Pesticide Use in California

 

            Needless to say, pPest control in California has been relying on intensive and extensive use of pesticides. Over the last two decades, California growers have been under the pressure from constantly changing and ever tightening regulatory policies, and they have also been faced with complicated and often contradictory issues concerning pesticides. Have our efforts through regulations, monitoring, outreach, and management practices worked? Are we seeing less usea decreased usage of pesticides than before?  Are we using better pesticides than before? And where do we go from here?

 

            In this introductory issue of PesticideWise, I will run a brief inventory checking. California surely has one of the largest inventories of pesticides. Fortunately, it seems that our inventories have been well maintained by the California Department of Pesticide Regulation (CDPR), which has probably the most comprehensive and effective use report system in the world.  CDPR has just released its compiled use report for 2000 (http://www.cdpr.ca.gov/docs/pur/pur00rep/ 00_pur.htm), and we are not finished withstill in 2001 yet!

 

Are we using less?

 


            California has gone through many phase-outs in pesticide use over the years.  Stringent reviews and re-reviewsmeasures have been imposed on the use of many of the surviving pesticides, including organophasphorous and carbamate insecticides, and pesticides that may cause groundwater pollution or health effects. At the same time, the push for non-chemical alternatives has become stronger than ever. Has the state as a whole seen a downturn in pesticide use? Figure 1 gives the annual pesticide use in California for 1992-2000.

 


            From the data and statements given by CDPR, prior to 1998, pesticide use remained roughly the same over the years. Fluctuations between years were more a result of variations in weather conditions, planting acreage, pest pressures and crop plantings than anything else. However, CDPR suggests that we are seeing some “real” reduction from 1998 to now. There were 187.6 mil lbs of pesticide active ingredients used in 2000, which were 15.4 mil lbs less than in 1999, and 26.4 mil lbs less than in 1998. This trend is new and deems seems to be significant. What has triggered this reduction?  To answer this question we need to look at what we useare using.

 

What do we useare we using?

 

“Pesticide” is an all-inclusive term. Just as it is the case with anything else in our life, there are a few “dominant” pesticides..  The ups and downs in the use of those pesticides generally swing the trend of total use.  Table 1 lists the top 10 pesticides that were used in California in 2000 and their respective uses in 1998 and 1999.

 

 

Table 1. “Top ten” Pesticides Used in California

 

Pesticide

1998

1999

2000

Mil lbs

%

Mil lbs

%

Mil lbs

%

Sulfur

78.1

36.5

68.6

33.8

62.9

33.5

Petroleum oil

21.7

10.1

20.1

9.9

19.8

10.6

Metam sodium

13.7

6.4

16.8

8.3

12.8

6.8

Methyl bromide

13.6

6.4

15.2

7.5

10.9

5.8

Copper sulfate

4.2

2.0

3.8

1.9

4.9

2.6

Glyphosate

4.6

2.1

4.3

2.1

4.6

2.5

1,3-D

2.9

1.4

3.1

1.5

4.4

2.3

Mineral oil

5.3

2.5

4.7

2.3

4.2

2.2

Chloropicrin

3.0

1.4

3.6

1.8

3.8

2.0

Copper Hydroxide

5.3

2.5

3.5

1.7

3.3

1.8

 

 

 

 

 

 

 

Total

152.4

71.3

143.7

70.8

131.6

70.1

 

 

            It is evident that 10 pesticides consistently make up 70% or more of all the pesticides used in California. Among these top 10, the use of sulfur alone constitutes about 1/3 or more of the total use. Sulfur certainly would not elicit the same environmental or health consequences as an OP insecticide. The same can also be said about petroleum oil, mineral oil, copper sulfate, and copper hydroxide. The sum of these “relatively” benign products always contributes over 50% to the total use.

 

Compared to 1999, the use of sulfur in 2000 decreased by 5.7 mil lbs, that of metam sodium by 4.0 mil lbs, and that of methyl bromide by 4.3 mil lbs. These three products alone amounted to 14.0 mil lbs – nearly all of the reduction from 1999 to 2000 (15.4 mil lbs). Likewise, the use of sulfur in 2000 saw a reduction by 15.2 mil lbs from 1998. Sulfur is mainly used for control of fungal diseases on grapes in California, and its use depends closely on how “damp” the year isannual precipitation. Therefore, a wet year can easily skew change the decreasing trend for the overall use of pesticides in California.

 

It is important to note that methyl bromide is irreversibly on its way out. The impact is was already showing in 2000. Since 4 out of the top 10 pesticides are fumigants (methyl bromide, metam sodium, 1,3-D and chloropicrin), the public will be watchful for any shift in use of the remaining fumigants. As there are essentially no other alternatives to methyl bromide, the use of 1,3-D, metam sodium, and chloropicrin will likely increase over the next few years.

 

The “Nasty”Harmful Ones

 

Pesticides are made different, so that they can be used for dealing with different problems. The different chemistry determines that some pesticides are more “nasty”harmful than others.  As we have witnessed all too often, the “good” pesticides today may become “bad” pesticides tomorrow.  As our knowledge stands now, we are especially concerned with the carcinogenic pesticides, the reproductive-toxic pesticides, and the cholinesterase inhibiting pesticides.

 


The “B2”s:        Some pesticides are classified by EPA as “potential” or B2 carcinogens. The annual use of these pesticides from 1992 to 2000 is shown in Figure 2. In 2000, a total of 22.9 mil lbs of B2s were used, of which metam sodium and 1,3-D alone constituted a phenomenal 75% (17.3 mil lbs). As just mentioned, aAs methyl bromide (not a B2!) is being discontinued, the use of 1,3-D and metam sodium may stay high for years to come. Because of this, it may be said that the overall use of carcinogenic pesticides may not decrease for years to come.

 

 


Reproductive Toxins:    Some pesticides are on the State’s Proposition 65 list of chemicals that are “known to cause reproductive toxicity.”.  The annual use of these pesticides from 1992 to 2000 is shown in Figure 3. In 2000, a total of 26.2 mil lbs of these pesticides were used, of which 90% was from the use of metam sodium (12.8 mil lbs) and methyl bromide (10.9 mil lbs). As methyl bromide is being banned, the overall use of this group of pesticides will likely decrease over the next few years, assuming under the condition that the void left by methyl bromide is not completely filled by metam sodium.

 


 


Cholinesterase Inhibitors:          Organophosphorous and carbamate pesticides can inhibit cholinesterase in mammals. These compounds have been under regulatory scrutiny over the last decade. The overall use of these pesticides in California is shown in Figure 4.  Unlike the carcinogenic or reproductive toxic groups, there is not a single dominant cholinesterase inhibitor. In 2000, the most used products are chlorpyrifos (2.0 mil lbs), diazinon (1.1 mil lbs), molinate (1.0 mil lbs) and thiobencarb (1.0 mil lbs). Chlorpyrifos and diazinon are OP insecticides, while molinate and thiobencarb are carbamate herbicides. Since 1997, there has been a steady and sizable decrease in the total use of cholinesterase inhibiting pesticides.  For instance, compared to 1997, the use of these pesticides in 2000 decreased by 4.6 mil lbs. This decrease is a result of decreases in the use of both OP and carbamate products. With the regulatory pressures placed on these compounds, this trend may likely continue over the next few years. Finding alternatives to these products would be critical to sustain this decreasing trend.

 


 


Conclusions

 

            The quantity and mix combinations of pesticides used in California have seen significant changes over the years. Because sulfur makes up over 1/3 of the total use and because its use depends closely on weather conditions, any change in total pesticide use may be seasonal and does not tell the whole story.  The heavy use of products such as sulfur, petroleum distillates, copper hydroxide, copper sulfate, and calcium hydroxide muffles covers up significant changes in the use of other “real” (synthetic) pesticides.  Soil fumigants are among the most heavily used pesticides in California. Due to the phase-out of methyl bromide, significant changes in the use of metam sodium, 1,3-D, and chloropicrin will occur, which will necessarily also alter the overall mix of pesticide uses in California. It appears that the use of reproductive toxic products and OP/carbamate pesticides has been on the decline, and this trend will likely continue, pending successful development and adoption of alternative products or practices.