Annual bluegrass is commonly controlled by acetolactate synthase (ALS)-inhibiting herbicides in managed turfgrass. An annual bluegrass population with suspected resistance to ALS-inhibiting herbicides was collected from Grand National Golf Course in Opelika, AL (GN population). Subsequent testing confirmed resistance of the GN population to foramsulfuron, trifloxysulfuron, bispyribac-sodium (bispyribac), and imazaquin when compared to a susceptible population collected locally at Auburn University (AU population). Sequencing of the ALS gene revealed a point mutation resulting in an amino acid substitution at Trp574. Cloning of the ALS gene surrounding the Trp574 region yielded two distinct ALS gene sequences: one producing Trp574 and one producing Leu574. Trp574 to Leu has been previously correlated with resistance to ALS-inhibiting herbicides. Both AU and GN gene sequences contained other similar silent and missense mutations. This research confirms resistance of annual bluegrass to ALS-inhibiting herbicides with Trp574 to Leu amino acid substitution being the most likely mode of resistance based on past literature.

There have been previous calls for, and efforts focused on, realizing the power and potential of weed genomics for better understanding of weeds. Sustained advances in genome sequencing and assembly technologies now make it possible for individual research groups to generate reference genomes for multiple weed species at reasonable costs. Here, we present the outcomes from several meetings, discussions, and workshops focused on establishing an International Weed Genomics Consortium (IWGC) for a coordinated international effort in weed genomics. We review the 'state of the art' in genomics and weed genomics, including technologies, applications, and on-going weed genome projects. We also report the outcomes from a workshop and a global survey of the weed science community to identify priority species, key biological questions, and weed management applications that can be addressed through greater availability of, and access to, genomic resources. Major focus areas include the evolution of herbicide resistance and weedy traits, the development of molecular diagnostics, and the identification of novel targets and approaches for weed management. There is increasing interest in, and need for, weed genomics, and the establishment of the IWGC will provide the necessary global platform for communication and coordination of weed genomics research. © 2018 Society of Chemical Industry.

Aryloxyphenoxypropionate (AOPP) herbicides are used to control bermudagrass contamination in various turfgrasses. Applying AOPP herbicides alone can cause unacceptable injury to zoysiagrass but injury can be reduced when tank-mixed with triclopyr. There are limited data illustrating the extent of bermudagrass control and zoysiagrass cultivar tolerance when these compounds are combined. Research was conducted to determine the efficacy of multiple AOPP herbicides applied alone and tank-mixed with triclopyr for bermudagrass control in zoysiagrass turf. Treatments include three sequential applications of cyhalofop (0.32 kg ai ha−1), fenoxaprop (0.14 kg ha−1), fluazifop (0.11 kg ha−1), or quizalofop (0.09 kg ha−1) applied alone and tank-mixed with triclopyr (1.12 kg ae ha−1) applied to ‘Tifway’ bermudagrass, and ‘Diamond’, ‘Palisades’, and ‘Zenith’ zoysiagrass. Tifway bermudagrass control ranged from 41 to 69% and digital image analysis turf coverage data ranged from 18 to 50% for AOPP herbicides applied alone. The addition of triclopyr to AOPP herbicides increased bermudagrass control (64–79%) and reduced turf coverage (8–29%). Palisades and Zenith zoysiagrass exhibited less injury (1–18%) and greater turf coverage (84–86%) when AOPP herbicides were tank-mixed with triclopyr compared to AOPP herbicides applied alone. Diamond zoysiagrass was not tolerant to any AOPP herbicides applied alone or tank-mixed with triclopyr, except for fluazifop alone (18% injury and 93% turf coverage). Visual ratings and digital image analysis turf coverage data had a strong negative correlation over all tested turfgrasses. In general, AOPP herbicides plus triclopyr will control bermudagrass greater and injure zoysiagrass less compared to AOPP herbicides applied alone; however, these mixtures can cause unacceptable injury to Diamond zoysiagrass.

Three sequential applications of fenoxaprop (1.0 lb/acre), fluazifop (0.09 lb/acre), fluroxypyr (0.23 lb/acre), and triclopyr (0.12 lb/acre) applied on 28‐day intervals were evaluated alone and in various combinations for bermudagrass suppression in zoysiagrass turf. Triclopyr safened the use of fenoxaprop and fluazifop on zoysiagrass turf without decreasing bermudagrass suppression compared to fenoxaprop or fluazifop alone. The addition of triclopyr improved fenoxaprop suppression of bermudagrass over fenoxaprop alone. While similar in chemistry to triclopyr, fluroxypyr was less phytotoxic to bermudagrass and did not provide beneficial safening of fenoxaprop or fluazifop. Based on this research, triclopyr should be utilized in combination with fluazifop or fenoxaprop to decrease injury from these herbicides and increase bermudagrass suppression when using fenoxaprop.

-In crop production, weeds must be controlled so as not to adversely affect crop yield and crop quality. Thus, a low level of weeds infesting a field, in most instances, is not a problem. Except in sod or seed production, turfgrass does not have a yield component. The value of turfgrass is its inherent aesthetic quality and usability. Aesthetic quality is the beauty and value that turfgrass adds to a managed landscape. Usability can be the durability of a sport field, trueness of golf putting green roll, or reduction in soil loss from water runoff or wind. Any weed presence in turfgrass can decrease the aesthetic quality and usability of turfgrass. Utilizing herbicides is the only way to completely control weeds in a turfgrass stand. While it is possible to reduce weed populations using cultural or mechanical management practices, it is impossible to completely eliminate weeds as can be accomplished with herbicides. This manuscript will review the major herbicides used in turfgrass in the United States with respect to their modes of action, herbicide family, and primary use in turfgrass.Keywords: preemergence, postemergence, selectivity, chemical control, weed.RESUMO -Nas culturas agrícolas as plantas daninhas devem ser controladas de modo a não afetar negativamente o rendimento e a qualidade do produto colhido. Deste modo, quantidades pequenas de plantas daninhas em um campo, na maioria dos casos, não é um problema, exceto na produção de sementes. Ressalta-se que em gramados não existe um componente de produção a se colhido. O valor do gramado é a sua qualidade inerente a estética e usabilidade. Qualidade estética é a beleza e o valor que acrescenta ao gramado em uma paisagem gerenciada. Usabilidade pode ser a durabilidade de um campo de esporte ou a redução na perda de solo pela erosão da água ou do vento. A presença de qualquer planta daninha em gramados pode diminuir a qualidade estética e usabilidade do gramado. Enquanto for possível reduzir a população de plantas daninhas utilizando práticas culturais ou mecânicas, não se poderá eliminá-las completamente. A utilização de herbicidas é a única maneira de controlar completamente as plantas daninhas em áreas de gramados. Esta revisão irá rever os principais herbicidas utilizados em gramados nos Estados Unidos com relação a seus modos de ação, a família de herbicidas e uso primário no gramado.Palavras-chave: pré-emergência, pós-emergência, seletividade, controle químico, plantas daninhas.

Glyphosate is used in the transition zone to control annual bluegrass in fully dormant warm-season grasses. A suspected resistant (R) biotype of annual bluegrass was identified on a golf course in South Carolina after at least 10 consecutive years of glyphosate application. Greenhouse bioassays revealed the R biotype was 4.4-fold resistant to glyphosate compared with a standard susceptible (S) biotype. Further studies were conducted to investigate the mechanism conferring glyphosate resistance in the R biotype. Leaf discs of both biotypes accumulated shikimate in response to increasing glyphosate concentration, but the glyphosate concentration resulting in 50% EPSP synthase inhibition as a result of shikimate accumulation (I50) was 4.2-fold higher in the R biotype compared with the S biotype. At the whole plant level, similar levels of shikimate accumulation were observed between biotypes at 6 and 24 h after treatment (HAT) with glyphosate, but greater shikimate accumulation occurred in the S biotype at 72, 120, and 168 HAT. Shikimate levels decreased in the R biotype after 72 HAT. There were no differences in14C-glyphosate absorption between biotypes. However, more14C-glyphosate translocated out of the treated leaf in the R biotype and into root tissues over time compared with the S biotype. Partial sequencing of the EPSP synthase gene revealed a point mutation that resulted in an Ala substitution at Pro106. Although other mechanisms may contribute to glyphosate resistance, these results confirm a Pro106to Ala substitution is associated with resistance to glyphosate in the R annual bluegrass biotype.

Laboratory studies were conducted to evaluate variation in germination response of eight annual bluegrass ecotypes (‘Augusta 4’, ‘Augusta 8’, ‘Augusta 14’, ‘Augusta 17’, ‘Auburn’, ‘Birmingham’, ‘Columbia’, and ‘Purchased’) to photoperiod, temperature, and fenarimol, a fungicide–herbicide used for preemergence annual bluegrass. Seed collected from greenhouse-grown plants and stored for > 2 mo were evaluated under 18 environments (three day and night temperatures by six day and night durations). There was a significant ecotype by environment interaction affecting annual bluegrass germination. High temperature markedly restricted germination, with only the Birmingham ecotype exceeding 20% germination at day and night temperatures of 39 and 29 C, respectively. Maximum germination of all ecotypes was observed at a day and night temperature of 19 and 10 C, respectively. Maximum germination for a specific photoperiod was not consistent across ecotypes; however, all ecotypes germinated to some degree in complete darkness, which indicates that maintaining a dense turf canopy to eliminate annual bluegrass germination may not be completely effective. Ecotypes did not differ with respect to root length response to fenarimol but did vary with respect to shoot length response. Purchased and Columbia shoot growth were the most tolerant to increasing fenarimol concentrations. This information will be used to develop improved management strategies for annual bluegrass.

Dinitroaniline‐resistant annual bluegrass (Poa annua L.) has been reported in several states; however, there are no standardized screening methods for detecting resistance. Research was conducted to evaluate screening techniques (Murashige and Skoog [MS] media, filter paper, hydroponics, and soil based) to detect herbicide resistance to dithiopyr, prodiamine, and pendimethalin in a suspected resistant ecotype of annual bluegrass from Chattanooga, TN (Chattanooga). A senstitive ecotype from Fresno, CA (Control) was also tested. All the bioassays were able to diagnose the ecotype from Chattanooga as resistant to prodiamine and pendimethalin. However, the degree of resistance was highly variable between bioassays. In hydroponics, the amount of prodiamine required to inhibit Chattanooga growth by 50% was 26 times more than Control. Comparatively, in MS media the amount of prodiamine required to inhibit Chattanooga growth by 50% was 80 times more than Control. Minor dithiopyr resistance from the Chattanooga ecotype was detected by the hydroponics, filter‐paper and soil‐based bioassays. Hydroponics provided the most rapid diagnosis of resistance, accessing resistance for a mature plant in 10 d. The MS‐media bioassay had the least amount of confounding variables. These findings highlight the potential variation in results that can occur in mitotic‐inhibiting herbicide resistance detection simply on the basis of how plant samples are assayed.