The organism which depends on another organism for food and cause harm to that organism is referred to as a

A parasite is an organism that lives on or inside another organism (called the host), derives its nourishment from the host, and causes harm to the host in the process. This relationship, called parasitism, is one-sided: the parasite benefits while the host suffers.

A predator kills and consumes its prey outright rather than living on it over time. A pest is a broader term for any organism that causes damage to crops, livestock, or stored products, but it does not necessarily depend on a single host organism for food. A disease is a pathological condition or state of ill health, not an organism itself (though diseases may be caused by parasitic organisms).

Examples of parasites in agriculture include ticks and lice on livestock (ectoparasites, living on the outside), and roundworms and tapeworms inside the digestive tract (endoparasites, living inside the host). The defining features are dependence on the host for nutrition and the harm inflicted on the host over a sustained period.