Most field data are recorded in a notebook or on paper in the field and later re-entered into computer files for statistical analyses. Using electronic field data recorders, data can be entered directly into computer files. Initial communication problems between electronic data recorders and personal computers and learning time requirements may limit effective use of these tools. Use of a dedicated field data recorder and software developed by the authors produced an estimated first-year labor cost savings of $500 to $700.

A greenhouse study was designed to evaluate a series of silicone adjuvants for increasing efficacy and rainfastness of Na-acifluorfen, isopropylamine-glyphosate, and Na-bentazon on velvetleaf and common lambsquarters. Silicone adjuvants were identified that increased both herbicide efficacy and rainfastness at 0.9 to 1.2 L ha-1. Specificity of adjuvants for specific target weed species and herbicides was evident. Effective silicone adjuvants were identified that did not increase soybean injury by Na-acifluorfen or Na-bentazon beyond that observed with crop oil concentrate. The efficacy of the best silicone adjuvant did not appear to be solely a function of reduced surface tension of the spray solution.

Experiments were conducted in the greenhouse and the field to determine the influence of various oil adjuvants on small grain and grass weed susceptibility to foliarly applied BAS-514 OO H (BAS-514). Barnyardgrass, green foxtail, and yellow foxtail were more susceptible to BAS-514 at 0.56 kg ai ha-1 applied with than without an oil adjuvant. Shoot fresh weight reductions of barnyardgrass, green foxtail, and yellow foxtail were greater when BAS-514 at 0.56 kg ha-1 was applied with a methylated seed oil than with a petroleum oil adjuvant in the greenhouse. Differences in the effectiveness among oil adjuvants in enhancing BAS-514 phytotoxicity were more evident in greenhouse than in field experiments. Oil adjuvant enhancement of BAS-514 varied with plant species. Oats, hard red spring wheat, and winter wheat tolerated BAS-514 at 1.1 kg ha-1 foliarly applied with or without an oil adjuvant in the greenhouse. BAS-514 at 0.56 kg ha-1 applied with oil adjuvants caused less than 5% injury to wheat in the field.

Bulbous oatgrass, a weed in parts of the United States and Europe, is an unusual grass, which forms corms at the stem base. Growth and development of this creeping perennial grass was investigated in the field and in pots outdoors. Under the mild climate of the Willamette Valley, Oregon, shoots emerged in early autumn. Plants grew vegetatively and formed corms during the winter and spring. Aboveground portions of the plant stopped growing and senesced in the summer. The absolute growth rate of the plants was highest in early May, shortly before the onset of flowering. In early May, the growth rate of corms was higher than that of the shoot.

Weed control and red pine release by spotgun-applied hexazinone in a northern Ontario plantation were evaluated 3 yr after treatment, while hexazinone residues and lateral movement in the sandy loam soil were determined 1 yr after treatment. Hexazinone, grid pattern spot applied at 480 mg ai/spot, approximating 1.6 kg ai/ha, resulted in 88% quaking aspen stem dieback and variable suppression of white birch and pin cherry. The height and basal diam of treated red pine were 131 and 150% of control, respectively, after 3 yr. Hexazinone residues were reduced to 1% at the treated spot and did not move laterally beyond 0.5 m, 1 yr after treatment. Detection of small amounts of metabolites A and B (0.2 and 0.3%) indicated the non-cumulative degradation of hexazinone in soils.

Experiments were conducted in North Carolina and South Carolina, 1989, to evaluate methods of infesting research plots with witchweed. At both locations sowing witchweed (mixed with very fine sand) in or beneath the maize planting hole resulted in more rapid attachment of witchweed than other methods. Sowing witchweed only in the maize planting hole increased significantly witchweed attachment compared to the control late in the season at Evergreen, NC. At Dillon, SC, in fumigated soil, sowing witchweed seeds to the side of the maize row in a band or in planting holes or broadcasting and incorporating with a hoe increased witchweed attack. Broadcasting and raking was ineffective.

Outdoor experiments were conducted at two locations in Minnesota to characterize the growth, development, and vegetative reproduction potential of giant burreed grown with and without wild rice. Giant burreed growth was influenced by environment more than the presence of wild rice. Shoots emerged from corms 2 to 3 wk after planting (WAP), and continued throughout the growing season. Giant burreed attained a maximum height of 135 cm with an average 36 shoots/plant. Rhizome production started 4 to 6 WAP, and continued throughout the growing season. Corm formation at the base of shoots started 8 WAP and continued throughout the growing season. Rhizomes grew to a maximum cumulative length of 2500 cm/plant spreading in all directions and produced up to 250 buds/plant. Corm and rhizome bud viability was 15 and 10%, respectively. These data suggest that giant burreed grown in wild rice should be controlled by 2 to 3 wk after emergence to prevent vegetative reproduction.

Mediterranean saltwort has become an established weed in the upper San Joaquin Valley and the Temblor Range areas of California. Fifteen herbicides were evaluated to determine their effects on 6- to 8-week-old plants grown in the greenhouse. Mediterranean saltwort was killed by chlorsulfuron3, hexazinone, and metribuzin at low rates. Triclopyr4 (Garlon 3A and Garlon 4), atrazine, imazapyr, glyphosate, dicamba, bromacil, karbutilate, and simazine were effective at higher rates. Four herbicides, asulam, pendimethalin, amitrole, and fosamine, did not kill Mediterranean saltwort at the rates tested.

Field experiments were conducted to determine wheat injury following clomazone application in soybeans and fallow in North Dakota. Clomazone at recommended rates generally caused 10% or less visible chlorosis in spring wheat planted 11 to 12 mo after application or winter wheat planted 11 mo after application, although greater chlorosis was observed in two of seven location/year environments. Tillage preceding wheat planting increased chlorosis from clomazone residues in some environments. Clomazone residues reduced wheat grain yield only in three of seven location/year environments and usually at application rates of 1.4 kg ai ha-1 or greater. Severe drought prevailed during the study and probably increased clomazone persistence and wheat chlorosis. Drought also may have limited expression of grain yield reductions attributable to clomazone residues.

Ten herbicides were evaluated for poison-hemlock control in established alfalfa in Utah. Hexazinone, metribuzin, and terbacil controlled poison-hemlock 90% or more but diuron and pronamide did not. Either glyphosate or 2,4-D applied in May at 1.1 kg ae ha-1 controlled poison-hemlock 97 to 98% compared to 60 to 75% with 2,4-DB at that rate. Dicamba and bromoxynil did not control poison-hemlock.

Herbicide-resistant weed species have become widespread in recent years. Fifty-five weed species, including 40 dicots and 15 grasses, are known to have biotypes resistant to the triazine herbicides. One or more resistant species have arisen in 31 states of the United States, four provinces of Canada, 18 countries in Europe, and Israel, Japan, Australia, and New Zealand. Resistance to other classes of herbicides is more restricted in distribution and recent in detection but is becoming more widespread. Trifluralin resistance has spread in the southeastern United States and has been detected in Canada, while 11 species with biotypes resistant to paraquat have been reported around the world. Diclofop-methyl-resistant weed species are problems in cereal production in Australia and have been found in Oregon, South Africa, and the United Kingdom. Resistance to the substituted ureas also is present in the United Kingdom, West Germany, and Hungary. Within the last 2 yr, biotypes of at least four weed species resistant to the sulfonylurea herbicides have arisen following several annual applications of these herbicides in wheat. Some resistant biotypes have multiple resistance to different classes of herbicides, which greatly exacerbates the threat of resistance. Herbicide resistance has reached the level where more concerted efforts are needed in research, education, and development of effective management strategies to preserve herbicides as essential tools of agricultural technology.

A rapid increase in the number of herbicides and herbicide mixtures registered for use in row crops has made herbicide selection difficult. WEEDS is a computer program that enables a weed management expert to build a list of recommended herbicides or herbicide mixtures based upon weed species, soil texture, and soil organic matter content. An example is given for soybeans.

Field studies were conducted in 1984 and 1986 to identify herbicides that would control woolly croton and bitter sneezeweed on grazing land in the Blackland prairies of Texas. Herbicides included chlorsulfuron, clopyralid, dalapon, dicamba, 2,4-D, glyphosate, metsulfuron, picloram, tebuthiuron, 2,4,5-T, and triclopyr. Chlorsulfuron and metsulfuron applied at 0.018 kg ha-1 and 2,4-D, picloram, 2,4,5-T, and triclopyr at 0.28 kg ha-1 controlled >80% of the woolly croton. Metsulfuron controlled more than 90% of the bitter sneezeweed at 0.018 kg ha-1. Similar control was obtained with clopyralid, glyphosate, and picloram each at 0.28 kg ha-1. Bermudagrass cover increased with all herbicide treatments except dalapon at one of three sites.

2,4-D diethanolamine control of kochia was influenced by the source of water used as the spray carrier. Sodium bicarbonate in one water source related to the reduced kochia control. Sodium bicarbonate in a water spray carrier antagonized 2,4-D control of all plant species evaluated. Antagonism increased with the tolerance of a species to 2,4-D, concentration of sodium bicarbonate, and spray volume. Sodium bicarbonate antagonism of 2,4-D phytotoxicity was greatest with low temperature and relative humidity.

Ten weed species have developed resistance to paraquat. Evidence supporting two potential mechanisms of resistance has been reported in several species. Resistance may be due to the rapid sequestration of paraquat thus reducing levels of paraquat at the site of action in the chloroplast; alternatively, resistance may be due to the rapid enzymatic detoxification of superoxide and other toxic forms of oxygen.

Two kinds of dinitroaniline-resistant biotypes of goosegrass have been found in counties in South Carolina where trifluralin is used for weed control. One biotype, termed the resistant (R) biotype, resists trifluralin about 1000- to 10 000-fold. The other biotype is intermediate (I) in resistance between the R and susceptible (S) biotypes, resisting trifluralin about 50-fold. Growth studies and root tip squashes were used to determine the level of resistance to other dinitroaniline herbicides. The R biotype is cross resistant to all dinitroaniline herbicides, and the I biotype is highly resistant to some and is resistant to others only at a low level. The cross resistance of the I biotype to other dinitroaniline herbicides does not correlate with structural or solubility characteristics of the herbicides. Electron microscopic investigations indicate that cell plate formation (controlled by phragmoplast microtubule arrays) is affected at lower herbicide concentrations than spindle microtubule formations. The level of herbicide resistance, the pattern of cross resistance, and the ultrastructural effects induced by the herbicide indicate that the I biotype has a unique mechanism of resistance from the R biotype.

Experiments were conducted for two years at one location and one year at a second location to determine the effects of paraquat on a range of peanut genotypes. Paraquat caused yield reductions of most Valencia-, Spanish-, and runner-market types as compared with hand-weeded checks. Virginia-market types were less affected by paraquat treatment. Most grade characteristics were adversely affected by paraquat. Because the paraquat treatments increased the proportion of other kernels, the herbicide may be affecting yield and grade by delaying maturity.

Field studies were conducted over 2 yr and two locations per year in soft red winter wheat to determine the efficacy of thifensulfuron and thifensulfuron plus DPX-L5300 (2:1 ratio) on all wild garlic reproductive bulbs. The herbicide formulations controlled wild garlic equally. Aerial bulblet control was excellent (>90%) with either herbicide regardless of application timing (March 21, April 8, and April 29) and significantly better than the standard treatment of the butoxyethanol ester of 2,4-D. Control of developing underground offset bulbs was less complete compared to aerial bulblets, and was found to depend on application time. Offset bulbs were controlled better when herbicides were applied in late March or early April compared to the April 29 treatment date. The rate response (9 to 70 g ha-1) was positive for the control offset bulb production at the two earlier dates but not at April 29. These herbicides also adversely affected the germination and viability of the bulbs that were produced.