engleski

The problem of development of resistance on some fungicide active substances intended for suppressing of Cercospora beticola Sacc.

Leaf spot caused by the pathogenic fungus Cercospora beticola Sacc. is the most important disease of sugar beet. The disease is very aggressive to sugar beet and in favorable conditions it is expanding rapidly and can completely destroy sugar beet leaves. Plants, whose leaves were destroyed, are developing new leaves (retro-vegetation), however, they are worn out and result in lower yields and sugar digestion. Generally, the occurrence and intensity of the attack by this fungus mostly depends on weather conditions during summer growing period. The amount of damage depends on the resistance of the genotype and all provided agro-technical measures. Agro-technical protection measures include sowing healthy and with fungicide protected seeds, then, a proper crop rotation and the timely and proper execution of procedures including tillage, fertilization and weed protection. The use of fungicides in our terms of production is certainly necessary no matter if we are sowing sensitive or tolerant sugar beet hybrids. However, C. beticola is a parasite which has high possibility to develop resistance to fungicides (8, 9). The reduced susceptibility or resistance is reflected in the reduced effectiveness of fungicides to control leaf spots and is recorded in almost all countries where this disease is important. Resistance or reduced susceptibility of these pathogenic fungi to fungicides is related to the mass application of systemic fungicides, particularly from the group of strobilurins The research was conducted during 2014 and 2015, on Mollic Gleysols and Eutric brown soil. The experiment was set up in a split-block scheme with 14 different variants in 4 repetitions: A. soil type (A1 – Mollic Gleysols ; A2 – Eutric brown soil) ; B. treatment with fungicides (B1 – control ; B2 – one time during vegetation – Rias 300 EC, 0.35 l/ha ; B3 – one time during vegetation – Bravo 720 SC, 1.5 l/ha ; B4 – one time during vegetation – Sphere 535 SC, 0.35 l/ha ; B5 – two times during vegetation – Rias 300 EC, 0.35 l/ha + Duett ultra, 0.6 l/ha ; B6 – two times during vegetation – Bravo 720 SC, 1.5 l/ha + Duett ultra, 0.6 l/ha ; B7 – two times during vegetation – Sphere 535 SC, 0.35 l/ha + Duett ultra, 0.6/ha). The best results in all investigated parameters were obtained in variant B5 (two times during vegetation – Rias 300 EC, 0.35 l/ha + Duett ultra, 0.6 l/ha) and B6 (two times during vegetation – Bravo 720 SC, 1.5 l/ha + Duett ultra, 0.6 l/ha). In addition to the control variant (B1), the worst results were achieved in variant B4– one time during vegetation – Sphere 535 SC, 0.35 l/ha.

sugar beet ; Cercospora beticola Sacc. ; strobilurin fungicides ; resistance ; root yield and quality

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