The hybrid Bohemian knotweed [Polygonum ×bohemicum (J. Chrtek & Chrtková) Zika & Jacobson [cuspidatum × sachalinense]; syn.: Reynoutria ×bohemica Chrtek & Chrtková] is part of the worldwide problematic rhizomatous invasive plants that impact (semi-)natural and agricultural systems. In this context, precise knowledge about the morpho-anatomy and resprouting capacity of the underground organs is key information for developing efficient eradication measures. In the present study, we aimed at (1) clarifying existing differences in the morpho-anatomical characteristics of rhizomes and roots, (2) developing an easy-to-apply field identification method for the underground organs, and (3) identifying the main morpho-anatomical features enhancing the rhizomes’ resprouting ability. For this purpose, we collected the underground organs of two wild populations of P. ×bohemicum in Canton Ticino (southern Switzerland) and analyzed the morpho-anatomical differences between rhizomes and roots, using high-resolution microscope images and microtome sections. Collected material was then used for a resprouting capacity test after assessing rhizome characteristics such as weight, total diameter, pith diameter, pith brightness, and pith color. In contrast to roots, rhizomes are characterized by pith tissue in the center and display nodes with peripheral dormant buds that enable them to resprout. Resprouting ability of rhizomes was high (87.1% on average) and depended on the ontogenetic developmental stage of the organs (peak values of 97% for young and clearer-colored organs, 50% for old and dark ones). In conclusion, the smooth pith tissue of rhizomes represents a key discriminating feature between rhizomes and roots, whereas relating existing nodes to the corresponding rhizome pith color allows assessment of the resprouting potential of a knotweed population.

Japanese knotweed (Reynoutria japonica Houtt.) is an invasive Asian plant abundant along rivers in its introduced range. In riparian areas, floods and ice flows uproot the rhizomes, facilitating their dissemination downstream. Control of large, well-established R. japonica clones in riparian areas is difficult if the use of herbicides is prohibited. An alternative to controlling entrenched clones is the rapid detection and manual unearthing of rhizome fragments that have recently rooted after being deposited by floodwaters. We applied this strategy along a Canadian river where spring floods with abundant ice are recurrent. Two river stretches, with approximately 10 km of shoreline each, were selected for the fragment removal campaign. One of the stretches was heavily invaded by R. japonica, while the other was only sparsely invaded. In the heavily invaded stretch, 1,550 and 737 R. japonica rhizome fragments were unearthed in 2019 and 2020, respectively. Unearthed fragments had an average length of 27 to 32 cm. Only 21 fragments were found in the sparsely invaded stretch in 2020. Despite similar distances being surveyed, the detection and unearthing took 62% less time (overall) in the sparsely invaded than in the heavily invaded stretch. Along sparsely invaded riverbanks, a rapid response removal campaign for R. japonica cost, including transportation and labor, an estimated Can$142 (US$105) per aborted clone (i.e., fragment removed). A rapid response removal campaign is economically advantageous compared with the hypothetical eradication of large, well-established clones, but for it to be cost-effective, the time spent locating rhizome fragments must exceed the time spent unearthing them. The question is not whether rapid response unearthing is economically feasible—it is—but rather what invasion level renders the intervention practicable. In highly invaded river stretches generating thousands of fragments annually, finding and removing these fragments year after year would require a massive, unsustainable effort.

Navua sedge is a creeping perennial sedge commonly found in tropical environments and is currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland, Australia. Pasture and crop productions have been significantly impacted by this weed. The efficacy of halosulfuron-methyl on Navua sedge plants with and without well-established rhizomes was evaluated under glasshouse conditions. Halosulfuron-methyl was applied to plants with established rhizomes at three stages; mowed, pre-flowering, and flowering growth stages, whereas plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, halosulfuron-methyl was applied at four dose rates of 0, 38, 75, and 150 g ai ha−1. Mortality of 27.5%, 0%, and 5% was recorded in rhizomatous Navua sedge when treated with 75 g ai ha−1 of halosulfuron-methyl at the mowed, pre-flowering stage and flowering stages, respectively. At 10 wk after treatment (WAT), there were no tillers in surviving plants treated at any of the application times. By 16 WAT, the number of tillers increased to 15, 24, and 26 in mowed, pre-flowering, and flowering stages, respectively. Although halosulfuron-methyl is effective in controlling aboveground growth, subsequent emergence of new growth from the rhizome confirms the failure of the herbicide to kill the rhizome. Application of 75 g ai ha−1 of halosulfuron-methyl provided 100% mortality in plants treated at seedling and pre-flowering stages, and 98% mortality when treated at flowering stage in non-rhizomatous plants. A single application of halosulfuron-methyl is highly effective at controlling Navua sedge seedlings but not effective at controlling plants with established rhizomes.

To identify literary influences is, conventionally, to build a genealogy—to, in Salman Rushdie’s words, “name one’s parents.” But can this family-tree view of literary influence hold up in postcolonial literature—a body of work that has so thoroughly deconstructed concepts of genealogy? This article turns to a pivotal case of “influence” in postcolonial Francophone literature and philosophy: among Édouard Glissant and Gilles Deleuze and Félix Guattari. The latter two writers are thought to have influenced Glissant’s thinking with their concept of the “rhizome,” but the rhizome directly counters such genealogizing as this “influence” would imply. In fact, this article shows, Glissant develops his own version of the rhizome from his very earliest writings, particularly his first poems. An analysis of them alongside Glissant’s subsequent essays and Deleuze and Guattari’s own writing, allows for a more complicated, multidirectional—that is, rhizomatic—theory of postcolonial influence.

A rhizotron containing 10 1.5-by 1.2-by 2.4-m chambers and two 1.5-by 1.2-by 1.2-m chambers for plant growth was constructed for teaching purposes at Montana State University. The rhizotron, constructed of pressure-treated plywood and redwood lumber, has a life expectancy of 40 yr and a prorated cost of approximately $100/yr.

In glasshouse experiments, Panicum repens rhizomes with more than two nodes emerged from soil depths of 1 to 20 cm. Emergence from one-node rhizomes was greatly reduced at depths more than 5 cm. In contrast, culm emergence from ginger like rhizomes decreased when burial depth (BD) was greater than 20 to 30 cm. P. repens emerged from deeper soil levels with an increasing number of nodes per cutting. Culms emerged from 36% of total underground regenerative organs. About 75 and 95% of the emerged culms were recorded 30 and 60 d after burial, respectively, and 91% emergence was recorded from 20-cm BD. In field studies, only 9% of nodes produced culms following cross-plowing. About 61 and 67% of the emerged culms were recorded 50 and 60 d after land preparation, respectively. Results indicate that mechanical and chemical control methods could be most effective for P. repens when applied approximately 50 d after land preparation. Burying deeper than 30 cm by deep plowing and reducing rhizome length by cross-plowing might effectively reduce emergence of P. repens.

The translocation pattern and distribution in rhizomes of 14C-glyphosate, 14C-quizalofop, and 14C-sucrose was examined in five quackgrass biotypes. Translocation of radioactivity in the different plant parts varied among biotypes. Translocation in the whole plant after treatment with the three 14C-chemicals varied among biotypes but was not correlated with their tolerance to herbicides. Detailed analysis of distribution of radioactivity in the primary rhizome showed that more 14C was found in the apical sections after treatment with 14C-sucrose. A similar pattern was observed after 14C-glyphosate application with all biotypes except one. Very low radioactivity was found in rhizomes after 14C-quizalofop application, but a preferential accumulation in apical sections of the primary rhizome was detected in two biotypes. The tolerance of one biotype to glyphosate was explained by the absence of radioactivity accumulation in the apical sections of the rhizome.

An experiment was conducted to evaluate the translocation pattern of 14C-glyphosate and 14C-quizalofop in five quackgrass biotypes at two stages of growth. Whole plant translocation differed between stages for each herbicide. The percentage of 14C-glyphosate and 14C-quizalofop in the leafwash and in the treated leaf did not differ among biotypes, but differences occurred for the translocation to the underground parts. The partitioning of the 14C-glyphosate and 14C-quizalofop in the treated crown, other crowns, propagating rhizomes, and other rhizomes differed among biotypes. On a disintegration per minute (DPM) mg-1 basis, differences among biotypes were found with 14C-glyphosate but much less with 14C-quizalofop. Metabolism of 14C-quizalofop in the treated leaf was similar in the two biotypes tested except for the percentage of polar metabolites 1 d after treatment. The percentage of 14C-quizalofop available for translocation was the same in both biotypes.

A growth room study was conducted to evaluate the effect that timing of application has on the distribution of several herbicides in quackgrass. Uniformly labeled 14C-sucrose and the radiolabeled herbicides glyphosate, sethoxydim, the butyl ester of fluazifop, and the methyl ester of haloxyfop were applied to quackgrass (ranging from the three- to eight-leaf stage) propagated from six-bud rhizome segments. Five days after treatment the plants were harvested, lyophilized, and later sectioned, mapped, and oxidized in preparation for 14C quantification. In most cases, slightly more 14C was translocated to the shoots than to the rhizomes. 14C translocation to the rhizomes was similar at all growth stages. The 14C accumulating in the rhizomes exhibited a nonuniform distribution pattern with more 14C in the distal areas of new rhizomes than in the other areas of the rhizome system. Plants treated with haloxyfop had a more uniform distribution of 14C along their rhizomes than did those treated with fluazifop or sethoxydim.

Field, greenhouse, and laboratory studies were conducted to examine the effect of application timing on the activity of DPX-V9360 on rhizome johnsongrass. Field and greenhouse studies indicated that johnsongrass treated with postemergence applications of DPX-V9360 at late growth stages (>5 leaves) was controlled more effectively than when treated in early growth stages (<5 leaves). Johnsongrass control was optimized with split-postemergence applications (treatments applied at early and late growth stages) in field studies compared to a single postemergence application at either early or late growth stages. The pattern of translocation of 2-14C (pyrimidine)-labeled DPX-V9360 applied to a fully expanded johnsongrass leaf did not differ significantly between three different growth stages of 10-, 30-, and 60-cm height. Over 60% of the absorbed 14C remained in the treated leaf. Most of the translocated 14C moved out of the treated leaf within 3 days after application and distributed to the shoot in greater quantities than to the rhizomes. About 40% of 14C-DPX-V9360 applied to the leaf surfaces of a tolerant species (corn) or susceptible species (johnsongrass) was absorbed into the leaf. Corn metabolized over 90% of absorbed DPX-V9360 within 20 h, while there was no perceptible metabolism of DPX-V9360 in johnsongrass leaves after 24 h. Late growth stage and split-postemergence applications appear to provide more effective control than early growth stage applications because of better control of regrowth (new shoot emergence from rhizomes after application) and because tillering and plant emergence are more nearly complete at application time.

A simple technique is described for rapid determination of weed seed, rhizome, corm, or bulb populations in soil. Soil samples were placed in nylon mesh bags. The soil was washed from the bags by machine leaving only a small residue including the desired propagules. These were hand separated and the soil population of a given plant species calculated. The total manipulation time per sample was approximately 10 min.

Imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} absorption, translocation, and toxicity were investigated in yellow nutsedge (Cyperus esculentus L. # CYPES) and purple nutsedge (C. rotundus L. # CYPRO) after foliar treatment. Imazaquin rates from 0.125 to 0.375 kg ai/ha were sprayed on nutsedge plants at the four-leaf stage. Compared to untreated plants, these rates reduced the main shoot growth of yellow nutsedge by 70 to 86% and that of purple nutsedge by 80 to 92% at 28 days after application (DAA). However, the regrowth as measured by tiller production was significantly greater at 0.125 and 0.188 kg/ha rates than at higher rates. The plants treated with 0.313 and 0.375 rates had no rhizomes or tubers at the 28 DAA sampling. In yellow nutsedge, absorption of 14C-imazaquin increased from 36% at 1 DAA to 57% at 8 DAA. of the total absorbed 14C, 12% translocated from the treated area by 8 DAA. Roots and rhizomes accumulated equal amounts of radioactivity. In purple nutsedge, the absorption of imazaquin increased from 17% at 1 DAA to 53% at 8 DAA. Translocation of absorbed 14C in purple nutsedge at 8 DAA was 21%. Rhizomes accumulated significantly greater amounts of 14C than the roots.

Experiments were conducted in 1996 and 1997 to determine the effects of postemergence (POST) application of rimsulfuron on quackgrass control. Rimsulfuron applied at 27 g ai/ ha to two-to four-leaf quackgrass controlled 100% of quackgrass 5 wk after treatment (WAT). Rimsulfuron applied to one- to two-leaf quackgrass was not as effective as the same rate applied to two- to four-or four- to six-leaf quackgrass. Stunting and leaf wrinkling of corn were observed 4 WAT when rimsulfuron was applied at 36 g/ha to four- to six-leaf quackgrass. The plants recovered from the stunting as the season progressed and by 12 WAT there was no appreciable stunting. Rimsulfuron (27 g/ha) applied to two- to four-leaf quackgrass increased grain and silage yield of corn by 36% and 45%, respectively, compared to the untreated check. The 27 g/ha rate of rimsulfuron applied to two- to four-leaf quackgrass resulted in 10% more grain yield than the same treatment applied to one- to two- leaf quackgrass. Rimsulfuron at 18 g/ha led to a 17% reduction of sitage yield when applied to the four- to six-leaf quackgrass. At all growth stages of quackgrass, rimsulfuron gave higher grain and silage yields than corn treated with the same rate and timing of nicosulfuron. Rimsulfuron reduced sprouting of quackgrass rhizome nodes, especially at higher rates.

Experiments were conducted to establish low temperature thresholds for initiation of bud sprouting in dormant vegetative propagules of johnsongrass, purple nutsedge, and yellow nutsedge, and seed germination in cotton. Weed propagule sprouting and cotton seed germination responses to temperature were determined in a series of experiments conducted on a temperature gradient bar. Four calculated indices were used to quantify germination: mean percent germination per day, reciprocal median response time, and two versions of germination rate index. Data were analyzed as a series of regressions of germination indices against temperature. Maximum and minimum temperatures for germination were derived directly from the regressions and compared among species. Yellow nutsedge had the lowest temperature threshold (6 C), while the other species had low temperature thresholds of 11 to 12 C. Upper temperature thresholds were similar among species and ranged from 42 to 44 C. The lower low temperature threshold of yellow nutsedge sprouting compared to those for cotton, johnsongrass, and purple nutsedge suggests that early establishment by yellow nutsedge is an important factor in competitiveness in mixtures of these species. The results presented here suggest that application of principles derived from studies in seed biology might advance our understanding and ability to manage perennial weeds.

A growth cabinet study was conducted to evaluate the effect of temperature on the distribution of several herbicides in quackgrass. Uniformly labeled 14C-sucrose and the radiolabeled herbicides glyphosate, sethoxydim, cloproxydim, the butyl ester of fluazifop, the methyl ester of haloxyfop, and the ethyl ester of quizalofop were applied to quackgrass grown at three day / night temperature regimes (10/5, 20/15, and 30/25 C). Seven days after treatment the plants were harvested, lyophilized, and later sectioned, mapped, and oxidized in preparation for 14C quantification. Quackgrass rhizome growth was more vigorous at 20/15 than 30/25 or 10/5 C. of the herbicides tested, haloxyfop was the most inhibitory to rhizome growth. Temperature increases from 10/5 to 20/15 or from 20/15 to 30/25 C resulted in more translocation to shoots. Increasing temperature had various effects on translocation to rhizomes depending on the chemical applied. At all three temperature regimes, more 14C was recovered from distal than basal buds in plants treated with 14C-sethoxydim. In contrast, at all three temperature regimes, similar amounts of 14C were recovered from the distal and basal buds of plants treated with 14-C-sucrose.

Genetic diversity and reproductive characteristics may play an important role in the invasion process. Here, we review the genetic structure and reproductive characteristics of common reed and giant reed, two of the most aggressive, large-statured invasive grasses in North America. Common reed reproduces both sexually and asexually and has a complex population structure, characterized by three subspecies with overlapping distributions; of which, one is introduced, one native, and the third is of unknown origins. These three subspecies show varying levels of genetic diversity, with introduced common reed having high levels of nuclear diversity, indicating that multiple introductions have likely occurred. In contrast, giant reed has low genetic diversity and appears to reproduce solely via asexual fragments yet is highly aggressive in parts of its introduced range. Both species are well-adapted for growth in human-dominated landscapes, which is presumably facilitated by their rhizomatous growth habit.