What Is an Herbicide Split Application?

Pre-Emergent Herbicides

• Pre-emergent herbicides prevent seeds from sprouting. They control several types of weeds, but are effective for only about 60 days. For effective control of weeds, apply the first application of pre-emergent early, before any weed seeds sprout, in winter or early spring depending on your climate. Apply the second about 60 days later. You may need a third application in areas with a long growing season. Activate the herbicide within 24 hours by irrigating with 1/4 to 1/2 inch of water.

Post Emergent Weed Control

• Splitting the recommended application of post emergent herbicide and applying it when the weeds are young and tender leads to more effective control. Apply the first dose early in the growing season of the weeds. Additional weeds may sprout within 7 to 14 days of the first application and can be controlled by a second application when new growth appears. Complete control is important to reduce the weed seeds in the soil. This sometimes requires a third application.

Less Herbicide Damage

• Because herbicides are plant poisons, they can damage desirable plants. Using less herbicide causes less damage to desirable plants and they will have time to recover before the second application of a split application. Timing is important for effective weed control without damaging garden plants. Always read the label carefully. Make sure the herbicide is safe for the desirable plants and will kill the weeds that are present.

Environmental Effects

• With split applications, the total amount of herbicide required may be less than the amount applied in a single application. Less herbicide means less potential for environmental damage. However, lower dose, split applications of the same herbicide may contribute to the development of herbicide-resistant weeds. Avoid developing herbicide resistance by using herbicides only when necessary, changing herbicides each year, using a mixture of herbicides with different modes of action, using mechanical control or tilling where feasible, rotating crops, monitoring weeds and controlling them quickly, and cleaning equipment after tilling or weeding.