Crop tour potatoes - week 23
Phytophthora strikes early in the season
It is all hands on deck to tackle phytophthora in potatoes. The fungus is affecting more and more young potato crops and has already been detected throughout the Netherlands. However, growers had difficulty getting across the land with their field sprayers because of the saturated spray marks. In addition, the potatoes that have just emerged often still need to be milled.
It's just June, but phytophthora is spreading aggressively in various areas of our country early in the season. Varying degrees of damage are found on the leaves and areas have even been identified. Various parties from the sector report this, such as Bayer CropScience and BO Akkerbouw.
The risk of infection of phytophthora in the potato crop has been high in recent weeks due to the humid weather conditions and temperature. In addition, the stems sprout from the ground like mushrooms. This makes the crop vulnerable and ensures that preventive spraying quickly loses its effectiveness due to the many new leaves. In addition, due to the heavy rainfall, it was not possible to immediately drive the field sprayer everywhere to protect the crops. Depending on the area, the leaf wet periods are still very long and it remains humid.
Latent diseased seed potatoes and lots of storage
Trade organization BO Akkerbouw also notes that growers sometimes do not even get the chance. As for phytophthora, they received the first signals of the fungus in the second half of May, especially in the southern regions of our country. Infections were found here, especially in the former ware potatoes, which are already a real crop. "It was also striking that these were plots where cultivation was done under plastic," says Geert Pinxterhuis, project leader for the Plant Health Action Plan at the trade association. This primarily concerns latently diseased seed potatoes.
Warnings have been issued about latently diseased seed potatoes since last autumn, after tuber phytophthora became visible during harvest. In addition to this source of spread, the large amount of potato storage from last growing season is also a primary source of phytophthora pressure. Pinxterhuis notes that there is quite a lot of storage due to the course of last season. Not all plots could be cleared and potatoes were left behind in the field during the difficult harvest. They have now been standing above other crops for a while. The situation is particularly worrying, especially with the current weather in which the fungus thrives, the trade organization explains. They therefore advise growers to alternate products with different mechanisms of action and to abandon the 'well-known block schedule', in which one product is used several times in succession.
Growers are on top of it
Potato growers of the Boerenbusiness Crop tour Due to the high disease pressure and the high risk of infection, they are already busy with preventive crop protection. They see that the crop is growing very fast and in order to properly protect the newest leaves, they keep their interval short. This is what grower Ruud Steinbusch from Voerendaal (Limburg) tells us. "We are already ready for our third phytophthora spraying of the season. The potatoes above are growing very fast, so it is also desperately needed." The weather conditions remain favorable for phytophthora in the area where Steinbusch grows again this week. "They are predicting rain again for Wednesday. Fortunately, we can ride in the field again here."
Many potato growers on heavier soils still have to till because the weather did not give them the opportunity. The potatoes have sometimes been upstairs for some time and have grown rapidly. Despite the fact that many plants or parts of them are milled back under, the majority of growers carry out preventive phytophthora spraying in advance. Spraying is very wise, especially when the crop has been growing for a long time, is quite large and the disease pressure in the area is high. But does the crop just break through, do you then completely cover it with soil and is phytophthora not present in the area? Then it is better to save spraying for later this season, explains Sander Uwland of Bayer CropScience. "You also have to be able to protect your potatoes at the end of the season." In addition, Uwland emphasizes that the situation regarding the fungus in the field should not be underestimated. “Continue to check your plots as the situation is worrying with what we are already seeing in several areas.”
Potato grower Daan Tap from Elst, Gelderland, also sprayed preventively against the fungus again today (Monday, June 3) with the field sprayer. This was his second spraying of the season and he also maintains a strict spraying schedule.
Jesse Torringa
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