Neco 2018 Agricultural Science Question 8

A smallholder farmer in Oyo State observes that many of his tomato plants show wilted leaves, brown lesions on stems and a characteristic "target" spot on fruits. A field survey of 100 plants gave the following disease ratings on a 0–5 scale: Rating 0: 10 plants Rating 1: 15 plants Rating 2: 20 plants Rating 3: 30 plants Rating 4: 15 plants Rating 5: 10 plants Additional data: - Expected yield of tomatoes per hectare = 20 tonnes - Market price = ₦150,000 per tonne - Each 1% increase in disease severity index (DS%) results in a 0.8% yield loss. - A fungicide application costs ₦30,000 per hectare and reduces disease severity by 60%. Using the disease severity index formula \(DS\% = \frac{\sum (rating \times number\ of\ plants)}{total\ plants \times maximum\ rating} \times 100\), answer the following: