Disease Management in Cocoa

Abstract

Cotton diseases are caused by microorganisms such as fungi, nematodes, and bacteria that grow on and within plant tissues. They often result in reduced vigor and yields, and sometimes death. Seeds and seedlings attacked by these pathogens often die, while older plants may survive but perform poorly. Diseases can also result from an inhospitable environment, such as a field with too much or too little water or fertilizer; or from air pollutants, temperatures unfavorable for plant growth, or chemical injury, such as herbicide injury or carryover. Diseases caused by organisms are contagious (will spread from plant to plant) and usually affect only one plant species, whereas disorders caused by environmental factors (abiotic) produce symptoms on all plants in the affected area but will not spread from plant to plant. Plants are more prone to attack by pathogens when stressed by an inhospitable environment, insects, or other causes. Thus, contagious diseases are often associated with insect infestations and poor growing conditions. For example, wet, cold soils often lead to fungal rotting of seeds and seedlings; insect injury to bolls increases the probability of fungal boll rots. This chapter discusses cotton diseases that affect seeds, seedlings, and mature plants. Emphasis is placed on fungi and nematodes, the two most important pathogen groups to cotton. Injury to plants caused by fertilizer, herbicides, or environmental problems is covered in other chapters of this publication.