CONTROL OF GARDEN DISEASES AND INSECTS. . 9 



needed for use. P'or most species of sucking insects 1 part of the 

 stock emulsion should be mixed with 15 parts of water. It is then 

 applied with a fine nozzle in the form of a mist spray or like a dense 

 fog, and is sprayed only long enough to cover the plants. 



If the spray is not applied properly it maj^ drip off the leaves, 

 causing the ground beneath to become soaked. As a result delicate 

 plants when exposed to direct sunlight may be injured or killed. For 

 this reason nicotine sulphate is preferable. 



LEAD ARSENATE. 



Paris green, formerly much recommended for biting and chewing 

 insects, such as the Colorado potato beetle, cucumber beetles, cabbage 

 worms, and tomato hornworms, because it was known to most farm- 

 ers and is for sale at drug stores, is being superseded to a consider- 

 able degree by other arsenicals, of which the most important is 

 arsenate of lead, or lead arsenate. 



The present high cost of all copper compounds has resulted in a 

 similar high price for Paris green. Although arsenate of lead has 

 also risen in price it is less costly and is preferable for the following 

 reasons: (1) It serves the same purpose as Paris green against ex- 

 ternal leaf -eating insects and certain other chewing insects; (2) it is 

 applied in the same manner; (3) it is less harmful to growing plants, 

 being less likely to burn delicate foliage; (4) it adheres better to the 

 foliage; (5) it is less troublesome to prepare; and (6) the white 

 coating which it leaves on the plants after spraying shows which 

 plants have not been reached by the treatment. 



Lead arsenate, however, does not kill insects as quickly as Paris 

 green, although the fatal dose is absorbed nearly as soon. 



Arsenate of lead is sold in both powder and paste forms. At the 

 rate of 2 pounds of powder or 4 pounds of paste to 50 gallons of water 

 or Bordeaux-mixture solution it w^ill destroy cabbage worms and most 

 other caterpillars, the " slugs " and adults of the Colorado potato 

 beetle, cucumber beetles, and most other insects of this nature. 



In small gardens two-thirds of an ounce of the powder form, or 

 10 level teaspoonfuls, to 1 gallon of water is used. 



Generally, the adhesiveness of lead arsenate is enhanced by the 

 addition of a "sticker" of about the same amount by weight of resin 

 fish-oil or other soft or dissolved soap as of the arsenical used. This 

 must be used in the case of cabbage and similar crops, since otherwise 

 the waxy bloom of the foliage repels the liquid, causing it to gather 

 in large drops, and a thorough distribution, on which the success of 

 the treatment depends, is not secured. If properly applied, the leaves 

 should show a thih white coating of the poison for a long time. 



The number of sprayings to be applied will depend on the insect 

 concerned in the injury and on local and seasonal conditions. Some- 

 106342°— 17— Bull. 856 2 



