Monday, October 21, 2013

VOG Equals Hawaiian SMOG

People living in the Los Angeles, California Basin have known for years that smog affects plants.  There exists a similar situation on the Big Island of Hawaii. It’s called VOG, emissions that spew from the Kilauea Volcano at Halemaumau. The discharges include sulfur dioxide, sulfites, ash and hydrochloric acid.

 Many gardeners, especially those living near the Volcano area, have experienced the distressing effects of vog on their plants.   Sulfur dioxide  enters the leaf through the stomata.  The degree of injury will depend upon its concentration and duration, and upon the sensitivity of the specific plant. The symptoms of low concentrations of sulfur dioxide are general chlorosis (yellowing) of the plant foliage. Higher concentrations cause a bleaching or browning of tissues between the leaf veins.

Volcanic ash appears as a dust and is composed of fine rock particles from the volcano. The ash does not damage plants directly but can block sunlight on foliage as well as detract from the appearance of the plant. Harvested fruits and vegetables should be thoroughly washed prior to their consumption.

There is not much that can be done about the harmful chemicals the volcano churns out. As far as the plant is concerned however,  leaves should be rinsed with adequate water after exposure. Susceptible plants can be grown under cover such as greenhouses, and during periods of intense vog, valuable plants can be temporarily covered with fabric or plastic.

Different plants have varying degrees of susceptibility to vog.  Here is a list of plants documented to be susceptible to vog:
Ornamentals - African lily, Oriental lily, cypress, Dutch iris, eucalyptus, ginger, hydrangea, heavenly bamboo, pine, podocarpus, rose and tuberose.
Native plants -  koa, naio, pilo, uki, akala.
Vegetables - broccoli, cauliflower, Chinese cabbage, daikon, lettuce, Swiss chard, tomato and watercress.

Some of the more resistant plants are asparagus, celery, coffee, corn, and ohia.

For a more in depth look at the volcano’s effects on plants, with some excellent photographs, read, “Volcanic Emissions Injury to Plant Foliage”, by Scot Nelson and Kelvin Sewake, UH Department of Plant and Environmental Protection Sciences. The publication can be found on the CTAHR website - http://www.ctahr.hawaii.edu/Site/Info.aspx