Tuesday, October 6, 2009

We generally don't see severe Northern Corn Leaf Blight ( NCLB ) in Southwestern Ontario for two very good reasons.Growers rotate their corn crops well and breeders have done a good job of selecting better NCLB resistant hybrids.The photo above depicts what NCLB looks like when it does pop up.The leaf on the right shows eliptical oblong lesions of northern leaf blight that are causing premature death of plant tissue.Because this infection is occurring very late in the grain fill period it will not likely have any impact on grain yield though it may have some affect at reducing stalk strength qualities.When NCLB hits hard and early which is generally infrequently, in SW Ontario, it can cause yield reductions and seriously impact stalk strength.
The above photo shows how NCLB is negatively impacting the hybrid on the right while the hybrid on the left is being barely impacted.Breeders have done an excellent job of breeding improved NCLB resistance into todays hybrids

The above photo depicts the impact of anthracnose stalk rot.The plant in the rear has already died from anthracnose infection.You can see how the stalk is already dead brown while the stalk in the foreground is a vibrant green.Anthracnose stalk rot is the #1 disease impacting Ontarios corn crop.Early premature death due to anthracnose stalk rot can cause considerable yield losses.Grain will be lighter in test weight and harvestability severely hampered when anthracnose hits hard.Infection takes place at an early stage in the plants growth and remains in remission within the plant until the stresses of grain fill create an opportunity for infection to spread into the stalks vascular bundles. When the plants phloem and xylem system are cut off any further uptake of water and nutrients is curtailed and so the upper part of the plant starts to display a grey green wilt.With time this grey green appearance turns to a dead brown senescence.This is often referred to as top dieback.There are significant differences in the degree of hybrid resistance to anthracnose stalk rot.This is one disease that you don't want to fool with.
My recommendation is to make sure that the hybrids you grow have a minimum 4 score for anthracnose stalk rot.Hybrids with a 5 score will give you an added insurance of protection.

When you see serious anthracnose stalk rot infection you need to make sure to do the PUSH TEST to evaluate which fields should be considered for early harvest.The last thing you want to do with serious anthracnose stalk rot is to leave a field to the ravages of mid to late November winds.I've seen fields in the past standing 95% one day and 100% flat on the ground the next.

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