Scout for Fusarium Yellows in Sugarbeet and Record Fields with the Disease (06/17/21)
Fusarium yellows and decline in sugarbeet are caused by Fusarium oxysporum and F. secorum, respectively. Fusarium yellows and decline may cause significant reduction in plant stand and root yield, and it is recommended that infected roots not be placed in long-term storage.
The pathogens may infect seedlings and older plants in fields where average soil temperature is at or above 55°F and in the presence of adequate moisture or wet conditions. We have observed Fusarium yellows and decline at our research site in Moorhead, MN in a year when conditions may be considered as dry. In seedlings and young plants, oldest leaves become yellow followed by wilting and death (Figure 1). Cross sections of infected roots will show darkening of the vascular system. On older plants (4 leaves and older), symptoms include interveinal yellowing and death of older leaves (Figure 2). Sometimes there is distinct necrosis of half the leaf on one side of the midrib which then spreads to the other side of the mid-rib (Figure 3). Typically necrosis occurs first on older leaves followed by death of the younger leaves. Under severe disease conditions, infected plants may die with seedling being more vulnerable. In fields where the disease is not severe, older leaves of infected plants display typical foliar symptoms but the plants survive. Roots of infected plants have no external symptoms, but when these roots are cut in a cross section, there is a distinct darkening and damage of the vascular system (Figure 4). Roots of infected plants do not store well in piles and have high respiration rates which results in low sugar concentration during storage. The best and only way to manage Fusarium yellows and decline is to pant resistant varieties. Consult your agriculturists or seed sales representatives for Fusarium resistant varieties appropriate for your growing area. At this time, fields should be scouted for Fusarium yellows and decline and records should be kept to be used when deciding on varieties the next time fields with these diseases are planted to sugarbeet.
NDSU & U of MN
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