imazapic rates from 9 to 53 g⋅ha –1 provided 100% tall fescue inflorescence and vegetative growth suppression through 84 d after treatment (DAT), with ≤ 20% injury. Jeffries et al. (2017) reported similar findings, with imazapic suppressing inflorescence
Abbreviations: EC, electrical conductivity; ICP, inductively coupled agron plasma; PL, peat-lite; RGS, related growth suppression; RW, rockwool. 1 Graduate Research Assistant. Current address: Dept. of Horticulture, Collepe of Horticulture
excellent growth suppression compared with PB or FP but do not result in effective annual bluegrass suppression. Nevertheless, TE can induce seedhead suppression; therefore, it is considered a positive addition to PGR mixes for annual bluegrass suppression
expansion ( Bacon et al., 1998 ; Van Volkenburgh, 1999 ). Thus, the overall effect of ABA is shoot growth suppression and an increase in root-to-shoot ratio. The potential of ABA as a growth retardant has been studied for some vegetable transplants. For
Abstract
Paclobutrazol (ICI PP333), an inhibitor of gibberellin biosynthesis, suppressed early season number of berries but did not affect seasonal yield of field grown strawberry plants. Plant growth was greatly suppressed at all application rates. Petioles, peduncles, and pedicels were shortened with leaves and fruit tightly appressed to the crown. Green leaf color was intensified in all paclobutrazol treatments, but fruit color was not appreciably influenced. Runner suppression was obtained in mid-July field applications, but runners were not inhibited by August application. In the greenhouse, PP333 applied directly to the soil of potted plants was more effective than foliar applications in suppressing crown, leaf, and root growth. The degree of suppression generally was related to increasing the concentration of the chemical.
Abstract
Amidochlor at 2.24 to 3.36 kg a.i./ha provided excellent (90% or better) seedhead suppression of ‘Baron’ Kentucky bluegrass (Poa pratensis L.) and 80% to 90% seedhead suppression for ‘Pennlawn’ red fescue (Festuca rubra L.) turf. Although amidochlor provided excellent shoot growth reduction up to 42 days after treatment (DAT), the greatest shoot growth reduction was noted during 28 DAT. In general, turfgrass injury was within acceptable limits over the entire study period except during the 28-day period when unacceptable injury (32% to 64%) was noted. Quality of amidochlor-treated turfs was unacceptable 28 DAT. Quality improved significantly over time, and the quality ratings ranged from 7.0 to 8.5. Maximum shoot growth reduction (85% to 93%) as measured by fresh clipping weight occurred during the initial 28-day period and thereafter declined, followed by a stimulation of turfgrass growth (56 DAT). Chemical name used: N-[(acetylamino)methyl]-2-chloro-N-2,6(diethylphenyl)acetamide (amidochlor).
Technical grade prohexadione-calcium (93.2% a.i. P-Ca) applied to `Fuji'/M.9 trees in three applications in deionized water reduced shoot growth by 25%, but the addition of (NH4)2SO4 to P-Ca suppressed shoot growth by 47%. If P-Ca was mixed in well water (high in calcium salts), P-Ca did not suppress shoot growth at all. The commercially formulated prohexadione-calcium [Apogee: 27.5% P-Ca + 56.1% (NH4)2SO4 + 16.4% other proprietary additives] + Regulaid in well water (high calcium) was not as effective (reduced growth by 30%) as when additional (NH4)2SO4 was added (reduced growth by 53%), and if CaCl2 (used to control corking) was tank mixed with Apogee + Regulaid, the Ca++ interfered with the growth suppression of P-Ca. If (NH4)2SO4 was added at the same rate as CaCl2 (w/w), the Apogee growth suppression was completely restored (reduced growth by 50%). Choice (a commercial water conditioner that has (NH4)2SO4 in the formulation, among other ingredients) + Li-700, or (NH4)2SO4 + Silwet L-77, or (NH4)2SO4 + Silwet L-77 + Oil were among the most effective adjuvant combinations with Apogee. The addition of ethephon at 270 mg·L-1 improved the growth suppression of Apogee + (NH4)2SO4 + Regulaid. Solubor compromised the effectiveness of Apogee + Regulaid. Adjusting the pH of the Apogee + (NH4)2SO4+ Regulaid spray to either pH = 4 or pH = 9 did not affect efficacy. The combination of Apogee + (NH4)2SO4 + Regulaid caused increased fruit cracking of `Empire' fruit as compared to the control (7%), presumably due to increased absorption of P-Ca. Chemical names used: Prohexadione-calcium (P-Ca, 3-oxido-4-propionyl-5-oxo-3cyclohexenecarboxylate) formulated as BAS-125 (10% P-Ca); Apogee (27.5% P-Ca), or Technical 93.5% P-Ca); Regulaid (polyoxyethylenepolypropoxy-propanol, alkyl 2-ethoxethanol, and dihydroxy propane); Silwet L-77 (polyalkyleneoxide modified heptametyltrisiloxane, silicon surfactant), LI-700 (80%, phosphatidylcholine, methylacetic acid and alkyl polyoxyethylene ether); Superior Oil (Drexel Damoil 70-second delayed dormant spray oil); ethephon (2-chloroethyl phosphonic acid); Solubor (20.5%, Boron equivalent); captan (N-Trichloromethylthio-4-cyclohenene-1,2-dicarboximide).
To test the effect of soluble salts on the growth of New Guinea impatiens (Impatiens platypetala), `Selenia' was grown for 70 days in a soilless medium and irrigated with solutions of 20N-4.3P-16.6K at rates of 0.5, 1.0, 1.5, or 2.0 g·liter-1. A fifth treatment was no fertilization for the first 14 days, 0.5 g·liter-1 for the next 14 days and 1.0 g·liter-1 till finish. At 14-day intervals shoot dry weight and growth medium soluble salts were measured. By 42 days after planting, differences between treatments were statistically significant with respect to dry weight. Over a 70-day period, growth was greatest with 0.5 g·liter-1. The 1.0 g·liter-1 treatment caused a similar growth response. Plants in delay treatment responded similarly to 0.5 and 1.0 g·liter-1. Higher rates, 1.5 and 2.0 g·liter-1, caused growth suppression and resulted in soluble salts buildup in the growth medium. Soluble salts levels of 1.5 dS·m-1 and above suppressed early growth. Results show that during the first 42-56 days of growth, New Guinea impatiens are sensitive to soluble salts and levels over 1.5 dS·m-1 are cause for concern.
Abstract
Primocanes were sprayed after they reached about 18 cm in height with 4, 6-dinitro-o-sec-butylphenol (dinoseb) plus superior spray oil to kill the tops down to ground level. Additional treatments involved spraying after the second flush of growth reached 18 cm in height. Primocane suppression by this means increased yields by up to 70% over unsprayed plots. Plots of vigorous ‘Williamette’ raspberries (Rubus idaeus L.) were re-sprayed each year for 4 years and maintained the yield increase. A less vigorous ‘Sumner’ planting subjected to similar treatments did not develop adequate cane height and number after 2 or 3 sprays and yields the following year were greatly reduced. Berry size was sometimes increased. Most of the increased yields were due to greater numbers of berries. Primocane suppression had no effect on the number of berries on the upper laterals but greatly increased the numbers on laterals that developed from the middle and lower portions of the canes. The amount of carbohydrates per bud in dormant canes was reduced by dinoseb sprays applied the previous growing season.
In 1995, BAS-125W applied at 125 to 500 mg/liter 23 days after full bloom (AFB) to `Starkrimson Delicious'/MM 106 and MM111 reduced average shoot weight and length of the longest shoots in the top and scaffold limbs by 50% at the highest rate. The number of nodes on the lower 40 cm of each shoot was increased by 1.8 times by the growth retardant. The number of pruning cuts, pruning time, and pruning weight per tree was reduce by 30%, 20%, and 29%. Fruit diameter, color, soluble solids, starch, fruit weight, and fruit number per tree were not altered by BAS-125 W. Growth suppression appeared to be greater on trees with heavier crop loads. In 1996, BAS-125W applied at 250 mg/liter 8 days after full bloom was more effective than when applied 19 days AFB to `Starkrimson Delicious'/MM 106 and MM111. Multiple applications of two, three, and four sprays to the same trees at 3-week intervals further reduced shoot growth with each application. Four applications reduced shoot weight by 72%, shoot length by 60%, and basal shoot diameter by 25%, and the number of pruning cuts, pruning time, and pruning weight per tree was reduce by 75%, 55%, and 80%, respectively. Thinning activity of NAA, Sevin, or Accel was not affected by tank mixed sprays with BAS-125W when applied to Gala/M.27 trees 20 days AFB. Tank mixing BAS-125W with combinations of Vydate + Accel or Carbaryl + Accel + Oil did not alter fruit thinning of Fuji/M.27 (at 10 mm fruit diameter). In one experiment, BAS-125 may have potentiated thinning by ethephon and NAA 10 days AFB in another experiment. BAS-125 W sprays at petal fall + 1 and 2 weeks later significantly suppressed % infection by fireblight, Erwinia amylovora, in inoculated shoots. In addition, BAS-125W reduced canker length in the first-year growth in shoots inoculated 2 weeks after treatment.