preparations, tyj^icallv combining insecticide and fungicide in one appli- 

 cation, and all put out for the purpose of giving to farmer or gardener, 

 in convenieiit form, something which will do the work at least moderately 

 well. No wonder that the government finds it difficult to fix standards, 

 and that purchasers find it difficult to interpret guaranties! 



The successful production of farm and orchard crops depends in large 

 measure on the protection afforded against injurious insects and bacterial 

 and fungous diseases. Obviously, there is no remedy — that is, no panacea 

 for all noxious insects and parasitic diseases of plant life — that would 

 not also destroy the host. The method of treatment, therefore, must be 

 essentially specific, and for convenience will be divided into three major 

 groups: (A) Insecticides, (B) Fungicides, and (C) Combined insecticides 

 and fungicides. 



A. INSECTICIDES. 



The injurious insects that infest the crops under consideration are of 

 two distinct types as determined by their mode of feeding, i.e., biting 

 and sucking. The former consumes organized tissue, and the latter draws 

 sustenance from plant juices. The respective treatment of the two types 

 is necessarily different and warrants a division of insecticides into (I) 

 Stomach poisons for biting insects, and (II) Contact poisons for sucking 

 insects. 



The acknowledged requisites for an msecticide are — 



1. Non-toxicity as to plant. 



2. Effectiveness in destroying the insect. 



3. Adhesiveness or persistence under all weather conditions. 



4. Fineness of particles and a light flocculent character (when insoluble) to 

 insure a high power of suspension and uniform distribution. 



5. Ability to indicate the surface covered. 



6. Reasonable cost. 



The factors that facilitate distribution naturally differ somewhat in 

 soluble and insoluble products, dust and spray apphcations. These 

 attributes comprise a standard for judging insecticides, and apply in 

 principle to fungicides as well. 



I. Stomach Poisons for Biting Insects. 



Nearly all stomach poisons employed to-day are compounds of arsenic, 

 and this has led to the general use of the term arsenicals for this group of 

 insecticides. The sprays consist of minute particles of poison suspended 

 in the water or other vehicle, which are deposited upon the food of the 

 insect and adhere to it upon drying. 



There are two forms of arsenical stomach poisons, — the arsenites and 

 arsenates. The former are more active poisons, but relatively unstable, 

 and more likely to cause injury to the plant. Chiefly for this reason the 

 arsenates are to-day largely used. Paris green is the prmcipal arsenite 

 now on the market, whereas lead arsenate and calcium arsenate are the 

 most important members of the other class. 



