Gce Model Questions Vol1 2021 Agricultural Science Question 8

Practice essay / theory question 8 from the 2021 Gce Model Questions Vol1 Agricultural Science examination. This question covers Plant Diseases .

Gce Model Questions Vol1 2021 Agricultural Science Essay / Theory
Topic: Plant Diseases
Question 8 GCE_MODEL_QUESTIONS_VOL1 • 2021 • AGRICULTURAL_SCIENCE • essay

A 4‑hectare cassava farm in the Niger Delta region shows the following symptoms: leaf necrosis with brown lesions, wilting of older leaves, and rotting of harvested tubers. The farmer suspects a disease problem and wishes to confirm the diagnosis, predict its spread, and plan control measures.

Question Parts

( a )
Identify the most likely disease, give its scientific name, describe the causal organism and outline the main epidemiological factors that favour its development in the Niger Delta.
( b )
During a six‑week monitoring period the proportion of infected plants was recorded as follows: Week 1 = 5 %, Week 2 = 12 %, Week 3 = 25 %, Week 4 = 45 %, Week 5 = 68 %, Week 6 = 85 %. Assuming the disease follows a logistic growth pattern \[P(t)=\frac{1}{1+e^{-(a+bt)}}\], where P is the proportion infected at week t, use a logit transformation to linearise the data and estimate the parameters a and b (show the calculation steps).
( c )
Using the parameters a and b obtained in part (b), predict the proportion of infected plants at week 8. Comment on the implication of this prediction for the farmer’s planned harvest date (which is at week 10).
( d )
Propose an integrated disease management plan for this cassava farm. Include (i) a cultural practice, (ii) a resistant variety recommendation, and (iii) a chemical control measure, explaining the rationale for each component.

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About This Question

This is Gce Model Questions Vol1 2021 Agricultural Science Question 8. It is one of the essay questions from the 2021 Gce Model Questions Vol1 Agricultural Science examination.

The question covers Plant Diseases .

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