Check beets on time and spray on time

Check the crop at an early stage, intervene immediately if aphids are found, keep the spraying intervals short and do not stop spraying too early. Beet specialist Sjors Leermakers once again sums up the measures to control aphids. He also emphasizes the importance of properly incorporating crop residues and storage beets. "Residual beets are a nice winter shelter for lice. We have to break that cycle."

The disappearance of the seed coating has turned beet cultivation upside down over the past 2 years. Previously you could count on a fairly carefree attendance, now a (very) early check for lice – and an early control – is essential to keep the damage within limits. "It is therefore a great pity that this application has been lost in practice. With very little active ingredient, we had the lice under control," says Sjors Leathermakers when he briefly looks back on the past few years. After a very high aphid pressure in 2019 – which caused a lot of damage, especially in the Southwest, the beet yellowing virus has steadily spread throughout the Netherlands over the past year. "There are very few areas left where you don't encounter yellow spots in the beets. In that regard, we have really gone backwards in the past 2 years."

Yellow versus green beets
Leermakers says that the damage caused by the yellowing virus can reach considerable proportions. Yellow beets contain about 2 to 3% less sugar and the yield of these beets is a quarter to a third lower than that of healthy beets. "As a result, beet cultivation is no longer profitable, if at all, on moderately to severely affected plots."

Of the 3 virus variants – strong beet yellowing virus (BYV), weak beet yellowing virus (BMYV) and beet chlorosis virus (BChV) – the first one is on the rise. Leermakers shows graphs in which the BYV virus has risen in 2 years from a share of barely 5% in the infected samples to more than 70%. "And the annoying thing is that it is this strong beet yellowing virus that causes the most loss of yield, about double that of the other 2 variants. The importance of stopping the yellowing virus is therefore extra great," he explains.

Processing crop residues
Although chemical aphid control is an important measure in the prevention of yellowing disease, Leermakers first mentions another preventive measure: incorporating harvest residues – especially where the beet heap used to be. "Residue of beet and also storage beet are an important source of infection for the following year. This applies to yellowing virus, but also to Cercospora. So many potential risks can be removed by turning the autumn tillage." The beet specialist recognizes that such tillage is not really in line with the current trend of minimal tillage. Still, in his opinion, something must be done in this area 'because with chemistry alone I'm afraid we won't make it in the long run...'.

Early Crop Control
For next spring, Leermakers is once again insisting on an early check for lice, especially when the temperature quickly rises above 15 °C. "Because whoever signals early and then intervenes early, keeps the lice pressure low and benefits from this throughout the season," he emphasizes once again. Leermakers acknowledges that it is quite difficult to find lice at an early stage. The young, non-winged aphids are especially difficult to see because they have approximately the same color as the beet plants. "So you really have to get down on your knees and unfold a few beets, otherwise you won't find them just like that."

Although there is a damage threshold of 2 green peach aphids per 10 plants, the beet specialist recommends spraying immediately with 'every finding' of aphids. "As soon as an infected louse sticks its snout in the beet leaf, there can be a huge transmission of virus within a few hours. So: the longer you wait with a spray, the greater the chance of damage from yellow beets."

Start with Batavia
For the coming season there are (probably) 3 products available for aphid control in beets. These are Teppeki® and – if an exemption is again granted – Batavia and Closer®.

Of these, Teppeki and Closer may be used once per season and Batavia 2 times. According to Leermakers, it is advisable to start the lice control with Batavia† He explains: "Batavia is the only agent that has both an upward and downward effect. As a result, the agent spreads optimally throughout the beet plant and also reaches the newly formed leaf. Especially with young beet plants that are vulnerable and also fully in the growth, this is an important plus, because young aphids like to sit on the young leaves and are therefore well controlled with Batavia." A spray with Batavia offers protection (from the 2-leaf stage) for about 10 to 14 days. If the beets are larger and stronger (and can absorb the agent better), the protection period increases to about 20 days.

Important at Batavia is that the agent can be well absorbed into the plant. For this, the addition of a liter of vegetable oil (eg. Robber) highly desirable. Trials have shown that the effectiveness of Batavia this clearly increases. Also can Batavia so well be added to weed control.

Favorable profile for consuming
One last point that Leermakers does not want to leave unmentioned is that Batavia is not harmful to beneficial insects. Important 'lice eaters' such as predatory bugs, hoverflies, parasitic wasps, earwigs, lacewings, soldiers and ladybugs are thus spared. "In tests we have seen that the population of beneficial insects can build up well in combination with Batavia† Especially later in the season, from mid-May to mid-June, these insects can make a nice contribution to aphid control," he concludes.

_{Teppeki® is a registered trademark of ISK
Closer® is a registered trademark of Corteva Agriscience}

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