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DISCUSSION OF IMPORTANT DISCUSSION OF IMPORTANT FACTORS FOR FORECASTING AND FACTORS FOR FORECASTING AND CRITICAL WEATHER MODEL OF LEAF CRITICAL WEATHER MODEL OF LEAF SPOT OF BANANASPOT OF BANANA

Objectives Objectives

TO KNOW THE FACTORS RESPONSIBLE FOR FORECASTING

TO KNOW THECRITICAL WEATHER MODEL OF LEAF SPOT OF BANANA

INTRODUCTION

Black leaf streak, also known as Black Sigatoka, was first recorded in 1964 from Fiji. This fungal disease of banana has since spread to most of the banana growing regions of the world and is regarded as one of the most important constraints on banana production worldwide. The disease is particularly important where growers cultivate monocrops of banana and cannot afford to use chemical fungicides for disease control. Black leaf streak can cause extensive defoliation. Yields are reduced, and fruit from affected plantations is prone to premature and uneven ripening. Because banana bunch weight is a function of the number of healthy leaves at flowering, it is critical to manage the crop and the disease so that an acceptable quantity and quality of fruit is harvested

WHAT IS FORECASTING?WHAT IS FORECASTING?

Giving information in advance about the epidemic of a disease and control measure.It is the applied epidemiology.

According to the Miller and O’Brien (1952) –“Forecasting involves all the activities in ascertaining and notifying the growers of a community that ----

conditions are sufficiently favourable for certain disease

applicatiom of control measures will results in economic gain

the amount of disease is enough to justify the cost of expenditure

CAUSAL ORGANISM OF LEAF SPOT OF BANANA

Mycosphaerella fijiensis

Cercospora musae

DISEASE SYMPTOMS The first symptom of LEAF SPOT OF BANANA is minute, chlorotic flecks that

appear on the undersurface of the third or fourth fully expanded leaf. The flecks develop into narrow (1-2 X 10-20 mm) rusty brown streaks and often have truncated ends and sides that are sharply limited by the leaf veins. During early stages, the streaks are visible only from the lower surfaces.

On some cultivars, and on very young plants (suckers) the streaks are less defined and have diffuse margins

The color of the lesions or streaks intensifies to dark red, brown, or black, sometimes with a purple tinge, and they become visible on the upper surfaces

The streaks enlarge, becoming fusiform or elliptical, and darken to give the characteristic black streaking of the leaves. Conspicuous yellowing of adjacent leaf tissue may also occur.

The lesions dry to light gray with definite dark brown or black borders and often have narrow, yellow transition zones between the borders and the green leaf tissue.

When disease severity is very high, large areas of the leaf may become blackened and water-soaked. As with yellow Sigatoka, the spots on juvenile leaves are oval or rounded and are often surrounded by a conspicuous yellow margin.

In extreme cases, all leaves can be destroyed before the bunch is mature, and the bunch may fall from the plant.

SYMPTOMS

LIFE CYCLE

FACTORS RESPONSIBLE FOR FACTORS RESPONSIBLE FOR FORECASTINGFORECASTING

HUMIDITYTEMPERATUREHUMIDITYRAINFALLWINDINOCULUMSOIL SOIL PH

CRITICAL WEATHER FOR LEAF SPOT OF BANANA

RELATIVE HUMIDITY 80-90%

TEMPERATURE 10-16 DEGREE CENTRIGRADE

CLOUDY WEATHER

MODEL FOR FORECASTING

A model is nothing but a sequential hypothesis of what to do before epidemic .It is the simple and easy expression of forecasting information. It can be expressed by graphically or diagrammatically

A Critical weather model for A Critical weather model for leaf spot of bananaleaf spot of banana ..

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February

January

December

November

OctoberSeptember

August

July

June

May

April

March

Time offorecasting

Control measure

Variety selection:The variety agnishar,sagor kola,amrito sagor etc.SPACING:Single-row or double row planting systems allow

best fungicide coverage for bananas and have superior air flow and reduced relative humidity levels in the canopy.

Weed control: Tall weeds (especially grasses) create high

humidity in the plant canopy, which favors black leaf streak disease.

CHEMICAL CONTROL

Febuconazole, tebuconazole are reported to be the most effective. As systemic fungicides, the triazole fungicides provide the longest duration of disease mitigation after application, but also pose a risk for the development of fungicide resistance if they are over used.

CONCLUTION:CONCLUTION:

BY FORECASTING MESSAGE OUR FARMERS BECOME ALERT ABOUT THE DISEASE AND TAKE APPROPRIATE MEASURES TO AVOID THAT DISEASE .THUS HIGH YIELD IS ACCEPTED.SO IT IS VERY LMPORTANT IN AGRICULTURE.