Integrated Crop Management

Fungicides: Safety and restrictions

Eighth in a series. See Part 7 [1].

Reading through a pesticide label will give you most of the needed information concerning safety for both yourself and others while spraying field crops. Below is a synopsis of some of the dangers and restrictions for some common fungicides. For details on a specific fungicide, please follow the label's directions for mixing and application along with the instructions for safe use.

Personal protective equipment

Fungicides labeled for use on field crops have minimal requirements for personal protective equipment, with a few exceptions:

Some fungicides require coveralls over regular work clothing, and some fungicides only require waterproof gloves. Also, nearly half of the available fungicides require protective eyewear.

Other requirements include chemical-resistant footwear, chemical-resistant headgear for overhead exposure, and a chemical-resistant apron when cleaning, mixing, or loading (Headline®, Headline® SBR, and Laredo® 25EC). A few fungicides may require the use of a respirator. The details about the specific type of respirator will be listed on the label.

The Worker Protection Standard (WPS)

The WPS is a federal regulation designed to protect agricultural workers and handlers. It covers pesticides that are used in the production of agricultural plants on farms, forests, nurseries, and in greenhouses. If the pesticide that you are using has an "Agricultural use requirement" statement in the "Directions for Use" section of the label, you must comply with the WPS. The most recent information about the Standard may be obtained by checking the September 2005 updated WPS How to Comply manual. A helpful Web site that has information about the WPS is

Protective eyewear [2]
Nearly half of the available fungicides require protective eyewear. (Joyce Hornstein)

Restricted-Entry Interval (REI)

All agricultural pesticides labeled after April 1994 are required to have a Restricted-Entry Interval (REI) stated on the label. REIs for fungicides, like other pesticides, are established to reduce pesticide exposure and are based on the product toxicity. REIs typically range from 12 to 24 hours for most fungicides available in Iowa for field crops.

In general, workers may not enter a treated area during a Restricted-Entry Interval. Early entry that will result in contact with surfaces treated with pesticides is permitted in only three work situations:

Preharvest Interval (PHI)

These intervals state the minimum amount of time that must pass between the last pesticide application and the harvesting of the crop, or the grazing or cutting of the crop for livestock feed. Typically, PHIs for fungicides applied to field crops range between 21-30 days. Chlorothalonil products have 42-day PHIs. Some triazoles and triazole + QoI fungicides have restrictions based on growth stages instead of a specific number of days--fungicides cannot be applied later than soybean growth stage R5.

Stricter residue limits from other countries are being established. If a crop is harvested before the PHI has passed, there may be excessive pesticide residues on that crop.

Other restrictions and precautions

Listed below are additional restrictions or precautions. These do not necessarily pertain to all fungicides. Carefully read labels prior to application to get specific information for the product being used.

The following Iowa State University Extension publications may be purchased or viewed by contacting Iowa State University Extension Distribution or by visiting their Web site,

This article originally appeared on pages 193-195 of the IC-496(18) -- July 3, 2006 issue.

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