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Scout for Fusarium Yellows/Decline of Sugarbeet (06/27/19)

Fusarium yellows/decline symptoms were observed in research plots and in several commercial sugarbeet fields in the Moorhead factory district.

Fusarium yellows/decline symptoms were observed in research plots and in several commercial sugarbeet fields in the Moorhead factory district. The fungi Fusarium oxysporum and Fusarium secorum cause Fusarium yellows and Fusarium decline, respectively, on sugarbeet. Fusarium yellows/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. In seedlings and young plants, oldest leaves become yellow following 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).

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Sometimes there is distinct necrosis of half the leaf on one side of the midrib (Figure 3) which then spreads to the other side of the mid-rib. Typically, necrosis occurs first on older leaves followed by death of the younger leaves. Under severe disease conditions, infected plants may die with seedlings 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 roots with no external symptoms but may be sprangled. When these roots are cut in a cross section, there is a distinct darkening and damage of the vascular system. Roots of infected plants do not store well in piles, having high respiration rates resulting in low sugar concentration during storage. The best and only way to manage Fusarium yellows/decline is by planting varieties with tolerance to Fusarium yellows and other root diseases common to specific fields. Consult your agriculturists or seed sales representatives for Fusarium tolerant varieties appropriate for your growing area. At this time, fields should be scouted for Fusarium yellows/decline and records should be kept to be used when deciding on varieties the next time fields with the diseases are planted to beets again.

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Mohamed Khan

Extension Sugarbeet Specialist

NDSU & U of MN

701-231-8596

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