Short run aspects of a genetic control program for Heliothis virescens (Lepidoptera: Noctuidae)

The possibility that suppressing the tobacco budworm, Heliothis virescens (F.), by means of genetic control will lead to short run crop yield sacrifices is examined. A simulation model of budworm/backcross population dynamics is used to investigate the effects of backcross releases which are too small or improperly timed. Apart from its potential for ultimate long-term suppression of the tobacco budworm, adverse short-term effects on crop yields are not likely to be a serious problem with a genetic control program. Furthermore, backcross release appears to have some potential as a substitute for chemical pesticides during the period prior to budworm elimination by genetic control.     

The non-fuel mineral position of the USA

In 1978 the USA used non-fuel processed mineral materials valued at over $200 billion (10⁹). Non-fuel mineral imports caused a trade imbalance of $8 billion. Imports supplied more than half of US supplies of 20 important minerals. The US stockpile of strategic materials is valued at over $11 billion. While world reserves of most minerals are now deemed adequate until 2000, demand for high temperature and special property materials requires careful monitoring and anticipation of disruptions in vulnerable sources.     

Approaches to environmental aesthetics

A synthesis of current empirical work in environmental aesthetics is overdue. Based on the twin criteria of methodological rigour and social relevance, four major approaches to environmental aesthetics are defined and described. A contemplative humanist approach is matched by goal-oriented activism. The planner, doomed to relevance, confronts the rigorously scientific experimentalist. Advances in environmental aesthetic research and practice will depend upon the fruitful collaboration of the four approaches.     

Control of bacterial speck of tomato by copper and ethylenebisdithiocarbamate fungicides: their efficacy and residues on leaves

Field studies were conducted to determine the synergism, persistence, and efficacy of a tank-mix spray of cupric hydroxide and mancozeb for control of bacterial speck of tomato. The increased efficacy of the cupric hydroxide-mancozeb mixture could not be attributed to the formation of a bacteriostatic compound in the tank mixture nor to a greater persistence of the mixture on the tomato foliage.     

Bioavailability to rats of bound [14C] pirimiphos-methyl in stored wheat.

Stored wheat treated with radiolabelled pirimiphos-methyl (0-2-diethyl-amino-6-methyl-pyrimidin-4-yl 0,0-dimethyl phosphorothioate) formed bound (nonextractable) 14C residues. Supercritical fluid extraction, gas chromatography and mass spectrometric techniques were used to identify and quantitate the 14C bound residues in wheat grains. The amount of bound 14C residues present after 28 weeks of storage was about 9.9% of the applied radioactivity. Pirimiphos-methyl accounted for 80% of the bound residue. Grain-bound residues were fed to rats for 5 days. After a total period of 8 days a substantially large percentage of the administered bound 14C residues (72.9%) was eliminated in urine while feces contained only 17.9%. Bound pirimiphos-methyl in wheat grain was metabolized in rats by processes involving hydrolysis, N-dealkylation and 0-demethylation. The results indicate that wheat-bound residues of pirimiphos-methyl are highly bioavailable to the rat and may possess a toxicological potential as manifested by a significant reduction in body weight gain.     

A test of two models of different levels of complexity for predicting changes of phosphorus concentration in a lake's outflow

The objective of this investigation is to compare the ability of a one-box model and a two-box model to predict the temporal variations of total phosphorus in the outflow of several lakes. The one-box model considers only total phosphorus and treats the lake as well-mixed, all year round. The two-box model considers two phosphorus fractions and the epilimnion and hypolimnion. For five shallow Canadian Shield lakes, some of the temporal variability in lake phosphorus concentrations can be explained on the basis of changes in hydraulic inflows and phosphorus loadings. Both models give roughly similar predictions for shallow lakes with high hydraulic loadings (1–200 m/year) and small variations in total phosphorus concentrations. In comparing the settling and hydraulic outflow mechanisms, a sensitivity analysis shows that both models are more sensitive to the settling rate if the lake's hydraulic loadings are less than 1 m/year, and more sensitive to the outflow rate if the lake's hydraulic loadings are greater than 100 m/year. This analysis suggests a priority for concentrating economic and other resources in conducting field measurement programs for testing phosphorus models.     

Using Wildlife Communities to Improve Vegetation Classification for Conserving Biodiversity

Determining which vegetation types organisms perceive similarly and classifying these types into groups that function as similar habitats are necessary steps toward expanding the focus of conservation strategies from single species to ecosystems. Therefore, the methods used to determine these habitat classifications are crucial to the successful design and implementation of these conservation strategies. Typically, this process has been accomplished through best professional judgement. We used quantitative techniques to group vegetation types into habitats based on the occurrence of breeding wildlife species ( n = 420) in Oregon. After calculating faunal similarities among all regional vegetation types ( n = 130), we used cluster analysis to group vegetation types into wildlife habitats. We classified the original 130 vegetation types into 30 wildlife habitat types that we believe function similarly. We tested this classification to assess whether vegetation types could be correctly classified into habitat types based on wildlife species composition. Discriminant analysis correctly classified 95% of the vegetation types into their wildlife habitat types, strengthening our confidence in this approach. This approach for classifying habitat types allows consistent development of conservation strategies at coarse resolutions and aids in identifying vegetation types where additional biodiversity surveys are needed. Finally, this approach can be refined continuously as the precision of vegetation mapping and our understanding of organism-habitat associations improve.