We have studied protectants for several years and have learned a great deal about 
them. Some appear to function through repellency, some through toxicity, and others 
through a combination of both actions. Some materials or some levels of application will 
protect only uninfested grain, whereas others willalsokill off existing infestations. There 
is a relation between the level of residue present in the grain and performance of the 
protectant. The rate at which the residue disappears governs the length of time it protects 
the grain. Such factors as grain moisture, grain temperature, and chemical nature of 
the protectant have an inter-related effect on the performance and on the rate at which 
the residue disappears. 
Protectant studies have been made on several grains such as wheat, corn, grain 
sorghum, and rough rice. They have been extended to farmers stock peanuts and were 
tentatively explored even in such products as stocks of dried raisins during the storage 
period before final cleaning and processing. The materials tested have included ryania, 
lindane, methoxychlor, synergized pyrethrum, and malathion. Part of the studies has in- 
cluded determining the fate of residues during the milling of treated wheat. Materials 
such as ryania and lindane have been droppedfrom further testing because of toxicological 
and residue factors. Tolerances have been established under the Miller Amendment to 
permit the use of malathion or pyrethrum plus piperonyl butoxide as grain protectants. 
We are continuing our search for materials that more closely approach our concept 
of the ideal protectant. Just what properties do we need in this ideal treatment? It should 
be long-lasting with a low residue hazard. It must be economical and easy to apply. It 
should not be sensitive to high temperature or high grain moisture, and must be effective 
against a wide range of insect species. It should destroy any existing infestation as well 
as protect against reinfestation, because grainis sometimes infested when it is harvested, 
It should not affect germination of grain and must not make the grain undesirable or 
disagreeable to handle in commercial channels. It must not have any adverse effect on 
grade, odor, flavor, or baking qualities. 
CHEMICAL ANALYSIS 
From the very beginning of the research on protectants it was evident that residue 
analyses were absolutely necessary as an integral part of the research program. There 
are many other phases of stored-product insect work where chemistry and residue 
analyses are important, but a discussion in relation to protectants will serve as an 
example to illustrate the advances that have been made in the use of chemistry. 
Chemical analyses are necessary to study and evaluate the rate of disappearance and 
fate of residues, as well as to correlate the level of residue with the degree of biological 
performance. Residue analyses are important not only as a research tool but also for 
obtaining data to be evaluated in the establishment of tolerances under the Miller and 
Food Additive Amendments. Theseanalyses also indicate tous how much unwanted or inci- 
dental contamination may result from a particular procedure in pesticide application. 
It is evident that much of the research on stored-product insects requires chemistry 
as a supplement and that as soon as we start to use pesticides we are immediately con- 
fronted with problems of potential residues and contamination. Therefore, it has become 
almost a standard procedure to set up parallel biological and chemical tests in many 
phases of our research program. In some cases there is even a preliminary conference 
with Food and Drug Administration officials to determine whether the planned chemical 
analyses will provide them the kind of data required to consider the establishment of 
tolerances. Although we receive much analytical assistance from the pesticide industry, 
it is impossible for them to provide the number and kind of analyses needed, to time 
them according to our requirements, or to provide close liaison with our research pro- 
gram. Therefore, the Stored-Product Insects Branch operates its own chemical analytical 
laboratory. 
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