Dutch Crop tour Onion Hotbox
Crop tour onions: the Good, the Bad and the Ugly
Halfway through the storage season, it's a good time to take stock of the average storage quality of Dutch seed onions. Based on hotbox samples, taken in collaboration with The Groot and Slot BV, are among the participants in the Boerenbusiness Dutch Crop tour Several batches were examined. The average quality varies considerably from plot to plot.
From the ten Gewastour plots, seven hotbox samples were taken in November and December. One hundred onions from each batch were examined to determine which potential diseases and deficiencies were present in storage.
Hotbox Monsters
In the study, made possible by De Groot en Slot BV, one hundred onions per sample are exposed for three weeks to optimal conditions for disease development, allowing any internal defects to manifest. During this period, the onions are exposed to a relative humidity (RH) of at least 95% at a temperature of 25 to 28°C.
|
Monster |
Fusarium |
Bacterium |
gill |
|
1. |
21 |
1 |
0 |
|
2. |
7 |
3 |
0 |
|
3. |
4 |
1 |
0 |
|
4. |
0 |
2 |
0 |
|
5. |
4 |
16 |
0 |
|
6. |
0 |
9 |
0 |
|
7. |
0 |
0 |
0 |
|
Intermediate |
5,14 (5,14%) |
4,42 (4,42%) |
0 |
*Percentage is based on number per 100 onions
Although the average internal quality is 9,56% tare of the total number of onions, the quality varies considerably between batches. Some samples showed only a few, if any, affected onions, while other samples showed significantly higher levels of infection, up to 21% for fusarium and 16% for bacteria.
On average, irrigation took place between three and four times this year, which is more frequent than in the two previous years. This doesn't necessarily mean it was a year of Fusarium or bacteria. However, frequent irrigation can temporarily create a favorable environment for fungal growth. Insect control is also becoming increasingly problematic. Pressure from onion fly, bean fly, and thrips, in particular, is increasing due to limited pesticides and increasingly warmer conditions, which cause the insects to develop faster and become active earlier. In areas with high pressure, growers are often satisfied if the decline remains below 30% to 40%. Moreover, the insects can attack the leaves, creating spores that allow Fusarium and bacteria to develop.
Onions affected by fusarium or bacterial disease.
Onions affected by fusarium or bacterial disease.
Onions affected by fusarium or bacterial disease.
|
Onions are like eggs
It's often suggested that you should treat an onion like eggs, referring to its sensitivity. Even the slightest damage during harvesting can lead to the introduction of spores for fungal diseases like fusarium or bacterial diseases. Carefully cleaning the fields after harvest is also important for controlling fungi. Onions left in the soil after harvest will create a much higher baseline pressure of fusarium or bacterial diseases years later when new onions are grown.
Hotbox research shows maximum internal defects
The conditions the onions are exposed to in the hotbox are deliberately extreme and optimal for disease development, so that all possible diseases and defects can manifest themselves in the batch, explains Jesse Torringa, commercial promoter for Northern Netherlands at De Groot en Slot.
It's important to emphasize that this doesn't mean every affected onion in the shed will actually become sick, says Torringa. "Under normal storage conditions, with drier air, lower temperatures, and better ventilation, not all infections will manifest." A high percentage of bacteria or fusarium in the hot box therefore primarily indicates the maximum percentage of internal defects in a batch, which doesn't necessarily say anything about the final situation during storage.
Jan Willem Veldman
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