Abstract
Antitranspirants (‘Vapor Gard’ and ‘Wilt Pruf’) effectively controlled powdery mildew on Hydrangea macrophylla Thunb. and Lagerstroemia indica Nana. A 2% antitranspirant emulsion was sufficient to suppress the pathogen’s development without causing visible phytotoxic effect or plant growth inhibition. The antitranspirants were as effective, and in some cases more effective (‘Vapor Gard’), than the systmic triazole fungicide ‘Tilt’ in controlling the disease. Hydrangea and dwarf Lagerstroemia (crapemyrtle) are grown commercially as flowering pot plants. Disease-free plants are required. Powdery mildew (Erisiphe polygoni DC) often causes severe damage on greenhouse-grown hydrangea. This fungus usually appears 1st on the lower leaf surface, where it produces a white, loose, cottony mycelium. Yellowish or purple-white blotches with mycelium also can be observed on the upper surface of the leaf. When the disease develops under favorable environmental conditions, the symptoms cover not only the entire leaf surface but also the bud clusters and flowers (11). Various fungicides control powdery mildew under greenhouse conditions.
The repellency and toxicity of a petroleum-based proprietary horticultural oil, Sunspray 6E Plus, was tested against the greenhouse whitefly, Trialeurodes vapor-ariorum (Westwood), on greenhouse-grown chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitamura cv. Iceberg]. A 2% (v/v) aqueous spray repelled adult whiteflies for at least 11 days after spraying and it was toxic to newly hatched and third stage larval whiteflies. No phytotoxicity was observed when four weekly sprays of 1%, 2%, and 4% oil were applied.
Abstract
Two experiments were conducted to determine if one-year-old field-grown Cornus florida L. seedlings could be transplanted successfully after leafing out. Survivability was improved with 100% defoliation at the time of planting. Vapor Gard used as a shoot dip and a whole plant dip had little positive effect. Root dips of a starch-based polymer and a peat and water slurry were not beneficial.
Abstract
Field measurements of leaf water potential were made on ‘Valencia’ orange trees subjected to varying degrees of soil water availability. During the night, leaf water potentials were reasonably well correlated with tensiometer estimates of soil matric potential. During the day, however, leaf water potentials were unrelated to matric potential because plant water balance was influenced by other factors in the shoot and root environments, including vapor pressure deficit, leaf diffusion resistance, and soil temperature.
Abstract
The overwintering of evergreens without irrigation in plastic structures was best accomplished in a house oriented in a north-south direction and covered with milky polyethylene. Dehydration of evergreens in a structure covered with clear polyethylene and oriented in an east-west direction was attributed to high vapor pressure gradients that occurred in clear days. Evergreens overwintered in structures covered with clear polyethylene should be inspected periodically and irrigated as necessary to prevent desiccation.
Abstract
Wine grape (Vitis vinifera L.) vineyards in much of the desert Southwest are frequently exposed to intense solar radiation, high vapor pressure deficits, and high air temperatures. Although wine grape production in this region has increased during recent years, the harsh environment often results in growth conditions that may be suboptimal for photosynthesis and other plant processes, ultimately affecting fruit yield, wine color, and acidity.
Abstract
Early winter flowering of Alstroemeria ‘Regina’ plants was accomplished by a long-day, high-pressure sodium vapor lamp (HPS) treatment before the low 5°C temperature induction treatment. This HPS treatment predisposed the plants to respond to a subsequent long photoperiod treatment during winter. Winter generative shoot yield was increased by 35% through the use of HPS pretreatment. Stem length increased as the duration of the HPS treatment prior to cold induction increased.
Abstract
Mechanically harvested fruits of A-5344 and ‘Earlibelle’ strawberry (Fragaria × ananassa Duch.) were stored at 24°C for 72 and 120 hours in atmospheres containing acetaldehyde (Aa) with and without prior dipping in 0 to 1.5% acetaldehyde solutions. Aa atmospheres and a combination of atmospheres and dips were most effective in maintaining visual color, freedom from browning, and product acceptability of machine harvested strawberries for processing. Fruit stored in atmospheres containing Aa vapor increased in acidity by 72 hours.
Abstract
Antitranspirants (Exhalt 4-10, Vapor Gard, Wilt Pruf, and Folicote) were more phyto-toxic when applied to detached florets than to detached leaves of hydrangea (Hydrangea macro-phylla Thunb. cv. Improved Merveille). Transpiration was high from hydrangea flowers as well as leaves. Folicote applied to intact flowering plants at concentrations of 1.25–5.00% was effective in reducing transpiration 10–15% compared to untreated plants.
Abstract
Antitranspirant chemicals Clear Spray (200 ml/liter) and Vapor Gard (50 ml/liter) significantly increased stomatal diffusive resistance in cineraria (Senecio cruentus DC.) on hot days. Foliar applications of the antitranspirants were effective in reducing plant water stresses for a period of 4 weeks. These chemicals did not have a significant effect on stomatal diffusive resistance when no water stress occurred in the plants. Foliage sprayed with these chemicals was more attractive and plants required less watering to maintain vigorous growth.