An intestinal diseases of humans caused by the bacterium Vibrio chlorae. This disease, and typhoid, caused by the bacterium Salmonella typhi, are spread by houseflies, and the Allied forces dusted the whole of Naples with DDT during World War II, in order to prevent major epidemics of insect-borne diseases, including malaria. DDT-resistant houseflies soon appeared and this was the first known example of the breakdown of an unstable, synthetic pesticide to new strains of the pests. It was this failure of DDT that initiated the 'boom and bust cycle' of pesticide production. Chromosome

Microscopic, threadlike bodies that occur in the nuclei of plant and animal cells. Each chromosome consists of strands of DNA, which is the protein that encodes all genetic information. This information is made up of units called genes. Chromosomes occur in pairs, with one of each pair coming from the male parent, and one from the female parent. Each gene normally consists of two alleles, with one on each of the pair of chromosomes. During the process of cell division, the pairs of chromosomes replicate in a process called mitosis. When gametes are produced, the pairs of chromosome separate, without replication, to form two haploid gametes. A chromosome is the most concentrated known system of storing information. Bacteria and viruses do not store their genetic information in chromosomes. See also: diploid , doubled monoploid, tetraploid, etc. Chrysanthemum cineriifolium

The species of daisy, called pyrethrum, from which natural pyrethrins are extracted. Pyrethrum originated in Dalmatia (the area that used to be called Yugoslavia) where people still put dried pyrethrum flowers in their bedding to kill fleas and bed bugs. They have apparently been doing this for centuries, without any resistant fleas or bed bugs appearing, demonstrating that natural pyrethrins are a stable insecticide. But this insecticide is currently too expensive for use in crop protection.

Pyrethrum is open-pollinated and is an excellent crop for amateur breeders . The breeding objectives should be both a high yield of flowers, and a high pyrethrin content in those flowers. The latter can be professionally assessed in a commercial or university laboratory, or an amateur bioassay can be obtained by adding a minimal amount of powdered, dried, flower to a jam jar containing an insect such as a housefly or a bee. Some agricultural engineering will also be required in order to produce a mechanical harvester. If the price of pyrethrins could be reduced significantly, the crop protection market would be virtually unlimited. This is thus a crop of great potential. See pyrethrins for a description of the insecticide itself. CIAT

Centro Internacional de Agricultura Tropical. This is the international research centre for tropical agriculture located in Cali, Colombia. It is one of the CGIAR research stations. Cicadulina spp.

Species of leaf hopper insects. Some species are vectors of virus diseases of plants, the most notable being maize streak virus in Africa.

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