MTCHIGAN EXPERIMENT STATION BULLETINS. 211 



INSEOTICIDEB. 



For most purposes, particularly where the insects eat the exposed por- 

 tions of plants, the chief reliance is still upon Paris green or London pur- 

 ple, although many persons use white arsenic and corrosive sublimata 

 The last two are very poisonous, and as they closely resemble many com- 

 mon household chemicals, they should be used with great care, if at all. 



For many plants, the Paris green or London purple can be used at the 

 rate of one pound to 200 gallons, but for the plum this should be some- 

 what reduced in strength, while for the peach, Paris green alone in water 

 can hardly be used at any strength without burning the leaves. As a rule 

 Paris green is less likely to burn the foliage than London purple and is 

 rather more effective. It is, however, heavier and more difficult to keep 

 in proper suspension in the water. 



Either of these insecticides can be used in combination with Bordeaux 

 mixture at the same strength as when used alone, but are hardly safe to be 

 used in ammonia-containing mixtures, unless a small quantity of lime is 

 added. 



The use of lime at the rate of one pound to 32 gallons of water will also 

 be of value when they are used only as insecticides, as it will allow of their 

 application to the plum, cherry, and even the peach, with safety. 



Although it may be desirable to use fungicides when there are no eating 

 insects upon the plants, it will generally be well to add a small quantity of 

 London purple, say one pound to 250 gallons, if there is any probability 

 of their appearance before another application will be needed. 



INSECTS AND DISEASES. 



It is not the intention at this time to go into a lengthy description of 

 the structure and life history of the different pests to which our agricult- 

 ural plants are subject, but it may be of value to have a brief statement of 

 the insects and diseases for which the spraying of our different plants will 

 be remunerative. 



THE STONE FRUITS. 



The peach, plum, and cherry are extensively grown in this state, and 

 suffer severely from the attack of the curculio and of rot, which destroy 

 both fruit and leaves. The plum is frequently defoliated by the "shot 

 bole" fungus and the peach by the "curl." 



While accurate data are not at hand regarding the effect of fungicides 

 upon the development of the "curl" of the peach leaves, it is quite certain 

 that the disease can be, to some extent, kept in check by their use, and 

 there can be no question but that combined Bordeaux mixture and Paris 

 green will save the fruit from the curculio and rot, and will maintain the 

 foliage in a healthy condition until autumn. 



While the spraying may not save every plum from rot and curculio, the 

 number lost, in average seasons, will be of advantage in aiding the proper 

 thinning of the fruit. Particularly, if the season is a wet one, an addi- 

 tional spraying of the combined mixture about two weeks after the fruit 

 has set will be of advantage. 



POME FRUITS. 



The most injurious insects of the apple and pear, for which spraying is 

 of value, are the codlin moth, tent caterpillar, canker worm, and curculio. 



