INSECT POWDER, PYRETHRUM, TIUTIACIT. DALMATIAN or PERSIAN INSECT l'owDER. A brownish-yellow powder obtained by grinding the dried flower-heads of two species of Chrysanthe mum (Pyrethrum), a genus of plants of the natural order Composite. The species employed are Chrysanthemum coceineum, popularly known as Pyrethrum roseum, and often grown as an ornamental summer-bedding plant, and Chry santhemum einerathrfolium, also called Pyre thrum eincrari•folium. From the flowers of the former, a Persian species, is made Dalmatian or Persian insect powde•—bette• known in Eu rope than in America; from those of the latter, a Caucasian species. extensively cultivated in California, is manufactured the insect powder hulmeh and pyrethrum, common in the United States. When fresh the powder made from each species seems to be equally effective; but since the volatile oil, upon which their effectiveness depends, is lost with age and also by exposure to air and heat, the California product is con sidered with more favor in America than the imported powder. Chrysa n t hem 14 rn einem rim foliwn. is preferred in California. because its flowers may he gathered at approximately one time. whereas Chrysanthemum coreineum has an extended period of bloom. The volatile oil acts upon insects by asphyxiation; upon man and other animals it has no serious effect: workmen in the pyrethrum-mills sutler no more incon venience than millers do trom the dust in flour mills. 'tie plants are fed to horses and other stock after the flowers have been gathered. In California, where some large farms are devoted wholly to this plant, the industry commenced in IS70, and three years later the small product was sold at $Ifl a pound. In ISS5 the price had
fallen to $0.15 a pound, and has never since risen to unreasonable figures. The seed is sown about half an inch deep in light soil during autumn or spring, and the young plants trans planted when a few inches tall to the field. 2 feet by 4 feet apart, given irrigation each month during the dry season, cultivated by horse, and kept free of weeds by hand. A partial crop may be obtained the first year after planting, but the crop of the third year is usually the largest. Generally the plants continue to bear profitably for six years. The tlowers are combed from their stems by hand during May and June, sun dried, and ground between burr-stones similar to those of old-fashioned flour•mills, and after bolting packed in air-tight tin cans. Insect powder is usually employed in household use as dust. When flies, mosquitoes, and other insects are numerous and troublesome, it is often heated in closed rooms and the stupefied creatures swept up and destroyed before they recover. It is similarly used in greenhouses. Frequently also it is applied as a solution in water (I ounce to 2 or 3 gallons) or in alcohol ( I ounce to 4 ounces by weight). The former is applied as mixed: the hitter, after daily shaking for a week or more, is filtered and the clear liquid applied with an atomizer. This decoction, if applied to plants, should he diluted somewhat. Pyrethrum is also sometimes mixed with kerosene emulsion or other insecticides. Sec INSECTICIDE.