A continuous-flow system was designed for the culture of aquatic weeds in the laboratory and used to examine the effects of low concentrations of terbutryn [N-(1,1-dimethylethyl)-N′-ethyl-6-(methylthio)-1,3,5-triazine-2,4-diamine] and diquat cation (6,7-dihydrodipyrido [1,2-:2′,1′-c] pyrazinediium ion) on algae (epiphyton) growing on surfaces of common elodea (Elodea canadensis L. C. Rich # ELDCA). Terbutryn did not affect the density of the epiphytic algal community, although development of the diatom component was favored at the highest concentration (50 μg/L). Diquat cation stimulated the growth of the epiphyton, particularly the diatoms, at concentrations as low as 5 μg/L. Possible reasons for this response included hormesis, differential tolerance to diquat, and facultative heterotrophy.

The effectiveness and profitability of weed control with herbicides and cultivation were determined in peanuts (Arachis hypogaea L. ‘Florunner′) infested with Texas panicum (Panicum texanum Buckl. # PANTE), sicklepod (Cassia obtusifolia L. # CASOB), and pitted morningglory (Ipomoea lacunosa L. # IPOLA). Highest peanut yield (4260 kg/ha) and net returns were achieved in 2 of 3 yr with benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] applied preplant incorporated followed by alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide] and dinoseb [2-(1-methylpropyl)-4,6-dinitrophenol] plus naptalam {2-[(1-naphthalenylamino)carbonyl] benzoic acid} applied at ground cracking, with two timely cultivations. Systems utilizing herbicides alone did not provide highest net returns, peanut yield, or weed control.

Twenty-two sweet potato [Ipomoea batatas (L.) Lam.] clones with a wide range in metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] tolerance were used to establish narrow sense heritability estimates (h2) using a greenhouse procedure. The heritability estimates were obtained from simple linear regressions (h2 = 2b) of injury rating, shoot fresh weight, and change in shoot fresh weight of offspring against the same responses of parents at metribuzin concentrations of 0, 0.3, and 0.6 ppm in the potting medium and averaged data for the two concentrations. These values ranged from 0.85 to 1.0, indicating that a recurrent mass selection process should be an appropriate approach to developing metribuzin-tolerant cultivars. Several highly tolerant clones were identified.

A model, based on a rectangular hyperbola, has been developed to describe the relationship between population density and relative time of seedling emergence of wild oat (Avena fatua L. # AVEFA) and yield of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.). The equation is where yL is percent yield loss, D is weed density, T is relative time of emergence of weed and crop, and a, b, and c are nonlinear regression coefficients. Significant differences in fitted equations were found between years. From the values of regression coefficients it was concluded that barley is a better competitor than wheat and is less affected by late-emerging wild oat. The model was tested on previously published data. It provided only a slightly better description of the data than a multiple-regression model, but avoided a number of undesirable, implausible properties inherent in the more frequently used approach. In particular, the model does not predict a loss in yield when no weeds are present or a yield increase from late-emerging weeds.

Lambert Erickson, retired professor from the University of Idaho Department of Agronomy, passed away July 7, 1986, in Moscow, Idaho. Dr. Erickson did his undergraduate work at the University of Minnesota. He earned a Master's degree in botany from the University of Wyoming in 1943 and a doctorate from the University of Minnesota in 1960. During his career, Dr. Erickson was active in professional and civic affairs. He was a member of the Weed Science Society of America; a Fellow of the Western Weed Science Society; and a member of the American Society of Agronomy, American Men of Science, and other professional groups. Dr. Erickson held Fulbright lectures on weed science in Europe in 1970 and was a Fulbright scholar to Norway in 1979. Dr. Erickson was a very active associate member of Farmhouse Fraternity. He was a long-time advisor and in 1978 was elected “Master Builder of Men.” He is survived by his wife Hazel and a son.