The timing of the MH spraying will be quite a challenge in many fields this year due to duality and delays in development. Thinking carefully about storability and marketing options is more important than ever. The spraying itself is also accurate.
The MH spraying is a common measure for many growers to suppress the germination of the onions and thus improve the storability. But the state of many onion plots makes the decision about MH spraying this year more difficult than ever. "This year, the growers have to think very carefully about what is possible with their batch. Can the onions be stored? Do they absorb enough MH?"
Michiel van Mol sees along the road that many onion fields have a developmental delay and are often also two-washed. This makes it difficult to determine the optimal time for MH spraying. "It's best to match it to the well-developed onions," says the onion expert from Syngenta Seeds. "And those who have the options can consider sorting out the small onions during harvest. Then you're left with a more homogeneous batch with onions that have absorbed enough MH."
Timing spraying
With the foregoing in mind, the grower has two starting points to determine the correct time for the MH spraying. "The most important and most commonly used criterion is that you spray as soon as 10% of the crop has been ironed," says Van Mol. "You can also look at the ratio of the diameter of the sphere to the neck, which should be at least 3 to 1. As a final handhold, you can squeeze the neck just above the sphere; the neck should feel soft." This last criterion has added value, especially when there is doubt as to whether it is a natural alloy or whether it is caused by the wind.
Optimal execution
With MH spraying, everything revolves around optimal absorption of the agent. That starts with a good cover of the leaf. "So use a lot of water," advises Van Mol. "Preferably at least 500 liters. The crop must also remain dry for at least 10 hours after spraying. And make sure that the crop remains green and vital for at least 14 days after spraying. MH needs a sap flow to ensure that the product comes into the bulb. So continue with the disease control for at least another two weeks."
If the spraying is carried out after a longer dry period and the onions have a thick wax layer, Van Mol recommends adding a wetting agent. "And certainly do not combine it with other means," he warns. "MH always sprays you solo."
Drop off early?
In case of serious doubts about the storability of a batch, Van Mol advises selling the onions before the holidays. "And if it is a variety with good dormancy and you are sure that you can get rid of them before Christmas, you can consider skipping the MH spraying. Because what is not optimal at harvest will be stored in storage. nor any more."
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