Split applications of Kerb in lettuce

By Barry Tickes, UA Area Agriculture Agent

The key to using the three pre-emergent herbicides registered in lettuce is to use the herbicide in the right place at the right time. In most cases, this is within the top one-half inch of soil when the weed seeds germinate.

Prefar and Balan stick strongly to the soil. Balan needs to be mechanically incorporated. Prefar needs plenty of water to push it into the soil.

Kerb is distinctly different. It leaches with the normal amounts of water used in the low desert and must be managed accordingly.

Widely used delayed chemigation applications are a means of accomplishing this. The timing rather than the application method is the most important.

Split applications to prolong the exposure of the weed seeds to the herbicide have been tried in recent years and recently registered for this use.

We have conducted trials with Dow Chemical to evaluate split applications of Kerb for the last few years. In one trial, a single application of 1.5 lb. produced similar control to all of the split applications except for 1.0 lb. followed by 1.0 lb. which was the best treatment. A single application made at the correct time and rate maybe the best recommendation.

Contact Tickes: (928) 580-9902 or btickes@ag.arizona.edu