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Magnesium-fertiliser had no effect on yields although leaf analyses indicated levels lower than recommended (average of four trials). In one trial, sugar content increased significantly.
Manganese-fertiliser had no effect on yields although leaf analyses indicated levels lower than recommended (one trial harvested).
Boron-fertiliser had no effect on leaf content, which in all cases (in contradiction to previous results) was above the recommended level (two fields investigated).
General, there was no obvious differences between the tested techniques when recommended N-levels were In applied and tillage could compensate for compaction caused by self-propelled slurry wagon.
Drilling directly on ridges made in the autumn was most suitable when drilling was performed well in advance of the optimal time for the specific field. Due to dissatisfactory plant emergence – especially when drilling later – this method is not advisable in its tested form.
Autumn drilling resulted in the best yields, when drilling was performed close to the optimal day for the field, whereas deep-harrowing gave the best yields when drilling was delayed beyond the optimal day.
Please confer to NBR-report 729 for a praxis-near comparison of ploughing and deep-harrowing.
Rust has been the dominant leaf disease in three field trials performed in 2020, where powdery mildew has developed 1-2 weeks later than usual. One trial has been inoculated with Ramularia. Two treatments with 0.5 liter Opera per ha have resulted in 15 pct. yield increase in relation to untreated, and net approx. DKK 2,000 per ha. Opera may no longer be sold and may only be used and stored until October 30, 2021. Amistar Gold as well as the new and unapproved products Propulse and Balaya have resulted in sugar yield and net excess no higher than Opera.
In two trials, three products, Kumulus S, Armicarb SP and Serenade ASO, are tested for their effect on leaf diseases as possible solutions for organic sugar beet cultivation. Kumulus S shows effect against powdery mildew and 5-7 pct. additional yield, which gives a positive net contribution for four treatments with 3.5 kg per. ha. Armicarb 85 SP and Serenade ASO show weak effects against powdery mildew and rust. Serenade ASO has in 2020 resulted in a small net profit, but this is not seen in an average of four trials in two years.
Rust has been the dominant leaf disease in 2020. The attacks began in late July and with a relatively weak development until mid-August, after which the attacks increased until harvest. Powdery mildew attacks have begun 1-2 weeks later than rust, and the attacks have been relatively weak. The attacks of Ramularia have been very weak. Cercospora has been less widespread than in 2019, but more widespread than in previous years.
In the leaf disease warning service, 20 fields have weekly been monitored for infestations in a number of varieties. The first attacks of rust have been seen week 30 (July 20-26), and treatments was recommended in fields with incipient attacks. Where first treatment has been performed in week 31 and where harvest has been planned for after mid-October, a follow-up treatment in week 34 has been recommended, where fresh rust pustules could be seen. For fields with lifting later than mid-November, a 3rd treatment could possibly be followed up 3-4 weeks later.
Fungicide seed treatments with Tachigaren and Vibrance SB has been studied in four field trials. The attacks have been more serious than in previous years’ trials – thus an average of 16% of the plants in untreated are attacked by damping off, which has caused plant losses. In 2020, there have been no additional yield in the treated entries. Several years of trial results with Tachigaren show reduction in damping off and higher final plant numbers. Variable yield increase has been obtained with a tendency of 1 per cent increase in average.
Two field trials were carried out to test different fungicide strategies to control powdery mildew (Erysiphe beta) and to minimize fungicide resistance. The treatments included registered products as well as new products including Propulse and Revysol in combination with Comet Pro. Serenade ASO and Kumulus S were also included as alternative products. All fungicide treatments controlled powdery mildew effectively. Kumulus S reduced powdery mildew significantly and comparable to the fungicide solutions. Serenade ASO showed only a low effect on powdery mildew.
Powdery mildew samples from Denmark and Sweden were tested for strobilurin resistance in 2020. Two samples from Denmark and two samples from Sweden were tested positive for strobilurin resistance in a trial under semi-controlled conditions. All four samples harbored point mutation G143A, which has been associated with strobilurin resistance.