by Jerry Brust:

US (MD): A closer look at ethylene problems in vegetable high tunnels

In Maryland we have seen a few problems with ethylene interactions with tomatoes in high tunnels. Ethylene (C2H4) occurs in trace amounts in gasoline and natural gas and is produced when these substances are burned. It is present in wood and tobacco smoke. Ethylene is also a plant hormone produced by plants during their growth and development. However, ethylene produced through defective heating equipment can be detrimental to protected crops, because the ethylene is produced in much greater quantities. Ethylene pollution influences the activities of plant hormones and growth regulators, which affect developing tissues and normal organ development, many times without causing leaf-tissue damage.

by Jerry Brust, IPM Vegetable Specialist, University of Maryland;

Injury to broad-leaf plants occurs as a downward curling of the leaves and shoots (epinasty); some growers think that this is wilting in the plant and look for root or irrigation problems that are not there. But a wilting plant is flaccid or soft and droopy with the leaves collapsed, while in epinasty the plant is turgid and firm, but with the leaves turned down (Fig. 1). How bad the down-turning of leaves is depends on the tomato variety, temperature, ethylene concentration, and the duration of exposure (see study by M. Jones at: The epinasty then can be followed by stunting of growth.

Figure 1. Tomato plants with a downward curling of leaves (epinasty) due to different levels of ethylene exposure.

Other symptoms of excess ethylene exposure include the abscission of flowers (Fig. 2), petals or leaves; water-soaking of older leaves; chlorosis; and wilting of flowers. Crops vary in their sensitivity and response to ethylene toxicity. High temperatures and high light levels will increase the severity of ethylene damage. In high tunnels that burn propane, kerosene or use motors that burn gasoline and have poor or no ventilation, even minute amounts of this pollutant can cause some damage to tomatoes. Symptoms of ethylene damage can be subtle, especially if there are no plants grown in non-polluted air for comparison. Often times the damaged tomatoes show up in unexpected areas of a high tunnel–sometimes in the middle of the high tunnel with a group of 5-10 plants affected and no tomato plants around them with any symptoms. This is due to the patterns of air movement in high tunnels that are passively vented and not as predictive as in actively vented situations. At times air patterns can concentrate the ethylene in certain areas one week and then in different areas the next week, making diagnoses of the problem difficult.

Figure 2. Flower abortion on a tomato plant exposed to ethylene in a high tunnel.

Proper heating system installation and maintenance are the best ways to prevent problems. Propane flames should have a small yellow tip when properly adjusted and natural gas flames should be a soft blue with a well-defined inner cone. To ensure proper combustion, heater units should have a clean air intake and should be vented to the outside with a stack, which keeps exhaust gas from being drawn back into the greenhouse through the ventilation system.

Source: University of Delaware

Publication date: 5/12/2017



Other news in this sector:

7/21/2017 US (FL): $3 million grant helps researchers look for new growing locations
7/21/2017 Photosynthetic responses of leafy veg to irradiance and CO2 concentration
7/21/2017 Production potential generates interest in Dutoli
7/21/2017 Cucumbers in space provide insights on root growth
7/20/2017 Spain: Hydroponic tomatoes as alternative to peppers in Murcia
7/20/2017 Fruit and fruiting disorders in summer squash and cucumbers
7/20/2017 Ph effects: The difference between soil grown and aquaponics
7/19/2017 Ag-tech startup gives farmers insight into soil health
7/19/2017 "When cultivating on water, we can't work with chemical products"
7/18/2017 US: SIFT and Montana State partner in strawberry trials
7/17/2017 Research investigates best growing conditions for Malling Centenary strawberries
7/14/2017 The impact of transplanting times, light exposure on hydroponic crop production
7/13/2017 Reduce your disposal fees with biodegradable twine
7/13/2017 Farmer Tyler shines his light
7/12/2017 Vitamin C content in arugula skyrockets with new growth recipe
7/11/2017 Nutrient guidelines for hydroponic tomato production
7/10/2017 US (NH): Researchers extend growing season for strawberries
7/10/2017 US (TX): High tunnel value proven in High Plains vegetable production
7/10/2017 A closer look at mulch bell peppers
7/7/2017 Dutch MP harvests peppers grown without daylight