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  • Author or Editor: R. S. Lindstrom x
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Abstract

Brassaia actinophylla Endl., Dieffenbachia maculata (Lodd) G. Don ‘Perfection’, Maranta leuconeura var. kerchoviana E. Morr., and Stromanthe amabilis (Linden) E. Morr. were grown in an organic potting medium at either 325 μE m−2s−1 (16.1 klx) or 9 μE m−2s−1 (0.7 klx). Brassaia and Dieffenbachia height and dry weight were unaffected by NaCl levels with potting medium solution electrical conductivity (EC) values ranging from 2.5 to 10.2 mmho/cm under low light or from 0.5 to 5.2 mmho/cm under high light levels. Maranta dry weight was reduced and leaf necrosis was increased at an EC value of 4.2 mmho/cm when compared to lower EC values under low light; under high light, leaf necrosis was greater at EC values of 2.7 and 4.3 mmho/cm than at 0.5 mmho/cm. At low light levels, Stromanthe dry weight, leaf count, and leaf necrosis were unaffected by NaCl level, but at high light levels, shoot dry weight was reduced at media EC values above 0.5 mmho/cm.

Open Access

Abstract

Rooted cuttings of poinsettia (Euphorbia pulcherrima Willd. ex. Klotzsch cvs. Annette Hegg Dark Red and Eckespoint C-1 Red) were grown under a 16-hour photoperiod in aggregate culture to determine the influence of NH4-N and NO3-N on plant growth. Plant height, number of nodes, and shoot dry weight were reduced with NH4 in comparison to NO3.NH4:NO3 combinations containing more than 50% (6 meq) NO3 produced superior growth. Stunting, leaf chlorosis and abscission, and stubby brown roots were observed on plants receiving any level of NH4 in the nutrient solution and increased in severity as the NH4 concentration increased. Inferior growth observed with the NH4 treatments was not due solely to the higher levels of Cl and SO4 in those solutions.

Open Access

Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.

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