Evaluation of low risk weed management options in sweet corn, tomatoes, sugar beets, peppers, cole crops and vine crops

Project code: MU03-WEED1

Project Lead

Al Hamill - Agriculture and Agri-Food Canada

Objective

To screen new, reduced-risk or low rate herbicides as potential weed control solutions in cole crops, sweet corn, sugar beets, and other vegetables

Summary of Results

Researchers have followed up on preliminary work which suggested that some of the new, reduced-risk herbicides registered for use on major crops may be of value in controlling weeds in other crops.

Research studies were conducted to test efficacy and crop tolerance in these new chemistries at one and two times the label rate. Crops investigated in the project were: sweet corn, cucumber, pumpkin, squash, broccoli, cabbage, cauliflower, tomato, peppers, and sugar beets. Tolerance and efficacy of a number of tank mixes were evaluated, and promising candidates put forward for consideration within the AAFC Minor Use Pesticides program for the URMULE (User Requested Minor Use Label Expansion) registration system.

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 preemergence 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.

To control insects and disease, insecticides and fungicides were applied following OMAFRA recommendations. In each trial herbicide injury ratings were taken at 7, 14, and 28 days after the herbicide was applied in each treatment at each site. Percent weed control was measured at 14, 28, and 56 days after herbicide treatment.

Conclusions

1) the potential to use pyrazon + ethofumasate should desmedipham/phenmedipham no longer be available for use in sugar beets; 2) the screening of Goltix (ai=metamitron) a possible European alternative to desmedipham/phenmedipham for weed control in sugarbeets; 3) Development of best management practices for timing of Roundup application and possible tank-mixes with PRE herbicides and fungicides in Roundup Ready sugarbeets; 4) Investigation into the feasibility of reduced or split rates of s-metolachlor/benoxacor in sugarbeets; 5) flumioxazin, mesotrione and sulfentrazone each provided an early indication for good weed control in tomatoes although in some cases some injury was observed and this needs to be resolved; 6) Processing tomatoes showed good tolerance to thifensulfuron-methyl; 7) a number of materials looked promising for use preemergence under plastic managing weeds in sweet corn, however, pendimethalin was not acceptable to use this way; 8) Topramezone, KIH-485, and nicosulfuron have been screened and shown good tolerance in a wide selection of sweet corn varieties; 9) ethametsulfuron-methyl was used successfully in broccoli, cabbage and cauliflower; and 10) clomazone or halosulfuron-methyl alone, or a tank mix together provided good weed control and caused only slight temporary injury to cucumber and muskmelon plants.

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