Insect pests and plant disease don’t often respect our schedules. There can still be risks as crops begin to mature, especially considering the wet conditions in many areas of the province. It is important to scout for disease and insects and weigh the risk to the crop based on economic thresholds. It is also important to know when the window to act has passed and it is no longer possible or economical to act.
Insect pests such as grasshoppers may feed on developing lentil (blooming or podding) or flax seeds (green boll stage). Aphids are also a potential issue before the plants are at the soft dough stage.
In terms of plant diseases, for crops such as cereals (Fusarium Head Blight) and canola (sclerotinia stem rot) the spray window is during crop flowering. Once the window for fungicide application has passed, there are no registered fungicides available for disease management. However, for indeterminate crops such as lentil or pea, there may still be the potential to control disease if it is present in the crop, conditions favour further development, it will be economical to control it and there is a chemical option with the appropriate pre-harvest interval (PHI).
A pre-harvest interval (PHI) is the number of days that must past between the application on the chemical and the swathing, desiccation or otherwise cutting/termination of the crop’s growth. For any chemical application, as we get closer to harvest it is critical to consider the PHI. All pesticides: herbicides, fungicides and insecticides will have a PHI that is set so that harvested crops do not exceed the maximum residue limit (MRL) of that chemical. If the crop is harvested prior to the indicated PHI, there could be unsafe or unacceptable residues of the pesticide in or on harvested seeds.
The PHI information for a specific pesticide can be found on the product page of the Guide to Crop Protection and on the pesticide label itself.