Research Projects

Project at a Glance

Project Status: complete

Report Published September 1983:

Title: Effects of ambient air pollution on Thompson seedless grapes

Principal Investigator / Author(s): Brewer, Robert F.

Contractor: University of California, Riverside

Contract Number: a1-132-33

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Agriculture, Ecosystem Impacts


Thompson seedless grapes (Vitis vinifera L. Thompson Seedless) are the most important single grape variety grown in California. With slight modifications in cultural practices it is grown for the fresh fruit market (table grapes), raisin production and for crushing to be fermented for wine or brandy production. Over 250,000 acres of Thompson Seedless worth in excess of $200,000,000 are grown in the seven county area encompassing Fresno, Madera, Tulare, Stanislaus, San Joaquin, Merced and Kern Counties. An additional 30,000 acres of Thompsons are grown near Indio in the Coachella Valley of eastern Riverside County; an area experimenting increasing air pollution due to intrusion over the San Gorgonia Pass from the Los Angeles air basin.

Oxidant injury on vinifera grapes, usually characterized as "oxidant stipple", has been recognized since the mid 1950's as an air pollution problem on certain wine grape varieties growing in the Los Angeles basin (1).Providing pollution free, carbon filtered air to vines enclosed in plastic chambers or spraying periodically with an antioxidant reduced the visible leaf injury and increased yields of Zinfandel vines growing near Cucamonga-(2)about forty miles east of the city of Los Angeles. In New York, Lambrusca type grapes growing east of Lake Erie were also found to be suffering from oxidant stipple, sometimes combined with sulfur dioxide injury.{3,4,5) Attempts to quantify the effects of ambient pollutants under New York conditions on grapevine growth and fruit production using open top chambers were frustrated mainly due to large within-treatment variations which clouded the results (4). Results of these tests did show significantly reduced leaf stipple increased soluble solids and a four year mean increase in pruning weights as a result of providing carbon-filtered, pollution-free air.

In 1978 an experiment was initiated at the Kearney Agricultural Center near Parlier to answer a simple, but important, question:

* Are present levels of oxidant air pollution in the central San Joaquin Valley having a detrimental impact on the Thompson seedless grape industry?

To accomplish this objective it was decided to provide enough grape-vines with pollution-free air to determine differences exceeding 10 percent with a confidence level of .05 percent (19 to 1 odds). Statistical analysis of cane prunings and fruit production during the 1977 and 1978 production years indicated that four replications with three vines per replication should achieve the desired confidence level.

Eight large blower ventilated plastic covered open-top chambers (Figure 1) were constructed during the winter of 1978-1979 and installed over the north row of a block of ten year old own-rooted Thompson Seedless vines previously used in a nutrition and weed control experiment. There should have been no carry over effects of the previous experiments because the row in question, adjacent to an open field had been used as a guard row in previous experiments with no special fertilizer treatments. The adjacent middles had been clean cultivated, the usual means of weed control in most vineyards. The open space to the north provided room for the blowers and sampling equipment where they would not interfere with incident light on the chambers. The blowers were initially adjusted


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