Evaluation of low risk weed management options in dry edible beans and seed corn

Project code: MU03-WEED2

Project Lead

Al Hamill - Agriculture and Agri-Food Canada


To screen new, reduced-risk or low rate herbicides as potential weed control solutions in dry bean and seed corn inbreds

Summary of Results

In collaboration with the Ontario Seed Corn Grower's Association, a number of trials comprising more than 1000 treatments have been conducted in Essex and Kent Counties with reduced-risk or low rate herbicides over a three year period on numerous in-bred lines. Assessments were carried out using the manufacturers' recommended rate for corn (or soybean) as well as at twice the label rate to simulate spray overlap in the field. At the same time, studies were being conducted to determine the tolerance of various market classes of dry bean to low risk and post-emergence herbicides. The data collected from the almost 600 different treatments included visual crop injury ratings, weed control ratings, yield, etc. The project resulted in the identification of new herbicides for use in dry edible bean and seed corn inbred production, and the development of crop tolerance and efficacy data packages in support of potential registration submissions. All crops were seeded each year under good planting conditions. In 2004, planting was followed by a cooler than normal summer with ample rainfall which resulted in not only good crop growth but good pre-emergence herbicide activation. The timely rains; however, meant that there were multiple weed emergence events. In 2005, a little over 50mm of rain fell in the last two weeks of April. However, from May to mid July only 34mm of rain was received, and over the time period from June to September there were 40 days that were over 30 °C. Therefore, the results of the weed control depended heavily on the early treatment applications. The 2006 growing season was extremely wet. Precipitation was 112mm (May), 103mm (June), 104mm (July), 88mm (August), and 158mm (September). This represented a 30% increase in comparison to the 30 year average. In all cases, insecticides and fungicides were applied to control insects and disease following OMAFRA recommendations.

Conclusions : 1) although considerable variability was observed in the edible dry bean trials at the Greenhouse and Processing Crops Research Centre (GPCRC), nine treatments showed promise for continued evaluation on some or all of the 10 varieties; 2) depending on the site, trifluralin, s-metolachlor or imazethapyr applied PPI caused some injury to adzuki beans but did not reduce crop yield; 3) imazethpyr applied PRE resulted in variable injury but did not reduce crop yield; 4) fomesafen + imazamox applied POST caused variable injury to adzuki beans but did not reduce yield whereas either of the two materials alone mostly resulted in unacceptable injury and yield reduction; 5) white beans tolerated a PRE application up to 75 g ai/ha whereas kidney beans tolerated a rate of 150 g ai/ha; 6) generally, smaller seeded market class beans (black, otebo, pinto and white) had greater visual crop injury to KIH-485 applied PRE than the larger seeded market class beans (brown, cranberry, kidney and yellow eye); 7) there is potential for the use of linuron PRE for weed management in pinto, brown, cranberry, kidney and yellow eye beans; 8) new opportunities within seed corn occurred with the use of prosulfuron/dicamba, KIH-485, topramezone, mesotrione (PRE and POST) or a tank mix of reduced rates of bromoxynil + atrazine + nicosulfuron.

Weed control and crop safety data generated in the course of this project was used to support 18 registration submissions and will be incorporated into the OMAFRA Guide to Weed Control.

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