Optimal time of application of the isopropylamine salt of glyphosate for long-term control of foxtail barley was studied near Delta Junction, AK in 1992 and 1993. Applications of either 0.6 or 1.1 kg/ha of glyphosate with 2.2 kg/ha of ammonium sulfate and 0.5% (v/v) nonionic surfactant were made to different foxtail barley plots at approximately 2-wk intervals from May to September. Control was rated in July of the year following application. The 0.6 kg/ha rate produced ≤ 60% control on all application dates. At 1.1 kg/ha, foxtail barley control was best from applications made between early August and mid-September. May and mid-June applications provided up to 80% control in 1993 but ≤ 50% control in 1992. For both rates, applications made from late June through July, during foxtail barley flowering and seed fill, consistently provided little control (< 50%).

Fourteen field experiments were conducted from 1988 to 1991 in Oklahoma to evaluate herbicides for red horned poppy control in winter wheat. Chlorsulfuron applied alone PRE at 9 to 26 g ai ha-1 or with metsulfuron controlled red horned poppy 90 to 100% in four of five locations. MCPA at 420 g ae ha-1 and MCPA + bromoxynil at 140 + 140 g ae ha-1 applied POST in mid November controlled red horned poppy 100%. All herbicides applied POST in mid March failed to control the weed consistently.

Field experiments were conducted to determine the efficacy of fluazifop-P-butyl for the control of green foxtail, wild oat, barley, and wheat in flax as influenced by spray nozzle orientation, time of day, and growth stage. Under drought conditions in 1988, control of wild oat, wheat, and barley with fluazifop-P-butyl was enhanced 75%, 53% and 78%, respectively, when nozzles were oriented to spray forward 45°. Under adequate soil moisture conditions enhancement of control was minimal. Green foxtail control improved when fluazifop-P-butyl was applied from 1700 to 2100 h, but time of day had no effect on control of wild oat, barley, or wheat. Fluazifop-P-butyl effectiveness was reduced when applied 4 d after flax emergence due to late emerging grass seedlings. Green foxtail was the most tolerant to fluazifop-P-butyl, whereas wild oat, wheat, and barley were the most susceptible.

Paraquat was applied at 0.28 and 0.56 kg ai ha-1 to winter wheat at five growth stages at 0800, 1300, and 1600 hr to determine whether growth stage or time of application influenced winter wheat response to paraquat. Paraquat bioactivity was affected by growth stage. Biomass reduction by paraquat was 84% when winter wheat was in the 1 to 3 leaf stage, but only 68% when application was delayed until tillering. Paraquat bioactivity continued to decrease at later growth stages. The time of day when paraquat was applied did not affect its bioactivity on winter wheat.

Field experiments were conducted in 1986, 1987, and 1988 to evaluate imazethapyr rate and time of application on postemergence control of 24 weed species. Contour graphs were developed that predicted imazethapyr rates required for various levels of weed control based upon weed leaf number at application. Rates below the labeled rate (70 g ha−1) provided 90% or greater control of common cocklebur, smallflower morningglory, and smooth pigweed if applied to 3 true-leaf or smaller weeds and of barnyardgrass, seedling johnsongrass, and Palmer amaranth if applied while weeds were in the cotyledon or 1 true-leaf stage. A rate of 70 g ha−1 provided 90% control of large crabgrass in the 1 true-leaf stage. Entireleaf morningglory, red rice, pitted morningglory, and velvetleaf are not susceptible enough to imazethapyr for 90% or greater control to be obtained with rates lower than 70 g ha−1 at the 1 true-leaf growth stage. These data demonstrate how control data can be used for developing effective reduced-rate herbicide recommendations based on weed leaf number.

Glyphosate, alone and in combination with other herbicides or additives, was evaluated as a spot or shielded treatment for the control of silverleaf nightshade in cotton in three experiments over four years. Glyphosate used at 10.8 g ae/L in 1985 on dryland cotton controlled 81 to 98% of the silverleaf nightshade, but cotton lint yields were reduced by all treatments compared to the weed-free check. Glyphosate used at 7.2 g ae/L in 1986 on irrigated cotton controlled 6 to 83% of the silverleaf nightshade, and lint yields were reduced only when multiple spot applications were made. Spot applications of glyphosate were effective for silverleaf nightshade control when applied 7 wk after crop emergence in 1988. Weed control and cotton injury were lower with shielded applications than spot applications. In 1989, retreatments during a season or the next year resulted in 95% or greater silverleaf nightshade control. Cotton yield increases from herbicide treatment were not observed in 1988; however, yield increases were observed in 1989 when spot treatments were applied to the more successful 1988 plots.

Optimal rates and time of application of glyphosate for control of the native perennial bluejoint reedgrass [Calamagrostis canadensis (Michx.) Nutt.] were determined from 1986 to 1989 near Delta Junction, AK. Applications were made 2 wk apart from late May or early June to September. Glyphosate did not provide control before June 15 or after September 1. Bluejoint reedgrass was controlled best when glyphosate was applied from late July to mid-August. Ammonium sulfate (2.2 kg ha-1) or nonionic surfactant (0.5% v/v) increased control except on the earliest and latest application dates. Control was consistently better with 1.1 than 0.6 kg ha-1 (ai) of the isopropylamine salt of glyphosate.

Experiments were conducted in the greenhouse and field to investigate differential tolerance among tall, pitted, red, entireleaf, and ivyleaf morningglory species to DPX-PE350. Tall morningglory in the greenhouse was more tolerant of DPX-PE350 at 7 and 14 g ai ha-1 applied POST than were other species of morningglory. Increased tolerance of tall morningglory also was observed under field conditions with DPX-PE350 applied PRE and POST. Adjuvants did not increase biomass reduction of tall morningglory by DPX-PE350 applied POST.

Field and laboratory investigations were conducted from 1983 through 1985 to evaluate morphological and environmental influences on the performance of imazaquin on 26 weed species common to the Mississippi Delta. Imazaquin applied preplant incorporated or preemergence at 140 g ai ha–1 controlled 16 species but controlled only five species at 140 g ha–1 foliar applied. Contour graphs accurately predicted imazaquin postemergence rates necessary to control a given weed species at a given time after emergence. Imazaquin applied preemergence with a sequential postemergence application controlled entireleaf morningglory and sicklepod better than a single soil application. Imazaquin at 140 g ha–1 applied preemergence required at least 50 mm of supplemental water following application to control sicklepod and was more phytotoxic to sicklepod grown at 25/10 C day/night temperatures than those grown at 32/22 C.

Downy brome is one of the leading plant pests in winter wheat and no-till spring wheat in many areas of the country. It has recently been studied in North Dakota where it is emerging as a serious crop competitor. Downy brome plants produced up to 60 tillers and more than 7,500 seeds when no control measures were used and densities were less than 2 plants m−2. Experiments focusing on herbicide-application timing identified differences in downy brome control and the grain yield of spring wheat. Regardless of fall or spring application timing, glyphosate applied PRE to wheat completely controlled downy brome in 2007. In 2008, control was not achieved with the earliest glyphosate-application timings because of late-emerging plants. When comparing fall and spring application timings of other herbicides, imazapic provided at least 79% control at each timing and location, resulting in the highest imazamox-resistant spring wheat yield. In general, herbicides performed better when applied in fall than they did when applied in spring. When herbicides were applied POST, imazamox provided the greatest downy brome control and usually caused the largest numerical reduction in downy brome biomass, seed, and stem number. If downy brome was left untreated, regression analysis predicted approximately 2,000 stems m−2 could result in total yield loss of spring wheat.

Wild oat (Avena fatua) control often is an integral management practice in cropping systems that include cereal crops. Experiments were conducted at two locations in Saskatchewan (Saskatoon and Scott), Canada, from 1994 to 1997 to determine the influence of ICIA 0604 rate (50, 100, 150, and 200 g ai/ha), water volume (30, 50, and 100 L/ha), spray mixture pH (unbuffered, close to pH 7.0; reduced, pH 4.0), late morning and evening application times, and sodium bicarbonate concentration of water source (Saskatoon water, negligible; Scott water, 695 mg/L) on wild oat fresh weight and wheat (Triticum aestivum) grain yield. Reducing ICIA 0604 rate below the recommended label rate (200 g/ha) increased wild oat fresh weight by 22% and decreased wheat grain yield by 7% when applied with 50 or 100 L/ha of water. Applications with 30 L/ha of water resulted in more wild oat growth (19%) and less wheat yield (6%), regardless of the ICIA 0604 rates. Spray mixture pH or time of application did not modify the effects of ICIA 0604 rate and water volume on wild oat fresh weight and wheat yield at Saskatoon. At Scott, the negative effects of ICIA 0604 rates lower than 200 g/ha applied with 50 or 100 L/ha of water were most apparent when applications were made in the morning, especially with an unbuffered spray mixture. ICIA 0604 applications made in the evening with 50 or 100 L/ha of water resulted in the lowest wild oat fresh weights and greatest wheat yields, regardless of the ICIA 0604 rate or spray mixture pH. Antagonism between sodium bicarbonate in the unbuffered water from Scott, as indicated by the spray mixture pH effect, and the time of application effect were important factors controlling treatment responses at Scott. Lower than recommended ICIA 0604 rates often maintained net returns, even though wheat yield responded negatively to reduced ICIA 0604 rates. Understanding the effects of water quality on wild oat control will allow producers to make prudent decisions regarding the optimal application parameters for ICIA 0604.

There are several stem-borer species recorded on important cereals such as rice, maize and sorghum as well as on grain legumes like cowpea. Those of considerable economic importance are: Chilo partellus, Sesamia infer ens, Sesamia eretica, Busseola fusca and Eldana saccharina on maize and sorghum; Sesamia infer ens. Chilo spp., Maliarpha separatella and Tryporyza incertulas on rice; and Maruca testu-lalis on cowpea.

Chemical control of insect pests will continue to be a major component of integrated pest management. However, control of tissue borers with insecticides is relatively more difficult than control of the insect pests feeding externally on foliage, shoots and stems. The foliar application of dust and spray formulation of most of the available insecticides has generally proved to be unsatisfactory as these cannot penetrate deep inside the tissues in sufficient quantities to kill the borers.

The recent advances in pest control technology, placing greater emphasis on use of various pest management components as well as insecticide selectively based on improved application methods has now made the control of stem-borers more effective and economical. Advantage can now be taken of the knowledge of the specific habits of the pests, period of peak activity of the most vulnerable stage and the economic thresholds for determining the appropriate time of application to control these pests. The development of new systemic insecticides and their granular formulation has further contributed towards the effective control of these borers. The recent research findings and recommendations for the control of cereal stem-borers are reviewed and discussed.