Negative screening

A screening technique designed to identify and eliminate the least desirable plants, as opposed to positive screening, which involves identifying and preserving the most desirable plants. This technique is often used with recurrent mass selection , in which the undesirables are weeded out, and the best plants are left to cross-pollinate. It can also be used with genetically diverse populations of a tree crop in order to reduce parasite interference, and promote population immunity. See also: Cocoa. Nematocide

A pesticide that kills nematodes, or round worms. These worms are often parasites of crops. They are usually soil-borne, and nematocides are usually applied as soil fumigants.

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