356 iSTATE BOARD OF AGRLCULTURE 



Late Blight causes rotting of the leaves and stems and may also cause a 

 rotting of the tubers. The attacks occur during cool, wet seasons. Thorough 

 spraying with bordeaux mixture before these diseases appear is essential for 

 their control. 



Colorado Potato Beetle: This insect causes serious losses every j^ear. 

 Growers should secure poisons early in the season, and have everything ready 

 so that spraying can be done at the first appearance of the young bugs. 

 If spraying is delayed until the bugs are five or six days old, a poison spray 

 of much greater strength will be required. 



Add one to one and one-half pounds of calcium arsenate to every 50 gallons 

 of bordeaux mixture. Before the calcium arsenate is added to the bordeaux 

 mixture it should be mixed with a small quantity of water until it is free from 

 lumps and is of the consistency of thin cream. While calcium arsenate is 

 recommended in preference to arsenate of lead powder, if the latter is used it 

 should be combined with the bordeaux at the rate of one and one-half to two 

 pounds to 50 gallons. While paris green is not to be preferred, if used, it 

 should be combined with the bordeaux at the rate of one-half to one pound to 

 50 gallons of the mixture.* 



Flea Beetles: These small black insects often damage the crop severely 

 by riddling the leaves with small holes. Bordeaux mixture and calcium 

 arsenate or arsenate of lead will repel their a ttacks. 



Aphids or lice suck the juice from the under sides of the leaves. Add one- 

 half pint of forty per cent nicotine sulphate solution to each 50 gallons of 

 bordeaux mixture and apply the spray so that it will actually hit the lice. 

 Spray appHcations containing nicotine sulphate should b3 applied as soon as 

 possible after the lice are first noticed in the field. 



Tomato Worms: These insects can be controlled when they are small with 

 the same poisons that are used for the Colorado Potato Beetle. If spraying 

 is delayed until the worms are half grown, add two and one-half [)ouiids ot' 

 calcium arsenate to every 50 gallons of bordeaux. 



Hon- to Make Bordeaux Mixture 



Bordeaux mixture (4-4-50) is made as follows : Dissolve 4 pounds of copper 

 sulphate (blue vitrol) crystals in a wooden barrel containing 25 gallons of 

 water. Put the crystals in a burlap bag and suspend the bag so that the 

 crystals are just under the surface of the water. It will require several hours 

 for them to dissolve. 



In a separate barrel, slake 4 pounds of stone lime by adding small quanti- 

 ties of water to it, so that the lime crumbles into a fine powder. Gradually 

 add more water until the lime is of the consistency of thin cream. Then add 

 water to make 25 gallons. When stone lime is not available, hydrated lime 

 may be used in the proportion of 6 pounds of lime to 4 pounds of copper 

 sulphate to 50 gallons of water. 



Pour the copper sulphate solution (25 gallons) and the lime solution (25 

 gallons) together through a fine meshed strainer into the spray tank and 

 apply it to the potatoes at once. 



Where several acres of potatoes are to be spraj^ed, stock solutions of copper 

 sulphate and lime should be made. Dissolve 50 pounds of copper sulphate in 



*Kedzie mixture or arsenite of calcium is recommended by Prof. R. H. Pettit, Entomologist, Michigan 

 Agricultural College, for the control of the Colorado Potato Beetle and the flea beetle. See Michigan 

 Agricultural Experiment Station Special Bulletin No. 114. 



