Sugarcane wilting syndrome worries sugarcane farmers

Brazilian sugarcane growers need to be aware of yet another problem that has been observed in sugarcane fields: sugarcane wilting syndrome, characteristically evidenced by the presence of withered stalks. In some sugarcane fields, the disease has caused a significant reduction in stalk productivity and ATR (theoretical recoverable sugar). Depending on the variety planted and the location, losses can be greater than 25%. 

In addition to these losses, the disease also affects the quality of the raw material. Researchers from the Cana IAC Program are developing studies to solve this problem, in partnership with the Research Center for Engineering-Phytosanitary in sugarcane (Cepenfito), at Unesp, with support from the São Paulo State Research Support Foundation (Fapesp) and the São Martinho Group.

Occurrence of the disease

The disease has been occurring at a gradually increasing rate, affecting all varieties, in several producing regions of Brazil. Withered or dry stems can indicate several diseases. According to IAC researcher Ivan Antônio dos Anjos, these symptoms may result from an attack by leafhoppers on the roots (Mahanarva spp.) or fungi. 

“Among these, the species Colletotrichum falcatum, which causes Red Rot, Phaeocytostroma sacchari (Pleocyta sacchari), responsible for Bark Rot or Sour Rot, and Fusarium spp. (Fusarium wilt)”, explains the IAC researcher.

These symptoms result from infections originating from these mentioned fungi, occurring in isolation or, less frequently, in co-infections. “There are situations in which wilt symptoms arising from infections caused by C. falcatum, now for P. sacchari and, less frequently, Fusarium spp.”, he says.

the fungus P. sacchari, in particular, it has been recurrently isolated from withered culms, unlike its sporadic occurrence in previous years. “The typical symptoms of its infection are discoloration of the bark and loss of wax; Internally, the culms exhibit a frosty brown color and, as symptoms progress, reddish internodes and a characteristic fermentation smell”, comments the scientist. Due to the loss of water, cavities form along the stem and, consequently, wilting. As the disease progresses, dark globose structures, called cirri, form in the bark.  

In the case of Colletotrichum wilt, the most obvious symptom is the presence of white bands contrasting with the reddish color of the inner part of the stem. Externally, fungi form structures that are characterized by the presence of dark arrows, similar to spines.

According to the researchers, the evolution of symptoms and, consequently, losses, increase considerably as stalk maturation advances, especially in the final thirds of the harvest in the Center-South. “Anticipating the harvest, in areas with disease problems, is the most recommended measure to mitigate losses,” he says.

Faced with the challenges posed by the disease, several studies have been conducted in laboratories at the IAC and Unesp, in Jaboticaba. The development of resistant varieties is one of the objectives.

Early harvest

While scientific research works to solve the problem, the recommendation for sugarcane growers is to cut sugarcane in advance, the only effective measure against the disease to date.

“Many producers have applied chemical and biological fungicides and carried out tests with different types of fertilizers, with macro and micronutrients, but without effect. So far, no resistant varieties have been detected”, says Ivan.