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

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.