Management Options and Factors Affecting Control of a Common Waterhemp ( Amaranthus rudis

Repeated use of protox-inhibiting herbicides has resulted in a common waterhemp (Amaranthus rudis Sauer) biotype that survived lactofen applied up to 10 times the labeled rate. Field and greenhouse research evaluated control options for this biotype of common waterhemp. In the field, PRE applications of flumioxazin at 72 g ai ha−1, sulfentrazone at 240 g ai ha−1, and isoxaflutole at 70 g ai ha−1 controlled common waterhemp >90% up to 6 weeks after treatment. POST applications of fomesafen at 330 g ai ha−1, lactofen at 220 g ai ha−1, and acifluorfen at 420 g ai ha−1 resulted in <60% visual control of common waterhemp, but differences were detected among herbicides. In the greenhouse, glyphosate was the only herbicide that controlled protox resistant waterhemp. The majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% regardless of placement. Control of common waterhemp seeded at weekly intervals after herbicide treatment with flumioxazin, fomesafen, sulfentrazone, atrazine, and isoxaflutole exceeded 85% at 0 weeks after herbicide application (WAHA), while control with isoxaflutole was greater than 60% 6 WAHA. PRE and POST options for protox-resistant common waterhemp are available to manage herbicide resistance

Weed management systems for environmentally sensitive areas (2002)

"New 11/02/5M.""Integrated pest management.""Plant protection programs : College of Agriculture, Food and Natural Resources.""This publication is part of a series of IPM Manuals prepared by the Plant Protection Programs of the University of Missouri. Topics covered in the series include an introduction to scouting, weed identification and management, plant diseases, and insects of field and horticultural crops.

Seedbank Persistence of Palmer Amaranth (\u3ci\u3eAmaranthus palmeri\u3c/i\u3e) and Waterhemp (\u3ci\u3eAmaranthus tuberculatus\u3c/i\u3e) across Diverse Geographical Regions in the United States

Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems

Integrated management of cutleaf teasel (Dipsacus laciniatus) along roadsides in Missouri, USA

Cutleaf teasel is a biennial, invasive weed found along roadsides throughout much of the central USA. Long-term management should, ideally, integrate chemical and cultural practices. Research in Missouri along Interstate Highway 70 was initiated to combine chemical applications with overseeding perennial grasses. A field experiment was carried out with a split-plot design (four replications), where the main plot factor was herbicide applied, and the sub-plot factor was grass species overseeded. Herbicide treatments comprised dicamba þ diflufenzopyr, aminopyralid, triclopyr, and metsulfuron. Grass species included tall fescue þ buffalograss or Canada wildrye þ buffalograss. Cutleaf teasel coverage was reduced from 79% to 93% for all herbicide treatments except triclopyr, 5 months after the last herbicide application. Seedling counts of cutleaf teasel were lowest for aminopyralid by 6 months after the last herbicide application. The herbicide programme that provided 490% cutleaf teasel control and resulted in at least 65% grass establishment resulted in up to a 93% reduction in cutleaf teasel emergence by 363 days after initial herbicide application. Integration of applications of herbicides and desirable seeding grasses are needed over a long period to exclude cutleaf teasel in roadside areas.Fil: Bentivegna, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. University Of Missouri; Estados UnidosFil: Smeda, Reid J.. University Of Missouri; Estados Unido

Seed production of cut-leaved teasel (Dipsacus laciniatus L.) in central Missouri

Cut-leaved teasel is an invasive weed in Missouri that reduces the diversification of native species along roadsides and impairs traffic visibility. Teasel is a biennial and grows as a rosette in the first year and flowers the second year. Reproduction is only by seed. Field studies were conducted in 2004 and 2005 at two locations to assess the seed production of cut-leaved teasel. From a natural stand, fifteen plants were tagged at the onset of flowering. Selected plants included those considered growing in a group and those growing alone; a plant was considered alone when no other plant was adjacent for at least 60 cm. Whenever a seedhead completed flowering, it was covered with a cellophane bag and harvested one month later. Linear regression was used to correlate the weight of seeds from a single seedhead and number of seeds to estimate the total seed production per seedhead. The number of seedheads per plant varied from 3 to 56. On average, plants growing alone had 64% more seedheads per plant than plants occurring in a group. Seed numbers in the primary seedhead ranged from 511 to 1,487. Total seed production per plant ranged from 1,309 to 33,527. Seed production was 61% greater for plants growing alone versus those growing in a group and was more prolific in 2005 than in 2004. In addition, seed production per plant varied between locations for plants growing alone, but seed yield per plant was similar for plants growing in groups. Colonization of teasel in new areas is facilitated by higher seedhead numbers per plant and total seed production compared to reproduction of plants in areas of intraspecific competition.Fil: Bentivegna, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; ArgentinaFil: Smeda, Reid J.. University Of Missouri; Estados Unido

Detecting Cutleaf Teasel (Dipsacus laciniatus) along a Missouri Highway with Hyperspectral Imagery

Cutleaf teasel is an invasive, biennial plant that poses a significant threat to native species along roadsides in Missouri. Flowering plants, together with understory rosettes, often grow in dense patches. Detection of cutleaf teasel patches and accurate assessment of the infested area can enable targeted management along highways. Few studies have been conducted to identify specific species among a complex of vegetation composition along roadsides. In this study, hyperspectral images (63 bands in visible to near-infrared spectral region) with high spatial resolution (1 m) were analyzed to detect cutleaf teasel in two areas along a 6.44-km (4-mi) section of Interstate I-70 in mid Missouri. The identified classes included cutleaf teasel, bare soil, tree/shrub, grass/other broadleaf plants, and water. Classification of cutleaf teasel reached a user’s accuracy of 82 to 84% and a producer’s accuracy of 89% in the two sites. The conditional k value was around 0.9 in both sites. The image-classified cutleaf teasel map provides a practical mechanism for identifying locations and extents of cutleaf teasel infestation so that specific cutleaf teasel management techniques can be implemented.Fil: Bentivegna, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentina. University Of Missouri; Estados UnidosFil: Smeda, Reid J.. University Of Missouri; Estados UnidosFil: Wang, Cuizhen. University Of Missouri; Estados Unido

Management Options and Factors Affecting Control of a Common Waterhemp (Amaranthus rudis) Biotype Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Repeated use of protox-inhibiting herbicides has resulted in a common waterhemp (Amaranthus rudis Sauer) biotype that survived lactofen applied up to 10 times the labeled rate. Field and greenhouse research evaluated control options for this biotype of common waterhemp. In the field, PRE applications of flumioxazin at 72 g ai ha −1 , sulfentrazone at 240 g ai ha −1 , and isoxaflutole at 70 g ai ha −1 controlled common waterhemp &gt;90% up to 6 weeks after treatment. POST applications of fomesafen at 330 g ai ha −1 , lactofen at 220 g ai ha −1 , and acifluorfen at 420 g ai ha −1 resulted in &lt;60% visual control of common waterhemp, but differences were detected among herbicides. In the greenhouse, glyphosate was the only herbicide that controlled protox resistant waterhemp. The majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% regardless of placement. Control of common waterhemp seeded at weekly intervals after herbicide treatment with flumioxazin, fomesafen, sulfentrazone, atrazine, and isoxaflutole exceeded 85% at 0 weeks after herbicide application (WAHA), while control with isoxaflutole was greater than 60% 6 WAHA. PRE and POST options for protox-resistant common waterhemp are available to manage herbicide resistance

Spring-Interseeded Winter Rye Seeding Rates Influence Weed Control and Organic Soybean Yield

Field research in 2002 and 2003 evaluated spring-interseeded winter rye (Secale cereale L.) at 67, 134, or 200 kg ha−1 at two soybean (Glycine max (L.) Merr.) row spacings (19- and 76-cm) on weed control, yield, and gross margins. Based on regression analysis, wide-row (76-cm) soybean grain yield and gross margins were greatest when winter rye was interseeded at 114 and 106 kg ha−1, respectively. Yields and gross margins for wide-row soybean were 8 to 55% greater than narrow-row (19-cm) soybean seeded at 494,000 or 742,000 seeds ha−1 which was probably due to flexibility for implementing cultivation. As interseeded rye rates increased from 67 to 200 kg ha−1, yields and gross margins for narrow-rows decreased. Soybean row spacing had minimal impacts on specific weed species and total weed biomass or density. The use of wide-row soybean and spring-interseeded rye at 67 kg ha−1 was more cost-effective compared to narrow rows

Comparing classification approaches for mapping cut-leaved teasel in highway environments

Cut-leaved teasel is an invasive weed thriving in roadside environments and needs to be detected for implementation of management programs. This study tested several commonly applied classifiers to map teasel with an aerial hyperspectral image along the Interstate Highway 70 in central Missouri. A teasel/non-teasel mask was first built to exclude dominant land-covers that had distinct spectral differences from teasel. The spectral angle mapping (SAM) had the best results of delineating teasel from herbaceous background with its user’s and producer’s accuracies of 80 to 90 percent. Large commission errors of teasel were observed in the probability-based maximum likelihood classifier (MLC) and spectral information divergence (SID) methods. Compared with a regular land-use/land-cover classification in an unsupervised/supervised hybrid method, the post-masking SAM had much easier process of training data collection and achieved similar accuracies. It could be an optimal approach for mapping teasel and other weeds in highway environments.Fil: Wang, Cuizhen. University Of Missouri; Estados UnidosFil: Bentivegna, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiarida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiarida; ArgentinaFil: Smeda, Reid J.. University Of Missouri; Estados UnidosFil: Swanigan, Randy E.. Missouri Department of Transportation; Estados Unido

Practical Weed Science for the Field Scout: Corn and Soybean (2009)

This publication is intended to serve as a practical reference and educational tool to be used in scouting corn and soybean fields for the presence of weeds, identifying whether a rescue treatment is necessary, and determining crop response to herbicide activity. This publication consists of two main sections. The first section includes information on weed identification, scouting and mapping procedures, and a discussion of economic thresholds for weeds. An identification key and color photographs of weeds common to Missouri are also included. The second section includes information on diagnosing herbicide injury. It discusses the various causes and conditions contributing to herbicide injury. It also includes a key to help determine which herbicide family might have caused the injury symptoms, and color photos of herbicide injury caused by various herbicide families