Observing harvest withholding periods in broadacre crops

What is a harvest withholding period (WHP) for grain crops?

The minimum amount of time that must elapse between the application of a pesticide and the harvesting of a crop. You must not harvest a crop before the withholding period has expired.

What is the purpose of a WHP?

To ensure that the maximum residue limit (MRL) is not exceeded in the harvested grain or in the forage.

Do all crop protection products have a withholding period?

Yes. All insecticides, fungicides and herbicides will have a specific WHP listed on the label.

Where can I find this information?

WHPs are always stated under the ‘Table of Directions for Use’ on the product label and in some cases also within the Table of Directions for Use. See Image 1.

Are WHPs the only factor that can affect MRLs?

No. It is important to comply with all instructions on the label, particularly the rate of application, number of applications permitted, and crop application timing.

What does NOT REQUIRED WHEN USED AS DIRECTED mean?

When the time that will elapse from the application timing stipulated in the Directions for Use table is sufficient to ensure an MRL is not exceeded in the harvested grain. For example some products may state: Do not apply after flag leaf emergence, or similar.

What about the grazing WHP?

Grazing WHPs refer to grazing whole plant residues whereas harvest refers only to the harvested part of the plant (grain). There are separate MRLs for the fodder component and the grain component. Grazing WHPs should be observed before allowing stock into treated areas.

**Consult your agronomist if unsure about the harvest or grazing WHP for any particular product

Image 1: Withholding Periods from the Roundup UltraMAX label

Table 1: Withholding periods of some crop protection products