University of California

Pesticide Use on the Decline in California Cut Flower Production: The Untold Story

by Michael Parrella, Christine Casey, Andrew Melicharek, Machiko Murdock and Daniel Klittich

Excessive use of pesticides in the production of floricultural crops has been an issue for decades. While certainly not true when focusing on most individual growing operations, the industry as a whole is defined by its bad actors and the result is that the entire industry has a negative association with pesticide use. This seems to come to the fore and makes good press around Valentine’s Day.[1]  Much of the focus on excess use of pesticides in cut flowers has been in South America (Stewart, 2007) and this has led to some harsh criticism of the industry (Donohue, 2008). However, there has been concern in California[2] as well, where approximately 80% of the cut flowers in the United States are produced. The negative aspects usually focus on the health and safety of farm workers, and historically the floriculture industry does not have a good track record. For example, data from 2003[3] indicate that almost 30% of all the incidents involving farm workers and pesticide residue exposure in California occurred in ornamental crops, and this ranked second among all agricultural crops produced in the state. Of course this information is close to 10 years old, so what is the situation today?  In order to address this question accurately, pesticide use in greenhouse cut flowers needs to be examined in comparison to overall pesticide use in California agriculture.  In addition, the changing size of floriculture industry over the past decade also needs to be considered.

Trends in Pesticide Use In California

In 1990, California became the first state to require full reporting of agricultural pesticide use. Growers were required to turn in monthly Pesticide Use Reporting forms to their County Agricultural Commissioner. The result has been a massive database (compiled and maintained by the California Department of Pesticide Regulation [CA DPR]). This allowed a comprehensive look/analysis of overall pesticide use in the state and these data can be examined by commodity, by pesticide, by county, etc.  Of course there have been changes over the more than 20 years that these data have been collected. During the early years of data collection, ornamental production was not broken down into subcategories, so it was not possible to separate pesticide use in greenhouse cut flowers, for example, from pesticide use in field-grown nursery stock.   This made an analysis of pesticide use in ornamental production more difficult.  However, this has changed and by 2001 the categories were more clearly defined.  Therefore a comprehensive look at pesticide use in greenhouse cut flower production really has to start in 2001.

From 2006 to 2009, overall pesticide use in California dropped and the state was very proud of this decline. However from 2009 to 2010, pesticide use increased by 9.5 % (15 million pounds active ingredient), [4]  and in 2010, California used more than 173 million pounds of pesticide active ingredient.  How did the cut flower industry contribute to these pesticide figures? Despite an increase in pesticide use across all of California crops in 2010, pesticide use in greenhouse cut flowers continued to decline (fig. 1). For some, this decline in pesticide use was not fast enough, but it is still positive and the cut flower industry needs to be recognized for this. In 2001, cut flowers ranked 49th among all agricultural commodities in terms of total pesticide use. By 2010, this rank had dropped to 82nd. (The farther down on this list you are as a commodity, the better.)  

Parella fig1

Fig. 1.  Pounds of pesticide applied in California on all crops (red bars) and on cut greenhouse cut flowers (blue bars) from 2001-2010.  The amounts applied to all crops must be multiplied by 1000.

There has been a decline in cut flower acreage from 2006 to 2010: As one looks at the cut flower statistics in California, in 2006 the total value was $318 million and in 2010, this had dropped to $286 million. However this reduction does not explain the dramatic 50% reduction in pesticide use that occurred from 2001 to 2010. In fact the data from these dates are remarkably similar. In 2001, 48,469 pesticide applications were made to 86,800 acres and in 2010, 45,894 applications were made to 81,695 acres. It is important to note that along with a reduction in pesticide use has come a reduction in the number of reported incidents related to field worker exposure to pesticides. For greenhouse cut flowers in 2009,[5] this dropped to 2% of the total number of cases in California agriculture. 

A simple reduction in pesticide use does not tell the full story. Altering the type of pesticides used may be even more important. As noted above, CA DPR recorded an increase in pesticide use in 2010, but much of that use was attributed to the increased use of sulfur for control of powdery mildew in crops such as grapes. Inorganic sulfur, although not benign environmentally, is approved for organic production, and the increased use of such a pesticide takes some of the sting out of a negative scenario where pesticide use is increasing statewide. Likewise, the mix of pesticides used by floriculture producers is changing. It is slanting away from the use of traditional, broad-spectrum materials such as organophosphates and carbamates towards inorganic products like soaps and oils, botanicals, insect pathogens, insect growth regulators and the use of biological control agents.

Statistics on pesticide use can often be confounded by the activity of the pesticide itself. For example, older chlorinated hydrocarbon insecticides (like DDT) were applied at rates of 4 pounds active ingredient per acre, while the pyrethroid insecticides (like permethrin) are applied at 0.1 pounds active ingredient per acre. Therefore, simply switching from DDT to permethrin would achieve the goal of using less pesticide active ingredient per acre, when in fact you are making the equivalent (and in many cases more) pesticide applications per acre. The reverse also can be true. Application rates of sulfur are often many times that of conventional powdery mildew materials (something that is generally true for “safer” insecticides), so switching to sulfur (often viewed as positive because of its organic certification) will increase the total amount of pesticide applied per acre. The bottom line is that when you switch from one pesticide to another you need to take into consideration the activity and application rates in order to really determine whether there has been a reduction in active ingredient per acre in addition to the number of applications per acre. 

Reasons Underlying the Change

Over the past ten years, there have been some profound changes that have led to the reduction in pesticide use and the types of pesticides applied in cut flowers in the state. These include: (1) the advent of 3rd party certification organizations that ultimately lead to pesticide reduction and a wiser choice of pesticides; (2) the greater use of screening in many greenhouses in the state; (3) the ever-increasing rules and regulations focusing on groundwater and farm worker health and safety; (4) the greater acceptance of thresholds, where some insects can be tolerated on a crop before a pesticide is applied; (5) greater use of monitoring with light traps, pheromone traps and yellow/blue sticky cards; (6) increased frequency of spot spraying to control early pest infestations without treating the entire greenhouse; (7) the advent of effective “reduced risk” materials that can replace traditional chemistry; (8) a new generation of growers who have grown up under the concept of going green; (9) a consuming public with a greater acceptance of organic production and with an increasing negative perspective of pesticides; and (10) the widespread use of biological control agents — the three Ps: insect pathogens, parasites and predators.

The Role of Research and Extension

For many years there has been considerable research funded in California by national organizations (American Floral Endowment, Fred C. Gloeckner Foundation, Joseph H. Hill Memorial Foundation, to name a few), state commodity organizations (e.g., California Cut Flower Commission) and state agencies (e.g., CA DPR and the California Department of Food and Agriculture). In addition, the USDA ARS Floriculture and Nursery Research Initiative has provided continued funding to UC Davis and UC Riverside (as well as other universities nationwide). The ultimate goal of some of these research projects is to produce healthy plants while using less pesticide. 

As noted earlier, pesticide use declined in cut flower production in California by almost 50% from 2001 to 2010. However, from 2008 to 2010, there was only a slight decline (50,105 pounds to 49,250 pounds, respectively). In 2009 there was actually a slight increase up to 51,000 pounds — this suggests a trend where things have leveled off. Have we bottomed out in terms of reducing pesticide use? Is the law of diminishing returns playing a role here?  The challenge will be to keep this total pesticide use declining in addition to altering the types of pesticides used. We think the industry is poised for this challenge and look forward to what the next 10 years will bring.

Michael Parrella is Professor and Chair, Christine Casey is Staff Research Associate,  Andrew Melicharek is Agricultural Technician, Machiko Murdock is Staff Research Associate,  and Daniel Klittich is Graduate Student, Department of Entomology, University of California, Davis.

References Cited

Donohue M. 2008. Flowers, diamonds and gold: The destructive public health, human rights, and environmental consequences of symbols of love.  Human Rights Quarterly 30(1): 164-182.

Steward A. 2007. Flower Confidential. Algonquin Books of Chapel Hill, Chapel Hill, NC. 306 p.


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