LEADING VEGETABLE CROPS 211 



and eating numerous tiny holes in the foliage. 

 This insect has been found to be effectively con- 

 trolled in those regions where bordeaux mixture is 

 regularly used for the late blight. Bordeaux mix- 

 ture does not kill the insect, but acts in the nature of 

 a repellent. 



The so-called late blight is by far the most serious 

 disease. It attacks the leaves and stems, quickly spread- 

 ing to the tubers, which are checked in growth, and rot 

 usually results. Spraying with bordeaux mixture 

 has been found to effectively control this disease. 

 The first application should be made when the 

 young plants are four to five inches high. This treat- 

 ment should be repeated at intervals of lO days to 

 two weeks until the crop is practically mature. 

 Lime and sulphur has likewise proven an effective 

 remedy used at the rate of one gallon of the commer- 

 cial form to 40 gallons of water. 



The potato scab, already briefly described in con- 

 nection with the seed and its treatment, appears as 

 rough, irregular brownish black spots upon the sur- 

 face of the tuber. The fungus causing this trouble 

 lives from year to year in the soil primarily upon 

 decaying organic matter, but under certain condi- 

 tions this disease is able to transfer itself to the de- 

 veloping tubers of the potato, and is also found to a 

 considerable extent upon the beet. The disease is 

 communicated to the new potato, both from the old 

 seed and directly from the soil, but apparently to a 

 much greater extent directly from the seed. Treat- 

 ment from the seed, as described on pages 204 and 

 205, prevents the troubles spreading from the same, 

 but does not, of course, prevent all scab, as some of 

 the tubers are likely to be attacked directly from the 

 soil. Such a large percentage of scab is prevented 



