.

No abstract

Plywood panels (15 x 15 cm) were treated with 8 insecticides from June 23-27, 1975, to determine effectiveness in controlling smaller European elm bark beetles attracted to Multilure-baited surfaces. The experiment was a 5 x 3 x 8 factorial design. The treatment factors were 5 chemical concentrations (1, 3, 6, 12, and 18 or 24%; Baygon 1, 3,6, and 12%), 3 beetle exposure times (5, 20, and 60 sec), and 8 bioassay periods (every 2 weeks for 16 weeks). Each combination was replicated 3 times. Concentrations were prepared by serial dilution; 2 ml of each were pipetted onto a 144-cm2 center surface area (1% = 0.14 mg/cm2 ai) of each panel, and were spread evenly with a glass rod. Panels were weathered outside; the mean tempergture was 18°C (range: -1.6 to 34.4°C), and total rainfall was 26 cm during the study. Bioassays were conducted by confining 20 newly emerged beetles between a treated panel surface and an inverted plastic petri dish (15 x 100 mm) for specified lengths of time at appropriate posttreatment intervals. After each exposure, beetles were placed on filter paper in petri dishes, and held in darkness for 24 h at 30 ± 1°C and 92 ± 2% RH before mortality was determined. Mortaility was pooled and averaged for all 3 exposure times at each concentration, because there were no significant differences in mortality among exposure times. LC50 and LC90 values were determined by interpolation.