The Additional Crabgrass Control is highly recommended for lawns that have a history of crabgrass. Additionally, lawns that are thin or stressed from environmental factors, or those that are continually mowed very short will benefit tremendously. This application is applied approximately 4 to 6 weeks after your first lawn treatment with pre-emergent controls. The treatment is usually done in the month of May using a different product. The combination of the two treatments will give you a much longer soil residual, and provide protection from crabgrass throughout the summer. An additional benefit of this treatment is the material also gives a post-emergent control for any emerging crabgrass plants. The pre-emergent controls are also more effective at controlling a wide variety of summer annuals in addition to crabgrass. Past results have proven this treatment to be highly effective, and have delivered very positive results.