It looks like pesticide injury. The effectiveness of a spray depends on products, plant growth stage, weather conditions etc. Leaf injury and other damage may happens due to poor mixing and agitation, highly concentrated materials, faulty spray equipment, or extremes of weather during or after spraying.

1. Type of plant and growth stage: Some plants are very sensitive to pesticides at particular growth stage. So make sure the pesticide is suitable for that stage.
2. Weather conditions: Spraying during drought stress or extremely dry, cold and wet, or hot conditions increases the chance of injury.
3. Faulty spray equipments may spray bigger droplets and increases concentration of pesticide on plants which causes injury.
4. Products: Most of the pesticides are crop specific, so make sure you choose the right one. Also select the correct formulations (for example- emulsifiable materials as foliage applications are more likely to cause injury than wettable powders).