Grower response from a mail survey indicated that musk thistle is a common and spreading problem in Tennessee nurseries. Poor herbicide selection and timing were reasons for the lack of control in most nurseries. At 31 wk after treatment preemergence herbicides or herbicide mixtures that gave 80% or greater musk thistle control in evaluation studies were atrazine, simazine, simazine + metolachlor (1.1 + 4.4 kg ai ha-1), oryzalin + isoxaben, or dithiopyr. Oryzalin, metolachlor, napropamide, or simazine + metolachlor (0.5 + 2.2 kg ha-1) gave 65, 35, 0 and 78% control of musk thistle, respectively. Glyphosate or SC-0224 at 1.7 and 2.2 kg ha-1 gave 89% or greater control of emerged musk thistle. Lactofen or HOE-39866 at 0.8 kg ha-1 gave less than 66% control of emerged musk thistle at 8 wk after treatment.

Access to detailed descriptions of the effects of applying specific rates of herbicides to crops and weeds in various growth stages is hampered by the format in which the relevant information is stored. Compared to traditional formats of journal articles and herbicide registration labels, computer database systems could easily cross-reference data from large numbers of experiments and answer specific questions concerning herbicide performance under particular conditions. Availability of this type of information could have far-reaching consequences for herbicide users, consultants, researchers, and regulators. A preliminary format for storing weed control information in IBM-PC compatible computers was developed, including procedures to enter data and retrieve information. Weed control efficacy or crop injury data for all rates of a herbicide or tank-mixture applied at a specific growth stage in a single test are used to generate dose/response equations by means of regression analysis routines. The best fitting of these equations is then used to estimate herbicide rates that would provide ten categories of control, ranging from a “no observable effect level” (NOEL) up to complete control. Rates are estimated only for those categories either within or bordering the range of the observed data, the remaining categories are empty. The estimated rates are stored in the database, along with the original data and other qualifying information. Access to information is organized around searches for a single herbicide, plant species, or pair of species. Search output is presented in a tabular format listing species, growth stage, herbicide name, and herbicide rates for the ten categories: NOEL, 10, 30, 50, 70, 83, 90, 95, 98, and 100% control or injury.

Glyphosate effectively kills duncecap and tall larkspur on mountain rangelands but it is nonselective and kills all other vegetation it contacts. Two selective application methods to treat individual plants were compared to demonstrate their efficacy in controlling larkspur and their effect on associated plant species: (1) spot spray with glyphosate concentration at 2% product solution (0.8% ai); (2) hand held wiper applicator with glyphosate concentration at 33% production solution (13.5% ai). The two methods were equally effective in killing most of the larkspur plants, but the sprayer applicator was more rapid and easier to apply. Neither method adversely affected foliar cover of associated perennial species. Glyphosate must be applied to the entire plant to ensure its mortality.

New or recently introduced weeds are biological pollutants in our natural and agricultural ecosystems. Unlike chemical pollutants, new weeds left unchecked often proliferate and pose problems that may not become apparent until eradication is too expensive or impractical. Management strategies for weeds should include: 1. prevention (from entering foreign commerce); 2. exclusion (detection of weed contaminants in imported products at ports of entry); 3. detection, containment, and eradication of incipient infestations; and 4. perpetual control (of widespread species that cannot otherwise be addressed). Appropriate legislative authority, modern weed technology, funding, and a renewed commitment to the concept of prevention are needed to prevent the introduction of new weeds. A national initiative to prevent the establishment of new weeds would be beneficial by saving on future losses and perpetual control costs. Actions taken now will prevent the continued introduction and spread of new weeds in the United States.