'Every hour counts in crop protection'

Agricultural meteorological specialist Erno Bouma expects that the use of crop protection will become more difficult due to climate change. The infection pressure is increasing and favorable weather conditions are less common. This increases the peak load in crop protection.

Together with the Wageningen professor Bert Wartena Bouma, he wrote several standard works on agricultural meteorology. He worked with NOS weather forecaster Gerrit Hiemstra for years. Bouma can call itself an authority in the field of weather and crop protection.

This is also the title of a book written by him. He also gives lectures on the weather and crop protection. Anyone who attends his lecture may count that towards the spraying license. This winter there are 20 evenings on the program. Hence the question to him:

What effect does climate change have on crop protection?
"A simple question with a somewhat complex answer. I'll split it up into 4 themes:

• This is how the crops used to be;
• Are there any new diseases/pests/weeds;
• Do the crop protection products react differently;
• And we are dealing with flooding."

Does spring really come that much earlier?
"The crops are on average 10 to 15 days earlier in their development than in the period before 1970. That is a statistical fact. For example, fruit trees bloom earlier, grains grow earlier and sugar beets have reached their growing point date earlier. This creates a greater sensitivity to for example, a "late" night frost, such as we saw this year. Because they are physiologically further at a certain stage, the moisture consumption is also greater and it seems that the crops suffer more from moisture deficiency. The crops are also ready for harvest earlier. This year with the grain harvest and with the maize silage, it seems to be going in the same direction this year."

How many new diseases and pests should we fear?
"Cold-loving species, for example grange (Phoma) in potatoes, are seen less and less. While heat-loving species, such as the Firebug (Pyrrhocoris apterus), Brown rust (Puccinia recondita) and Helminthosporium (leaf spot disease), are increasingly encountered. Also difficult uncontrollable diseases will become a problem. In addition, most fungi and insects have a faster population growth.Take the green peach aphid (Myzus persicae) which develops 25% to 30% more generations with every temperature increase of 2 degrees Celsius. To think that this louse also leaves its winter values ​​earlier and early in the year the crops (for example the seed potatoes) are also more sensitive to virus infection. The same also occurs with many insect species, such as the cabbage fly and the cabbage gall midge."

And the crop protection products react differently due to climate change?
"Because it gets warmer and drier in the summer, the leaf skin of plants gets a thicker wax layer and the cutin layer does not swell. So the effect of leaf herbicides decreases. Difficult, because the decreasing rainfall in the spring means the soil herbicides also work less well. The solution to this is the use of advice systems, such as SpuitWeerWijzer. The SpuitWeerWijzer app collects weather data with big data technology and combines it with an effectiveness model. The result is advice for the best spraying moment for the next 48 hours. combined with the FieldMate Weather Station, with which the weather conditions are measured on site in the field, it is very easy to keep one's finger on the pulse. The trick is that you use every hour that is suitable for spraying. I expect that there will be companies that will invest in a second sprayer, because of the increasing peak load in crop protection."

Flooding has been a problem in arable farming for decades. So that's only going to get worse?
"Because the temperature is at a higher level earlier in the year, there are heavy showers earlier in the growing season that cause flooding and hail damage. Think of May and June last year. These showers will occur more regularly and the infrastructure is in place in most areas. /water boards have not yet adapted to this. There is simply too much 'hard' surface and the capacity of the ditches/canals is too small."

This article is part of the summer series on climate change. All articles can be found here.

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