2.4 Effect of chitosan on expansion of necrotic lesionsA zoospore suspension was obtained by rinsing with 15 ml sterilized DW into culture plates with Phytophthora. Culture plates were incubated at 4°C for 15 minutes and then placed at room temperature for 30 min to release zoospores. Zoospores were then counted in a Petroffhausser counting chamber prior to inoculating the para rubber leaves. Individual para rubber leaves were split into two parts, to ensure the control and treated samples were as similar as possible. Treatment was by immersion into 0.5, 1 or 2 mg/ml chitosan solution for 1 hr, while immersion into 0.05% acetic acid served as control. The treated para rubber leaves were cleaned with sterilized distilled water (DW). The Para rubber leaves were wounded with detached leaf method. The 1x105 zoospores/ml concentration was inoculated into chitosan treated para rubber leaves, then incubated in moist chamber for 24, 48, and 72 hrs. The lesions from Phytophthora penetration in leaves were measured. Percent inhibition was calculated using the formula shown above.