White Mould Prevalent In Soybeans-OMAFRA

on September 10 | in Tek Talk | by | with No Comments

From the OMAFRA Field Crop Report 

Soybeans: Horst Bohner

Soybeans are now at the R6 (full seed) to R7 (beginning maturity) growth stage. Many short season varieties are turning colour and leaves are beginning to drop in stressed parts of the field. Due to a cool growing season and later seeding, the majority of the crop is delayed by at least 7-14 days depending on the variety and planting date. An extended open fall will be required for some fields to reach maturity.

Plant lodging and white mould is evident right across the province. The weather was ideal for white mould development in 2014. Most fields have low disease pressure with pockets of dead plants, but severely impacted fields are also widespread. Most plants are infected during flowering in July and early August. A low level of white mould pressure is common in Ontario and has limited impact on yield. Severe infestations will reduce yields significantly. Fungicide efficacy has been variable depending on disease pressure and spray timing. Early spray timings did a better job of suppressing white mould than later sprays. Take note of fields with white mould to make future management decisions. Fields with white mould should not be seeded to soybeans next year or to other susceptible crops like edible beans or canola.

Some soybeans were sprayed for soybean aphids in Eastern Ontario, but numbers were low in southwestern Ontario. Once the fields have reached the R6 (full seed) growth stage spraying is no longer warranted under normal conditions.

With frequent rain events over the growing season weed pressure is high in some cases. A preharvest herbicide may be warranted as a harvest aid in weedy fields. This will not speed up crop maturity, but will helps dry down the crop and weeds more evenly, allowing timely harvest and reduced field losses. Perennial weeds such as milkweed, Canada thistle, and perennial sow thistle can be controlled by a pre-harvest glyphosate application when weeds are actively growing and in the bud to flowering stage. Glyphosate will not be effective on some perennial or annual weeds (e.g. ragweed) that have already set seed, nor will the seed bank of these weeds be reduced. Glyphosate should be applied at least 7 days prior to harvest, when the soybean grain moisture is less than 30%, and leaf drop is at 80-90%. Check IP contracts before applying pre harvest herbicides.

Forages/Pastures: Joel Bagg/Jack Kyle

Forages: While cutting alfalfa in the fall is often practiced in Ontario, it does create some risk to stand health, depending on the location, stand age, harvest frequency and other factors. The decision to cut alfalfa should weigh these factors and the immediate need for forage against the increased risk of winterkill and reduced yield next year. Fall cutting contributed to some of the alfalfa winterkill that occurred this spring, including areas of western Ontario where it is normally considered low risk.

The Critical Fall Harvest Period for alfalfa is the 6-week period preceding the average date of killing frost. Not cutting during this rest period allows alfalfa plants to re-grow and build up sufficient root reserves to survive the winter and grow more aggressively in the spring. When cut early in the period, the alfalfa will use the existing root reserves for regrowth, “emptying the tank”. Later in the period, the alfalfa uses photosynthesis to produce carbohydrates and stores them as root reserves, “refilling the tank”. The Critical Fall Harvest Period begins as early as August 10th in northern Ontario, August 25 – 30th for eastern and central Ontario, and September 4th in the southwest. However, it is difficult to predict when that killing frost will actually occur. Cutting in the middle of the Critical Period is higher risk than cutting at the beginning or end.

Forage harvest schedules are delayed this year, and harvesting the normal number of cuts may require cutting during the Critical Fall Harvest Period. Even when winterkill does not occur, the extra yield harvested during the critical period is often offset by reduced 1st-cut yield the following spring. Some areas, such as the Ottawa Valley, are at significantly higher risk. Fields with older stands, a history of winterkill, low potassium soil tests, low pH, poor drainage, or insect/disease pressure are at increased risk of winterkill and are poor candidates for fall harvesting unless you are planning to rotate.

Pastures: Pastures have benefited from adequate moisture and cool temperatures through the summer months. Rotational grazed pastures that have adequate rest periods between grazing are showing good growth of new clover plants. These plants will provide quality pasture for next year. How pastures are managed in the fall period has a big effect on the productivity in the coming year.

September and October growth will allow the grass and legume plants to develop a strong root system and provide adequate reserves of sugars and starches to survive the winter months. Maintain a good amount of residual forage in your pastures during the fall grazing period to facilitate the development and maintenance of a strong root system.

In a pasture that is going to be frost seeded with legumes next spring, it is best to graze very short this fall to weaken the existing plants and slow their spring development. This will give the new seeds an opportunity to germinate and grow with minimal competition – this is the one exception to maintaining a strong plant stand in the fall.

With a cooler growing season, some corn fields may not make grain corn. This corn could be grazed, allowing perennial pastures an opportunity to have an extended rest period. When grazing corn use an electric wire to allow access to 1-3 days feed supply at a time.

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