Waec Model Questions Vol1 2024 Agricultural Science Question 8

Practice essay / theory question 8 from the 2024 Waec Model Questions Vol1 Agricultural Science examination. This question covers Plant Diseases .

Waec Model Questions Vol1 2024 Agricultural Science Essay / Theory
Topic: Plant Diseases
Question 8 WAEC_MODEL_QUESTIONS_VOL1 • 2024 • AGRICULTURAL_SCIENCE • essay

A cocoa farmer observes a leaf‑spot disease caused by Phytophthora megakarya. From the lower canopy a random sample of 200 leaves was taken and the severity of each infected leaf was rated on a scale of 1 (mild) to 5 (severe). The recorded data are: 80 leaves with rating 1, 50 leaves with rating 2, 30 leaves with rating 3, 20 leaves with rating 4 and 10 leaves with rating 5.

Question Parts

( a )
Calculate the disease incidence (percentage of leaves infected) in the sample.
( b )
Compute the disease severity index (DSI) using the formula DSI = (Σ (rating × number of leaves)) / (maximum rating × total number of leaves) × 100. Provide the DSI value.
( c )
Based on the DSI obtained, recommend an appropriate chemical control measure, specifying the active ingredient, its mode of action, and the optimal timing of application. Justify your recommendation.
( d )
Outline two cultural practices that can reduce the occurrence of Phytophthora leaf‑spot in cocoa, and explain the principle behind each practice.

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About This Question

This is Waec Model Questions Vol1 2024 Agricultural Science Question 8. It is one of the essay questions from the 2024 Waec Model Questions Vol1 Agricultural Science examination.

The question covers Plant Diseases .

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