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--- 02_user_tutorials:exercises:apple_scab_and_canker_on_a_virtual_plant [2026/09/30 21:55] – barley1965
+++ 02_user_tutorials:exercises:apple_scab_and_canker_on_a_virtual_plant [2026/09/30 22:15] (current) – barley1965
@@ Line 83: / Line 83: @@
 During an infection period, every leaf is infected with a probability:
 <code java>
-float sus = (lf[age] < SUSC_AGE) ? 1 - (float) lf[age] / SUSC_AGE : 0;   // young leaves are most susceptible
+float scabInfectionProb(Leaf lf) {
-pressure  = PRIMARY_INOCULUM * exp(-height / ASCO_HEIGHT)                 // ascospores from the ground
+	float sus = (lf[age] < SUSC_AGE) ? 1 - (float) lf[age] / SUSC_AGE : 0;   // young leaves are most susceptible
-          + sum over sporulating leaves of
+	if (sus <= 0) return 0;
-            SECONDARY_INOCULUM * nLesions * direction * exp(-distance / SPLASH_DIST);   // conidia
+	float zLeaf = (float) location(lf).z;
-probability = (1 - RESISTANCE) * sus * (1 - exp(-pressure));
+	float pressure = 0;
-</code>
+	// primary inoculum: ascospores from the leaf litter, decreasing with height
-(simplified from the function ''scabInfectionProb''). Ascospores are only released between ''PRIMARY_START'' and ''PRIMARY_END''. ''direction'' is 1 if the source leaf is above the target leaf, and ''UPWARD_SPLASH'' (0.3) otherwise.
+	if (time >= PRIMARY_START && time <= PRIMARY_END) {
+		pressure += PRIMARY_INOCULUM * (float) Math.exp(-zLeaf / ASCO_HEIGHT);
+	}
+	// secondary inoculum: conidia splashed from sporulating lesions, mostly downwards
+	for ((* src:Leaf, (src[nLesions] > 0) *)) {
+		float d = (float) distance(lf, src);
+		float dir = (location(src).z >= zLeaf) ? 1f : UPWARD_SPLASH;
+		pressure += SECONDARY_INOCULUM * src[nLesions] * dir * (float) Math.exp(-d / SPLASH_DIST);
+	}
+	return (1 - RESISTANCE) * sus * (float) (1 - Math.exp(-pressure));
+}</code>
+Ascospores are only released between ''PRIMARY_START'' and ''PRIMARY_END''. ''direction'' is 1 if the source leaf is above the target leaf, and ''UPWARD_SPLASH'' (0.3) otherwise.
   * **Q6.** Calculate the infection probability of a leaf aged 0 h at ground level, during the ascospore season, when no leaf is sporulating yet (''PRIMARY_INOCULUM'' = 0.5, ''RESISTANCE'' = 0). Same for a leaf aged 75 h.