Corn Plant Health Evaluation

With serious corn plants working to finish growing, there are issues that could threaten a successful end of the season. Diseases of leaves and corn stalks can weaken the stalks and cause lodging. Other known stresses of the year can, in turn, cause the plant to loosen toward the grain and weaken the corn stalk, making it susceptible to lodging and stem rot.

Evaluations should be made between stages R5 (generally serrated kernels) and R6 (ripening: maximum dry matter accumulation, formation of a black spot at the base of the kernels).

The Pest Alert Network (RAP) recommends two methods if problems arise. Fields with sandy soils, known for their compaction that limit root growth or foliar problems present since the beginning of the season, should be given priority.

Payment Test

• Randomly select 20 plants from five well-distributed locations in the field, for a total of 100 plants.
• Push the top of the plant 15 to 20 cm (6 to 8 inches) away from the vertical axis to see if the push causes dormancy.
• Determine the percentage of weak stems.

pinch test

• Randomly select 20 plants from five well-distributed locations in the field, for a total of 100 plants.
• Remove the lower leaves and press the stem over the rootstock. If she can easily
Powdered stalk rot is more likely to develop. Symptoms can also be
It is observed cutting the stem in half lengthwise.
• Determine the percentage of rotten stems.

The damage attributed to stem rot is mainly due to three genera of fungi, namely CladosporiumAnd the colitotrichum where Gabriella / Fusarium. The first two factors affect the transport of mineral elements in the plant, which can affect the filling of the grain and make the stems more susceptible to lodging. Type fusarium It is one of the main producers of mycotoxins. Infected plants wilt and leaves turn from light green to dull grayish-green, as if they had suffered a frost or drought. The interior of the rails will also show a change in its appearance. They will appear worn and can vary in color from white, pink, salmon, and yellow to orange.

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With regard to foliar diseases, the RAP notes that the main foliar diseases of corn currently are common rust, dieback, captella disease, and anthracnose. The latter can attack both the leaves and the stem.

RAP also suggests screening for diseases affecting the ears because some fungi can cause mold to develop on the ears. Evaluation should be done in R5 and R6 stages, either in mid-September or a few weeks before harvest. You have to harvest at least 30 ears manually from different random places in the field. The leaves covering the cob must then be removed to notice the presence of mold on the surface of the grain. If mold is observed, it is recommended that the grains be tested for the presence and levels of mycotoxins.

Depending on the situation, an early harvest may be appropriate. In Ontario, it is recommended to harvest a field with 10% of the ears affected by rot as soon as possible. If bird damage is obvious (most often at the edges of the field), it is recommended to harvest the damaged rows separately, and it is preferable to store and handle the grain from these rows separately. Likewise, if a corn field has 10 to 15% rotting stems or endemic plants, it is best to start harvesting early and quickly to slow disease progression and potential production of mycotoxins. Any additional drying costs will be offset by increased ease of harvest and reduced loss in the field.

The grain should be dried immediately after harvest so that the grain moisture is not more than 14% because beyond this rate the growth of fungi and mycotoxins continues.

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As for the corn silage, once placed in the silo, the fungus should not grow and produce toxins, but for this the conditions should be completely anaerobic (lack of oxygen).

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