Purpose of HUA
The Idaho Snake-Payette Rivers Hydrologic Unit Area (HUA) is one of 74 projects funded nationally by USDA. These 5-year projects have the purpose of accelerating the transfer of best management practice (BMP) technology necessary to protect both ground and surface waters while still maintaining farm profitability. Program efforts focus on irrigation, nutrient, and pesticide management for groundwater protection, and on structural practice implementation for surface water protection. The HUA projects offer agriculture the opportunity to demonstrate that education coupled with a voluntary BMP implementation program can protect and even enhance existing water quality.
The Snake-Payette Rivers HUA comprises over 840,000 acres in Canyon, Gem, Payette, and Washington counties in southwestern Idaho. Within the project area are 3,400 farms covering more than 500,000 acres. Virtually all of the productive farmland is irrigated. Agriculture within the HUA is very diverse as over 50 different high value crops are grown.
Pesticides have been detected in aquifers in the Snake-Payette Rivers HUA and across the USA. The public is demanding that agriculture judiciously use pesticides and minimize potential environmental contamination -- such as leaching losses of Dacthal into groundwater. The groundwater resource beneath much of the Snake-Payette Rivers HUA is particularly vulnerable to nonpoint source contamination due to its shallow depth and the intensity of irrigation and agrichemical use above it. Breakdown products of the herbicide Dacthal have been detected at low concentrations in many areas of the Snake-Payette Rivers HUA. The herbicides 2,4-D and metribuzin, and the insecticide Diazinon have also been found in rural well water samples.
This survey of current grower pesticide management practices was a necessary first step for the development of both education and implementation plans focusing on the improvement of pesticide management in the HUA. Specific survey objectives included:
|Crop||Acres in HUA||Fields surveyed|
Pesticide - any chemical used to kill pests
Herbicide - any pesticide used to kill weeds
Insecticide - any pesticide used to kill insects
Fungicide - any pesticide used to kill fungi causing a plant disease
Miticide - any pesticide used to kill mites
Growers reported a large number of pests in the fields surveyed.
Most commonly reported pests in HUA:
|Alfalfa-hay||quackgrass||aphids||phytophthora root rot|
|-seed||nightshade||lygus bugs||phytophthora root rot|
|Field corn||pigweed||aphids||none reported|
|Sweetcorn||nightshade||corn earworm||corn smut|
|Hops||kochia||spider mites||powdery mildew|
|Mint||field bindweed||spider mites||verticillium wilt|
|Potato||nightshade||spider mites||early die|
|Small grains||kochia||aphids||stem rust|
The quantity and types of pests reported would render farming uneconomical in most cases if pesticides were not applied. Satisfactory non-chemical alternative pest control measures are not available for many crops grown in the Snake-Payette Rivers HUA.
Growers in the HUA rely on multiple applications of the same and different pesticides for chemical control. Depending on the crop, between two and 12 pesticide applications are made each year. With 12 pesticide applications, onions are the most intensively managed crop. Conversely, field corn receives an average of two pesticide applications per season.
Types of Pesticides Used
The practice of fumigation before planting is common for both onions and potatoes. Fumigants suppress pests such as nematodes and soil-borne root diseases. The use of fumigation on sugarbeet fields and new orchards has increased over the past decade.
Between one and six separate herbicide applications are applied each season to crops in the HUA. Sugarbeets receive the greatest number of applications, while sweet corn, hops, and small grains generally receive only one application.
Dacthal, a pre-emergence herbicide, is commonly applied to onions, beans, and turf in the Snake-Payette Rivers HUA. The breakdown products of Dacthal have been found in groundwater within the HUA. Currently, about 70 percent of the onion growers surveyed apply Dacthal. Growers that use Dacthal as a band application compared to broadcasting reduce the quantity of chemical applied by one-third.
One to five insecticide applications are common on crops in the HUA. Onions and orchard crops receive the greatest number of insecticide applications due to onion thrip and codling moth pressures. Field corn and small grains average only one insecticide application each season.
Fungicides are routinely applied to six of the 11 crops surveyed. With an average of 3.5 applications, onions receive the greatest number of fungicides which are primarily directed at powdery mildew.
Miticides are often applied to alfalfa, beans, hops, mint, orchard crops, potatoes, and sweet corn in the HUA. The greatest number of miticide applications are made on sweet corn for processing to control spider mites.
Pest pressure and consequent pesticide management within the Snake-Payette Rivers HUA is intensive. The 11 crops evaluated in this survey receive many pesticide applications each season. Chemical pest management is most intensive with onions as an average of 12 pesticide applications are made each season. In contrast, field corn receives an average of two pesticide applications each season.
The ranges in average number of pesticide applications for the 11 crops in the HUA survey were 1 to 6.5 for herbicides, 1 to 4.7 for insecticides, 0 to 3.6 for fungicides, and 0 to 2.9 for miticides.
The results of this survey will allow the targeted development of education and implementation programs to best meet the goals of the Snake-Payette Rivers HUA.
This brochure, WQ-19, was prepared by T. D. Steiber and R. L.
Mahler. Mahler is the University of Idaho extension water quality coordinator,
located in the Soil Science Division, University of Idaho, Moscow, Idaho
83844-2339. Stieber is a water quality extension agent. Project office is
located at 1630 Third Ave. S. #3, Payette, ID 83661. Telephone: (208)
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All contents copyright © 1997-2003. College of Agricultural and Life Sciences, University of Idaho. All rights reserved. Revised: January 3, 2003