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Yaws
Bacterial disease caused by the spirochete Treponema pertenue, often transmitted by flies.

Yearling
An animal of either sex of 12-20 months of age: the term is used loosely.

Yeast
A unicellular ascomycete that multiplies typically by a budding process.

Yellow fever
Virus disease transmitted by the mosquito Aedes aegypti.

Yellows or yellowing
A plant disease characterised by yellowing or green tissues and stunting of the host plant.

Yield
Measurable produce of economic value, necessarily related to a specified crop or animal, or to an area, and to a period of time.

Yield, actual
Yield obtained under current management (crop husbandry, animal welfare).

Yield, attainable
Yield obtainable under optimal conditions using fully modern technology.

Yield components
Individual plant parts directly contributing to yield based on their number, size and/or weight.

Yield correction, small
A numerical factor correcting for differences between plot to large field yield obtained in small plot experiments and those obtained on farmers fields.

Yield, economic
The yield providing a profitable return for a given investment.

Yield, potential
The theoretical maximum yield obtainable under optimum conditions as calculated by crop/plant physiologists.

Yield, primitive
Yield obtainable without any modern agricultural inputs.

Yield, reference
The yield of a region, inclusive of all existing constraints.

Yield source components
Plant parts contributing to the critical physiological requirements for plant growth and yield production.