Factors that affect Colletotrichum growth and infection include inoculum concentration, wetness duration, temperature, age of plant, resistant plant cultivar, pH, nutrient and light.
2.4.1 Inoculum density
One of the main factors that facilitate Colletotrichum sp. infection and growth is inoculum density. Up till now, according to Diéguez-Uribeondo et al. (2011), disease severity increased exponentially with increasing concentration of inoculum. For instance, an increase in lesion number and bigger necrotic lesion diameter was observed on cucumber plant as inoculum concentration was increased (Dean and Kúc, 1986). Based on the study by Forcelini (2013) highest disease incidences …show more content…
Inoculum on Plants
There were a few methods used to create humidity in experiments. Humidity is created for the fungus to germinate and grow. Fungus cannot germinate and grow without humidity. Bertetti et al. (2009) studied the effect of leaf wetness duration by covering the inoculated plants with moist plastic bags for 0, 12, 24 and 48 hours in growth chambers. Besides using moist plastic bag, Dillard (1989) used two humidifiers (Welbilt Ultrasonic Humidifier, Welbilt Corp, Korea) to maintain humidity in the moist chamber for the inoculated tomatoes for 10, 20, 24, 29, 44, 48, and 58 hours whereas Aqeel et al. (2008) also used a humidifier (Humidifier 1626D, Phytotronics, Inc., Earth City, MO) to maintain the humidity of the inoculated vegetable samples.
Another method used by researchers was the use of misting chamber. Chongo and Bernier (2000) kept the inoculated 4 weeks old plants under continuous plant wetness periods of 6, 12, 24, 36, and 48 hours in a misting chamber. Similarly, Holtslag et al. (2003) also used continuous mist provided from a mist humidifier located to one side of the humidity chamber and above the plant