cutleaf groundcherry and spiny amaranth represented 35% and 3% of weed cover, respectively. Yellow nutsedge represented less than 2% of the weed cover. Weed control and crop phytotoxicity ratings were collected at 1, 3, 7, 9, 11, 16, 21, and 28 DAIT (17
Charles L. Webber III, Merritt J. Taylor, and James W. Shrefler
Peter H. Dernoeden
Festuca species are being seeded into golf course roughs and natural or out-of-bound areas as alternative turfgrasses to replace perennial ryegrass (Lolium perenne L.) in the mid-Atlantic region. The tolerance of fine-leaf fescues to herbicides targeted for annual bluegrass (Poa annua L.) control, such as ethofumesate and prodiamine, is unknown. The objectives of this field study, therefore, were to assess the tolerance of `Rebel II' tall fescue (Festuca arundinacea Schreb.), and the fine-leaf fescue species `Reliant' hard fescue (Festuca longifolia Thuill.), `Jamestown II' Chewings fescue (Festuca rubra L. ssp. commutata Gaud.), and `MX 86' blue sheep fescue (Festuca glauca L.) to various rates, combinations, and times of application of ethofumesate and prodiamine. `Rebel II' was most tolerant of ethofumesate; however, sequential rates ≥0.84 + 0.84 kg·ha-1 reduced quality for 1 or more weeks and 2.24 + 2.24 kg·ha-1 caused unacceptable injury. Single applications of ethofumesate at rates of 0.56, 0.84, and 1.12 kg·ha-1, and sequential treatments of 0.56 + 0.56 and 0.84 + 0.84 kg·ha-1 reduced `Reliant' quality temporarily. Sequential treatments of high rates (i.e., 1.12 + 1.12 and 2.24 + 2.24 kg·ha-1), however, significantly reduced `Reliant' cover. `Jamestown II' was very sensitive to ethofumesate, but recovered from single applications of 0.56, 0.84, and 1.12 kg·ha-1; sequential applications (≥0.84 + 0.84 kg·ha-1) caused unacceptable injury, and rates ≥1.12 + 1.12 kg·ha-1 caused significant loss of cover. The cultivar MX 86 tolerated single applications of 0.56 to 2.24 kg·ha-1 of ethofumesate, but sequential treatments generally reduced quality to unacceptable levels. In one study, `Jamestown II' and `MX 86' were more severely injured when ethofumesate (1.12 or 2.24 kg·ha-1) was applied in October rather than in November. The fescues generally best tolerated a single, November application of ethofumesate at ≤1.12 kg·ha-1. Prodiamine (0.73 kg·ha-1) caused only short-term reductions in quality of `Jamestown II', but was generally noninjurious to the other fescues. Ethofumesate tank-mixed with prodiamine (0.84 + 0.36 or 1.12 + 0.73 kg·ha-1) elicited some short-term reduction in quality, but the level of injury was generally acceptable and injured fescues had recovered by spring. Chemical names used: [±]2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); N 3,N 3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridine-dicarbothioate (dithiopyr).
Patrick E. McCullough, Haibo Liu, and Lambert B. McCarty
Ethephon is an effective growth retardant for suppressing Poa annua (L.) seedheads in creeping bentgrass putting greens; however, ethylene induction may cause bentgrass leaf chlorosis, reduced rooting, and quality decline. Two greenhouse experiments investigated the effects of nitrogen (N) fertility and ethephon applications on `L-93' creeping bentgrass over 9 weeks. Ethephon was applied at 0, 3.8, and 7.6 kg·ha–1 a.i. per 3 weeks and N was applied at 4 and 8 kg·ha–1·week–1. Ethephon applications linearly reduced bentgrass quality on every weekly observation. Increased N rate to 8 kg·ha–1·week–1 improved turf quality about 10% to 20% and 10% to 30% from ethephon applied at 3.8 and 7.6 kg·ha–1 per 3 weeks, respectively. Increased N rate to 8 kg·ha–1·week–1 enhanced shoot growth 30% but reduced root mass and length 12% and 11%, respectively. After 9 weeks, ethephon reduced root length by about 30% and root mass about 35% at both rates. From nine weekly samples, ethephon reduced dry clipping yield 10% and 16% at 3.8 and 7.6 kg·ha–1 per 3 weeks, respectively. From 2 to 9 weeks after initial treatments, ethephon linearly increased leaf water content. Increasing N fertility effectively reduced bentgrass leaf chlorosis from ethephon; however, repeat applications of ethephon and increased N may restrict bentgrass root growth. Chemical names used: [(2-chloroethyl)phosphonic acid] (ethephon).
James E. Ells and Ann E. McSay
Growth chamber tests demonstrated that alfalfa (Medicago sativa L.) residue is toxic to cucumber (Cucumis sativus L.) seed germination and seedling growth. Ground alfalfa roots at 0.5% (w/w, dry weight) inhibited germination when added to the growing medium. Alfalfa roots at 0.5% were also toxic to pregerminated cucumber seed. However, cucumber seedlings grew normally if this same medium was watered and incubated for >1 day before planting. Alfalfa particle size in media influenced cucumber performance, with the intermediate size (1 to 2 mm) being lethal to cucumbers.
T.L. Creger and F.J. Peryea
Phosphate fertilizer additions to soils containing lead arsenate (LA) pesticide residues can increase As volubility. Apricot (Prunus armeniaca L.) rootstock liners were grown in nondraining pots containing Burch loam soil that received a factorial treatment combination: 1) LA enrichment [no added LA (-LA), and LA added at 138 mg Pb/kg and 50 mg As/kg (+LA)]; 2) fertilizer type [monoammonium phosphate (MAP) and its sulfur analog ammonium hydrogen sulfate (AHS)]; and 3) fertilizer anion rate (0-26.1 mol/m3 soil). Measured response variables were soil salinity and pH, plant biomass, and plant As and Pb concentrations. Both MAP and AHS increased soil electrical conductivity (EC) and decreased soil pH, with AHS usually being more salinizing and acidifying than MAP was at equivalent rates. Adding LA reduced shoot and root mass and increased As and Pb concentration in shoots and roots. Shoot and root mass were inversely related to soil EC in the -LA soil but not in the +LA soil. Adding MAP increased shoot and root As concentration in the +LA soil, but adding AHS had no effect. Fertilizer type and rate did not influence shoot As concentration or root Pb concentration in the -LA soil or shoot Pb concentration in either the +LA or -LA soil. Adding AHS to the +LA soil increased root Pb concentration. These results are consistent with a P-enhanced solid-phase As release mechanism, which consequently increases plant uptake of soil As. Phosphate amendment had no effect on soil Pb phytoavailability.
Thomas M. Kon, Melanie A. Schupp, Hans E. Winzeler, and James R. Schupp
Blossom thinning can confer significant benefits to apple growers, including increased fruit size and annual bearing. However, current blossom thinning practices can damage spur leaves and/or fruit. We evaluated the use of short duration forced heated air treatments [thermal shock (TS)] as a blossom thinning strategy for ‘York Imperial’. Using a variable-temperature heat gun, TS treatments were applied to solitary blossoms 24 hours after pollination. Effects of output temperature (five levels) and treatment duration (four levels) were evaluated using a completely randomized design with a factorial treatment structure. Short duration treatments (0.5 and 1.0 seconds) were ineffective for arresting pollen tube growth in vivo. TS temperature required to inhibit stylar pollen tube growth was inconsistent across years. In 2014, TS temperatures ≥56 °C inhibited pollen tubes from reaching the style base at 2.0 and 4.0 second durations. However, in 2015, TS temperatures ≥81 °C at 4.0 seconds prevented pollen tubes from reaching the style base. Inconsistent effects of TS across years were attributed to treatments being applied too late due to optimal conditions for pollen tube growth during the intervening 24-hour period after pollination. Excessive injury to spur leaf tissue was observed at temperatures higher than 84 °C and 70 °C (2.0 and 4.0 seconds, respectively). Pollen tube growth was reduced or arrested at temperature and duration combinations that caused minimal visible injury to spur leaves. Identifying and exploiting structural differences between apple blossoms and vegetative spur leaves may provide insight for the future development of TS or other attempts at developing selective thinning technologies.
Monoammonium phosphate (MAP) is a popular starter fertilizer in Pacific Northwest tree fruit orchards; however, its use on soils contaminated with lead arsenate pesticide residues can enhance As solubility, thereby increasing As phytoavailability. `Fuji'/EMLA.26 apple trees (Malus ×domestica Borkh.) were planted in Mar. 1992 on a lead arsenate—contaminated Cashmont gravelly sandy loam soil (HCl-extractable soil As range: 60-222 mg·kg-1) using in-hole starter fertilizer application of either MAP or ammonium sulfate at equivalent N and anion rates. In ensuing years, all trees received identical applications of ammonium nitrate only. Relative trunk cross-sectional area was inversely related to soil As concentration in the year of planting but not in subsequent years, and was independent of starter fertilizer treatment. Leaf and fruit As were positively related to soil As in all years. Leaf As was initially higher in the MAP-treated trees; however, this effect diminished over time and disappeared by 1995. Fruit As was independent of starter fertilizer treatment, and was substantially lower than the tolerance established for As in fresh produce. The experimental results indicate that MAP starter fertilizer can increase soil As phytoavailability to apple trees grown under field conditions; however, the effects on tree growth and food safety are insignificant.
Longyi Yuan, Yang Gao, and Deying Li
Petroleum-based spills on turfgrass often occur during lawn care maintenance. Damage caused by diesel and hydraulic fluid is particularly difficult to correct. The objective of this study was to compare the effectiveness of combining mulching with remediation for reseeding spilled areas in lawns. Diesel and hydraulic fluid were applied to plots at a rate of 15 L·m−2. Immediately after the spill treatments, two liquid humic amendments and an activated flowable charcoal were applied at a volume rate of 8 L·m−2, respectively, with tap water/dishwashing detergent used as a control. Nitrate nitrogen was added to each remediation treatment to facilitate remediation. The spilled areas were reseeded with perennial ryegrass (Lolium perenne) and then mulched with biochar, peat pellets, and paper pellets, respectively. At 6 weeks after seeding, humic amendment 1 and activated charcoal showed better turf quality than humic amendment 2. Peat pellet mulching presented better turf quality than other mulching methods. Reseeding perennial ryegrass and mulching with peat pellets after remediation with either humic amendment 1 or activated charcoal resulted in acceptable turf quality 6 weeks after diesel and hydraulic fluid spills. Therefore, this reestablishment method is recommended as a practical way to deal with diesel or hydraulic fluid spills in cool-season turfgrasses.
Hisashi Kato-Noguchi and Yukitoshi Tanaka
The allelopathic potential of Citrus junos Tanaka waste from food processing industry after juice extraction was investigated under laboratory conditions. C. junos waste powder inhibited the growth of roots and shoots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), crabgrass (Digitaria sanguinalis L.), timothy (Phleum pratense L.) and ryegrass (Lolium multiflorum Lam.). Significant reductions in the growth of roots and shoots were observed as the powder concentration increased. The concentration of abscisic acid-β-d-glucopyranosyl ester (ABA-GE) in C. junos waste was determined to be 17.9 mg · kg–1 dry weight. Its concentration in C. junos waste appears to account mostly for the observed inhibition of tested plant seedlings. These results indicate that C. junos waste is allelopathic with potential for use in agriculture to suppress weed emergence, which should be investigated further in the field.