
Rev. Téc. Ing. Univ. Zulia. Vol. 44, No. 1, 2021, January-April, pp. 04-58
9
Evaluation of the severity of Black Sigatoka (Mycosphaerella fijiensis Morelet) ) in ‘Barraganete’
(317.63; high severity level) and 0 kg/ha of MgO when 
compared with treatments 25 (156,67; mild severity 
level), 50, 75 and 100 kg/
 
Statistical differences were foundin weeks 21 
and 22 for leaf 3 treatments 50, 100, and 125 kg/ha of 
MgO when compared with treatments 0, 25, and 75 kg/
ha of MgO. Similarly, differences (P<0.01) were found in 
week 25 for leaves 3, 4, and 5. In leaf 3 the differences 
were between treatments 0, 75, and 125 kg/ha of MgO 
when compared with treatments 25, 50 and 100 kg/ha of 
MgO. In leaf 4, the differences were between the treatment 
75 kg/ha of MgO when compared with the treatments of 
0, 25, 50, 100, and 125 kg/ha of MgO; while in leaf 5 the 
differences were between treatments 0, 50, 75, 100, and 
125 kg/ha of MgO when compared with the treatment 25 
kg/
 
The progression of the disease is considered to 
have been very rapid when leaf 3, which was the youngest, 
was ill; so that, since the degree of infestation was mild, 
it was relatively low and can be controlled or managed 
through cultural practices and, if necessary, in the face of 
increased damage, with the use of protective or systemic 
fungicides, coinciding with what was pointed out by 
Muñoz and Vargas [29].
 
Concerning to leaves 4 and 5 in general, from 
week 21 onward, the severity levels values obtained 
          
           
      
situation in El Carmen, Ecuador, regarding agroecological 
and management conditions, which would lead to further 
research where the constant values that were used to 
determine the severity level of the disease in this area 
are adjusted according to the prevailing environmental 
scenarios.
 
This led to six applications of fungicides for 
the entire period evaluated, which were scheduled after 
        
the disease determined in weeks 14 and 15 (mancozeb 
(100 g) + tebuconazole + triadimenol (20 mL) + a mixture 
of alkylaryl and polyglycol 12.5% (two applications, 
eightday interval), in weeks 20 and 22 (difenoconazole 
(20 mL) + propineb (100 g) + a mixture of alkylaryl and 
polyglycol12.5% (two applications, 15day interval) and 
in weeks 24 and 26 (carbendazim (20 mL) + mancozeb 
(100 g) + a mixture of alkylaril and polyglycol 12.5% 
(two applications, 15 days interval), surgery and weekly 
leaf removal. On the other hand, the application program 
of preventive and curative fungicides for BS should be 
designed considering the fungicides active ingredients 
different mechanisms to reduce the risks of the 
development of resistance to those molecules.
 
All the aforementioned is in agreement with 
Cervantes et al. [21] who reported that the chemical 
management of BS has been carried out with the use of 
protective and systemic fungicides in aqueous suspension, 
in oil and water emulsions or direct mixture with mineral 
oil alone, with activators of host resistance mechanisms, 
and most recently through the use of nutrition-related 
compounds, both of chemical and natural origin. However, 
the overlap of the applied products with the presence of 
mineral oil, suggests an impediment to the penetration 
of sunlight to the leaves, which affects the content of 
chlorophyll, photosynthesis and therefore crop yields.
 
This methodology was used to determine 
the early detection of BS symptoms in leaves 3, 4 and 
5; however, to be able to establish the severity level 
requires great precision in the recognition of the disease 
symptomatology, this knowledge allows to establish 
the frequency and level of cultural management and 
fungicides with both protective and systemic action; This 
makes it possible to have indicative values of the damage 
level present in the plantation.
 
Pérez [30] indicated that the use of fungicides for 
disease protection receives important attention, because 
in areas with adequate rainfall regimen for banana 
production of susceptible clones, if chemical controls are 
not applied, satisfactory disease control is not achieved.
 
It has been pointed out that through fertilization, 
it is nutritionally promoted the presence of epiphytic 
populations of chitinolytic and glucanolytic bacteria that 
have bioregulatory capacity on the pathogen and are 
naturally found in the ecosystems of cultivated plants [31]. 
However, in the rainy season, there was less availability 
of macronutrients such as sodium, magnesium and 
ammonium; in addition, to the protein content favouring 
epiphytic microbiota [32].
  This control strategy seeks to reduce the 
inoculum of the pathogen, before environmental 
conditions favor its dissemination and establishment. 
   
in times of low pressure of the disease such as the dry 
season, and thus achieve more abundant and effective 
populations of antagonist microbiota in rainy seasons, 
where the pressure of the disease is strongest [30]. 
Conclusions
 
The equations of the polynomial models predict 
that the lowest incidence of the disease occurs with 
the lowest dose of Mg (25 kg/ha of MgO), perhaps due 
to the mobilization of Mg to the vacuoles to act in the 
maintenance of the osmotic potential, as well as to store 
the Mg found in excess within plants.
  The management of Black Sigatoka should 
remain focused on the integration of cultural and chemical 
procedures.Changes in consumer perceptions of healthier 
products and public concern to stop environmental