By: Autumn Lawson, Summer Student, Regional Services Branch; Dena Lamb, Summer Student, Regional Services Branch; Kaitlyn Kitzan, Summer Student, Regional Services Branch; Paige Straf, Summer Student, Regional Services Branch; & Isabelle Piché, Summer Student, Regional Services Branch
Noxious weeds and commonly mistaken weeds in Saskatchewan
One of the #SKcropwalks for the week of July 22 discussed noxious weeds in Saskatchewan and some weed identification tips. This discussion took place at the weed ID demo station available during Crop Diagnostic School.
Noxious weeds in Saskatchewan are a prominent issue across the province. Some of the noxious weeds discussed at Crop Diagnostic School were yellow toadflax, nodding thistle, absinthe, common burdock, common tansy and scentless chamomile.
- Common tansy can be found on roadsides and pastures. The umbrella-like display of yellow, "button-like" flowers are a distinctive feature of the plant. Common tansy can be an issue for ranchers because some populations of the plant can cause abortions for pregnant livestock. It is important to control this noxious species if it is present in a field.
- Nodding thistle has large (approximately two inches), magenta-to-purple seed heads that nod to one side. It is found on roadsides and pastures. It can grow up to two meters tall.
- Scentless chamomile has a daisy-like flower and lacy, divided leaves. One plant can have more than 300,000 seeds.
- Absinthe is a noxious weed that is commonly confused with biennial wormwood and pasture sage. Crushing the leaves of absinthe or pasture sage will produce a sage-like odour that biennial wormwood does not. Pasture sage only reaches a height of 18 inches, whereas absinthe can reach four feet in height
There are many weeds that are commonly mistaken for each other, such as flixweed and scentless chamomile. Flixweed seedlings have three lobes on the first leaves, whereas scentless chamomile can have five or more present on the first leaves. Flixweed has a blue-green tinge to the leaves that helps to distinguish it from scentless chamomile. Scentless chamomile often doesn't have an odour and has lacy leaves as a distinguishing characteristic. Wild chamomile will have a tea odour when the flower buttons are crushed, which is how the wild species can be distinguished from the noxious scentless chamomile. Pineapple weed is also a commonly confused weed for scentless chamomile, since they both have lacy leaves. However, when the leaves of pineapple weed are crushed, it will have a pineapple-like odour. Another distinguishing characteristic of pineapple weed is the lack of petals on its flowers.
These noxious weeds can be found in a wide range of habitats across the province. Noxious weeds tend to move with people, animals and machinery, so this emphasizes the importance of practicing biosecurity measures.
Intercropping with Dr. Chapagain
Intercropping is becoming a popular topic. The difference between intercropping and sole cropping (a.k.a. monocropping) systems was discussed this year by Dr. Chapagain, who shared his research on the potential benefits of intercropping. He had two different plots at the Scott site. One of the plots was a wheat and faba bean mixture: two rows of wheat and one row of faba beans. The other mixture was a barley and pea intercrop. Dr. Chapagain stated that intercropping has agronomic, plant health, soil health, environment and economic benefits. Intercropping has proven to increase yield anywhere between 30 and 50 per cent, as well as seven to 10 per cent of carbon dioxide uptake. He states the importance of finding crops and varieties that you can plant and harvest together.
Fungicide timing and diseases
At the Fungicide Timing and Disease Identification station, Shannon Chant (Crop extension Specialist at the Saskatchewan Ministry of Agriculture's Swift Current office) explained that you need the right host, pathogen and environment for disease to occur. When scouting for diseases, you need to know what you are looking for and when you need to be looking for it. There are two common classifications of diseases: monocyclic and polycyclic.
Monocyclic diseases only have a single disease cycle per year and scouting should be focused on the risk of the disease occurring, which can be assessed by monitoring for environmental conditions that favour disease development. For monocyclic diseases such as sclerotinia stem rot and fusarium head blight, fungicide application needs to occur prior to disease infection and symptoms development. Risk assessment tools such as SaskWheat's FHB risk assessment maps or the sclerotinia stem rot checklist can be used to estimate risk and help you make informed fungicide application decisions. On the other hand, polycyclic diseases have multiple infection cycles within a single year. Scouting for polycyclic diseases should involve scouting crops for the presence of visible symptoms. When disease risk is high, fungicides can be applied to reduce disease progression and prevent yield loss. Most of the foliar diseases that we see in Saskatchewan include mycosphaerella blight, cereal rusts and leaf spots, anthracnose of lentils, and ascochyta blight. For some of the diseases, there are checklists that can be used to determine when to scout to assess risk and guide fungicide application decisions.
When making fungicide or disease management decisions, it is important that you are able to accurately identify the disease. For example, in canola, it is useful to be able to tell the difference between sclerotinia stem rot, blackleg and verticillium stripe lesions. Blackleg lesions can be present on the surface of foliage, stems and pods. Stem lesions often occur at the base of the plant and can be associated with hail damage. Within the lesion, there will usually be tiny, black fungal structures, called pycnidia, present. Severely infected plants may girdle due to basal cankers. The best way to scout for blackleg at the end of the season is to clip the stem at the base of the plant and look for black discoloration of the internal stem tissue (pith). Early sclerotinia stem rot symptoms are visible as soft watery lesions or discoloured areas of the plant. Lesions will expand and cause necrotic areas of the plant that are light grey in colour. At swathing, these lesions will often shred when they are scraped with your finger or nail or when the stem is twisted. When the stem is infected, the infected area will become hollow. Later in the season, black fruiting bodies will develop inside the stem, which can be seen when the stem is cracked open. These black bodies are called sclerotia and will eventually germinate to produce mushrooms called apotheica, which release the spores that initiate the sclerotinia stem rot disease cycle. When sclerotinia infects pulse crops, the small, hard, black bodies will be located on the outside of the stem. Verticillium stripe can appear as chlorotic (yellow) stripes along one side of the plant. However, the disease is most easily identified later in the season (after swathing) during which the outer stem tissue begin to peel back, revealing tiny, black bodies (microsclerotia) that resemble pepper.
It is important to apply fungicide at the right time. For example, when looking at peas with mycosphaerella blight, you want to apply fungicide when the bottom third of the plant is infected and conditions are right for the disease to move up the plant. If the whole pea plant is infected, there is not much use applying a fungicide, because the majority of the tissue is already affected, which means there will be little to no yield benefit. It is also important to not apply fungicide too late, because there can be fungicide residue in the plants if the product is applied too close to harvest. Pre-harvest intervals must be followed to ensure that residues do not exceed the maximum residue limit (MRL) of the fungicide being applied. Pre-harvest intervals can be found on the product label and in the Guide to Crop Protection.
Inoculant demonstration station with Gary Kruger
Another #SKcropwalk on July 24 focused on an inoculant demonstration with field peas and dry beans.
There were three different treatments shown in the video: no inoculant, inoculated and a "farmer practice" plot. The "farmer practice" plot means that 80 pounds of actual nitrogen was applied in order to avoid deficiency.
On the non-inoculated plot, there was little to no nodule development. This was due to dry bean rhizobium not being present in the soil. Species of inoculum that are naturally occurring in the soil do not effectively nodulate dry beans.
The inoculated field peas had many nodules and fixed about 30 to 80 lbs. of nitrogen. Dry beans, on the other hand, only fix about five to 30 lbs. of nitrogen. This means that farmers must apply nitrogen for bean production.
On the treatment with the added 80 lbs. of nitrogen, nodule numbers were much lower on the peas, and the dry beans had very few nodules.
If you have any questions about growing field peas or dry beans, please contact Gary Kruger in Outlook.