At a field day in Lower Franconia, experts discussed opportunities and challenges in sugar beet cultivation. Special attention was given to the reed leafhopper and its control. "The future of sugar beet cultivation," is the title of a field day to which the government of Lower Franconia and the Office for Nutrition, Agriculture, and Forestry (AELF) Kitzingen-Würzburg invited participants in mid-May. The focus of the event was on the reed leafhopper-SBR-Stolbur complex and digitalization in sugar beet cultivation. Emergency authorizations should only be used after a warning service call! For sugar beet growers present at the KWS research station in Seligenstadt, the use of insecticides authorized under Article 53(1) of Regulation (EC) No 1107/2009 was of great interest. The key point is that the use of these substances is generally only permitted in hotspot and transition regions and only after a call from the warning services. According to Matthias Strebel of the ARGE Franken, hotspot regions are those where an intense host plant cultivation with > 50% infestation is present, high adult reed leafhopper (SGFZ) catch numbers with evidence of pathogens and significant nymph infestations have been identified, high yield losses have been recorded, and a high proportion of double infections prevail. The exact nature of hotspot, transition, and border regions in Bavaria is expected to be published in the coming days. Treatment strategies against the reed leafhopper According to Achim Jesser of Südzucker, it is important to treat as soon as possible after the warning service call. Regarding the use of insecticides, he made the following specific recommendations: Combine systemic active ingredients (acetamiprid or flupyradifurone) with those that have contact action (pyrethroids). For the first treatment, Jesser recommends using Sivanto Prime (flupyradifurone) combined with a Decis Forte. The time-limited application possibility of Sivanto makes the product ideal for early use. For the second treatment, the expert recommends a combination of an acetamiprid (Mospilan SG, Danjiri, or Carnadine 200) and Karate Zeon. Treatment 3 can then, again - considering the approved frequency of use - be an acetamiprid. The intervals between treatments should be 10 to 14 days. "If you wait too long, the protection is lost," says Jesser. He also emphasizes the importance of complying with the requirements and application regulations, such as the maximum application frequency per season or drainage restrictions. To maximize effectiveness To achieve the highest possible efficacy, Jesser recommends high water application rates of at least 300 l/ha. This is necessary to adequately wet the leaves, which is important for the leafhoppers to absorb the contact active substances through their tarsi ("feet"). "Make sure also that the pH of your spray solution is correct," adds Jesser. Ideally, it should be between 6 to 6.5 for good effectiveness and plant compatibility. Like with other insecticides, those against the reed leafhopper should also be applied in the evening. Early actions are crucial The importance of early treatment dates is also demonstrated by the "Cover-up Experiments" presented by Dr. Carsten Stibbe and Carolin Kunz (both KWS) in 2024. In these experiments, sugar beet plots were covered at different times to prevent the reed leafhopper from infecting the beets with SBR or Stolbur. Stibbe and his team wanted to determine if the infection timing influences the level of damage. Experiment 1, Large Block Covering: At the Seligenstadt location, a trial with five blocks was compared: Block 1: Open control (no covering) Block 2: Healthy control (covered from XX to XX) Block 3: Uncovered at the beginning of June Block 4: Uncovered at the beginning of July Block 5: Uncovered at the beginning of August The influx of the reed leafhopper from early July onwards had little effect on sugar yield. With nearly 15 tons of sugar per hectare, the open control produced almost 4 tons less sugar than the always covered one. However, the harvest of the trial also showed that the influx in July and August did not cause significant damage. Experiment 2, Tunnel covering of plots At the Seligenstadt, Ochsenfurter Gau, and Riedstadt Leeheim (southern Hesse) locations, sugar beet plots were spanned with small flow tunnels and opened for 10 days at certain times. One variant was always open throughout the entire flight period. As can be seen from the overviews, this experiment also showed that an influx from early/mid-July onwards had little effect. Although caution must be exercised in interpreting the data, according to Carsten Stibbe, as they are only one-year experiments, it is clear to him: "Early infestation causes damage!" An experiment on sowing dates at the same locations also made it clear, according to Stibbe, that later sowing dates are more susceptible. "The later you sow, the greater the yield loss," warns Stibbe. When can the start of flight be expected? According to Achim Jesser, one can expect it from the end of May after a call from the warning services. This, in turn, refers to the monitoring by the federal states, which started last week. At www.isip.de, monitoring locations and catch numbers can be viewed. To form their own opinion, individuals can hang transparent adhesive boards in the field against which the leafhoppers fly randomly. "However, determining the reed leafhopper on the boards is not always easy," Carolin Kunz points out.
