"The damage caused by yellowing disease was much less last season than the year before. Many beet growers then paid a tuition fee and were therefore much more alert to lice." That says Jan Dingemans, technical advisor at Theunisse BV in Steenbergen (North Brabant). As far as he is concerned, the same advice will remain in effect for next season: check beets early for aphids, keep an eye on the damage thresholds and carry out pest control in good time.
"Fortunately, last year everything went well here," says Jan Dingemans when the subject of yellowing disease in beets is discussed. "If you compare it with 2019, there has been much less damage in our working area - West Brabant, Tholen and Schouwen-Duiveland. And that is remarkable when you consider that the aphid pressure was even higher last year than in 2019 In that respect, growers have really learned from that disaster year."
Dingemans can still remember how badly some plots were damaged. "I've seen plots that were at least 30% yellow. With that you quickly lose 1% sugar and 5 to 10 tons of yield. With the current beet price, there isn't much left."
Young farmers in particular 'overtaken' by lice
According to the advisor, it is mainly the younger farmers who have been 'overtaken' by the lice (and the virus). "The young generation grew up with treated beet seed and has never had to worry about aphids in beets. The neonics always did their job, so it's a bit of a switch when you have to spray against aphids so early in the spring." Also the fact that the beet plants sometimes only have 2 leaves when sprayed for the first time - and so a lot of product ends up on the bare ground - also met with quite a few growers. "Many then waited until the plants were a little bigger; unfortunately, those growers often suffered the most damage."
Another 'learning moment' was that initially a lot of (cheap) pyrethroids were sprayed to combat beet beetles and flea beetles. However, this also sprayed away the natural enemies of lice, so that the damage caused by the yellowing virus was extra high.
Need all available resources
Last season the lice were there even earlier than in 2019 and the lice pressure was also much higher. Dingemans shows photos - dated 24 April - in which beets with hardly any real leaves are already well covered with aphids. "I've been involved in this profession for almost 50 years, but I've never experienced it this early and so massive." According to the advisor, growers have (now) reacted alertly and quickly to the high aphid pressure. In addition to being more attentive to the IRS alert service, growers and advisors have also become much more involved in looking for lice. Dingemans: "Especially on the early sown plots, it was immediately all hands on deck. If you found 1 aphid there, you could assume that the damage threshold of 2 green peach aphids per 10 plants was almost certainly exceeded and that you would immediately have to spray Some growers had to spray up to 4 times to keep the aphids under control."
According to Dingemans, all available resources are therefore required to be able to combat lice effectively. For next season these will be Teppeki® and - if an exemption is granted again - Closer® and Batavia† Teppeki and Closer may only be applied once per season and Batavia 2 times. "With a high aphid pressure, such as last season, we may need all these 4 applications very badly."
Worrying about storage beets
For the coming season, Dingemans is mainly concerned about the beet residues that are left behind on many plots. Lice can easily survive on these storage beets, especially when the winter remains mild again. The emergence of non-turning tillage (NKG) - which means that more crop residues remain on the land - and the increase in green manures that remain over the winter can also provide a pleasant hiding place for aphids. "There are good reasons to apply NKG and to leave green manures for a long time, but it does not help to keep the aphid pressure low. It is therefore difficult to advise on this; every grower has to make his own assessment." said Dingemans.
He finds the ever-increasing requirements for drift reduction another worrying development. "At the moment most products can still be applied with 90% drift-reducing nozzles. But there is a good chance that we will have to reach a minimum of 2% drift reduction within 3 years. Except that this makes the control of aphids more difficult - because the coarser the drop, the smaller the chance that all aphids are hit - it also requires additional investments from the growers."
Early control crucial
When asked for a last tip for 2021, Dingemans recommends checking for lice again early, especially in sheltered places and near bushes, where the first lice are often found. "Checking and signaling in time is crucial to keep the aphids under control for the rest of the season. Every grower knows that by now, but you have to do it in the end." to do."
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