Spotlight

in HortTechnology

WEED MANAGEMENT IN APPLE PRODUCTION

Derr (p. 11) summarizes the impact of weeds on apple tree growth and yield, and discusses orchard weed control systems. Weeds compete with fruit trees for water, nutrients, light and pollination by insects. Weed control practices can impact rodent populations, and insect and disease management. Weeds are generally controlled within the row using herbicides, while grass sod is often used in row middles for erosion control. Results from a survey of the major apple-producing states lists application rate and use pattern for the most frequently applied preemergence and postemergence herbicides.

BLACK-EYED SUSAN FROM DIFFERENT SEED SOURCES EVALUATED

A commercial Texas selection, a central Florida selection, and a northern Florida ecotype of black-eyed susan were evaluated at four low-fertility sites in Florida during the 1998 growing season. Differences in growth and flowering observed by Norcini et al. (p. 26) were mainly affected by the location of the evaluation site rather than the seed source. Although the Texas selection was the showiest in flower, the central Florida selection and northern Florida ecotype were better able to survive the low input conditions in which these plants were grown.

COMMERCIAL MIXES AMENDED WITH COMPOST PRODUCE MARKETABLE GOLDEN SHRIMP PLANTS

The increased use of peat as an organic amendment for containerized nursery production is challenged by economic and environmental pressures. Wilson et al. (p. 31) evaluated waste products as potential alternatives to peat. They found that either peat- or coir-based media amended with 25% or 50% compost produced golden shrimp plants comparable in growth, size, and color to plants grown in standard, commercial soilless mix. Higher volumes of compost (75% and 100%) produced marketable plants, but of smaller sizes.

GROWTH STIMULANTS ARE INEFFECTIVE ON SHORT-DAY ONIONS

Several growth stimulants have been marketed to Vidalia onion growers in southeastern Georgia with the promise of increasing bulb size and yield. In a 3-year study, these products were ineffective (Boyhan et al., p. 38). None of the tested products had any effect on bulb size or yield. However, in one year only, three of the products, a humic acid/micronutrient mix and two different formulations of cytokinin, increased the percent of marketable onions after 4.5 months of controlled atmosphere storage.

OPPORTUNITIES FOR NO-TILL IN CALIFORNIA

Furrow irrigation has been seen as a limitation to the adoption of no-till vegetable production systems. In experiments using off-season cover crops as mulches, Herrero et al. (p. 43) demonstrated that no-till systems might be feasible for processing tomato production in California's central valley. Although tissue nitrogen content was higher in the conventionally tilled system, no differences in yields were observed between conventional and no-till plots. Additionally, there was suppression of early weed growth exerted by some of the mulches. This may provide an advantage to growers seeking to reduce agrichemical inputs.

ROOT PRUNING PIN OAK LINERS AFFECTS GROWTH AND ROOT MORPHOLOGY

Harris et al. (p. 49) report that root pruning only the developing radicle of pin oak seedlings did not affect the total root length, but the number of main lateral roots increased as shallowness of pruning increased. Producing liners in bottomless containers root pruned all roots when they reached the substate:air interface. The height of the original container affected growth when seedlings were planted in containers up to 2-gal size. The largest plants were originally grown in 4-inch containers, the smallest in 2-inch containers, and intermediate in 6-inch and 8-inch-tall containers.

TRANSPLANT PRODUCTION REGION INFLUENCES EARLY SEASON STRAWBERRY PRODUCTION IN FLORIDA

Geographical location of strawberry transplant production has been found to influence crop performance in central Florida; however, this influence varies with cultivar. Over 50% of Florida's 6,000 acres of strawberries are currently planted with `Sweet Charlie.' Stapleton et al. (p. 61) report that `Sweet Charlie' plants from southern-latitude sources produced significantly less fruit in December and the greatest volume of fruit in February, when compared to plants from northern and mid-latitude sources. Early-season production is critical to profitability of Florida strawberries. This study also observed that the types of foliar diseases which may be introduced on transplants varies with plant source region.

FIELD-GENERATED SOIL-WATER CHARACTERISTIC CURVES FOR TROPICAL ORCHARDS IN TRENCHES

Capacitance sensors and tensiometers were used in the field to generate soil-water characteristic curves for star fruit and avocado orchards in trenched calcareous soil (Núñez-Elisea et al., p. 65). Sensors and tensiometers were placed at 10-cm and 30-cm soil depths. Roots in trenches concentrated in the top 10-cm soil layer. Soil at 30-cm depth had a high content of rock fragments, which affected tensiometer readings. Curves for the 10-cm soil depth can be used to determine parameters needed for irrigation scheduling by techniques such as the water budget method.

PERFORMANCE OF STRAWBERRY CULTIVARS ON FUMIGATED AND NONFUMIGATED SOIL IN FLORIDA

A major reduction in fruit yield occurred when plants of several strawberry cultivars were grown on soil that had not been fumigated prior to planting, but was essentially free of lethal pathogens (Chandler et al., p. 69). Plants of all cultivars were similarly affected by the nonfumigated soil environment, and produced only 54% and 68% of the yield obtained from the plants grown in soil fumigated with methyl bromide in 1995 and 1996, respectively. The average fruit weight from plants grown in nonfumigated soil was also reduced, compared to that of plants grown in fumigated soil.

ZINNIA CULTIVARS MORE PRONE TO ALTERNARIA BLIGHT AND BACTERIAL LEAF AND FLOWER SPOT THAN POWDERY MILDEW

Powdery mildew is the foliar disease most associated with zinnia, but a disease resistance study of 57 varieties by Gombert et al. (p. 71) found that alternaria blight and bacterial leaf and flower spot are more likely to damage or kill plants. In the17-week study, only 11 cultivars were rated acceptable for the landscape at week 10; by week 17, all were unacceptable. Zinnia appears to be an acceptable choice for short-term landscape color (10-12 weeks).

UCC-C4243 DESICCATES POTATO VINES

Growers find diquat to be an unsatisfactory chemical desiccant of potato vines due to poor effects on stem tissue. Pavlista (p. 86) evaluated a new herbicide, UCC-C4243, as a replacement for diquat in field studies using the chipping potato `Atlantic.' UCC-C4243 improved leaf and stem desiccation, and suppression of regrowth. Single and split applications were equally effective. Tuber skin set was promoted by all treatments. Specific gravity was not lowered by UCC-C4243 and yields were not affected

IMPROVING GROWTH AND UNIFORMITY OF SWEETPOTATO PLANTLETS USING A FORCED VENTILATION MICROPROPAGATION SYSTEM

In conventional micropropagation, plantlets are cultured on a media containing sugar in relatively small culture vessels and at low light intensities. Conventional culture vessel closures restrict the gas exchange between the inside and outside of the culture vessel. Heo et al. (p. 90) developed a forced ventilation micropropagation system for growing plants without sucrose on a large scale. Increasing the forced ventilation rate during the culture period with air distribution pipes in the culture vessel resulted in uniform spatial distributions of air current and CO2 concentration, which, subsequently, increased growth uniformity of plantlets.

EFFECTS OF FORCED VENTILATION ON CARBOHYDRATE STATUS OF MICROPROPAGATED SWEETPOTATO PLANTLETS

Eliminating sucrose from tissue culture media reduces both cost and the potential of contamination, which may facilitate the success of large-scale operations. Wilson et al. (p. 95) found that supplying forced CO2 at varying rates effects the carbohydrate status of plants. Sweetpotato plantlets were grown in vitro without sugar (photoautotrophically) for 12 days in a forced ventilation system designed with air distribution pipes for uniform spatial distributions of CO2 concentration. Low air exchanges in the vessel correlated with decreased net photosynthetic rates, decreased total soluble sugars, and decreased starch, which may effect ex vitro performance.

INDOOR CONTROLLED-TEMPERATURE STRATIFICATION OF NORTH AMERICAN GINSENG SEED

Traditionally, ginseng seed harvested in August or September, is placed outdoors in a wooden stratification box for about 12 months and then direct seeded into raised beds. Seeds germinate the following spring, some 18 to 22 months after seed harvest. Premature seed germination and disease spread in the box have been linked to the seed stratification process. Proctor et al. (p. 100) report that indoor, controlled-temperature stratification of ginseng seed was an acceptable alternative to outdoor stratification. This method allowed control over the environment and easier seed handling, avoided premature seed germination, and may have application in spring seeding.

FUNDAMENTAL CHANGES OBSERVED IN THE U.S. PECAN INDUSTRY

Wood (p. 110) reports a trend toward industrialized agriculture in the U.S. pecan industry that was associated with the declining dominance of the southeastern U.S. (although Georgia is increasing), and the increasing importance of production from southwestern states. These shifts were partially linked to price variations, production efficiency, and degree of biennial bearing. Eighty percent of year-to-year variation in national average wholesale price was associated with supply at beginning of the season, size of current crop, and the price of walnuts.

OPEN-POLLINATED AND HYBRID ONION VARIETIES COMPARED

For many vegetable crops, hybrid varieties are reported to outperform comparable open-pollinated (OP) varieties. Cramer (p. 119) compared hybrid and OP onion varieties when grown in New Mexico for 2 years. In general, hybrid varieties produced larger plants with more leaves than OP varieties; however, bolting and disease resistance, marketable bulb yield, and bulb size were comparable between hybrid and OP varieties. In New Mexico, growers can plant OP onion varieties that perform comparably to and may cost less than hybrids.

SMALL-SIEVE, SNAP BEAN CULTIVARS PERFORM WELL IN TENNESSEE

Eleven small-sieve, snap bean cultivars were evaluated in trials in Tennessee by Mullins and Straw (p. 124). Most cultivars had excellent plant and pod characteristics, and were well adapted to mechanical harvest. Pod color and sieve size varied considerably with cultivar. `Carlo' and `Minuette' were among the most productive cultivars, but pods of these cultivars were relatively large.

INSTRUCTOR GUIDE FOR STUDYING THE AMERICAN STANDARD FOR NURSERY STOCK

Schuch (p. 128) describes an exercise to familiarize students with the American Standard for Nursery Stock (ASNS). The exercise is applicable to laboratory instruction and extension or accreditation courses where learners are introduced to ASNS. Immature ornamental plants in a landscape or nursery are used to introduce students to the relationship of root ball or container size to shoot dimensions recommended by the ASNS for various categories and types of ornamental plants. Two realistic situations are used to practice and apply the use of ASNS, and encourage active problem solving in informal groups.

HORTICULTURE STUDENTS EXCEL IN GRAPHICS AND DRAWING

A fundamental strength of the programs in horticulture and landscape architecture at Temple University is a core curriculum that includes graphics and design studios for horticulture students, and classes in woody and herbaceous plants for landscape architecture students. Hurley-Kurtz (p. 129) discusses the benefits of visual and graphic arts instruction in a horticultural curriculum, as a means of fostering creativity and “reading” the landscape; and describes the curricular sequence in a joint studio for horticulture and landscape architecture students. All classes and studio projects support an ecological, sustainable approach to the planning, design and maintenance of the land.

ECOLOGICAL LANDSCAPE DESIGN FUNDAMENTALS

There are growing employment opportunities in the landscape industry for well-trained, ecologically sensitive landscape designers. Hurley-Kurtz (p. 136) describes an approach to beginning design for horticulture and landscape architecture students at Temple University, where the emphasis is on teaching design process and principles within an ecological framework. Horticulture students learn the language and process of design. As graduates, they can be effective communicators and participants in the multi-disciplinary teams that now typically address issues associated with the design, construction, maintenance, and stewardship of the land.

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