Task 5: Pesticide Use Reports

In a report written for the Almond Board of California by Susan Bassein and Lynn Epstein both from the University of California Davis titled "Reduction in use of organophosphates in Almond Orchards During the Rainy Season in California" shows that the amount of organophosphates are being applied with more discretion today than in the early 1990’s. By accessing the Pesticide Use Reports from 1990 to 1997, they have shown a reduction of growers using organophosphate dormant sprays by 31 to 48%, depending on the region. The researchers also show the use of organophosphates applied during the dormant season was reduced 22 to 57% depending on the region. Furthermore, they reported a significant increased use of Bt. This research is based upon the rainy season, a time period where organophosphate dormant sprays are typically applied. The results are promising, indicating a positive and proactive response the almond industry has adopted in order to curb organophosphate use.

The results reported here are show a similar trend to the report submitted by Bassein and Epstein. With the increasing amount of commercial almond acreage in the 10 counties used in this report, the amount of organophosphates and carbamates applied per acre are decreasing and the use of Bt applied per acre is increasing across the state in commercial almond orchards. Table 5.1 shows the commercial almond acreage in ten counties. Organophosphates, carbamates, pyrethroids, and Bt use were tracked in 10 almond growing counties in California using the Pesticide Use Reports from 1990-1998. The counties included in this report are Butte, Kern, Stanislaus, Colusa, Fresno, Glenn, Madera, Merced, San Joaquin, and Tulare. Pounds or applications per acre are reported since there is a large difference in the amount of acres in each county.

Table 5.1. Almond Acreage in 10 California almond producing counties 1990-1999.

Organophosphates used in these results are: azinphos-methyl, chlorpyrifos, dvvp, diazinon, disulfoton, fenamiphos, malathion, methidathion, naled, parathion, and phosmet. Since each county has various amounts of almond acreage, pounds per acre were analyzed. Table 5.2 depicts the 10 county use of organophosphates from 1990-1998. The use of organophosphates has dropped in this period. A two-way ANOVA for pounds per acre was performed for the year and county. Furthermore, a two-way ANOVA for pounds per acre was performed for the month and county. The results show that there is no difference (p=0.2) in OP use throughout the 1990-1998 period, however, there is a decrease in OP use. There is a significant difference in the counties that apply the organophosphates (p>0.05). Fresno and Kern counties have applied the most OP’s throughout the 9-year period, averaging 0.3 pounds per acre in each county. The two counties using the least amount of OP’s during this 9-year span are Colusa and Glenn counties. There is also a significant difference in the time of year the organophosphates are being applied (p>0.05). As expected, the heavy organophosphate use occurs in January and July. This corresponds to dormant and hullsplit sprays.

Table 5.2. Organophosphate use from 1990-1998 in California almonds.

Carbamates used in these results are methomyl and carbaryl. The use of carbamates has not altered significantly in the past 9 years (p=0.59) despite the spike in 1997 (Table 5.3). However, counties do apply carbamates significantly differently (p<0.05). Kern and San Joaquin counties apply significantly more carbamates per acre than any of the other counties in this study. Similar to organophosphate use, there is a significant difference in the month which carbamates are applied. January and July have significantly more carbamate applications than any other month. Again, these two months correspond to dormant and hullsplit sprays.

Table 5.3. Pounds of Carbamate Applied in 10 California Almond Producing Counties 1990-1998.

Pyrethroids were calculated according to application numbers. The application numbers from 1990-1998 have significantly increased (p<0.05) and are shown on Table 5.4. Fresno, San Joaquin, and Stanislaus counties significantly have the most applications of pyrethroids than the other counties in this report (p<0.05).

Table 5.4. Pyrethroid applications in 10 California Almond Producing Counties 1990-1998.

There has been a significant increase in the use of Bt in commercial almonds (p<0.05). The pounds of Bt applied per acre has risen steadily since 1990 when virtually no Bt was applied statewide. Madera and Merced counties apply the most pounds per acre, followed by Fresno and Kern counties. San Joaquin county applies the least amount of Bt (p<0.05). There is also a significant difference in the month in which Bt is applied (p<0.05). Bt is applied most in February and March. Bt use spikes again in July but is not significant.

Table 5.5. Pounds Bt applied in 10 California Almond Producing Counties 1990-1998.