Theory question 106
Crop DiseasesWrite short notes on the following plant diseases.
(a) black pod of cocoa.
(b) leaf blight of cassava.
Show the model answer
(a) Black pod of cocoa: caused by the fungus Phytophthora palmivora; spread by rain splash, insects and contact in wet weather; symptoms – brown/black spots on pods spreading to cover them, beans rot; control – remove and destroy infected pods, regular harvesting, pruning and shade reduction for aeration, spraying copper fungicides (e.g. Bordeaux mixture, Perenox)
(b) Cassava bacterial leaf blight: caused by the bacterium Xanthomonas (axonopodis) pv. manihotis; spread by infected cuttings, rain splash and tools; symptoms – angular water-soaked leaf spots, leaf wilting and blight, gum exudate, stem dieback; control – plant resistant varieties and clean cuttings, crop rotation, uproot and burn infected plants
For each: cause, spread, symptoms and control.