The OxG hybrid bunches contain more parthenocarpic fruits (PF) than normal fruits (NF) and present problems of development and ripening due to either an asynchronous opening of flowers or insufficient pollination. The objective of this study was to compare the effect of α-naphthaleneacetic acid (NAA) and gibberellic acid (GA3) in the induction and development of PF and NF, the fatty acid profile (FAP), and the oil potential in the ‘Coari x La Mé’ oil palm hybrid. NAA and GA3 induced parthenocarpy in the fruits and did not alter the FAP of the mesocarp oil. The commercial dose of pollen (0.9 g talc + 0.1 g pollen) resulted in increased bunch weight (BW) (20.8 kg) and lower percentage of PF in the bunch (65.4%). The most effective hormonal doses to induce the formation of PF in the bunch were NAA 300 and 600 mg L-1. GA3 alone or in mixture with NAA increased the percentage of PF but did not increase the BW, indicating that GA3 had no synergistic effect on BW. The NAA applications represent alternatives to complement assisted pollination of OxG hybrids to increase bunch production and oil yield.

The annual bluegrass weevil (ABW) is a pest of fine turfgrass, but recent research has found that withholding insecticides for ABW control can reduce annual bluegrass cover. The objective of this research was to evaluate threshold-based insecticide and paclobutrazol programs for annual bluegrass control. The effect of three insecticide programs (preventive, threshold, and no insecticide) and four rates of paclobutrazol (0, 70, 105, or 210 g ha−1 applied monthly) were evaluated. Replicate experiments were conducted from April to November in both 2018 and 2019 on a mixed creeping bentgrass and annual bluegrass fairway in North Brunswick, NJ. By the conclusion of both experiments, all paclobutrazol programs exhibited reduced annual bluegrass cover compared with the nontreated plots. In threshold and no-insecticide programs, reduction in annual bluegrass cover was enhanced by paclobutrazol applied at 105 g ha−1 in both years, and at 70 g ha−1 in the 2019 experiment. Paclobutrazol at 210 g ha−1 resulted in annual bluegrass cover of <20% regardless of insecticide program. In 2019, threshold-based ABW control without paclobutrazol provided similar annual bluegrass control as monthly applications of paclobutrazol at 70 and 105 g ha−1 with the preventive insecticide program. A reduction in turfgrass quality from threshold-based insecticide programs persisted for a shorter duration than the no-insecticide program, regardless of paclobutrazol treatment. Threshold-based ABW insecticide programs that allow ABW feeding damage to occur can result in reduced annual bluegrass cover. These reductions were further enhanced by paclobutrazol applications. The combination of threshold-level insecticide with moderate rates of paclobutrazol (70 to 105 g ha−1) provided reductions in annual bluegrass cover that were similar to the highest rate of paclobutrazol (210 g ha−1) without ABW damage. Turfgrass managers who integrate the threshold-level insecticide approach and monthly paclobutrazol applications may achieve greater annual bluegrass control than either strategy alone if temporary reductions in turf quality can be tolerated.

Weed management in carrot is challenging, given slow and inconsistent crop emergence and early-season growth and the lack of practical season-long management tools such as herbicides. We investigated holistic carrot production systems with a focus on minimizing inputs while optimizing resource use. In an overall sense, results of this work were consistent between years, and stark. The choice of carrot variety had a moderate influence on carrot foliar canopy development and, subsequently, weed density. For example, ‘Cupar’ carrot formed a complete crop canopy sooner than the other dicer-type ‘Canada’ variety. Likely as a result, density of weed species such as spotted ladysthumb and common lambsquarters was less where ‘Cupar’ was grown compared with where ‘Canada’ was grown. Gibberellic acid as a foliar application was not successful in these studies and, in a few cases, may have even increased weed-seed germination and establishment. Adding two carrot rows to the current regional industry-standard three-row bed system not only enhanced competitiveness with weeds but also improved carrot yield without additional fertilizer, water, or pest management inputs. By far, though, the most successful strategy to reduce weed density while maintaining or improving carrot yield was to delay seeding by 17 to 19 d. We anticipate more holistic production system research that integrates low-input alternatives in other crops as herbicide-resistant weeds proliferate while few new herbicides are developed. As was demonstrated in this research, such novel approaches can be successful without adding significant economic burden to the farmer or increasing risk of crop failure.

Plant growth regulators paclobutrazol and flurprimidol were evaluated for suppression of Poa annua spp. reptans, a perennial biotype of annual bluegrass, in a creeping bentgrass green. Paclobutrazol at 0.6 kg ai/ha applied on Mar. 15, followed by 0.3 kg/ha on Apr. 29, 0.6 kg/ha on Oct. 1, and 0.3 kg/ha on Nov. 12 for each of 2 yr suppressed P. annua spp. reptans 28% approximately 4 mo after the final treatment. When paclobutrazol was applied at 0.3 kg/ha in each of four applications during the same period, suppression was similar to that with the higher rate 1 and 2 mo after final treatment but declined to 7% by 4 mo. Suppression of P. annua spp. reptans from flurprimidol applied four times during each of 2 yr was 22 to 27% 1 mo after final treatment but no suppression was noted 2 mo after the final treatment. Maximum creeping bentgrass injury was less than 20% when either paclobutrazol or flurprimidol was applied in the spring. However, creeping bentgrass injury was approximately 30% in the fall when either chemical was applied in the spring and repeated in October at 0.6 kg/ha.

Optimum germination of Canada thistle [Cirsium arvense (L.) Scop.] occurred at alternating temperatures of 20 to 30 C and 30 to 40 C and at a constant temperature of 30 C. Osmotic pressures of 7 bars and greater reduced germination, but 2% of the seeds germinated at 15 bars. Canada thistle seeds (14%) were able to germinate in NaCl concentrations of 20,000 ppmw. Light was important in seed germination, however, its effect could be overcome by adding GA3 (gibberellic acid) to the germination medium. Optimum pH for germination was between 5.8 and 7.0. Depth of planting influenced emergence; the highest percentage of seedlings emerged from depths of 0.5 to 1.5 cm. Canada thistle seedlings tolerated average soil moisture tensions of 1.3 bars and continued to grow. Canada thistle seedlings 19 days old and with two true leaves were able to resprout after top-growth removal. Regrowth was evident on 8% of the clipped plants 4 days after initial top-growth removal.

A laboratory bioassay showed that inhibitors of gibberellin synthesis (flurprimidol, paclobutrazol, and uniconazole) reduced plant height but did not affect physiological parameters such as photosynthesis, respiration, and chlorophyll content in two weedy submersed aquatic plants, hydrilla and Eurasian watermilfoil. Eurasian watermilfoil was sensitive to these compounds at concentrations as low as 0.75 μg L−1. Hydrilla sensitivity was in the range of 75 to 750 μg L−1. The three compounds reduced main and lateral stem lengths in hydrilla; however, at 75 μg L−1 the number of lateral stems and roots was greatly increased over untreated controls resulting in a stoloniferous growth habit. Dominant growth form of treated Eurasian watermilfoil was a single shortened stem with numerous compacted buds. Photosynthesis, respiration, and chlorophyll content were not affected in either plant at nontoxic dosages in which stem reduction was obtained. Both plants required only a 24-h exposure to maintain main stem length reduction for 6 wk after transfer to untreated medium. Our results indicate that these gibberellin synthesis inhibitors would be effective in reducing plant height in aquatic systems.

Laboratory, greenhouse, and field experiments were conducted at the Lacombe Research Station to determine if CCC, ethephon, or CCC/ethephon had direct activity on quackgrass rhizome buds, and to determine if foliar applications of CCC/ethephon could predispose quackgrass to more effective control with sethoxydim. CCC, ethephon, and CCC/ethephon had growth regulating effects on the axillary buds and the apex of detached quackgrass rhizomes. CCC increased rhizome bud sprouting on rhizomes with the apex excised, but not on rhizomes with an intact apex. Ethephon or CCC/ethephon inhibited bud sprouting on rhizomes with an intact or excised apex. CCC/ethephon, but not CCC or ethephon alone, increased rhizome elongation on rhizomes with intact apices. In the greenhouse, pretreatments of CCC/ethephon increased sethoxydim activity on quackgrass rhizome buds and caused lower shoot emergence from one-bud rhizome segments. Results of field experiments were less consistent than those in the greenhouse. However, sometimes CCC or CCC/ethephon pretreatments resulted in increased quackgrass control in the field with sethoxydim.

Uptake, translocation, and metabolism of 14C-MBR-18337 {[N-[(4-ethylthio)-2-(trifluoromethyl)phenyl] methanesulfonamide]} in soybean [Glycine max (L.) Merr.] and johnsongrass [Sorghum halepense (L.) Pers.] plants and cell cultures were studied. Sixty-five percent of the 14C recovered from soybean (65% of applied) was on or in the treated leaf, compared to 81% of the 14C recovered from johnsongrass (43% of applied). Translocation of the 14C from the treated leaf of soybean was greater than from the treated johnsongrass leaf, and was primarily to the apical leaves of both species. MBR-18337, its sulfoxide, sulfone, and an unidentified polar component(s) were isolated from intact plants and cell cultures of both species. Soybean plants and cells contained greater proportions of the polar component(s) than johnsongrass plants and cells.

Field experiments were conducted in Alabama from 1992 through 1994 to evaluate the potential of the methyl ester of bensulfuron applied at sublethal rates as a plant growth regulator for reducing plant height and boll rot in cotton. Bensulfuron at 0.017 and 0.034 g ai/ha or mepiquat chloride at 10 g ai/ha was applied POST alone at the pinhead square or early-bloom stage of cotton growth or sequentially at 0.017 followed by (fb) 0.017 g/ha, 0.034 fb 0.034 g/ha of bensulfuron and 5 fb 5, 10 fb 10, 10 fb 20, or 20 fb 20 g/ha of mepiquat chloride. Mepiquat chloride had no effect on yield in 1992 and 1994 but decreased yield when applied sequentially in 1993. Bensulfuron was generally detrimental to first position fruit retention, and it delayed maturity. Treatments that reduced plant height did not reduce boll rot. Bensulfuron treatments that reduced plant height also reduced yield; therefore, the potential for its use as a growth regulator in cotton appears limited.

Field research was conducted in 1985 and 1986 to compare the efficacy of fluazifop and quizalofop on production of panicles and seeds of red rice. Single and first sequential treatments were applied to red rice in the early-tillering, midtillering, and panicle initiation stages of growth. Sequential treatments were applied 14 days after each earlier application to red rice in the midtillering, late-tillering, and early-heading growth stages, respectively. Both herbicides were applied singly or sequentially at 70, 140, and 280 g/ha. Sequential applications of fluazifop and quizalofop at 280 g/ha caused the greatest reduction of red rice panicle and seed production. Fluazifop at 280 g/ha applied sequentially reduced panicle production 75 to 80% and seed production 80%; 140 g/ha applied sequentially reduced seed production 83%. Quizalofop at 280 g/ha applied sequentially reduced panicle production 75 to 100% and seed production 91%. Sequential applications of either herbicide applied to red rice plants in the panicle initiation and early-heading growth stages were the most effective treatments.

Clethodim was applied to tall fescue to determine the effects of application timing (fall, early spring, mid-spring), rate (0, 5.6, 11.2, or 22.4 g ai ha−1), and use of crop oil (0 or 2.3 L ha−1) on seedhead density and forage yield and quality of tall fescue. Increasing the rate of clethodim or adding crop oil reduced seedhead density and forage yield, and generally improved forage quality. There was no effect of application date in 1988 and 1990, but seedhead density and forage yield decreased from the November to the March application date in 1989.

Two field experiments were conducted from 1986 to 1988 to determine efficacy of herbidices and plant growth regulators for red rice control and suppression in water- and drill-seeded rice. Molinate applied PPI with fenoxaprop applied at panicle initiation (PI) of rice controlled 94 and 86% of red rice in water- and drill-seeded rice, respectively, compared with 79 and 49%, respectively, for molinate PPI alone in the two cultures. Although this treatment injured rice slightly (< 30%), rice so treated produced high yields with improved grain quality. Sequential treatments of molinate PPI followed by sethoxydim applied at PI or amidochlor applied at > 90% heading produced comparable rice yields with improved red rice control or suppression and grain quality in both cultures, compared with PPI molinate. Drill-seeded rice treated with molinate PPI followed by fenoxaprop applied at late boot or MH (maleic hydazide) applied 7 d after heading produced higher yield than rice treated with molinate PPI.

Paclobutrazol and flurprimidol were evaluated for suppression of a perennial subspecies of annual bluegrass in a creeping bentgrass green. Three applications of paclobutrazol in the spring (Mar. 17, Apr. 17, and May 17) followed by three applications in the fall (Oct. 2, Nov. 2, and Nov. 30) suppressed the perennial subspecies ≥ 72% at 3 wk after the final treatment. However, suppression was reduced to ≤ 57% by 4 mo after the final fall application. Flurprimidol applied in three spring and three fall applications did not suppress the perennial subspecies as effectively as paclobutrazol. Suppression was ≤ 47% at 3 wk after the final flurprimidol treatment and was only ≤ 20% by mid-March. Neither chemical injured creeping bentgrass greater than 20% in the spring. However, leaf discoloration injury from the initial October application ranged from 26 to 30% for paclobutrazol in 1993 and 21 to 28% for flurprimidol in 1994. When injury occurred in October it was temporary and the creeping bentgrass recovered within 3 to 4 wk. Paclobutrazol and flurprimidol applied in November did not injure creeping bentgrass.

Optimum germination of fringed sagebrush (Artemisia frigida Willd.) occurred at alternating temperatures of 10 to 20 C. Seeds were able to germinate (15%) in NaCl concentrations of 5000 ppmw. Light was important in seed germination; however, its absence could be overcome by adding 30 ppmw GA3 (gibberellic acid) to the germination medium. Optimum pH for germination was between 5.8 and 7.0. Depth of planting influenced seedling emergence; the greatest emergence occurred when seeds were planted on the soil surface; emergence was lower when seeds were buried at any depth in the soil. Osmotic potentials of −13 bars and greater reduced germination, but 6% of the seeds germinated at −15 bars. Fringed sagebrush seedlings tolerated average plant water potentials of −10 to −19 bars and died when water potentials were decreased to −22 bars. Mature fringed sagebrush plants were capable of producing from 16500 to 190000 seeds/plant.

The use of plant growth regulators (PGRs) on winter wheat in the UK is a common practice. Significant yield benefits can be gained from its use. For the most efficient use of PGRs the rates of application must be matched to the crop canopy. The variation of crop growth was monitored during the spring growing season using vegetation indices derived from satellite imagery. Application rates of PGRs were matched to changes in biomass as measured by the imagery. Final yields were measured using a GPS combine yield meter. The variable application showed an average yield benefit of 0.4 t/ha over the uniform full recommended application rate.

Fall applications of fenarimol on hybrid Bermudagrass (Cynodon dactylon × C. transvaalensis) provide effective preemergence Poa annua (L.) control and suppress Ophiosphaerella spp. pathogens; however, concerns exist for turf injury and root growth restrictions. Two 60-d greenhouse studies were conducted to evaluate the effects of fenarimol at 0, 1.6, and 3.2 kg ai/ha per 30 d with and without trinexapac-ethyl (TE) at 0.017 kg ai ha/15 d on ‘TifEagle’ Bermudagrass. Turf color was enhanced by TE 14 d after initial treatment (DAIT) and was continually superior throughout the experiment. Fenarimol at 3.2 kg/ha per 30 d decreased turf color 14 DAIT, but was similar to nontreated turf on all other observation dates. Increased fenarimol rates applied twice caused approximately 10% injury at 42, 49, and 56 d after treatment; however, injury was acceptable after initial and repeat applications. TE reduced clipping yield an average 39% from six sampling dates. Initial fenarimol applications (without TE) reduced clippings by 37% 20 DAIT and repeated applications reduced clippings 40, 50, and 60 DAIT. Increased fenarimol rate linearly decreased root mass for turf treated with and without TE; however, Bermudagrass receiving TE averaged 23% enhanced root mass 60 DAIT over all fenarimol rates. Bermudagrass receiving fenarimol at 0, 1.6, and 3.2 kg/ ha per 30 d with TE averaged 27, 24, and 16% higher root mass, respectively, compared to turf receiving fenarimol without TE. Treatments had no influence on root length. Results indicate that two consecutive fenarimol applications at 1.6 and 3.2 kg/ha per 30 d may cause minor injury to TifEagle Bermudagrass and restrict root growth. Repeated TE applications, however, could decrease injury from fenarimol and enhance rooting relative to fenarimol applied exclusively.

Understanding seed biology and onset of germination requirements is a key point for designing effective weed management programs. Gibberellins (GAs) are known to play a role in onset of germination of several species. Onset of germination often requires an increase in de novo GA content or an increase in sensitivity to GAs. Reduced germination of seeds incubated in solutions containing compounds that inhibit GA synthesis provide evidence that GAs are required to trigger germination. Trinexapac-ethyl (TE), a GA synthesis inhibitor, is frequently used as a plant growth regulator in crop production. However, to the best of our knowledge, TE has not been used to study the requirement of GAs in onset of germination. Germination studies were conducted using seeds of artichoke thistle and common teasel under a range of TE concentrations (0 to 500 μM TE), a combined solution of 125 μM TE + 100 μM GA3 for artichoke, and 250 μM TE + 100 μM GA3 for common teasel. Germination tests were conducted at 20/10 C (12-h thermoperiod) in darkness for artichoke and at constant 15 C with 12 h of light for common teasel. Germination of artichoke in 125 μM TE was reduced to 47% when compared with the check (95%), but the combined TE + GA3 solution maintained germination at 84%. Germination of common teasel in 250 μM TE was reduced to 10% when compared with the check (91%), and the combined TE + GA3 solution increased germination to 63%. These results demonstrate the utility of TE to study the role of GAs in onset of germination. This novel use of TE is a valuable option to study germination requirements of weed species, and therefore contributes to the design of weed management programs.

Although seed dormancy of temperate legumes is well understood, less is known about it in species that grow in subalpine/alpine areas. This study investigated dormancy and germination of four Vicia species from the Tibetan Plateau. Fresh seeds of V. sativa were permeable to water, whereas those of V. angustifolia, V. amoena and V. unijuga had physical dormancy (PY). One year of dry storage increased the proportion of impermeable seeds in V. angustifolia, but showed no effect on seed coat permeability in V. amoena or V. unijuga. Seeds of all four species also had non-deep physiological dormancy (PD), which was especially apparent in the two annuals at a high germination temperature (20°C). After 1 year of storage, PD had been lost. The hydrotime model showed that fresh seeds obtained a significantly higher median water potential [Ψb(50)] than stored seeds, implying that PD prevents germination in winter for seeds dispersed without PY when water availability is limited. After 6 months on the soil surface in the field, a high proportion of permeable seeds remained ungerminated, further suggesting that PD plays a key role in preventing germination after dispersal. Addition of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis, evened-out the differences in germination between fresh and stored seeds, which points to the key role of ABA biosynthesis in maintaining dormancy. Further, fresh seeds were more sensitive to exogenous ABA than stored seeds, indicating that storage decreased embryo sensitivity to ABA. On the other hand, the gibberellic acid GA3 increased germination rate, which implies that embryo sensitivity to GA is also involved in seed dormancy regulation. This study showed that PY, PD or their combination (PY+PD) plays a key role in timing germination after dispersal, and that different intensities of dormancy occur among these four Vicia species from the Tibetan Plateau.

The contents of the cytokinins zeatin (Z), zeatin riboside (ZR), and isopentenyladenine (IPA), the combined contents of gibberellins1 + 3 (GA), and the contents of indoleacetic acid (IAA) and abscisic acid (ABA) were measured during the development of the desiccation-sensitive seeds of Avicennia marina (Forssk.) Vierh. During the stage of histodifferentiation the amounts of these plant growth regulators (PGRs) were measured on whole fruits. During the phase of seed growth and reserve accumulation measurements were made on the embryonic axis, cotyledons and pericarp separately. Patterns in the amounts of PGRs present during histodifferentiation were similar to those reported for desiccation-tolerant seeds and it suggested that this process is under similar ‘hormonal’ control in A. marina as in orthodox seeds. Very high contents of cytokinins, particularly ZR, were present in both axes and cotyledons during reserve accumulation. This is thought to be related to the nature of the reserves accumulated (soluble sugars), rather than to the phenomenon of desiccation sensitivity. With the exception of ABA, embryonic contents of PGRs were relatively high at seed shedding, consistent with the rapid germination of this highly recalcitrant seed. ABA contents in the embryo were low during reserve accumulation, but concentrations in the pericarp increased throughout this development stage. ABA in the perticap could act to prevent precocious germination. The low concentrations of ABA in the embryo could be related to the desiccation-sensitivity of the seeds of A. marina.