From MSU Extension:
Most greenhouse employees know that greenhouse sanitation is critically important to managing pests in the production environment. However, when incoming plant material containing pests is planted in the propagation house, even the cleanest greenhouse can turn into a problem. This is because the propagation environment is ideal for many diseases to develop and you may find yourself propagating the disease rather than the plant.
Michigan State University Extension recommends that the first step to keep this from happening is to purchase high quality certified pest-free stock whenever possible. You may even want to visit your plant supplier to see their sanitation program before purchasing from them. While the initial investment in purchasing high quality propagules may seem more expensive than other sources, consider the cost of not doing so. Receiving inexpensive and potentially low quality plants in the beginning of the season costs more by the end of the season because of increased management costs, lower crop quality, and lost sales revenue. In addition, your reputation may be tarnished which may influence next year’s sales.
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