In F2 progeny, derived from F1 hybrids, shoot growth of seedlings, measured 4 d after germination, distinguished susceptible (S) and resistant (R) phenotypes. Chisquare values indicated that the F2 data fit a 3:1 (S:R) ratio for both populations and all trifluralin concentrations in which S and R phenotypes could be differentiated. Results indicate that trifluralin resistance in these green foxtail populations is controlled by a single, nuclear recessive gene. This study is the first to demonstrate recessive gene control of herbicide resistance in a weed species. The highly selfed nature and prolific seed production of green foxtail may have facilitated evolution of the recessive trait.

Introduction of purple loosestrife into North America and its spread into wetlands has led to the degradation of these important habitats for wildlife. Conventional control efforts are unsuccessful in providing long-term control. A classical biological control program offers the best chance for reducing the numbers of this invasive plant and improving regeneration of the native flora and fauna. European studies demonstrated that the root boring weevil Hylobius transversovittatus is highly host specific to the target weed. Attack of two test plant species (winged lythrum and swamp loosestrife) during host range screening was most likely due to artificial test conditions. An environmental assessment of the potential effects of the release of the purple loosestrife borer in North America indicated that benefits outweigh any potential negative impact Therefore its field release was approved in 1992.

Many prime wetlands in North America have been degraded following encroachment by the exotic plant purple loosestrife. Conventional methods are unsuccessful in providing long-term control. Host specificity studies demonstrated the suitability of two leaf beetles, Galerucella calmariensis and G. pusilla, as biological weed control agents. Adults oviposited only on plants within the genus Lythrum. The only species other than purple loosestrife where adult feeding and oviposition occurred and that supported successful larval development was winged lythrum. Swamp loosestrife and winged lythrum may be vulnerable to limited attack by newly emerged teneral adults. Evaluation of the potential environmental impact of the two leaf beetles showed that benefits of an introduction outweigh potential risks to winged lythrum or swamp loosestrife. Their field release was approved in 1992.

The presence of wheat straw mulch in no-tillage systems can increase corn yields in the central Great Plains, but information is needed on the optimal mulch level and the toxicity of metolachlor on corn growth. Research was conducted to determine the effect of winter wheat straw mulch levels of 0, 1.7, 3.4, 5.1, and 6.8 t ha–1 and metolachlor rates of 0, 0.5, 1.0, and 1.5X-rates on corn growth and yield in a winter wheat-ecofallow-corn-fallow rotation at three locations across Nebraska. Response of corn to different mulch levels and metolachlor rates varied with climate and location. In general, early corn growth was retarded by increasing amounts of mulch due to reduced soil temperatures, but after tasseling corn grew taller under increasing mulch levels because of increased soil moisture. Soil water content, kernel moisture at harvest, stover dry matter, total dry matter, ears per plant, and kernel weight increased with increasing mulch level. Corn grain yield reached a maximum at a mulch level of 5.1 t ha–1. Kernel weight, kernel number, and grain yield increased with higher mulch levels and 0.5 and 1.0X metolachlor rates as weed competition was reduced, but decreased at the 1.5X-rate of metolachlor due to corn injury. Lack of sufficient growing degree-days to compensate for lower soil temperatures or corn injury reduced corn yields at the higher mulch levels and 1.5X-rate of metolachlor in west-central and western Nebraska. From a practical standpoint, a mulch level of 3.4 to 5.1 t ha–1 and a metolachlor rate near the X-rate should increase corn yield (14 to 15%) over unmulched corn in the central Great Plains.

Cultures of Streptomyces tendae grown on Actinomyces medium containing clomazone contained less geosmin 48 h after inoculation than untreated controls, suggesting a possible inhibition of reactions prior to sesquiterpenoid biosynthesis. However, exposure to clomazone increased geosmin accumulation in S. tendae cultures grown on Hickey-Tresner medium and in cultures of the fungus Penicillium expansum. Additionally, clomazone increased accumulation of a sesquiterpenoid tentatively identified as a eudesmol in S. tendae, indicating possible point(s) of inhibition subsequent to sesquiterpenoid biosynthesis. Geosmin biosynthesis was induced by transferring cultures of S. tendae inoculated on Actinomyces medium to Hickey-Tresner medium 24 h after inoculation. When harvested at 48 h, geosmin biosynthesis-induced-cultures exposed to clomazone contained more geosmin than untreated controls, indicating that response of a single taxon to clomazone can be rapidly altered by changing medium composition.