Field studies were conducted to determine the selectivity and efficacy of pronamide alone or with sethoxydim and trifluralin, in Belgian endive. Pronamide at 1.68 with sethoxydim or alone or at 2.24 kg ai ha−1 controlled weeds better than trifluralin at 0.6 or 1.0 kg ai ha−1 in the field. Pronamide at 2.24 kg ha−1 was the best at controlling grass and broadleaf weeds season-long. In nutrient culture studies, Belgian endive roots were injured at 5 mg L−1 of pronamide, whereas redroot pigweed and green foxtail were inhibited at 0.5 and 0.1 mg L−1, respectively. Shoot weights showed similar differences but were less sensitive than roots.

Weed Science is facing two critical challenges. They are funding and interdisciplinary research, which to some extent are intertwined, but I will attempt to discuss them separately. Although some of my remarks may be critical of weed scientists let me say at the outset that the main reason we have these two challenges is because we have been highly successful, thanks to our visionary and dedicated scientists over the years. We have stayed ahead of the curve and have done too good a job. I would like to point out here that contrary to the beliefs of many outside our profession, we do more than spray and pray. We are ahead of the curve because we have conducted extensive and intensive research on application technology, formulations, environmental impacts, metabolism, mode of action, tillage practices, and many other areas.

The tolerance of two proso millet cultivars to atrazine preemergence and postemergence applications of bromoxynil, clopyralid, dicamba, or metsulfuron plus amine formulations of 2,4-D was studied in the field. Proso millet grain yield, test weight, seed weight, moisture content, and plant height at harvest were not affected by any of the herbicide treatments, despite some early-season injury observed in 1990.

Of the approximately 120 species of milkweeds (Asclepias spp.), the majority are American natives, principally the U. S. and Canada, where they are widely distributed. Milkweeds are erect, coarse growing perennials with showy white, pink, purple, or orange colored flowers. Milkweed gets its name from the abundance of sticky milky-white juice that exudes from broken stems.

There are about 130 species of Linaria, a genus of hardy herbs with whorled or opposite leaves; a few species are sub-shrubs. The genus, native to Eurasia, is widely dispersed. Closely related but separated from Linaria are the genera Kickxia and Cymbalaria.

Orobanchaceae, the broomrape family, comprises approximately 150 species in 17 genera. Four genera represented by four species occur in the southeastern U.S. A majority of the genera and about 90% of the species in Orobanchaceae are Old World natives. The family is primarily one of the northern warm and temperate zones. Only about 10% of the species occur in the tropics; only one species reaches the arctic.

Rapid germination and root growth have been identified as important plant characteristics for establishment in arid environments. This study evaluates germination, radicle elongation, and root growth rates of two annual grasses, two forage species, and yellow starthistle. Yellow starthistle germination, radicle elongation, and root growth were faster than those of medusahead and hedgehog dogtailgrass. Subterranean clover possessed rapid seedling growth characteristics similar to those of yellow starthistle, whereas Palestine orchardgrass was most delayed.

Growing public concern for pesticide residues in drinking water has resulted in tighter federal and state regulations to prevent ground-water contamination. There are many uncertainties in estimating human exposure risk, yet standards are being set to protect human health. In the last several years, drinking water health standards have been developed for a number of pesticides, often at levels of a few μg L−1 or less. Ground-water monitoring studies, first required by the U.S. Environmental Protection Agency in 1984, have now become an integral requirement to support registration of pesticides shown to have leaching potential. Regulators are now faced with deciding the extent to which pesticides can still be used while continuing to meet legal requirements to protect the public and preserve ground-water resources. The implications are that pesticide use may be severely limited in regions with ground-water resources considered especially vulnerable to contamination, dramatically affecting the type of agricultural practices and crops grown in these regions.

Concerns about the effect of pesticides on our environment has stimulated questions about the direction of future research in weed science. Knowledge of crop losses due to weeds would be helpful in guiding research objectives by identifying areas of greatest need. A survey was conducted in 1991 to estimate losses due to weeds in 58 commodities in Canada. Data generated included: percent loss in production, quantity loss in production, and loss of production value (monetary value) for each commodity in each province. The estimated average annual losses caused by weeds in the 58 commodities were $984 million, with losses of $372 million in Eastern Canada and $612 million in Western Canada. In Eastern Canada, approximately 50% of the total loss occurred in hay crops and 33% in field crops, whereas in Western Canada, 84% of the total loss occurred in field crops. Loss of potential production due to weeds for each commodity is shown by province.