Pyrethrum extract is important to control of pest
insects in the household, in barns, and in stored
products, and for direct application to man and
livestock. Before the second World War, powdered
pyrethrum flowers or pyrethrum extract were employed
for control of agricultural and horticultural
insect pests, ause largely superseded in the 1940's by
the more effective and simpler chlorinated hydrocarbon
and organophosphorus- insecticides. Compared
with these synthetic organic insecticides, the
persistence of the pyrethrins, even with various
additives to retard photooxidation, is not adequate
for crop protection or silviculture. The present uses
for pyrethrum are well established and dependable
methods of insect control, but for very specific purposes
not likely to change in the foreseeable future.The selection of resistant strains, a problem with
most other insecticides, has had little impact on the
use pattern of the pyrethrins.