California Department of Pesticide Regulation
Environmental Monitoring and Pest Management
1020 N Street, Room 161
Sacramento, CA 95814-5624

October 26, 1995


Reducing Dormant Spray Runoff From Orchards


I. Introduction

In 1988, scientists from the Central Valley Regional Water Quality Control Board (CVRWQCB) began testing water quality in the San Joaquin River (SJR) watershed using bioassays. The purpose of these tests was to characterize water quality in the SJR, its tributaries and drains, and to identify sources of toxicity seen in bioassays (Connor, 1988). Results indicated waters from certain regions of the watershed caused significant mortality to the water flea, Ceriodaphnia dubia (Foe and Connor, 1991). The specific cause of toxicity was not determined but was attributed to pesticides in general.

During the winter of 1991-92, water samples collected in the SJR watershed were again found to be toxic to C. dubia (Foe and Sheipline 1993). In addition, chlorpyrifos and diazinon were implicated as a potential cause of toxicity. During the winters of 1991-92 and 1992-93, the Department of Pesticide Regulation (DPR) also conducted monitoring in the watershed for various organophosphate and carbamate insecticides (Ross 1992 and 1993). Ross (1992, 1993) found 10, 72, and 18% of the 108 samples collected contained chlorpyrifos, diazinon, and methidathion, respectively. In addition, 2, 13, and 1% of these samples exceeded the C. dubia LC
50 for chlorpyrifos, diazinon, and methidathion, respectively. The C. dubia LC50 values for chlorpyrifos, diazinon, and methidathion are 0.49, 0.11, and 2.2 :g/L, respectively (Fujimura 1993).

In addition to potential acute toxicity of these insecticides, data from the CVRWQCB and the U.S. Geological Survey indicate chronic toxicity may also occur. C. dubia mortality was found on 12 consecutive days in the SJR near Vernalis (Kuivila and Foe 1995). Diazinon was detected in all 12 samples at concentrations ranging from 0.148 to 1.07 :g/L. The 4-day chronic criterion recommended by the California Department of Fish and Game for diazinon is 0.04 :g/L, not to be exceeded more than once every three years (Menconi and Cox, 1994).

Due to repeated acute toxicity found during winter months and the potential chronic toxicity problems these insecticides may pose, this study will be conducted to investigate mitigation measures. Chlorpyrifos, diazinon, and methidathion are applied in winter as dormant sprays on almonds and stone fruits to control peach twig borer and San Jose scale. Dormant sprays are generally applied in December, January, and February during damp periods between rain events. Once applied, they are subject to rain runoff into the surrounding watershed. Research indicates vegetative strips have proven successful in slowing water movement and decreasing pesticide runoff from agricultural fields (Fawcett, et al. 1992). Therefore, in this study we will examine differences in insecticide runoff from an almond orchard using three cultural practices: 1. control (bare soil), 2. clover/grass mix in between the tree rows, and 3. barley planted in between the tree rows. Other practices may be substituted for two and three above, depending on field availability and grower preferences. Additional practices may be examined in subsequent years.


II. Objective

To determine if vegetation in between the tree rows of an orchard significantly reduces mass runoff of chlorpyrifos, diazinon, and/or methidathion during rainy periods. To determine dissipation half-lives for each insecticide.


III. Personnel

This study will be conducted by personnel from the Environmental Hazards Assessment Program in the Environmental Monitoring and Pest Management Branch of the California Department of Pesticide Regulation. Study personnel include:

Project Leader: Lisa Ross
Field Coordinator: Kevin Bennett
Technical Coordinator: Dave Kim
Consulting Statistician: Rosie Gallavan
Laboratory Liaison: Nancy Miller
Senior Scientist: Heinz Biermann
Chemist: Jorge Hernandez and Karen Hefner
Agency & Public Contact: Peter Stoddard

ALL QUESTIONS CONCERNING THIS STUDY SHOULD BE DIRECTED TO PETER STODDARD AT: (916)324-4078.


IV. Study Plan and Sampling Methods

Chlorpyrifos, diazinon, and methidathion are applied in winter as dormant sprays on almonds and stone fruits to control peach twig borer and San Jose scale. Dormant sprays are generally applied in December, January, and February during damp periods between rain events. Once applied, they are subject to rain runoff into the surrounding watershed. Research indicates vegetative strips may be successful in slowing water movement and decreasing pesticide runoff from agricultural fields (Fawcett, et al. 1992). Therefore, potential reduction in insecticide runoff will be examined in one orchard cultivated with two types of vegetation in between the tree rows (i.e. row middles). In addition, a control treatment, consisting of bare soil, will be used for comparison. All three insecticides will be applied simultaneously on the same plot, in accordance with label instructions. Also, the dissipation half-life of each insecticide will be determined for soil and vegetation.

Rows in an orchard will be arranged in a randomized complete block design with three treatments and three blocks (Table 1). The three treatments are a control (no vegetation in the row middles), clover/grass mix in the row middles, and barley in the row middles. Other practices may be substituted for the vegetation treatments, depending on field availability and grower preferences. With this design, the field site requires a minimum of 27 rows to accommodate buffer rows between treatments. In addition, rows should be approximately equal in length, with a slope in one direction only.


Table 1. Analysis of variance table.a

Source of variation

Degrees of freedom

Total


8


Blocks


2


Treatments


2


Error (BxT)


4


a. The proposed design reflects the minimum amount of replication. If a large orchard is located for study and enough equipment can be borrowed, the number of replicates, (blocks), will be increased.


The volume of rain runoff from each treated row in each block will be measured using 75- mm flumes equipped with a still well, housing a pressure transducer. Each pressure transducer will be connected to a Campbell 21X datalogger to continuously monitor water height in the flume. Water height will be converted to volume using calculations experimentally determined by Clemmens et al. (1984). Water samples will be automatically collected as soon as water flow is detected in the flumes by the Campbell datalogger. Water samples will be collected using an ISCO7 automated water sampler operated with a 12-volt, deep-cycle battery.

In addition, soil and vegetation samples will be collected to determine the field dissipation rate for each insecticide.

Application: A single application of all three insecticides, chlorpyrifos, diazinon, and methidathion will be applied, each at the same rate. The initial concentration of each insecticide applied will be determined from a tank mix sample.

Meteorological Data: At minimum, temperature and rainfall will be collected at the site using a Met-One7
Weather system and a Texas Instruments tipping rain bucket, respectively. Data will be recorded using a Campbell CR10 or 21X datalogger operated with a 12-volt, deep-cycle battery.

Deposition: Deposition on trees in the orchard during application will be estimated using absorbent fall-out sheets placed at three heights on a single mast located in the tree rows. Fall-out sheets will be placed at approximately 4, 7, and 10 feet. One mast will be randomly located in each treatment row, within a single block, for a total of 9 masts. Each fall-out sheet will be chemically analyzed separately, to examine deposition at each height. This information will be used for mass balance calculations of the applied pesticides and not to determine within treatment differences. Concentrations will be reported in mg/m
2.

Soil Sampling: Two composite soil samples will be randomly collected from each treatment row, in each block on days 0 (within 24 hours of application), 3, 7, 14, 21, 28, and 35. One of the two composite samples will be collected in the tree row, the other in the row middles. In treatments with vegetation, soil will be collected from beneath the vegetation. A single composite sample will consist of four to eight soil plugs, randomly collected in each treatment row, within a single block. Soil plugs will be collected with stainless steel cylinders (about 4.13 cm in diameter), pushed about 2.54 cm into the soil. Soil plugs will be composited into glass jars, pre-labeled with sample numbers. Each composite sample will weigh a minimum of 50 g (required for chemical analysis). Samples will be weighed in the field to determine the wet weight. The concentration of each insecticide will be reported in total :g per sample. Prior to chemical analysis, an aliquot of soil will be removed to determine percent moisture; wet and dry weight of this aliquot will be reported.

In addition, three composite background soil samples (one from each block), will be collected for chemical analysis prior to application. Also, samples to determine soil bulk density, pH, organic carbon content, and percent sand, silt, and clay will be collected prior to application (if not already completed in a prior study).

Vegetation Sampling: Vegetation samples will be collected on the same days as soil samples. Two composite vegetation samples will be randomly collected from the treatment rows with vegetation, in each block. Each composite will consist of four to eight sub-samples of vegetation. Sub-samples will be collected randomly in each treatment row, within a single block. Composite samples will weigh between 35 and 80 g for chemical analysis and percent moisture determination. Sample fresh weights will be recorded in the field. The concentration of each insecticide will be reported in total :g per sample. Prior to chemical analysis, approximately 10 g of vegetation will be removed to determine percent moisture; wet and dry weight of this aliquot will be reported.

Water Sampling: During two rain events (after application), water will be collected from each treatment row and analyzed for all three insecticides. Water will be collected at specific intervals, evenly spaced to cover the entire runoff event, whenever possible. The number of water samples required to cover each runoff period will vary depending on: rain intensity and duration, field dimensions, soil type, etc. Whole water samples will be analyzed. Filtered water samples might also be analyzed. In addition, a back-up sample will be collected for each sample analyzed.

Total number of samples for chemical analysis:
Tank mix: Three per tank (one for each insecticide), up to 4 tanks = 12
Deposition: 3 treatments x 3 heights x 3 blocks = 27
Soil: 2 per treatment x 3 treatments x 3 blocks x 7 days = 126
Background soil (one per block) = 3
Vegetation: 2 per treatment x 2 treatments x 3 blocks x 7 days = 84
Background vegetation (two per block) = 6
Water, whole: 6 samples x 3 treatments x 3 blocks x 2 rain events* = 108
Quality Control: blind spikes and field blanks about 10% of total number of samples = 36
TOTAL = 394
* = estimate

V. Data Analysis

Mass balance of each insecticide deposited on site during application will be determined from deposition cards, soil, and vegetation concentrations measured within 24 hours of application. Runoff mass of each insecticide in water will be expressed as total mass, and as a percent of the total amount applied (theoretical) or deposited (measured) on site. For each insecticide, normalized mass values (either per unit area or application mass) will be used in the analysis of variance (Table 1) to determine if treatment differences exist. In addition, a mean separation test of the three treatments will be conducted for each insecticide. Finally, field dissipation half-lives for each insecticide will be calculated for soil and vegetation.

VI. Chemical Analytical Methods and Quality Control

Chemical analysis will be performed by the California Department of Food and Agriculture Laboratory. Method development and validation work will be conducted in accordance with Standard Operating Procedure QAQC001.00, prior to study commencement. Continuing quality control will also be conducted in accordance with this Standard Operating Procedure.

Soil texture and organic carbon will be determined in our Fresno facility. Soil texture will be determined using the hydrometer method (Bouyoucos 1962) and soil organic matter by dichromate reduction with silver sulfate (Rauschkolb 1980).


VII. Timetable

Field location October to November, 1995
Equipment Purchases September to December, 1995
Equipment Installation December 1995
Sample Collection January to March, 1996
Chemical Method Validation September to December, 1995
Chemical Analysis January to April, 1996
Draft Report July, 1996

VIII. References

Bouyoucos, G.J. 1962. Hydrometer method improved for making particle size analyses of soils. Agronomy J. 54:464-465.

Clemmens, A.J., M.G. Bos, A. Replogle. 1984..Portable RBC flumes for furrows and earthen channels. Trans. ASAE 27(4):1016-1020.

Connor, V. 1988. Survey results of the San Joaquin River watershed survey. CVRWQCB memorandum dated March 10, 1988.

Fawcet, R.S., B.C. Christensen, and J.M Montgomery. 1992. Best management practices to reduce runoff of pesticides into surface water: A review and analysis of supporting research. Ciba-Geigy Corp. Technical Report: 9-92. Environmental and Public Affairs Department, Greensboro, NC.

Foe, C. and V. Connor. 1991. San Joaquin Watershed Bioassay Results, 1988-90. CVRWQCB Report, July 1991.

Foe, C. and R. Sheipline. 1993. Pesticides in surface water from applications on orchards and alfalfa during the winter and spring of 1991-92. CVRWQCB Report, February 1993.

Fujimura, B. California Department of Fish and Game. Personal communication, November 22, 1993.

Kuivila, K. and C. Foe. 1995. Concentrations, transport and biological effects of dormant spray pesticides in the San Francisco estuary, California. Environ. Toxicol. Chem. 14(7):1141-1150.

Menconi, M. and C. Cox. 1994. Hazard assessment of the insecticide diazinon to aquatic organisms in the Sacramento-San Joaquin River system. CA. Dept. Fish and Game Administrative Report 94-2. Rancho Cordova, CA.

Rauschkolb, R.S. 1980. Soil analysis method S:18.0, Organic matter dichomate reduction. In: California Fertilizer Soil Testing Procedures Manual.

Ross, L.J. 1992. Preliminary results of the San Joaquin River study; Winter 1991-92. Memorandum to Kean Goh, Environmental Hazards Assessment Program, California Department of Pesticide Regulation, May 22, 1992.

Ross, L.J. 1993. Preliminary results of the San Joaquin River study; Winter 1992-93. Memorandum to Kean Goh, Environmental Hazards Assessment Program, California Department of Pesticide Regulation, Sept. 23, 1993.

Standard Operating Procedure Number: QAQC001.00. Chemistry Laboratory Quality Control. California Department of Pesticide Regulation, Environmental Hazards Assessment Program, Sacramento, CA.