appropriate dosage of cyanamide for citrus and to get initial data on effects on shoot flushing, cyanamide was applied 23 Dec. 1999, at concentrations of 0.125%, 0.25%, 0.5%, and 1.0% a.i. to 2-year-old potted plants of six different citrus types readily
Ed Stover, Youjian Lin, Xiaoe Yang, and Tripti Vashisth
David G. Hall and L.G. Albrigo
The need to manage insects that feed on foliar flush growth has increased in Florida citrus as a result of recent establishment of invasive plant diseases promoted by insects that develop exclusively on flush growth, notably Huanglongbing (citrus
Jer-Chia Chang and Tzong-Shyan Lin
from current assimilations in the leaf next to the inflorescence. Through investigating the effects of leaf age and location on gas exchange in ‘73-S-20’ litchi, Chang and Lin (2007) also reported that leaf photosynthesis on younger flushes and
L. Gene Albrigo
The recent infestation of Florida citrus by the Asian citrus leafminer required that more information be obtained about the time interval for a flush to expand and the leaf area contributed by flushes in seasons when leafminer populations are likely to increase and cause leaf area loss. Time for leaf and shoot expansion was determined for spring and summer flush. Leaf area contribution from previous-year and current flushes was determined by seasonal tagging and measuring leaf area for flush in frame areas of 1/4 m2 surface projected to the center of the tree. Flush of 1/3 m length required 30 days to expand from first leaf feathers to full expansion. Summer flush in 1994 was 40% to 45% of total leaf area. Spring and previous year's flush averaged 20% each. Fall flush contributed 5% to 12% to leaf area, more on young, low-bearing trees. Summer flush resulted in more canopy leaf area and previous year's flushes less leaf area than expected by the end of the growing season.
Yu-Chi Lee and Jer-Chia Chang
primordia, comprising leaf and floral primordia as a result of cool-temperature induction ( Batten and McConchie, 1995 ; Li, 2008 ). The flowering shoot of litchi has a characteristic of flush cycles, and the process of inflorescence initiation and flower
M.A. Nagao, E.B. Ho-a, and J.M. Yoshimoto
To study the vegetative flushing pattern of M. integrifolia (cvs. Keaau, Kau and Kakea) trees in Hawaii and determine when these vegetative flushes flower, trees were monitored for an entire year (1988), and shoots from these flushes were monitored for flowering during the 1988-89, 1989-90 and 1990-91 flowering seasons. Flushing occurred year-round but was most frequent during the spring-summer and fall months which coincided with the end of the flowering season and the period of fruit maturation. For all cultivars, sporadic flowering occurred in 1988-89 on shoots that were less than one year-old but was not always associated with the oldest shoots. Flowering in 1989-90 and 1990-91 was observed on a larger proportion of the shoots and occurred on shoots that had emerged throughout 1988. Flowering was most abundant on two year-old shoots (1990-91) and could occur on shoots that had flowered in the previous season (1989-90).
R.E. Gaussoin, J.A. Murphy, and B.E. Branham
A method for measuring soil water potential in field soils was adapted for use in turfgrass soils. The system uses tensiometers installed flush with the soil surface and permits a measuring depth as shallow as 2.5 to 5.0 cm. Water potential within a tensiometer was measured with a portable pressure transducer. Linear relationships between water potential measured with mercury manometers or vacuum gauge-equipped tensiometers and the pressure transducer were obtained (r2 = 0.99 and 0.97, respectively). The system accurately measures soil water potential of turfgrass soils, while permitting routine cultural practices to be performed.
Qinglong Zhang and Patrick H. Brown
In this study, we investigated the effectiveness of several Zn formulations applied at various times of the year in increasing Zn status of pistachio and walnut leaves. Formulations included inorganic and organic forms of Zn. Fall sprays was ineffective at supplying Zn to developing leaves even when very high rates (5000 ppm) were used. Late dormant and budbreak sprays were effective at supplying Zn to developing leaves and nuts only when extremely high rates (5000 ppm) were applied. Spring flush sprays were the most effective, while late spring and summer sprays were ineffective. The majority of the Zn applied remained in the epidermis of the sprayed leaves, which resulted in high Zn content of leaves but poor correction of Zn deficiency and little or no translocation of Zn to other plant parts. Many of the Zn formulations sprayed at spring flush at a rate of 1000 ppm effectively increased leaf Zn values by at least 10 μg–g–1. Addition of an appropriate organic acid to the spray solution and adjustment of pH to ≈4.5 improves leaf uptake and translocation of Zn. Addition of specific surfactants into the spray solution is also recommended. Use of N- and P-containing Zn spray formulations is less effective than sulfur-based sprays (i.e., ZnSO4). Significantly, there is little residual effect of foliar sprays (even at spring flush), indicating that consecutive sprays for several years are needed to maintain productivity in Zn-deficient regions.
Samuel Salazar-García, Luis E. Cossio-Vargas, Carol J. Lovatt, Isidro J.L. González-Durán, and María H. Pérez-Barraza
Several studies were undertaken in commercial nonirrigated `Hass' avocado orchards under the subhumid semiwarm subtropical climate of the state of Nayarit, Mexico, with the following objectives: 1) to determine the frequency and intensity of vegetative shoot flushes and their contribution to the production of floral shoots, 2) to quantify the effect of tree fruit load on the occurrence of vegetative shoot flushes during the year and the relationship between vegetative and reproductive shoot number during flowering, and 3) to determine the time when apical buds borne on the major vegetative shoot flushes reached irreversible commitment to flowering (floral determination) through the use of shoot defoliation and girdling. Data trees were selected in two orchards based on their current crop load. Four to five branches per tree were tagged, and the number and intensity of vegetative flushes that developed during 2 years, as well as the type of growth produced by apical buds of shoots of different ages, were recorded at the end of the winter bloom periods for two separate years, 1999 and 2001. In a separate experiment using a different set of trees, winter and summer flush shoots were defoliated (year 1) or defoliated and girdled (year 2) at different stages of bud development from September to January in each case. Four vegetative flushes occurred each year. The winter flush that emerged in Feb. 1998 made the greatest contribution to the 1999 winter bloom—76.5% of the shoots produced floral shoots. Contributions of the summer 1 (late July 1998), summer 2 (early Aug. 1998), and summer 3 (late Aug. 1998) flushes to flowering were intermediate. A total of 30.6%, 36.4%, and 19% of the shoots produced floral shoots respectively. All four vegetative flushes produced a similar number of vegetative shoots during winter bloom. Evaluation of the 2001 winter bloom for trees with high (>95 kg fruit/tree) and low (<70 kg fruit/tree) crops showed no effect of tree fruit load on the production of vegetative or floral shoots by winter or summer vegetative flushes. Irrespective of time of treatment (shoot defoliation and girdling) or shoot age, irreversible commitment to flowering of apical buds occurred by 15 Oct., and this stage was associated with an average of 27.5 chilling days (temperature, ≤19 °C) for both years. Buds irreversibly committed to flowering were closed and pointed, with partial senescence of bud scales. Anatomically, the buds showed a convex primary axis meristem and four secondary axis floral shoot meristems.
Charles F. Forney, Roger E. Rij, Ricardo Denis-Arrue, and Joseph L. Smilanick
The potential use of vapor phase hydrogen peroxide (VPHP) to prevent decay caused by Botrytis cinerea Pers. ex Fr. in table grapes (Vitis vinifera L.) was investigated. `Thompson Seedless' and `Red Globe' grapes, inoculated with Botrytis cinerea spores, were placed in polyethylene bags and flushed for 10 minutes with VPHP generated from a 30% to 35% solution of liquid hydrogen peroxide at 40C. Immediately after treatment, bags were sealed and held at 10C. Vapor phase hydrogen peroxide significantly reduced the number of terminable Botrytis spores on grapes. The number of terminable spores on `Thompson Seedless' and `Red Globe' grapes had been reduced 81% and 62%, respectively, 24 hours following treatment. The incidence of decay on inoculated `Thompson Seedless' and `Red Globe' grapes was reduced 33% and 16%, respectively, after 8 days of storage at 10C compared with control fruit. Vapor phase hydrogen peroxide reduced the decay of noninoculated `Thompson Seedless' and `Red Globe' grapes 73% and 28%, respectively, after 12 days of storage at 10C. Treatment with VPHP did not affect grape color or soluble solids content.