Pesticide use in California rose in 2010 after declining for four consecutive years, according to data released by the Department of Pesticide Regulation (DPR). More than 173 million pounds of pesticides were reported applied statewide, an increase of nearly 15 million pounds - or 9.5 percent - from 2009.

The increase reflected a 15 percent jump in acres treated with pesticides - up 9.7 million acres to a total of 75 million acres in 2010. The Summary of Pesticide Use Report Data 2010 is posted at http://www.cdpr.ca.gov/docs/pur/pur10rep/10_pur.htm.

As in previous years, sulfur was the most highly used pesticide in both pounds applied and acres treated. By pounds, sulfur accounted for 27 percent of all reported pesticide use. Its use grew by 4.4 million pounds, or 10 percent, and 141,826 acres, or 9 percent.

Sulfur is a natural fungicide favored by both conventional and organic farmers mostly to control powdery mildew on grapes and processing tomatoes. Other pesticides with high use in 2010 treated a variety of diseases and pests that affected rice, walnuts, oranges, almonds, grapes and strawberries.

“The winter and spring of 2009 and 2010 were relatively cool and wet, which probably resulted in greater fungicide use to control mildew and other diseases,” DPR Chief Deputy Director Chris Reardon explained.

“Summer and fall temperatures were also below average, which led to late harvests, more insect damage to some crops and additional treatments.”

Overall, most of the growth in pesticide use was in production agriculture, where applications increased by 12 million pounds.

Post-harvest treatments went up by 657,000 pounds, structural pest control by 760,000 and landscape maintenance by 374,000 pounds. Reports are mandatory for agricultural and pest control business applications, while most home, industrial and institutional uses are exempt.

Pesticide use varies from year to year depending on many factors, including weather, pest problems, economics and types of crops planted.

Increases and decreases in pesticide use from one year to the next or in the span of a few years do not necessarily indicate a trend.

Greatest pesticide use

The greatest pesticide use occurred in the San Joaquin Valley. The top five counties in order of most pesticide pounds applied in 2010 were Fresno, Kern, Tulare, San Joaquin and Madera. All are major producers of agricultural products.

Pesticides with the greatest increase in pounds applied included 1,3-dichloropropene (1,3-D), a fumigant whose use went up by 2.4 million pounds, or 37 percent. It is used on strawberries, almonds, sweet potatoes, carrots, and table and raisin grapes. This fumigant is an alternative to methyl bromide, which is being phased out under an international treaty to protect the ozone layer.

Other pesticides that showed growth in pounds applied were metam-sodium, a fumigant used on carrots, processing tomatoes and potatoes; glyphosate, an herbicide used on orchard floors, rights of way and preplanting for row crops; metam-potassium, a fumigant used to prepare fields for processing tomatoes, sweet potatoes and carrots prior to planting; and kaolin, a clay-based fungicide and insecticide commonly used on organic crops.

Major crops that showed an overall increase in pounds of pesticides applied over the previous year included wine grapes, carrots, cotton, almonds, and table and raisin grapes. The data indicated declines in pounds applied to rice, processing tomatoes, alfalfa, peaches, nectarines and applications to fields before crops are planted to control pests.

DPR has the most extensive pesticide use reporting system in the United States and oversees one of the most comprehensive pesticide regulatory

programs in the world. These data support a variety of regulatory efforts, including compliance efforts for clean air and water laws, continuous evaluation to determine potential risks to human health and the environment, estimating dietary risks, protecting workers in the field, preserving endangered species, assisting product registration and review and helping local pesticide law enforcement.

Reported pesticide applications are only a portion of the pesticides sold each year. Approximately two-thirds of the pesticides sold, including chlorine used primarily for municipal water treatment and home-use pesticide products, typically are not subject to reporting.

Total pounds of pesticide active ingredients reported in each county and rank during 2009 and 2010 are posted at http://www.cdpr.ca.gov/docs/pur/pur10rep/lbsby_co_10.pdf.

One of five departments and boards within the California Environmental Protection Agency, DPR regulates the sale and use of pesticides to protect people and the environment.