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Publication #CIR997

Managing Pesticides for Peppers Production and Water Quality Protection1

T. M. Buttler, A.G. Hornsby, W.M. Stall, F.A. Johnson, J.W. Noling and T.A. Kucharek2

WATER QUALITY CONSIDERATIONS IN PEPPER PRODUCTION

Concern about the harmful effects of pesticides on surface water and groundwater quality should motivate pepper growers to select pesticides with the least potential to cause water quality problems. Many pepper growers live in rural areas near where they and other growers grow peppers, therefore, their personal water supply is susceptible to contamination. Unfortunately, information that allows growers to select pesticides less likely to affect water quality has not previously been readily available.

Our purpose is to provide information that can help growers select pesticides that will have a minimum adverse impact on water quality. The procedure considers the soil properties of the application site, the mobility and persistence of pesticides in these soils, and the toxicity of the pesticides in water to humans and aquatic species. A proper selection will decrease chances of adversely affecting surface water and groundwater quality. Certain combinations of soil and pesticide properties (along with weather conditions) can pose a significant potential hazard to water quality. Our goal is to identify and avoid these circumstances. Information contained in this circular can help pepper growers make better decisions about the pesticides that they use. This document in no way endorses any particular pest control product. All products must be used in accordance with the label.

MATERIALS NEEDED TO USE THIS PROCEDURE

To effectively use this procedure you will need the following source materials:

  1. A copy of the current IFAS Pest Management Guides or other appropriate information sources that identify pesticides that control specific pests.

  2. A copy of your county soil survey report to identify the soil types found in your fields.

  3. A copy of the Soil Science Fact Sheet entitled "[Name of your county]: Soil Ratings for Selecting Pesticides" for your county, available from your county Cooperative Extension Office. The basis of these ratings are given in the IFAS Extension Circular 959 entitled "Soil Ratings for Selecting Pesticides for Water Quality Goals," which is also available from your county Cooperative Extension Office.

Note: If your county has not yet been mapped by the Natural Resources Conservation Service (formerly the Soil Conservation Service), you will need to contact the local NRCS office for a site evaluation and determination of soil types and ratings for leaching and runoff of pesticides.

IMPORTANT FACTORS THAT AFFECT PESTICIDE SELECTION

How pesticides behave in the soil is determined by many factors including properties of the pesticides and of the soil at the application site. Some of the factors that should be considered when selecting pesticides with minimal potential for water quality impacts are:

Pesticide Properties

  1. The organic carbon adsorption coefficient, K oc , describes the relative affinity or attraction of the pesticide to soil materials and therefore its mobility in the soil.

  2. The biological degradation half-life, T ½ , is a measure of persistence of the pesticide in soil.

  3. The maximum contaminant level (MCL), or the lifetime health advisory level (HAL), or equivalent ( HALEQ), is a measure of health risk to humans of pesticide contaminated drinking water.

  4. Aquatic toxicity, LC 50 , is a measure of the ability of the pesticide to cause 50% mortality in aquatic test species.

Soil Properties

  1. Hydraulic permeability is a measure of the soils ability to allow water to percolate through it.

  2. Organic matter is important for providing binding sites for pesticides, thus reducing their mobility and increasing their opportunity to be degraded by soil microorganisms.

  3. Slope affects the potential for water to run off the land surface.

Management Practices

  1. Pesticide application frequencies and rates determine the total amount applied. Lower frequencies and rates reduce the potential for contamination.

  2. Application methods affect the amount of pesticide subject to transport by water. For example, if applied directly to the soil, there is a greater probability that more of the product will be available for leaching or runoff than if applied to the foliage. If the product is incorporated into the soil, leaching may be the most important loss pathway. Pesticides applied to the foliage may be lost to the atmosphere, decomposed by sunlight, or absorbed by the foliage, thereby reducing the amount available for wash-off and transport to water bodies.

  3. Irrigation practices can also determine the loss pathways of pesticides. Pesticides often move with water, so the less excess water that is applied, the less potential there is for a pesticide to move past the crop root zone or to run off in surface water. Rainfall or overhead irrigation can wash off significant quantities of pesticides from foliage immediately after application.

INDICES USED TO SELECT PESTICIDES

Table 1 contains two important indices, the pesticide leaching potential (RLPI) and the pesticide runoff potential (RRPI). Both indices are relative. For a given soil, these indices rank the pesticides by their potential to move from the application site by the indicated pathway (leaching or runoff). The indices are based on the organic carbon sorption coefficient and degradation half-life values of each pesticide. Values for these parameters have been taken from scientific literature, technical manuals, and company product literature.

Relative Leaching Potential Index

The Relative Leaching Potential Index (RLPI) defines the relative attenuation(reduction in mass as it moves through the soil) of each pesticide in soil, and therefore its potential to leach to groundwater. Pesticides that are very mobile, for example, those that have K oc values less than 100 in sandy soils, or 50 or less in fine-textured soils should be used with caution. There is some uncertainty in the data used to calculate this index. However, since the values are relative they can still be used. It is important to realize that the smaller the RLPI value of a pesticide, the greater is its potential to leach.

Relative Runoff Potential Index

The Relative Runoff Potential Index (RRPI) defines the relative immobility and availability of each pesticide in soil, and therefore its potential to remain near the soil surface and be subject to loss in the aqueous phase or sediment phase of runoff. There is some uncertainty in the data used to calculate this index. However, since the values are relative they can still be used. The smaller the RRPI value of a pesticide, the greater is its potential to be lost in runoff.

Maximum Contaminant Level, Lifetime Health Advisory Level or Equivalent

Table 1 also contains information on the toxicity of pesticides to humans and aquatic species. This information can be used as a secondary consideration in the pesticide selection procedure.

The Maximum Contaminant Level, MCL, is the highest allowable concentration in drinking water supplied by municipal water systems. It is a Primary Drinking Water Standard based on health considerations and is enforceable by the USEPA. Pesticides that may potentially cause chronic health effects such as cancer, birth effects, miscarriages, nervous system disorders or organ damage are assigned a MCL value by the USEPA. Although the MCL is usually expressed in milligrams per liter (mg/L), in this circular it will be expressed as micrograms per liter (g/L, or ppb). The Lifetime Health Advisory Level, HAL, provides a measure of pesticide toxicity to humans. The HAL as defined as the USEPA is the concentration of a chemical in drinking water that is not expected to cause any adverse health effects over a lifetime of exposure (70 years), with a margin of safety. If the chemical has not been assigned a MCL or HAL value, a health advisory level equivalent, HALEQ, (denoted by an asterisk) has been calculated using the same formula as the USEPA (HALEQ = R f D x & 7000) where R f D is the reference dose determined by the USEPA. For non-carcinogenic pesticides the calculated HALEQ should not differ by more than a factor of 10 from the value forthcoming from the USEPA. The Hal and the HALEQ have units of micrograms per liter (g/L or ppb). If a pesticide has a MCL value assigned, we use that value rather than the HAL or HALEQ. The smaller the value the greater is the toxicity to humans.

Aquatic Toxicity

The Aquatic Toxicity provides a measure of pesticide toxicity to aquatic species. The values given in Table 1 are the lethal concentrations at which 50% of the test species die (LC 50 ). Unless otherwise noted by a lower case letter following the value, the test species was rainbow trout. The smaller the value the greater is the toxicity to aquatic species.

Data for K oc , RLPI, RRPI, MCL/HAL/HALEQ, and aquatic toxicity are given for the active ingredient (common name) of a product. When using a product that is a mixture of two or more active ingredients use the RLPI, RRPI, MCL/HAL/HALEQ, and Aquatic Toxicity value for the most restrictive active ingredient in the mixture.

Important Note : The information presented in Table 1 DOES NOT supersede or replace the information on the pesticide container label or product literature.

PROCEDURE FOR SELECTING PESTICIDES TO REDUCE ADVERSE WATER QUALITY IMPACTS

A "Pesticide Selection Worksheet" is provided as a convenient way to organize the information needed to select pesticides to avoid water pollution by pesticides in a particular production or management unit. Instructions for using the worksheet are provided. The function of the worksheet is to match the soil leach and runoff ratings at the application site with the pesticide RLPI (leaching) and RRPI (runoff) indices and toxicity values given in Table 1 .

This will indicate the relative potential for pesticides to leach or run off from a particular site and consider the toxicity of the pesticides to humans or aquatic life if the pesticides leach into groundwater or if runoff enters surface impoundments or streams. The last two columns are for recording the pepper grower's choices and reasons for selecting particular products.

Our intent is to provide a decision support tool for the pepper grower. The grower is responsible for making the final choice. The completed worksheet can serve as a permanent record of the selection process used and decision made by the grower.

Using the Worksheet

  1. Target Pest: Correct identification of the pests that need to be controlled is essential! Check with knowledgeable experts and utilize competent diagnostic laboratories so that a proper diagnosis can be made. Misdiagnosis results in the wasteful use of unnecessary pesticides and needless increases in production costs. List confirmed pests in column 1 of the PESTICIDE SELECTION WORKSHEET .

  2. Recommended Pesticides: Use the current IFAS Pest Management Guides, or other appropriate information sources to identify the pesticides that control the pests of concern. List these pesticides in column 2 of the PESTICIDE SELECTION WORKSHEET.

  3. Pesticide Properties : For each pesticide listed in column 2 on the PESTICIDE SELECTION WORKSHEET , copy the numeric value for K oc , RLPI, RRPI, MCL/HAL/HALEQ, and Aquatic Toxicity from Table 1 into columns 3, 4, 5, 6, and 7 of the PESTICIDE SELECTION WORKSHEET.

  4. Soil Properties : Consult the County Soil Survey Report soil map sheets to locate your production fields and to identify the soils that occur in these fields. Use the Soil Science Fact Sheet entitled "[Your County]: Soil Ratings for Selecting Pesticides" (available from your county Cooperative Extension Office) to determine the leaching and surface runoff rating of the soils in your fields. As you determine the soil leach rating and the soil runoff rating for each soil in each field, list the soil name, soil leach rating, and soil runoff rating in columns 8, 9, and 10, respectively, of the PESTICIDE SELECTION WORKSHEET.

  5. Selection of Pesticides : Using information that you have compiled on the PESTICIDE SELECTION WORKSHEET , select appropriate pesticides using the Pesticide Selection Criteria to match soil and pesticide properties. The selection made can be recorded in column 11 and notes relating to the selection can be recorded in column 12.

Notes:

  1. If the pesticide product selected is a formulated mixture or a tank mix, each active ingredient must be considered. The most restrictive pesticide in the mixture will determine the choice. Trade names in Table 1 followed by (M) are formulated mixtures.

  2. Sometimes there may not be a clear choice from among the alternative chemicals available to control a particular pest. In these cases, first order screening using the RLPI or RRPI only can suffice.

  3. Depth to groundwater and local geohydrology may influence your final selection. Shallow groundwater is more vulnerable to contamination Deep water tables with intervening impermeable geologic layers are much less vulnerable.

  4. Distance to surface water bodies may also influence your final selection. Surface waters adjacent to or near the pesticide application site are more vulnerable to contamination than those further away. If surface runoff from the application site usually infiltrates into the soil off site before reaching a surface water body, then the MCL/HAL/HALEQ should be considered as the secondary screening index.

ACKNOWLEDGMENTS

The development of this document was supported by the USDA/ES Water Quality Initiative Project #89EWQI-1-9134 and the Center for Natural Resources, University of Florida, Gainesville, FL.

Tables

Table 1. 
Criteria for Matching Soil Ratings with Pesticide Indices
Pesticides with less potential to adversely affect water quality can be selected by matching the soil ratings and pesticides with the following criteria:
PESTICIDE SELECTION CRITERIA
IF SOIL RATINGS ARE: THEN
LEACH RUNOFF SELECT PESTICIDE WITH:
HIGH LOW Larger RLPI value, AND Larger MCL/HAL/HALEQ value.
MEDIUM LOW Larger RLPI value, AND Larger MCL/HAL/HALEQ value.
LOW LOW Larger RLPI and RRPI values, AND Larger MCL/HAL/HALEQ and Aquatic Toxicity values.
HIGH MEDIUM Larger RLPI and RRPI values, AND Larger MCL/HAL/HALEQ and Aquatic Toxicity values.
MEDIUM MEDIUM Larger RLPI and RRPI values, AND Larger MCL/HAL/HALEQ and Aquatic Toxicity values.
LOW MEDIUM Larger RRPI value, AND Larger Aquatic Toxicity value.
HIGH HIGH Larger RLPI and RRPI values, AND Larger MCL/HAL/HALEQ and Aquatic Toxicity values.
MEDIUM HIGH Larger RRPI and RLPI values, AND Larger Aquatic Toxicity and MCL/HAL/HALEQ values.
LOW HIGH Larger RRPI value, AND Larger Aquatic Toxicity value.
Table 2. 
Table 1. Peppers-Pesticide parameters for selecting pesticides to minimize water quality problems.
Trade name1 Common name Application Type2 Sorption Coefficient3 Relative Losses Toxicity
Soil Foliar Koc (ml/g) Leaching RLPI4 Runoff RRPI5 MCL, HAL or HALEQ6 (ppb) Aquatic LC507(ppm)
Herbicides
Command clomazone   x 300   125 125 300 * 19
Dacthal DCPA x   5000   500 2 4000   100a
Devrinol napropamide INC   700   100 20 700 * 16.6
Diquat H/A diquat dibromide salt   x 1000000 E >2,000 1 20 * 10
Dual metolachlor PRE   200   22 22 100   2
Enquik monocarbamide sulfate   x nd   nd nd 0   nd
Gramoxone Extra paraquat dichloride salt x x 1000000 E >2,000 1 30   15
Poast sethoxydim   x 100 EpH7 200 200 600 * 170
Treflan trifluralin INC   8000   1330 2 5   0.041
Insecticides/Miticides
Admire imidacloprid x   200   18 18 400 * 211
Agree Bacillus thuringiensis   x nd   nd nd nd   95b
Ambush permethrin   x 100000   >2,000 1 350 * 0.0041
Asana XL esfenvalerate   x 5300   1510 5 nd   0.00068j
Bactospeine Bacillus thuringiensis   x nd   nd nd nd   95b
Bactur Bacillus thuringiensis   x nd   nd nd nd   95b
Baythroid cyfluthrin   x 100000 E >2,000 1 175 * nd
Cygon/Dimethoate dimethoate   x 20   28 28 1 * 6.2
Cythion malathion x x 1800   >2,000 555 200   0.2
D.Z.N. diazinon INC x 1000 E 250 25 0.6   0.09
Di-Syston disulfoton x   600 E 200 55 0.3   1.85
Dibrom naled   x 180   1800 >1,000 10 * 0.195
Dipel Bacillus thuringiensis   x nd   nd nd nd   95b
Dyfonate fonofos INC   870   217 28 10   0.02
Guthion azinphos-methyl   x 1000   1000 100 9 * 0.0043
Javelin Bacillus thuringiensis   x nd   nd nd nd   95b
Kelthane dicofol   x 5000 E 1110 4 7 * 0.52b
Kryocide cryolite   x 10000 E 33 1 nd   47
Lannate methomyl   x 72   24 24 200   3.4
Lorsban chlorpyrifos   x 6070   >2,000 5 20   0.0071
M-Pede insecticidal soap   x nd   nd nd 0   nd
Marlate/Methoxychlor methoxychlor   x 80000   >2,000 1 400   0.062
Metasystox-R oxydemeton-methyl   x 10   10 10 4 * 6.4
Meticide methyl parathion   x 5100 E >2,000 39 2   3.7
Neemix azadirachtin   x 0   nd nd 0    
Orthene acephate   x 2   6 6 30 * 730
Phaser endosulfan   x 12400   >2,000 1 40 ** 0.0014
Pounce permethrin   x 100000   >2,000 1 350 * 0.0041
Provado imidacloprid   x 200   18 18 400 * 211
Pyrellin rotenone   x 10000   >2,000 33 30 * 0.031
Pyrellin (M) pyrethrins   x 100000 e >2,000 1 70 * 114a
Pyrenone (M) pyrethrins   x 100000 e >2,000 1 70 * 114a
Pyrenone (M) piperonyl butoxide   x 2500 E nd nd 100 * 0.0034
Pyrenone(M) piperonyl butoxide   x 2500 E nd nd 100 * 0.0034
Pyrenone(M) pyrethrins   x 100000 e >2,000 1 70 * 114a
Rotacide rotenone   x 10000   >2,000 33 30 * 0.031
Safer Soap insecticidal soap   x nd   nd nd 0   nd
Sevin carbaryl   x 300   300 300 700   114
Spectracide diazinon   x 1000 E 250 25 0.6   0.09
Telone C-17 (M) chloropicrin   x 62   620 620 nd   nd
Telone C-17 (M) 1,3-dichloropropene   x 32   32 32 0.2   5.5
Telone II 1,3-dichloropropene   x 32   32 32 0.2   5.5
Thiodan endosulfan   x 12400   >2,000 1 40 ** 0.0014
Trigard cyromazine   x 200 E 13 13 50 * >100
Vydate oxamyl   x 25   62 62 200   4.2
Xentari Bacillus thuringiensis   x nd   nd nd nd   95b
Nematicides
Furadan carbofuran INC   22   4 4 40   0.38
Vydate L oxamyl x   25   62 62 200   4.2
Fungicides
ATO Maneb + Zinc (M) zinc   x nd   nd nd 0   nd
ATO Maneb + Zinc (M) maneb   x 2000 E 285 7 40 * 1.9
Agri-mycin streptomycin   x nd   nd nd 0   nd
Basicop copper sulfate,basic   x nd   nd nd nd   nd
Blue Shield cupric hydroxide   x nd   nd nd nd   0.08
Brom-O-Gas methyl bromide INJ   22   4 4 7 * 2.5
Brom-O-Sol methyl bromide INJ   22   4 4 7 * 2.5
Brozone methyl bromide   x 22   4 4 7 * 2.5
COC copper oxychloride   x nd   nd nd 0   nd
CP Basic copper sulfate   x nd   nd nd nd   0.14
Captan captan x   200   800 800 900 * 0.0732
Champ cupric hydroxide   x nd   nd nd nd   0.08
Champion cupric hydroxide   x nd   nd nd nd   0.08
Chlor-O-Pic chloropicrin INJ   62   620 620 nd   nd
Citcop copper salts of rosin acids   x nd   nd nd 0   toxic
Copper-Count-N copper ammonium carbonate   x nd   nd nd 0   0.0204
Cuproxat copper sulfate   x nd   nd nd nd   0.14
Hydrox cupric hydroxide   x nd   nd nd nd   0.08
JMS Stylet Oil peteroleum oils   x 1000 G 1000 100 nd   nd
Kocide cupric hydroxide   x nd   nd nd nd   0.08
MC-2R methyl bromide INJ   22   4 4 7 * 2.5
MC-33 (M) methyl bromide INJ   22   4 4 7 * 2.5
MC-33 (M) chloropicrin INJ   62   620 620 nd   nd
Manex maneb   x 2000 E 285 7 40 * 1.9
Oxycop copper ammonium carbonate   x nd   nd nd 0   0.0204
Picfume chloropicrin INJ   62   620 620 nd   nd
Ridomil metalaxyl x   50   7 7 400 * >100
Ridomil Copper metalaxyl   x 50   7 7 400 * >100
Subdue metalaxyl x   50   7 7 400 * >100
Subdue II metalaxyl   x 50   7 7 400 * >100
Tenn-Cop copper salt of rosin acids   x nd   nd nd 0   toxic
Terr-O-Gas methyl bromide INJ   22   4 4 7 * 2.5
Terraclor PCNB x   5000 E >2,000 9 20 * low tox
Thiram thiram x   670   446 99 40 * 0.13
Top Cop + Sulfur (M) copper sulfate   x nd   nd nd nd   0.14
Top Cop + Sulfur (M) sulfur   x nd   nd nd nd   non toxic
Tribasic copper sulfate,basic   x nd   nd nd nd   nd
Vapam metam sodium INJ   10 E 14 14 nd   0.079
Fumigants
Terr-O-Gas (M) chloropicrin INJ   62   620 620 nd   nd
Vapam metam sodium INJ   10 E 14 14 nd   0.079
Vorlex (M) 1,3-dichloropropene INJ   32   32 32 0.2   5.5
Vorlex (M) methyl isothiocyanate INJ   6   8 8 nd   0.37
1Tradename: (M) indicates that the product is a mixture of two or more active ingredients.
2Application Type: INC: incorporated; INJ: injected; PRE: preemergence; X: applied to soil surface or foliage
3Sorption Coefficient: E: estimated G: educated guess
4Relative Leaching Potential Index (RLPI): Smaller number indicates greater leaching hazard.
5Relative Runoff Potential Index (RRPI): Smaller number indicates greater runoff hazard.
6Drinking Water: Maximum Contaminant Level (MCL), Lifetime Health Advisory Level (HAL); * Lifetime Health Advisory Level Equivalent (HALEQ);
7Aquatic Toxicity LC50:

value is for rainbow trout 48 or 96 hr exposure time, unless otherwise specified.

a=channel catfish b=bluegill c=carp j=fat head minnow

nd: no data available
Table 3. 
PESTICIDE SELECTION WORKSHEET
Landowner/Operator Name:___________________________________________________________County:_________________________________________________Date:________________
Crop:__________________________________________________________Farm ID:_______________________________________Field ID___________________________Sheet____of______
      Relative Losses Toxicity          

Target Pest

(1)

IFAS Recommended Pesticides

(2)

K

oc

Value

(3)

Leaching RLPI

(4)

Runoff RRPI

(5)

MCL/HAL HALEQ (6) Aquatic Toxicity (7) Soil Type (8)

Soil Leaching Rating

(9)

Soil Runoff Rating (10) Selected Pesticide (11)

Comments

(12)

                       
                       
                       
If the Koc value is 100 or less or if the RLPI value is 10 or less and the soil leach rating is high, then the pesticide has a high potential for leaching and should be used with extreme caution. Alternative pesticides and reduced rates should be considered if possible. Apply pesticide during periods with low potential for rainfall if possible.

Footnotes

1.

This document is Circular 997, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Last revision: January 1998. Please visit the FAIRS Website at http://hammock.ifas.ufl.edu.

2.

T.M. Buttler and A.G. Hornsby, Soil and Water Science Department; W.M. Stall, Vegetable Crops Department; F.A. Johnson, Entomology and Nematology Department; J.W. Noling, Citrus Research and Education Center, Lake Alfred, FL; T.A. Kucharek, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.