Abstract
Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and after herbicide application can further complicate decisions because they influence herbicide efficacy. Eleven field trials were conducted at three locations in Southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST corn herbicides for weed control. The most abundant weed species across all locations were redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and green foxtail (Setaria viridis (L.) Beauv.). Nine PRE herbicide treatments and eleven POST (applied at the 3-4 leaf stage of corn) herbicide treatments were tested. Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy. For example, precipitation levels 0-17 mm within seven days after herbicide application (PRE or POST) provided unacceptable weed control in treatments that included atrazine, dimethenamidp, isoxa-flutole/atrazine or S-metolachlor/benoxacor. Cumulative precipitation during the 14 days after PRE application that exceeded the monthly average (by at least 64%) reduced Setaria viridis control with pendimethalin. This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure.
Highlights
Weather conditions, precipitation amount and timing, can significantly impact the efficacy of individual preemergence (PRE) and postemergence (POST)herbicides [1,2,3,4,5]
Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy
This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure
Summary
Herbicides [1,2,3,4,5]. When tank-mixed, the conditions underwhich each herbicide has the greatest efficacy can differ [1]. This means that tank-mixtures have the potential to provide more consistent weed control over a broader range of climatic conditions [6]. The grower always has the opportunity to apply a POST herbicide should a failure occur [11,12]. The benefit of including a POST component is that it allows the grower to make herbicide choices based on the weed spectrum in
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