Browsing by Author "Lindstrom, Richard S."
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- Chemical pinching of Chrysanthemum x morifolium Ramat. with undecanolGarner, Jerry (Virginia Polytechnic Institute and State University, 1983)Concentrations between 5000 and 15000 mg/liter undecanol applied as foliar sprays were effective in pinching most varieties of chrysanthemum tested. Cultivars varied in their response. Subapical phytotoxicity increased with increasing concentrations and was generally more variable among cultivars than was the pinch response. Concentrations effective in pinching without subapical phytotoxicity resulted in plants similar to manually pinched plants with respect to height and number of branches. Studies conducted in the growth chamber and greenhouse indicate environmental factors exert a major influence on plant response to undecanol. In general, conditions which favor more rapid drying tended to decrease the number of plants pinched and reduce the number of plants showing subapical phytotoxicity. Comparing air temperature, air flow, relative humidity, and light (PAR), temperature was the single most highly correlated environmental variable with both pinching and phytotoxicity in the greenhouse study. Many of these variables are, however, highly interrelated with one another so that a change in one results in a change in others. Prediction equations using concentration and environmental variables were developed for pinching and phytotoxicity. Undecanol foliar sprays of 7500 mg/liter were nearly 100% effective in pinching two cultivars with minimal phytotoxicity when applied 9 to 18 days after planting. Pinching was significantly reduced in plants treated prior to 9 or later than 18 days after planting. Manually pinched plants were generally taller than chemically pinched plants treated the same day. Chemically pinched plants generally produced more branches than manually pinched plants. Day of treatment did not affect flowering of chemically pinched plants; however, chemically pinched plants tended to flower slightly later than manually pinched plants. Finished plants pinched chemically were comparable to those produced by manual pinching.
- Chemicals for the control of diseases of floral cropsLambe, Robert C.; Lindstrom, Richard S. (Virginia Cooperative Extension Service, 1980-12)The conditions under which many floral and foliage crops are produced, i.e., high humidity, low light intensity and frequent watering are favorable for the development 0£ fungal and bacterial diseases. If insects are uncontrolled in the greenhouse, viruses can become a major problem. Nematodes may be introduced on infected plant material or unsterilized soil. Sanitation in propagation and growing will reduce the incidence of disease. Soil-less culture, healthy plant material, clean containers and benches, and pathogen-free water are important. considerations. Plant culture on wire benches will avoid soil-borne pathogens. Most fungicides are protectants and require frequent re-application. Early correct identification of causal agents is important in preventing heavy disease losses and avoiding improper use oi pesticides.
- Effects of nitrogen source and level on the growth and composition of Sinningia speciosa LoddNolan, Sharon Lee (Virginia Polytechnic Institute and State University, 1982)Gloxinia (Sinningia speciosa Lodd.) seedlings were grown in 2 media to determine the maximum percentage N that can be supplied as NH₄ and the minimum concentration of a soluble complete fertilizer that can be applied without reducing plant quality under different light and temperature conditions. In one group of experiments, plants were supplied modified Hoagland's solutions in which the N source and level were varied. Shoot dry weight of gloxinias grown in an organic medium in the winter was lower with 100% NH₄ than with 100% NO₃ but was unaffected by N level, while in the fall shoot dry weight was lower with 100% NH₄ than with 0 or 50% NH₄, and was reduced at 16 rather than 8 meq N liter⁻¹. In the summer, shoot dry weight did not vary with N source or concentration when treatment solutions were collected and reused for 1 week. Flower bud count at harvest did not vary with N source in the winter but was reduced at 100% NH₄ in the fall and summer. Time to flower bud set was unaffected by N source, but was increased by applying 16 rather than 8 meq N liter⁻¹. In the winter, leaves of plants receiving 75-100% NH₄ were dark green early in the studies, but became chlorotic, twisted and quilted before plants matured; in the summer and fall these symptoms of NH₄ toxicity were absent. Leaf chlorophyll content was greater for plants grown in quartz sand when given 100% NH₄ rather than 100% NO₃. In related studies, gloxinias were treated at every watering with a soluble 20N-8.7P-16.7K fertilizer. Shoot dry weight was greater and time until flower bud set shorter at 200 than at 0, 400 or 600 ppm N in the summer; shoot dry weight and flower bud count were greater at 100 than at 200-400 ppm N in the winter. Days until flowering in the summer and days until bud set in the winter were unaffected by fertilizer levels. Tissue composition varied with N source and level and Ca(OH)₂ treatment although lime application did not affect any external plant characteristics.
- Insect control for commercial greenhouse and floral cropsWeidhaas, John A., Jr.; Schultz, Peter B.; Lindstrom, Richard S. (Virginia Cooperative Extension Service, 1981-01)Relatively few kinds of insects and related pests occur on greenhouse and floral crops, but they attack a wide range of plants and can be highly destructive. Many insecticide and miticide formulations are available to growers, but specific uses may be quite limited for any one and plants vary greatly in susceptibility to chemical injury. Your local Extension Agent may be able to help you or obtain the technical information you need.
- Propagating and growing disease free plantsLambe, Robert C.; Baldwin, Robert E.; Lindstrom, Richard S. (Virginia Polytechnic Institute and State University. Extension Division, 1975-03)Provides information for propagating and growing disease-free plants.
- Propagating and growing disease-free plantsLambe, Robert C.; Baldwin, Robert E.; Lindstrom, Richard S. (Virginia Cooperative Extension Service, 1980-04)Avoiding root rot in cuttings when propagating new plants