Kalmia angustifolia is a problematic understory shrub in boreal forests of eastern Canada. In this article, we discuss the nature of its interference with conifer regeneration, and control measures using herbicides. Although laboratory studies suggest the leaching of water-soluble phenolic compounds from Kalmia, allelopathic interference cannot be invoked as a cause of conifer regeneration failure because of lack of field evidences. Because of severe inhibitory effects of Kalmia on conifer growth and its role in long-term habitat degradation, the development of strategies for Kalmia management is a priority research area. Neither prescribed burning, plowing, scarification, nor 2,4-D application was proven effective in Kalmia control. Two studies were carried out using transplanted Kalmia to determine the efficacy of several herbicides and a herbicide plus burning treatment to control Kalmia. In one experiment, eight treatments were applied. They were control, glyphosate (3.36 kg/ha), glyphosate (2.88 kg/ha) plus surfactant Tween 20 (0.2%), glyphosate (2.88 kg/ha) plus surfactant Triton XR (0.2%), fosamine ammonium (5.38 kg/ha), triclopyr (4 kg/ha), hexazinone (2.2 kg/ha), and hexazinone (5 kg/ha). Triclopyr (4 kg/ha) provided the best control with significant reduction in the number and dry weight of sprouts, rhizomes, and current-year foliage of Kalmia compared with control. In another experiment, triclopyr (4 kg/ha), hexazinone (5 kg/ha), and hexazinone (2.2 kg/ha) plus burning treatments were applied. To determine the response of black spruce seedlings to the herbicide treatments, black spruce seedlings were planted in all the Kalmia pots except the ones that received the hexazinone (2.2 kg/ha) plus burning treatment. Triclopyr (4 kg/ha) caused the maximum damage to Kalmia, affecting all the above- and below-ground components of the plant. We recommend that an experimental field trial be established using triclopyr to test its efficacy for Kalmia control under field conditions.

Several herbicides were evaluated as seed-applied treatments to determine the feasibility of controlling cheat by applying herbicide directly onto the cheat seeds during the wheat harvesting process and returning the treated seeds to the field. Seed-applied trifluralin reduced cheat emergence 80% in exploratory evaluations. In herbicide-seed mixing time and spray volume experiments, short mixing times were adequate, and spray volumes from 113 to 227 ml/kg seeds did not affect results. Herbicides applied with a sprayer-equipped auger reduced cheat emergence >90% and were as effective as herbicides applied with a rotary drum seed-treater. Increasing spray volume increased the efficacy of auger-applied treatments. Adjuvants did not improve the efficacy of seed-applied trifluralin.

The effect of CGA 152005 residues in the soil on six crops grown in rotation with field corn was investigated over a 2-yr period. CGA 152005 at 10, 15, 20, and 30 g ai/ha was applied postemergence (POST) to corn in 1994. CGA 152005 at 15 and 30 g ai/ha, atrazine at 1,000 g ai/ha, CGA 152005 at 15 g plus atrazine at 500 g ai/ha, and CGA 152005 at 30 g plus atrazine at 1,000 g ai/ha were applied POST to corn in 1995. Soybean, pea, cabbage, tomato, pepper, and potato were planted each spring, 1 yr after herbicide application. Cabbage exhibited injury and yield reductions that increased with increasing application rate, and pepper exhibited slight injury at the highest rate and yield reduction in 1995. Cabbage yields were reduced by CGA 152005 plus atrazine, and tomato yields were reduced by CGA 152005 and CGA 152005 plus atrazine in 1996. Yields of other crops were not affected in either year.

Pollen allelopathy results when pollen releases toxins that inhibit seed germination, seedling emergence, sporophytic growth, or sexual reproduction. Of the six known pollen-allelopathic species, two are crops (timothy and corn and four are weeds (orange hawkweed, parthenium, yellow hawkweed, and yellow-devil hawkweed). Allelopathic pollen in weeds could pose threats to crops, especially if both are wind pollinated. Even if it is the crop that is pollen-allelopathic, other crops could be threatened, or more likely, weeds might adapt to pollen allelopathy and pose a greater problem. Nonetheless, pollen allelopathy could be a useful approach to biological control because allelochemicals are packaged in a natural targeting system (pollen grains) and are biologically active at low doses (<10 grains/mm2 on stigmas). If it is to be an effective biological control agent, pollen allelopathy must be examined within the wider context of farming systems management and used as one method of varying selection pressures to prevent weeds from adapting to any one particular management technique or suite of techniques.

Metham has been reported as an acceptable weed control alternative to methyl bromide. However, modified application equipment is required to allow its effective use in crops that are grown on polyethylene-covered seedbeds. A power tiller was modified using commonly available materials to apply metham in a 61-cm band and shape seedbeds for laying a black polyethylene tarp. Additional modification allowed the implement to be used in strip tillage and conventional tillage systems. Metham applied using this modified power tiller effectively controlled many species of weeds, including yellow nutsedge, in transplanted watermelon.

Dr. Lawrence R. “Dick” Oliver is University Professor and Elms Farming Chair for Weed Science at the University of Arkansas. Agriculture was the backdrop of his youth in Stuttgart, AR, which profoundly affected his career choice. Dr. Oliver received his B.S. and M.S. degrees from the University of Arkansas and his Ph.D. degree from Purdue University. He has been actively involved in weed science research and teaching in Arkansas since 1972. His research in weed biology, weed interference, reduced herbicide rate programs, and control of specific problem weeds in soybean, corn, and wheat has earned him recognition throughout the United States and especially in the southern region.

Dr. Oliver has served the Weed Science Society of America (WSSA) as member-at-large and on numerous committees before being elected Vice President in 1998. He has also been Secretary-Treasurer and President of the Southern Weed Science Society (SWSS). Dr. Oliver has received numerous awards for contributions to teaching, research, and service, such as Outstanding Teacher and Fellow in WSSA; Outstanding Young Weed Scientist, Weed Scientist of the Year, Outstanding Educator, and Distinguished Service Awards in SWSS; Outstanding Teacher and Researcher in Bumpers College of Agriculture, Food, and Life Sciences; and University of Arkansas Alumni Association Faculty Distinguished Achievement Award for Teaching and Research

A morningglory at my window satisfies me more than the metaphysics of books.

Song of Myself, Walt Whitman, 1855 (Mitchell 1998)

Several weed species have been reported to have allelopathic activities. However, most of these studies indicate the probable involvement of allelochemicals but are not conducted in field settings. In addition to their adverse effects on growth and yield of many crop species, many troublesome weeds such as mugwort and lantana influence biodiversity. More studies on the ecological, physiological, and molecular aspects of weed allelopathy should be conducted in order to better understand community structure and declining biodiversity.

Field studies were conducted from 1997 to 1999 in Westminster, MD, to evaluate a variety of preemergence (PRE) and postemergence (POST) herbicide programs on crop injury and control of triazine-resistant common lambsquarters (TR-CHEAL) in no-till corn. In 1997 PRE studies, combinations of metolachlor with flumetsulam or halosulfuron and high rates of rimsulfuron + thifensulfuron (0.02 + 0.009 kg ai/ha) injured corn most 4 weeks after treatment (WAT), averaging 11 to 15%. In 1998 and 1999, metolachlor plus a high rate of halosulfuron (0.07 kg/ha) injured corn most 4 WAT, averaging 13 and 10%, respectively. High rates of rimsulfuron + thifensulfuron also provided a higher level of corn injury in 1998 and 1999 in comparison with many of the other treatments. However, for all three years of the study, no injury was observed from any PRE treatment 8 WAT. In 1997 and 1998, at 8 WAT, combinations of metolachlor with flumetsulam or halosulfuron provided greater TR-CHEAL control than many of the other treatments, averaging 98 and 100%, respectively. In 1999, however, control of TR-CHEAL with these same treatments did not vary in comparison with most of the other treatments. At 8 WAT, there was a trend for increased TR-CHEAL control as the rates of RPA-201772 and rimsulfuron + thifensulfuron increased. Control of TR-CHEAL with metolachlor + atrazine + pendimethalin varied across years 8 WAT. Similar observations were made 16 WAT. In 1997, POST applications of dicamba, SAN 1269H at 0.3 lb ai/ha, primisulfuron + dicamba, and primisulfuron + CGA 152005 + dicamba provided the highest level of TR-CHEAL control 8 WAT, averaging 93, 93, 95, and 93%, respectively. In 1998, with the exception of carfentrazone + atrazine, all POST treatments provided 90% control of TR-CHEAL or better 8 WAT. In 1999, POST applications of SAN 1269H at 0.3 kg/ha, pyridate + atrazine, and primisulfuron + CGA 152005 + pyridate provided the highest level of TR-CHEAL control, averaging 80, 90, and 96%, respectively, 8 WAT. With the exception of carfentrazone + atrazine, control of TR-CHEAL with the other POST treatments varied in 1999 from 60 to 74% 8 WAT. Carfentrazone + atrazine applied POST provided the lowest level of TR-CHEAL control 8 WAT averaging 28, 37, and 17% for 1997 to 1999, respectively.

The competitive ability of five cool-season grasses relative to Dalmatian toadflax, musk thistle, and downy brome was assessed in two field studies. In 1994, Bozoisky Russian wildrye and four wheatgrass varieties (Critana thickspike, Hycrest crested, Luna pubescent, and Sodar streambank wheatgrass) were seeded into populations of downy brome and musk thistle at Riverside, WY. The same grasses were seeded into populations of Dalmatian toadflax at Cheyenne, WY, in 1995. In 1997 and 1998, weed populations at both study sites were reduced in areas seeded with the five grasses relative to unseeded controls. Hycrest crested and Luna pubescent wheatgrasses were the most competitive against the three weed species. Bozoisky Russian wildrye was more competitive against Dalmatian toadflax than against the other weeds. Sodar streambank wheatgrass suppressed musk thistle and downy brome but was not competitive against Dalmatian toadflax. Seeded grasses, such as Hycrest crested and Luna pubescent wheatgrass, appeared to limit the re-establishment of these weeds. Economic model predictions of the net present values and the internal rates of return suggest that Hycrest crested and Luna pubescent wheatgrass can provide financially feasible long-term weed control only if desired grass yields are maintained for more than 15 yr.

… on finding a root of shepherd's purse (Capsella bursa-pastoris) open a seed-vessel. If the seed is yellow you will be rich, but if green you will be poor.

Yorkshire Folklore, W.M.E. Fowler, 1909 (Vickery 1995)