Sigatoka
Causal agent: This disease is caused by the fungus Cercospora beticola, an ascomycete of the Mycosphaerellaceae family.
Description :
Sigatoka is the most serious and destructive leaf disease of sugar beet. Losses due to this disease can approach 40% and are represented by both the tonnage of roots and the percentage of sugar in the roots.
Sigatoka is distinguished from other leaf diseases (Alternaria, Phoma) by the presence of spots that are smaller in size and shape and by the presence of structures carrying black spores, called pseudostromata, which form in the center of the lesions.
As the disease progresses, heavily infected leaves initially turn yellow. Individual spots can coalesce and form larger areas of dead tissue, causing wilting and death of severely infected leaves. Severely attacked plants can be seen from a distance when dead or dying leaves give a burnt appearance.
Biology :
- The development of the disease is highly dependent on the presence of susceptible cultivars, adequate inoculum and favorable environmental conditions.
- The disease develops when leaf relative humidity is greater than 90% for more than 11 hours and temperatures above 15.5 ° C.
Symptoms :
- Individual leaf spots initially appear on older leaves, then progress to younger leaves.
- Individual lesions are about 4 millimeters in diameter with ash-colored centers and purple to brown borders, and are circular to oval in shape.
- Pseudostromata, which form in the center of the lesions are easily visible as black dots using a hand-held magnifying glass (10X magnification).
- During periods of high humidity, the blackheads will be covered with fuzzy, colorless masses of spore web-like spores, which serve as a source of secondary infections in the fields during the season.
- The disease is often unevenly distributed across fields, being usually more severe in protected areas adjacent to shelterbelts formed by taller trees or crops, or in other areas that can result in higher moisture levels.
Control :
- Start monitoring at protected areas adjacent to windbreaks or at areas that may cause higher humidity levels.
- Balanced plant nutrition.
- Chemical control: ACANTO PLUS at a dose of 0.25l / ha.
