INTRODUCTION The development and combat Black Sigatoka in banana and plantain, are two items very closely.
The first is the characteristic vegetative plant present a constant rate of leaf emergence, which leads to permanently this exposing new tissue to possible pathogen inoculation.
The other factor relates to the conditions of the regions most banana and plantain in Latin America, representing feature very favorable temperature and humidity on the biology of the fungus. An exception is high altitude where it is cultivated banana, so particular, in association with coffee or in some regions of marked dry season but where irrigation is practiced, which tend to create certain conditions that may be favorable to biology the fungus.
These characteristics, together with the action of the fungicide products have caused some assessment strategies to combat Black Sigatoka, within which the warning system has shown a high efficiency, reduced costs and less environmental pollution .
The methodology of the notice to combat this disease, based on the analysis of biological and climatic
descriptors so that fungicide applications can be made only when
initial development of the infection and when the parameters Weather you are favorable to the fungus.
This facilitates timely intervention is, by reversing the attack, a wider spacing between courses of treatment, lower levels of disease and consequently healthier plantations better articulate their productive potential.
as notice to combat Black Sigatoka refers to two systems: the notice biological and bioclimatic notice. This time we will only biological notice as to the bioclimatic notice requires certain conditions, which we have not yet. NOTICE
BIOLOGICAL
This methodology is independent of bioclimatic notice. In areas
which initiates the development of notice is the first step and not until years later that can be combined with climate studies to establish the bioclimatic notice.
biological warning system is based on the analysis of biological descriptors (disease assessment in relation to the plant, which can be concluded in the Statement of Changes).
For this purpose, conduct weekly evaluations so that the onset of disease symptoms on young leaves (II, III and IV) enable a constant and "accounting" the development of the disease.
Instruments This basic system is the observation plot and the curve of the state of evolution, which reflects the results of field observations.
OBSERVATION SITE
order to "measure" the constant development of the disease, it is necessary to weekly observations on the same plant until its height allow comments on the sheets II, III and IV or up to the issuance of the inflorescence (calving).
There are no rules in terms of density plots needed in a given area. This depends on the homogeneity of environmental conditions on the banana plantations under the premise that different farms (particularly in areas with small farms) have a similar operation.
To establish the place of observation in adult plantations should be planted in lots of 40 plants of which only 10 will be assessed. Avoid
plots near the location of facilities such as houses, packing plants, power lines, roads, etc.., Or where there are obstacles to flight of the aircraft that can not be eliminated.
farms with new plantings, the 10 plants evaluated can be placed with a wider distribution, it should be borne in mind that these measures should be easily located by the manager of the readings. Whether
plots established or selected plants in new plantings, they must be individually identified, it is recommended to use alpha-numeric. In these signs the letter corresponding to the line or row of plants and the number to the position of the plant in the row.
For ease of location of plants to observe, must be labeled at the beginning of the row with the letter that corresponds and plants, in addition to placing an identification card with the alpha-numeric, it is painted on the pseudostem, a ring that may be visible from a distance.
When you can not plant new plots (40 plants) for the observation plots, proceed to choose the children with 10 developed leaves of a plot in production and to establish with these the observation plot.
REPLACEMENT SITE
Due to the urgent need for consistent information should be provided for the availability of plants in which evaluations should be continued once reaching the issue of inflorescence which are being evaluated.
To this end, the plots should be established early enough replacement for that time. This anticipation depends on the material being employed, depending on whether rhizomes or seedlings from nurseries (tissue culture or shoots), the time to be determined and weather conditions.
Generally the time required to set the replacement parcel is approximately two (2) months before being tested which reaches parity.
is important to note that reading the time to abandon a plot should coincide with the second reading at the place of replacement, which means that in a given week, will be read out on the plots but in the manner indicated because otherwise, there may be gaps in information and problems with the results obtained.
In banana-producing areas that have a prolonged dry period and there is no irrigation, should be avoided
establish plots for the same. In these cases,
same shall be set at the start of the rainy season. Pose a problem
plots replacement? In fact the only drawback to this work, is the reluctance of producers to slaughter plants should lead to replacement plots. To this end it is necessary that it has a clear awareness of the
benefits derived from implementation of the application of this system as sacrificing a few plants, will be largely offset by the economy spraying cycles in the whole house or a given area and also it will provide a better health condition of the plantation and all the additional benefits to be derived from it.
There is an option to replacement plot establishment, which is to continue the observations on children.
This should be taken into account considerations such as:
• The system could run on low-bearing cultivars such as the Great Dwarf, since most other high as Valery, children sores to be very high before develop their functional leaves.
• The behavior of the state of evolution children differs from that seen in the templates, although the trend is similar. The amplitude of the curve representing the evaluation of the disease differs in both cases, which could cause difficulties of interpretation.
• If you decide to work with children, should be carried out simultaneously by a given time period, the respective assessments in both types of material so that the staff responsible for the interpretation of results and recommendations in each materials about the disease itself.
EVALUATION METHODOLOGY
The "Statement of Changes" is the expression of disease development in terms of development of plant material. It is therefore necessary when carrying out evaluations, taking into account the growth of the plant (leaf emission) as well as symptoms (stages) of the disease.
To start data collection, when first reading the plants must have a minimum of eight (8) leaves, preferably 10, and shall correspond to 10 plants with normal growth and uniform, properly distributed within the plot observation.
In this first reading, the total number of leaves present in the plant, is marked at the base of the midrib of the leaf 1, which is that wide open after cigarette or candle.
Weekly, sheet 1 will be marked with the progressive number that corresponds to the total leaf emergence at that time (10, 11.12, etc).
This information is recorded for each respective plant in the form of the EFA column field data (see example). In addition to the total number of leaves, must be made on state of development of cigarette or candle, which is noted on the form as a decimal fraction of the total issued to the observation sheets.
This decimal fraction will correspond to each stage of development of the cigarette or candle, it is noted in Figure 1.
-Figure
cigar-
states
OBSERVATION OF DISEASE AND CALCULATION OF THE STATE OF EVOLUTION.
As noted above, on a weekly basis should be evaluated the same plants and at every opportunity, always leaves II, III, and IV.
The rationale behind this rule is that:
• New leaves are usually first to become infected.
• The methodology is to intervene in the disease in its earliest stages of development.
• The symptoms on a same sheet may eventually be observed by more than a week and with it, as they have evolved.
To determine the presence of different stages, observation or search starts on the underside of semilimbo apical left hand as this being the first part of the sheet is exposed to unroll a cigarette or candle, is the area first to be inoculated with the disease.
From this area you look at the rest of the blade for the most advanced stage of disease as well as an estimate of the number of symptoms present (see stages). Stage
Black Sigatoka
This information is what takes the form for purposes of such calculations, scoring in the columns for each leaf (range Leaf). For each one is scored only one state, the highest and added a qualification that will be + (plus) when their density is estimated that more than 50 symptoms or-(less) when less than 50.
in banana plantations under chemical control and for this methodology is very difficult to find stages over 2 -. Only in very critical cases, probably influenced by hot spots, you will find cases of 2 +.
Symptoms usually controlled should not be taken into account during data collection, however, it is sometimes difficult to differentiate these symptoms of living. In case of uncertainty, it is preferable not to consider it and note the symptoms they are.
Although not part of the methodology or the calculations to determine the state of evolution, can also be observed and recorded, the information on the youngest leaf sick (HMJE) and the youngest leaf necrotic (HMSN), which gives a quick idea of \u200b\u200bthe condition of the plantation over Black.
From these observations, the calculations proceed as follows.
In the first evaluation, because they can not obtain the data rate of leaf emergence, as no one has the last leaf emission data (EFP), was not able to get the State Assessment data. What we have achieved this opportunity is the gross amount (SB).
The second data collection, as well as the following, you can calculate the rhythm of leaf (REF) for each plant, adding and subtracting from the current week's data (EFA-Emission Current Leaf), the data leaf emission obtained for the same plant, the previous week (EFP = Past Issue Leaf).
EFA-VET REF =
Adding the REF for each plant, and dividing this sum (S REF) by the number of days (N) that elapsed between the two observations, the data obtained Emission Rate Foliar Present (REFI) for the batch of plants under observation. REFI = SREF
N
then the information must be generated called Candela Correction (CC). This is obtained by multiplying in each plant, the value assigned to its cigarette or candle
by the number of leaves (II, III and IV) found with symptoms of the disease.
For example, if the plant A5, candela state corresponded to 4, the 3-leaf disease were observed, then CC = 4x3 = 12.
From CC data, we obtain the coefficient of Evolution (CE). This is achieved by multiplying the sum of CC for all plants by 2, which is a preset factor.
CE = S CC x 2
To finish with the necessary information related to the development of the plant (leaf development), is just get the data of Foliar Weighted Emission Rate (REFp), which is only the promise of Rate the amount of leaf present.
REFp = REF + REFI 2
The information in plant development (leaf emergence) is required to combine with the factors of clinical expressed in the plant, leading to obtain the Statement of Changes (EE) of the disease and led to a graph representing the behavior going development of the disease in the plantation.
This other process starts with the calculation of the gross amount (SB), for it is necessary to add the same amount of leaf numbering in all 10 plants tested showed the same stage (columns in the form number of damaged leaves), 5 with stage III leaves 1 +, for example.
The sum of the product of the multiplication of these data, the severity coefficients, given below for each sheet and each stage results in the gross amount (SB).
Table 2. Severity
coefficients for calculating the gross amount. Leaf Stadium
II III IV 1 to 60 40 20
1 + 80 60 40
2-100 80 60
2 + 120 100 80
3 - 140 120 100
3 + 160 140 120
As an example, in a given plantation is located in the observation plot is the stage 1 - sheet II in two plants, two sheet plants III and IV leaf of two plants.
Stage 1 + is III found in the leaf of a plant and leaf of two plants IV. Stage 2 - is in the leaf III on two floors while stage 2 + is in the leaf IV 3 floors, information that is configured and calculated in Table 3.
Table 3.
Number of Leaves Leaves Damaged Damaged coefficient
Stadiums
II III IV II III IV
1 to 2 February 2120 80 40
1 + 1 2 60 80
2 - 2 160 2 + 3 130_______
To continue shall calculate the sum of Evolution, which is obtained by subtracting the coefficient of Evolution (and as calculated above) of the gross amount.
SEV = SB - CE
This data (SEV) is multiplied by the Weighted Average Rate of leaf emergence and results in the State of Evolution (EE) of the disease for that week.
EE = SEV x REFI
This figure, taken to a graph is by allowing the trend or slope of the same between two or more weeks, to define when you make an application or fungicide treatment.
Interpretation of Results
The most important factor that can decide when to apply, not the amount of infection found in plants, but the evolution of the disease, which is reflected in the curve of a graph.
There is, in principle, a critical threshold. Only experience levels may be setting some special consideration to be defined for different sectors.
is logical that a lower level to maintain the state of development, better health will be planting and, consequently, fewer applications and fungicide treatments. This is achieved only by the applications in the most timely manner possible.
ASSESSMENT OF THE STATE OF INFECTION
You must have a clear and accurate picture of the health status of the property, to prevent severe damage to the crop and its production. For this reason we must make periodic evaluations (every week or two) on the incidence and severity of Black Sigatoka on each farm.
Below is the modified Stover methodology for the evaluation of incidence and severity of the disease, which will allow us to be properly built on the plant health of planting.
METHODOLOGY OF PROPERTY BY STOVER Gauhl
The incidence and severity assessment using the modified Stover methodology, yields fairly detailed information on the health status of the plantation.
Figure 1 shows the six degrees that includes the scale changed Gauhl Stover (1989).
The system consists of a visual estimation of leaf area affected in all the leaves around flowering plants, without having to download the sheet.
This assessment takes into account all the leaves except the leaf present fire, and leaves overwhelmed. The nearest leaf to leaf blade is considered candela No.1
FIGURE 1. Scale changed Gauhl Stover (1989).
. Counting is easy considering the spiral distribution (odd and even) from right to left from sections 1 and 2 (Figure 2), counting down. To determine the leaf area affected must visually estimated the total area covered by all the symptoms of the disease in each sheet and calculate the percentage of leaf covered by the symptoms. For this it is necessary to have a pattern that divides the sheet into percentage ratios, as shown in Figure 1.
The following is an example of the evaluation sheet (Table 1), as well as calculations to be performed to obtain the variables generated by this method.
TABLE 1. Example of calculating the number of leaves per plant (H / P).
NUMBER OR POSITION OF THE BLADE
Plant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 H / P
1 0 0 0 0 0 0 0 0 1 1 2 2 12 2 0 0
0 0 0 0 0 0 0 0 1 2 12
3 0 0 0 0 0 0 0 0 0 0 0 0 2 13
4 0 0 0 0 0 0 0 0 0 0 0 1 1 2 14
5 0 0 0 0 0 0 0 0 0 1 1 2 2 13 total 64
averaged 12.8
The number in each box indicates the degree of infection that has each page based on a scale of 0 a6 according to Figure 1.
To obtain the number of leaves per plant, all leaves counted and divided by the number of plants tested (Table 1). The number of leaf per plant was extracted from the last sheet is indicated (colored) in the formula assessment.
youngest diseased leaf (HMJE) is also on average younger leaves (colored) showing visible symptoms of the disease. (Table 2).
The HMJE gives an indication of disease progression. In other words, the younger the leaf with more symptoms, the greater the incidence of the disease, and arguably also the severity.
TABLE 2. Calculation of the youngest leaf sick (HMJE).
NUMBER OR POSITION OF THE BLADE
Plant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 H / P HMJE
1 0 0 0 0 0 0 0 0 1 1 2 2 9 2 0 0 0
0 0 0 0 0 0 0 1 2 11
3 0 0 0 0 0 0 0 0 0 0 0 0 2 13
4 0 0 0 0 0 0 0 0 0 0 0 1 1 2 12
5 0 0 0 0 0 0 0 0 0 1 1 2 2 10 total 55
average 11
Finally, to obtain the percentage of leaves infected by grade, the number of leaves in each grade, divided by the total number leaves and multiplied by 100 (Table 3).
The total percentage of infected leaves were obtained by adding the value of all grades, from first to sixth.
TABLE 3. Calculation of the percentage of infected leaves (% HJ)
NUMBER OR POSITION OF THE BLADE
Plant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 H / P HMJE 0 1 2 3 4 5 6
1 0 0 0 0 0 0 0 0 1 1 2 2 8 2 2
2 0 0 0 0 0 0 0 0 0 0 1 2 10 1 1
3 0 0 0 0 0 0 0 0 0 0 0 0 2 12 0 1
4 0 0 0 0 0 0 0 0 0 0 0 1 February 1, 1911 February 1
5 0 0 0 0 0 0 0 0 0 1 1 2 2 9 2 2 Total 50 7 July
averaged 78 November 1911
EXAMPLE: Percentage of leaves with grade 1: Floor 1
: 2 leaves
Floor 2: 1 sheet
Floor 3: 0 sheets floor
4: 2 sheets
Plant 5: 2 TOTAL 7
leaves leaves with grade 1
evaluated TOTAL SHEETS: 64 SHEETS WITH GRADE
% 1 = 7 x 100 = 11.0
64 TOTAL = SUM% leaves infected leaves in each grade (from 1 to 6) = 11 + 11 + 0 + 0 + 0 + 0 = 22
However, the total percentage of infected leaves underestimates the severity of the disease and that is why the use of a weighted average of infection (PPI) has been suggested to obtain a more accurate value. Its calculation is obtained by multiplying the percentage of leaves in each grade by the corresponding value of the magnitude of modified Stover. Each result is added and the total is divided by 100.
EXAMPLE: Weighted Average of infection (PPI)
SUM (% x blades in each respective grade level)
PPI = 100 (11 x 1) + (11 x 2) +...... .. + (0 x 6) PPI = 100
PPI = 0.33
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