Recent rains result in root rot potential for Ontario

FieldCropNews
Monday, 30 July 2018 | Ontario
By FieldCropNews
Recent rains result in increased risk for root rot, as well as black point or smudge in harvested wheat. Winter wheat yield reports are below average, but yield and quality are better than expected considering the heat and moisture stress endured throughout the season in Ontario, according to OMAFRA's latest crop report. 

Below are some highlights from OMAFRA's field crop report, July 26:
  • Recent thunderstorms across Ontario bring much needed relief to corn and soybean crops.
  • Black point or smudge has been found in some wheat sent to elevators or samples sent to the Canadian Grain Commission. Both diseases, at high enough levels, can result in a load being downgraded.
  • Sudden Death Syndrome (SDS) is present in southwestern Ontario, with the potential to increase given the recent rains. Scouting for SDS, soybean cyst nematode (SCN) and other root rots is recommended. 
The full report is available below and will be uploaded to FieldCropNews as soon as possible. 

Field Conditions

A rain system and thunderstorms brought much needed moisture to much of Ontario. Although rainfall accumulations remain highly variable across the province, corn and soybean crops showed immediate response to the moisture. Winter wheat harvest came to a halt on the weekend, but as field conditions become favourable again the harvest will start in central Ontario and continue west of Toronto. Quality remains good however yield reports continue below average, although better than expected considering the heat and moisture stress.

Black Point/Smudge in Wheat

As wheat harvest continues the overall quality has been very good especially with little to no fusarium head blight or DON issues to date. There have been some areas however where wheat going into the elevator or samples sent to the Canadian Grain Commission has been found to have “black point or smudge”. Both diseases are characterized by a black, smudge-like discolouration of the seed; the difference is where on the seed the colouration is found. For black point, the embryo or germ end (bottom) will be black or dark brown whereas for smudge the discolouration is only found along the crease or on the seed coat. Black point and smudge do not typically cause yield loss, but at high enough levels can reduce grain quality and result in load being downgraded (dockage losses).

Warm, wet conditions after grain fill and during ripening typically favour black point and smudge infection, but they can also occur when the weather is hot and dry or if maturity/harvest is delayed. There has been some bunt disease reported. Dwarf bunt, as well as common bunt, can be confused with black point and smudge. For all of these diseases, the first indication is the black cloud of spores which engulf the combine during harvest. With the bunts, there are massive amounts of fungal spores as well as a very prominent and often repulsive and memorable “fishy smell."

Differences in varieties have been observed this year. Generally, larger kernels are more susceptible to infection, so practices that encourage large kernels may contribute to higher levels of black point. Fungicide seed treatments can reduce black point and the bunt infection especially if seed is retained.

Sudden Death Syndrome (SDS) and Soybean Cyst Nematode (SCN)

SDS symptoms (Figure 1) are present in southwestern Ontario and will likely increase in infected fields as a result of the recent rains. Now is a perfect time to scout fields for SDS, SCN and other root rots. The hot, dry conditions have been favourable for SCN cyst development. Producers should make note of SDS and SCN ratings for varieties planted this year.

Figure 1. Typical SDS leaf symptoms. Note the interveinal tissue is yellow and brown areas while the veins remain green. posted as soon as possible on the Field Crop News website at: http://fieldcropnews.com/category/crop-report/

Sporecaster- White Mould Apothecia Risk Model

A new tool called “Sporecaster”, developed at the University of Wisconsin-Madison is now available to Ontario and US producers to assist with management decisions for white mould in soybeans. The best time to manage white mould is during flowering (R1 and R2 growth stages) when apothecia (small, mushroom-like structures) are present on the soil surface. Apothecia release spores which infect senescing soybean flowers, leading to the development of white mould. OMAFRA has assisted in field validation of the model for Ontario.

The Sporecaster model uses GPS coordinates (Figure 2) to determine if weather has been favorable for the development of apothecia during soybean flowering in a specific field. Models in the app use 30-day averages of maximum temperature, relative humidity, and maximum wind speed to predict favorable conditions for most soybean growing regions. However, fields still need to be scouted to determine if the soybean crop meets thresholds such as canopy closure and presence of flowers. Farmers input site-specific information about their soybean field into the app, which combines field information with the research-based models to predict the best timing for white mould treatment in that field.

Figure 2. Example of Model Output run Tuesday, July 24, 2018. Most fields in this example are considered “low risk” due to the hot, dry weather. Conditions can change quickly, so best to check Sporecaster regularly during the R1 to R3 growth stages. posted as soon as possible on the Field Crop News website at: http://fieldcropnews.com/category/crop-report/

To use the Sporecaster app, download it onto your phone from the Apple Store or Google Play. The app allows the user to locate and setup multiple fields and run the risk prediction model using weather data from a third-party provider (Dark Sky API).

Post Wheat Harvest Manure Application

For livestock producers and those using organic amendments, post cereal harvest is an excellent opportunity to apply manure for nutrients and organic matter. Spreading workload, reduced compaction and reduced risk of environmental losses from runoff and erosion, as well as the opportunity to combine the benefits of feeding cover crops with manure (Figure 3), are all benefits of application during the growing season.

Figure 3. Cover crops planted with manure application equipment posted as soon as possible on the Field Crop News website at: http://fieldcropnews.com/category/crop-report/

Where manure or other organic amendments are applied to fields, it is important to have an analysis to help determine available nutrients and potential commercial fertilizer savings. Along with analysis for N, P and K in manure, additional tests will help determine nutrient availability. Testing for organic matter, carbon-to-nitrogen (C:N) ratio, pH, and micro nutrients, including sulphur, will help to determine best management for optimum value. Sulphur results will provide an indication of elemental sulphur content which can provide some or all of the sulphur needs for most crops. Testing for C:N ratio will give an indication of how quickly the organic N will be mineralized. Testing the pH of organic amendments will help determine the potential for rapid ammonium N loss where manure is not injected or immediately incorporated. Liquid manure with high NH4-N levels combined with high pH (above 7.8) can lose the majority of the quickly available nitrogen in the first few hours after application, especially when combined with warm dry soils and/or high winds over bare soils.

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