362 INSECTS AFFECTING VEGETATION 



Worming. In case of most wood boring insects, digging the 

 larvae out with a knife is a method largely followed, and indeed the 

 one chiefly depended upon in many districts, where the worming of 

 the peach and other trees is as regular a part of the year's work as 

 plowing or cultivating. The forcing of a flexible wire into the bur- 

 row injures the bark less and in skillful hands may be quite effective. 



Hopper Dozers. For the destruction of young grasshoppers, 

 one of the most effective means is the use of shallow pans, made 

 usually of sheet iron, the bottom covered with kerosene or coal tar, 

 which are drawn over the ground by horses so that the insects in 

 trying to escape will leap into the pans. At the rear of the pan is a 

 vertical screen to prevent their leaping entirely over. The pans are 

 supported on low runners so that they slide easily over the ground. 

 Such an apparatus is called a hopper dozer. We believe that in many 

 cases its use would pay for the destruction of other insects than grass- 

 hoppers, especially in pasture lands that are badly infested with small 

 leaf hoppers. (Bui. 50, Iowa Agr. Exp. Sta.) 



CONTROL BY LEGISLATION. 



Most states have laws on the statutes governing the inspection, 

 sale and importation of nursery stock and some states have laws gov- 

 erning the sale of scale infested fruit. Under these laws the nurseries 

 are inspected for injurious insects and plant diseases and the stock 

 required to be fumigated before sale. To nurseries found to be ap- 

 parently free from pests a certificate is issued which must be attached 

 to the stock sold. In this way a great deal is done towards insuring 

 the farmer against the introduction of pests on his premises. (Cir. 

 75, Sec. Rev. U.S. D. A. B. E.) 



IMPORTANT INSECTICIDES : DIRECTIONS FOR THEIR PREPARATION 



AND USE. 



These are not covered by patents, and in general it is true that 

 the patented articles are inferior, many of the better of them being 

 in fact merely more or less close imitations of the standard substances 

 and compounds hereinafter described. Only such brief references 

 to food and other habits of insects will be included as are necessary to 

 illustrate the principles underlying the use of the several insecticide 

 agents. 



Relation of Food Habits to Remedies. For the intelligent and 

 practical employment of insecticides it is necessary to comprehend 

 the nature and method of injury commonly due to insects. Omitting 

 for the present purpose the exceptional forms of injury which neces- 

 sitate peculiar methods of treatment, the great mass of the harm to 

 growing plants from the attacks of insects falls under two principal 

 heads based on distinct principles of food economy, viz., whether the 

 insect is a biting or a sucking species. Each group involves a special 

 system of treatment. 



Injury from Biting Insects. The biting or gnawing insects are 

 those which actually masticate and swallow some portion of the solid 

 substance of the plant, as the wood, bark, leaves, flowers, or fruit. 

 They include the majority of the injurious Iarva3, many beetles, and 

 the grasshoppers. 



