Spray Timelines for Fruit Crops

By Forrest Scharf, PAg, Provincial Specialist Fruit Crops, Crops and Irrigation Branch, Regina

May 2024

Insects and diseases don’t often appear to be problematic during the earlier stages of crop development. However, it is best to deal with these crop threats as soon as possible, as the ability to control the pest greatly diminishes as the crop matures. In fruit crops, the best timeframe to control the majority of insect and disease pests is prior to and just after the bloom period. Many Saskatchewan fruit crops are currently in the blooming stage.

The use of pest control products is regulated, and growers must always follow spray recommendations found on product labels. Pest control product restrictions include pre-harvest intervals (PHI), re-entry intervals (REI) and the total number of applications allowable in a production season.

A PHI is the minimum amount of time that must occur between the last application and when the harvest of the crop is anticipated. For example, propiconazole is the active ingredient found in several fungicides registered to help control Entomosporium and Saskatoon Juniper rust diseases in the saskatoon berry. The PHI for propiconazole is 38 days before harvest, and up to three applications can be made. The first application is recommended at the “white tip” stage, when the white flower tip of the flower petals emerge. The second application is recommended when the white flower petals are falling off, and the final application can be made when small green fruit have formed. The fruit cannot be harvested within 38 days of the final pesticide application.

Without exceeding the maximum number of applications indicated in the product label, growers can decide how many applications to make. Several factors should be considered when applying pest control products:

• Climate Conditions – if it was raining over the blossom period, diseases have a greater potential to spread, and growers are recommended to consider the maximum number of applications. In dry conditions where disease is unlikely to spread, growers may be able to reduce the number of applications to two or fewer.
• Infection History – if there was no pest stress in the orchard in prior years, the number of applications can be minimized, but if pest pressure was strong in the previous year, the maximum number of applications should be implemented.
• Pest Control Product Rotations – using alternative chemical groups with different modes of action should always be incorporated in the spray scheduling. This is done to prevent the development of pesticide resistance.

REI is the minimum period that must pass before activity within a sprayed area is permitted. The length of an REI varies based on the chemistry of the pest control product, risk to human health, crop type and the type of activity to be performed within the space. For example, hand labour may be restricted longer than actions that do not require touching sprayed surfaces of plants. A minimum 12-hour REI must be observed in agricultural crops, even if no REI is indicated on the label.

Not all pests are active and susceptible to spray during the bloom period. Pest like fruit flies and other insects often emerge later in the season and should only be sprayed when they have emerged and are susceptible. Guides on what products to spray and the timing are available. If producers have questions, they should contact Forrest Scarf, Provincial Specialist, Fruit Crops, by calling 306-787-4666 or by email.