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Waterhemp Now a Manitoba Weed

Can you identify the plants in the two pots below?

waterhemp-and-redroot-pigweed

The plants on the right are redroot pigweed (Amaranthus retroflexus); the plants on the left are waterhemp (Amaranthus tuberculatus).

Unfortunately, the need to distinguish between these closely related weed species has become a reality for Manitoba producers and agronomists since waterhemp was found in the province in the fall of 2016. Suspect plant specimen collected from a soybean field in the RM of Taché was verified as waterhemp by staff with the Agriculture and Agri-Food Canada Collection of Vascular plants in Ottawa.  Waterhemp occurs in neighbouring states and provinces, including Minnesota, North Dakota and Ontario.

Both species thrive in agricultural fields where they compete with crops for nutrients, moisture and light. Waterhemp has no hairs on its stem or leaves, which can be used to distinguish it from redroot pigweed when plants are small.  The lack of hairs give waterhemp leaves a ‘glossy’ look unlike that of the ‘dull’ green leaves of redroot pigweed.  Also, waterhemp leaves are lanceolate in shape (longer than they are wide) compared to the more ovate leaves of redroot pigweed.  Colour is not a reliable identifying characteristic since both species can be green, red or variations of the two colours.

Mature waterhemp plants tend to be more branched than redroot pigweed. And unlike redroot pigweed, which has male and female flowers on the same plant, waterhemp has separate male and female plants.  Waterhemp inflorescence are long, slender and vary in colour compared with the compact, prickly inflorescence of redroot pigweed.  Like most pigweeds, waterhemp is a prolific seed producer with up to a million seeds per plant (under ideal conditions).

Waterhemp populations resistant to group 2, group 9 (glyphosate) and group 2+9 exist throughout the US, including Minnesota and North Dakota, and in Ontario. Seed from one of the plants found in Manitoba have been sent to Ontario for resistance testing.

Information on waterhemp will be added to Manitoba Agriculture’s weeds webpage shortly (http://www.gov.mb.ca/agriculture/crops/weeds/) and will be included at the Weed Seedling Identification Day (hosted by the Manitoba Weed Supervisors Association).  Manitoba Agriculture staff will conduct a waterhemp surveillance program in and around the RM of Taché in 2017.

Additional information on waterhemp is available at: http://www.extension.purdue.edu/extmedia/BP/gwc-13.pdf (excluding herbicide recommendations).

waterhemp-tone-ag-consulting

Photo: Waterhemp in Manitoba, Tone Ag Consulting

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture

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A Look at FDK & DON in Winter Wheat Varieties

In 2014, a study was initiated to evaluate how winter wheat varieties being tested post-registration by MCVET respond to fusarium head blight under non-misted conditions (natural infection) by assessing harvested samples for fusarium damaged kernels (FDK) and deoxynivalenol (DON) accumulation. The results from 2014 can be found here: Winter Wheat Varieties Response to Fusarium Head Blight in 2014 and Effect of Fusarium Head Blight on Winter Wheat Varieties in 2014.

2015 Results. With funding from Winter Cereals Manitoba Inc., the study continued in 2015. Composite samples of eight registered winter wheat varieties were collected from the three replicates at four MCVET sites: Carman, Hamiota, Melita & Minto.  BioVision Seed Labs in Winnipeg, Manitoba conducted the analysis. The level of FDK (%) was measured as per the Official Grain Grading Guide of the Canadian Grain Commission. The accumulation of DON (ppm) was measured using the ELISA test method.

The variety Emerson, rated as Resistant (R), had lower levels of FDK and DON compared to the other varieties (see Figure 1).  Some varieties rated as Susceptible (S) consistently showed higher FHB severity, FDK and DON levels across all sites. However, data also shows there is variability of performance within the five resistance categories of Resistant (R) to Susceptible (S).

Figure 1: Average Levels of Fusarium Damaged Kernel (FDK) and Deoxynivalenol (DON) by Winter Wheat Variety at Four MCVET Sites in 2015

2015-average-don-fdk-at-four-mcvet-winter-wheat-sites

Figure 2: Fusarium Damaged Kernel (FDK) and Deoxynivalenol (DON) Comparisons at Four MCVET Sites for Winter Wheat Varieties in 2015.

2015-fdk-don-comparisons-at-four-mcvet-winter-wheat-sites

 

2016 Results. In the 2016 Manitoba Fusarium Head Blight Survey, the average FHB index for winter wheat was 2.7% which was slightly below the 10-year-average (3.1%).  Winter Cereals Manitoba Inc. again is providing funding to have the MCVET winter wheat varieties tested for FDK and DON. Analysis is currently underway and results should be available for the Winter Cereals Manitoba Inc. Annual General Meeting on March 15, 2017.

Summary. Extensive research over the past 20 years shows using multiple management options, including crop rotation, fungicide application and variety selection, is the best way to mitigate the risk of FHB. Although FHB infection will always be highly influenced by environment, the first step is to select varieties with improved resistance and then use them in combination with other management strategies. In years where there is higher disease pressure, such as 2014, variety selection will be critical to minimize the impact of FHB on yield and quality. However, under high disease pressure yield and quality loss due to FHB can still happen in varieties that have improved resistance as resistance does not equal immunity.

Remember, caution must be used with one year of data, as presented here. Using data derived over two or more growing seasons over multiple sites is always recommended to provide the best indicator of variety performance.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Special thanks to: Winter Cereals Manitoba Inc. for providing funding to conduct FDK & DON analysis; BioVision Seed Labs who conducted the FDK and DON analysis; Manitoba Crop Variety Evaluation Team (MCVET) & contractors who provided the harvested samples.

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