Bacterial blight is becoming evident in growthy soybean fields in Southwestern Ontario.This shot was taken near Waterford.
In general bacterial blight is not considered to cause much yield reduction.Most varieties are susceptible to it.
Brown stem rot is another foliar disease becoming more and more evident in soybean fields.Brown stem rot infects through the roots by growth stage V3 and then colonizes in the stem causing interveinal leaf senescence as shown in the photo.Severity of infection is often correlated to soybean cropping history,soybean cyst nematode infection,optimal soil moisture conditions in the early pod fill stages and soil pH's below 6.5.Considerable research has been conducted on BSR and there are many good highly resistant soybean varieties available today.Given that soybean cyst nematode infection is often the precursor to brown stem rot infection
growers are best advised to sample their fields for cysts and begin growing Cyst nematode resistant varieties if they in fact have cyst pressure.
The above photo shows the early stages of white mould infection.Double click on the photo and you'll see the white cottony growth on the stem at each flower node.Development of white mould takes place when sclerotinia ascopores float up from the soil surface and land on the wet flower petals and then germinate and grow through the flower petals into the stem of the soybean plant.This eventually leads to a blockage of the phloem and xylem network causing nutrient flow to be cut off to the upper plant and ultimately leading to wilt and death.Areas with growthy soybeans that have received significant rainfall over the last two-three weeks are now starting to see the signs of white mould expression.Growers who experience serious white mould are best advised to reduce their plant populations, move to wider row production for better air circulation and sunlight penetration and grow the best white mould tolerant varieties available that provide the maturity and agronomic characteristics they require.