176 Diseases of Economic Plants 



plants in the seed bed should be sprayed with Bordeaux mix- 

 ture as soon as they are above ground, and once or twice a 

 week thereafter until transplanted. If the disease develops 

 in the field, the crop should be sprayed with Bordeaux mix- 

 ture at ten-day intervals. The following is taken from a 

 Michigan publication in 1915: 



One-sixth acre (from which accurate returns were 

 kept) sprayed with a knapsack sprayer at a total ex- 

 pense of 12.00 for labor and material gave 125 crates 



(10x10) fine quality at Sl.OO value $125.00 



A similar unsprayed area gave 18 crates poor quality 



at 50c 9.00 



Excess return of sprayed plot $116.00 



Cost of spraying 2 . 00 



Net gain $114.00 



On the rest of the acreage, at an expense of not more than 

 $12.00, Mr. Joldersma saved a crop valued at about $1500. 



To minimize loss no diseased plants should be stored. If 

 storage is imperative, badly infested leaves should be picked 

 off, and in extreme cases the plants should be dipped in a 

 fungicide (ammoniacal copper carbonate) before they are 

 stored away. 



Early-blight, leaf-spot, ^^^ (Cercospora apii Fr.). — Leaf- 

 spot is common on celery, parsley, and parsnip in both 

 Europe and America. It is reported from California to New 

 Jersey. In Florida in 1906 it is said to have injured 80 per 

 cent of the crop. The crop is largely reduced, and the un- 

 sightliness of the spots injures the sala])ility of the product. 



The spots appear first upon the outer, older leaves as 

 pale yellowish areas, showing from both sides of the leaf. 

 They are irregular with slightly raised border and are an- 

 gular in outline, owing to their limitat ion by the veins. They 

 seldom exceed 3-() mm. in diameter imloss by the coalescence 



