Pre-harvest applications of desiccants or harvest aidsare valuable tools for lentil producers. These chemical applications have eachhave strengths and weaknesses depending on the mode-of-action (MOA). Choosing the correctpre-harvest herbicide depends on the specific need or most vital concern as thelentil crop is maturing towards harvest such as the crop seed maturity stage orweeds present in the field (Menalled, 2009). Systemic herbicides such asglyphosate provides great weed control on all weeds with poor crop dry down,while contact herbicides will provide greater crop dry down but not controldifficult-to-kill weeds as well (Menalled, 2009). A lentil producer needs todecide on which need, crop dry down or weed control, is more important as thatmay have an impact on what pre-harvest herbicide is used and the applicationtiming.
Regardless of the rationalebehind applying a pre-harvest herbicide there are several considerations totake prior to the application such as: the correct herbicide, applicationtiming, and crop destination. Herbicide timing is important, as an incorrecttiming of application can reduce crop yield and quality (Fleury,2015). The effect of herbicide timingon yield harvest aid has been studied in many crops, including soybean (Glycine max), dry edible bean (Phaseolus vulgaris L.), and lentil (Lens culinaris Medik).
Glyphosateapplication in dry bean prior to 75% maturity can lead to reduced seed weightwhich indicates that harvest aid desiccations prior to 75% maturity may beaffecting seed quality (McNaughton, 2015). In soybean, a desiccationapplication prior to the R7 stage had the potential to negatively affect yieldand seed weight (Bennett and Shaw, 2000). Desiccation in lentil prior to 50% seedmoisture content can have a negative impact on yield (Zhang, 2015). Harvest aid application timing can alsoimpact the end use of the seed such as for export to another country or seedproduction to be used as seed the following year. Each pre-harvest herbicide has differentrestrictions on what can be done with the crop after harvest. For example,glyphosate cannot be used in lentil that is grown for seed production due toits systemic ability to move into the seed and reduce the quality, viability,and vigor of the seed (Baig et al.
, 2003). In Saskatchewan, it is notrecommended to use glyphosate as a harvest aid in any crop that it grown forseed production (Saskatchewan Ministry of Agriculture, 2014). Apart from seedproduction there is another important consideration for lentil producers whatcan affect both application timing and crop destination which is the maximumresidue limit (MRL) that different countries have set in place for differentherbicides.