Vegetable Disease Information Note 2 (VDIN-002)
Charles W Averre, Extension Plant Pathologist
Jean B. Ristaino, Research Plant Pathologist
Jonathan G. Shultheis, Extension Horticulturist
increased interest among greenhouse vegetable and herb growers in producing
crops with little or no input ("organic") of pesticides. Some
growers occasionally want to use fungicides and nematicides in minimal
amounts during emergency situations to reduce a disease. This information
note provides information on how to manage a greenhouse vegetable or herb
crop to avoid harsh ecological disruption of the environment and to avoid
or minimize losses due to plant diseases.
population densities in greenhouses are usually very high and closely
confined by the greenhouse walls, some virus diseases, foliar blights,
leaf spots, stem and fruit rots, root rots and other diseases can become
severe very quickly. The importance of using sound crop management practices
and integrated pest management (IPM) practices must be emphasized.
Most of the
steps described below are compatible with "organic culture".
In "organic culture" we assume that common sanitizers such as
soap, water, and bleach can be used. Occasionally, even under the best
management systems, a fungicide to reduce gray mold (Botrytis)
will be necessary if plant density is exceptionally high and temperatures
Use strict sanitation procedures for germinating seed and growing transplants. This should be done in a specially designated small, well screened, separate greenhouse. No other plants, including weeds, should be permitted in the plant propagation house.
Prior to setting transplants, the growing medium (soil, soil-less mix, or hydroponic solution) should be checked for nutrients, then monitored weekly for hydroponic culture or every two weeks for soil and soil-less mix culture until the crop has been harvested. Plant and soil samples should be taken according to directions provided by the laboratory and sent to the Agronomic Division, North Carolina Department of Agriculture, Raleigh, NC 27607 (located on Blue Ridge Rd., 919/733-2656) for plant nutrient and pH analyses. This is of prime importance when growing in hydroponic systems.
Maintain the relative humidity in the house as low as possible by:
Diagnose all problems promptly! These include diseases, insect, nutritional, and growth problems. See your county agent for assistance and for details on how to collect and send specimens to the Plant Disease and Insect Clinic at North Carolina State University.
Promptly remove all diseased leaves, fruits, or entire plants to avoid spread of disease. Discard debris in a paper bag in a compost pile for use in outdoor culti-vation. Do not reintroduce this compost into the greenhouse.
As soon as the crop is harvested sanitize the greenhouse by:
These procedures are recommended for all greenhouse vegetable and herb growers to minimize the risk of introducing plant pathogens, reduce disease severity if pathogens are present, and to lessen dependency on labeled fungicides and nematicides. Pesticides, including biological control agents that may be commercially available in the future, must be used exactly as stated on the current label; very few pesticides are labeled for food crops grown in greenhouses.
assistance with a specific problem, contact your local
Reformatted Dec. 2000 by Plant Disease and Insect Clinic