was to determine if increasing the N content of fertilizers applied to transplanted container-grown areca palm and chinese hibiscus plants could accelerate the rate of establishment without exacerbating K and/or Mg deficiencies. Materials and methods
Chinese hibiscus ( Hibiscus rosa-sinensis L.) or tropical hibiscus is extensively planted as a flowering pot plant worldwide and as a flowering shrub throughout tropical regions. Hibiscus rosa-sinensis has not been reported from the wild and is
Mefluidide was applied as a foliar spray to the point of runoff to plants of Hibiscus rosa-sinensis L. ‘Pink Versicolor’ at 0, 500, 1000, 2000, 4000, and 8000 mg/liter. Mefluidide treatment increased lateral branching, but inhibited the length of lateral growth and plant height as compared to untreated controls. Tip necrosis of young, expanding leaves was seen at the lowest mefluidide concentration, and increased to the point of severe defoliation of plants at the highest concentration. Mefluidide delayed flowering, but increased the number of flower buds produced. In a 2nd experiment, single and double spray applications of 0, 100, 200, 400, and 800 mg/liter mefluidide were evaluated in comparison to hand-pinching the plants. Both pinching and mefluidide application increased the number of lateral shoots, compared to an untreated control. In contrast to pinched plants, mefluidide treatment inhibited the average length of the lateral shoots. Double applications of mefluidide inhibited plant height, lateral shoot number, and shoot length, as compared to single applications. Treatment with 10 mg/liter gibberellic acid following mefluidide applications was ineffective in reversing the effects of mefluidide on hibiscus growth. Chemical name used: N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide).
. Also, another dicot species, chinese hibiscus, was included and no pour-through soil extractions were performed at week 26. Natural rainfall during this experiment was about 46 inches. All other procedures were identical to those used in Expt. 1
Succinic acid-2,2-dimethylhydrazide (SADH) was ineffective but (2-chloroethyl)trimethylammonium chloride (chlormequat) and α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol) retarded growth of several cultivars of the Chinese hibiscus (Hibiscus rosa-sinensis Linn.) inducing shorter internodes and more and earlier flowering during summer months. (2-Chloroethyl)phosphonic acid (ethephon) also reduced the length of terminal snoots, but reduced flowering and stimulated the growth of lower axillary shoots of unpruned plants.
In two experiments, chinese hibiscus (Hibiscus rosa-sinensis), bamboo palm (Chamaedorea seifrizii), areca palm (Dypsis lutescens), fishtail palm (Caryota mitis), macarthur palm (Ptychosperma macarthurii), shooting star (Pseuderanthemum laxiflorum), downy jasmine (Jasminum multiflorum), plumbago (Plumbago auriculata), alexandra palm (Archontophoenix alexandrae), and foxtail palm (Wodyetia bifurcata) were transplanted into 6.2-L (2-gal) containers. They were fertilized with Osmocote Plus 15N-3.9P-10K (12-to14-month formulation) (Expt. 1) or Nutricote Total 18N-2.6P-6.7K (type 360) (Expt. 2) applied by either top dressing, substrate incorporation, or layering the fertilizer just below the transplanted root ball. Shoot dry weight, plant color, root dry weights in the upper and lower halves of the root ball, and weed shoot dry weight were determined when each species reached marketable size. Optimal fertilizer placement method varied among the species tested. With the exception of areca palm, none of the species tested grew best with incorporated fertilizer. Root dry weights in the lower half of the root ball for chinese hibiscus, bamboo palm, and downy jasmine were greatest when the fertilizer was layered and root dry weights in the upper half of the root ball were greatest for top-dressed chinese hibiscus. Weed growth was lower in pots receiving layered fertilizer for four of the six palm species tested.
Dark storage of Chinese hibiscus (Hibiscus rosa-sinensis L. cv. Brilliant Red) for 5 days to simulate shipping promoted flower bud abscission. Less developed flower buds (<30 mm) were more susceptible than developed buds to dark-storage-induced abscission. Removal of mature buds (>30 mm) before dark storage reduced subsequent abscission of younger, less developed buds. Plants grown under low irradiance conditions (500 µmol·s–1·m–2 PPF) abscised more flower buds in response to dark storage than those grown in high irradiance (980 µmol·s–1·m–2 PPF). These results indicate factors that decrease the availability and partitioning of photosynthates to immature flower buds increase the incidence of abscission.
Boron (B) tolerance of 25 ornamental shrub species was determined in large, outdoor sand cultures. Tolerant species such as Natal plum (Carissa grandiflora (E. H. Mey.) A. D. C.), Indian hawthorn (Raphiolepis indica (L.) Lindl.), Chinese hibiscus (Hibiscus rosa-sinensis L.), oleander (Nerium oleander L.), Japanese boxwood (Buxus microphylla Siebold and Zucc.), bottlebrush (Callistemon citrinus (Curtis) Stapf), ceniza (Leucophyllum frutescens (Berland.) I. M. Johnst.), and blue dracaena (Cordyline indivisa (G. Forst) Steud.) were affected little, if at all, by 7.5 mg B/liter in the irrigation water. Sensitive species like yellow sage (Lantana camara L.), juniper (Juniperus chinensis L.), Chinese holly (Ilex cornuta Lindl. and Paxt.), Wax-leaf privet (Ligustrum japonicum Thunb.), laurustinus (Viburnum tinus L.), thorny elaeagnus (Elaeagnus pungens Thunb.), xylosma (Xylosma congestum (Lour.) Merrill), photinia (Photinia ☓ Fraseri Dress.), and Oregon grape (Mahonia aquifolium (Pursh) Nutt.) were severely damaged or killed by 7.5 mg B/liter and moderately damaged by 2.5 mg B/liter in the irrigation water. B tolerance and B accumulation in the leaves were not correlated and no correlation was found between B tolerance and salinity tolerance.
Insect growth regulators, which are primarily used to kill the larval stages of certain insect groups, have indirect effects on the adult stage of whiteflies. In this study, we assessed the effect of the insect growth regulator novaluron (Pedestal) on the reproduction of silverleaf whitefly (Bemisia argentifolii). Two experiments were conducted by exposing adult female silverleaf whiteflies to the low [0.47 mL·L-1 (6 floz/100 gal)] and high [0.63 mL·L-1 (8 floz/100 gal)] label-recommended rates of novaluron. There was also an untreated control. Infested plants [mist flower (Eupatorium coelenstinum) and transvaal daisy (Gerbera jamesonii) for Expt. 1 and Expt. 2, respectively] containing adult female silverleaf whiteflies were sprayed with novaluron using a carbon dioxide (CO2) backpack sprayer. Plants were immediately placed into cages covered with antivirus insect screening. After 24 hours, six adult female silverleaf whiteflies were aspirated from the treated plants, and immobilized with CO2 before being placed onto untreated plants [transvaal daisy for Expt. 1, and rose-of-china (Hibiscus rosa-sinensis) for Expt. 2]. Three munger cells containing two adult female silverleaf whiteflies per cell were attached to leaves of each of the untreated plants. The number of live and dead eggs, and live nymphs per plant was assessed 4 and 8 days after treatment (DAT). In Expt. 1, the low rate of novaluron significantly reduced egg viability compared to the untreated control based on live nymphal counts 8 DAT. In Expt. 2, both rates of novaluron significantly reduced egg viability compared to the untreated control, based on live nymphal counts and number of dead eggs 8 DAT. The results from this study indicate that novaluron negatively affected female silverleaf whitefly reproduction by reducing egg viability, which may decrease the number of silverleaf whiteflies produced during a cropping cycle. This is an important long-term pest management strategy that may reduce the number of insecticide applications and decrease labor costs.