Disease's can be transferred many different ways. One of the most over looked ways that they can be transferred from one plant to another is through improper irrigation techniques. Overhead irrigation either by hand or automated systems allow for splashing water to spread the disease form one plant to another and so on until the whole crop has become infested with the disease.

Sub-irrigation systems such as Ebb and Flood benches and floors in the greenhouse offer a unique way for the disease to spread. When the benches or floors fill up with water the disease can get into the water and float or actively swim, depending on the type of disease, to the next potted plant. The disease can also run back into the collection pond and the next time the water is used for irrigation, the disease is introduced back into the greenhouse. Greenhouse growers and managers need to pay special attention to the crops that they are growing in these type irrigation systems and look for diseases all of the time to prevent excessive spread of the disease. Proper sterilization of the collection pond might be needed and the use of chemicals might be advised to kill any bacteria that is in the collection pond.

Propagation greenhouses run the risk of transferring the disease anytime they are not properly cleaning the cutting tools in between uses on different crops or between cuts in suspected areas of disease. Simply using a mixture of bleach and water to clean the tools between uses will kill many of the bacteria and diseases that might be hiding out on the tools. In extreme cases the tools if not properly cleaned in time might need to be autoclaved or just thrown out and new tools be bought to replace them.

The last area of concern would be in greenhouses that have insect problems along with disease. Many of the insects that invade greenhouses are major contributors to the spread of the common diseases. Aphids, whiteflys, and thrips are just a few of the phloem sucking insects that will feed on a diseased plant and then fly to another plant and feed. When they move around and feed they are just transferring the disease to all the plants that they feed on. Proper control of these insects is crucial in the fight against disease spread in your greenhouse.