Gce Model Questions Vol1 2018 Agricultural Science Question 8

A farmer growing tomatoes in a greenhouse observes wilting, yellowing of lower leaves and a brown discoloration of vascular tissue in several plants. Laboratory analysis confirms the presence of Fusarium oxysporum f. sp. lycopersici. The following disease severity observations were recorded over a 10‑week period (severity expressed as the percentage of plants showing typical wilt symptoms): | Week (t) | Severity (Y) % | |----------|----------------| | 0 | 0 | | 2 | 20 | | 4 | 45 | | 6 | 70 | | 8 | 85 | |10 | 90 | Assume the intervals between observations are equal (2 weeks). The Area Under the Disease Progress Curve (AUDPC) is calculated using the formula: AUDPC = Σ [(Yi + Yi+1)/2] × (ti+1 – ti). For disease pressure classification, use the following thresholds: AUDPC < 100 – low, 100 ≤ AUDPC ≤ 200 – moderate, AUDPC > 200 – high.