Beyond on/off: Increasing the benefits of patch spraying with multiple treatments

Authors: Wiles, Lori

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/6/2007
Publication Date: 2/6/2008
Citation: Wiles, L. 2007. Beyond on/off: Increasing the benefits of patch spraying with multiple treatments. Weed Science Society of America Meeting Abstracts. February 4-7, 2008, Chicago, Illinois

Interpretive Summary:

Technical Abstract: Site-specific weed management can encompass both limiting treatment to areas of the field where weed pressure is above the economic threshold (patch spraying) and varying the choice of herbicide for most cost-effective weed control of local populations. The potential benefits of patch spraying with multiple, postemergence treatments in irrigated corn was evaluated in simulation studies using weed counts from 16 fields. Patch spraying with one, two or the number of treatments that maximized net return for a field was simulated. With patch spraying with one treatment, the average area of a field left untreated was 34.5% and net return increased $3.09/ha and crop yield decreased by.05% of weed-free yield compared to the uniform application. Patch spraying with two or more treatments in a field increased net return by more than $4.94/ ha with just a small increase (4%) in the area of the field treated. Net return increases with patch spraying with one treatment because herbicide cost is reduced. With additional treatments, net return increased in a field because herbicide cost was reduced, crop yield was increased or both. Grasses were controlled better with multiple rather than a single treatment for patch spraying and the variability of escapes within a field was changed. Up to eight treatments were recommended for patch spraying with multiple treatments, but there may be little benefit in using more than three treatments within a field. Moreover, herbicide use may be substantially increased. Benefits varied among fields with a net return of $8.23/ha or more in half of the fields and a maximum of $19.20/ha with two treatments. Patch spraying may be best recommended as a strategy of using multiple treatments within a field in addition to leaving some areas untreated in a field and as a strategy that is appropriate in some fields rather than a standard replacement for uniform application.