Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
We have recently seen suspected exhaust damage to greenhouse transplants. This can occur where coal or wood burning stoves are used and exhaust escapes when loading, where temporary unvented heaters are used in greenhouses, where heat exchangers in vented heaters have cracks, where exhaust pipes are leaking, or where fumes from burn piles or other sources are drawn into houses.
In fuel combustion, noxious gases can be produced if combustion is not complete. This can include: ethylene, sulfur dioxide, nitrous oxide and carbon monoxide. Even a clean burning furnace can have problems in airtight plastic greenhouses in cold periods where heaters are in constant operation. The level of oxygen can be depleted over several hours of continuous heating thus starving the combustion process of adequate oxygen and contributing harmful gasses.
Of particular concern is ethylene which acts on plants as a hormone. Ethylene is a clear, odorless gas is a byproduct of the combustion of fuels. Ethylene can be damaging at levels as low as 0.05 ppm and even short exposures can cause leaf distortion, abortion of flower buds, defoliation and chlorosis.
To reduce chances of damage from ethylene and other exhaust gasses, only use vented heaters for transplant production. Inspect heaters and exhaust stacks for potential leaks or damage, maintain heaters so that they burn clean, and provide an outside air source to the heater during times when greenhouses are sealed tight.