574 IOWA DEPARTMENT OF AGRICULTURE 



FUNGUS DISEASES OF PLANTS FOR 1916 



BY L. H. PAMMEL 



The past year has been, on the whole, a good one for crops, as s>hawn 

 l>y the crop report of Dr. Chappel. The tables and charts showing tem- 

 perature and precipitation at Ames and for the state, which have been 

 compiled for me from the reports of the Iowa Weather and Crop Service, 

 by Misis Charlotte M. King, show that there were deficiencies in precipita- 

 tion at Ames in all months, March to September, inclusive, the greatest 

 deficiencies occurring in March, 1.17 inches; June, 1.69 inches; and 

 July 3.54 inches. These data are graphically represented by the tables 

 and charts accompanying this article. 



Dr. George M. Ohappel gives the follov/ing yields; corn, 346,193,200 

 bushels, having a value ot $280,416,500. The loss from corn smut at 

 6 per cent would mean a loss of $18,000,000 in round numbers. The oat 

 crop amounted to 184,131,000 bushels with a value of $90,224,100. The 

 loss from both kinds Off oat smut is about 7 per cent. This would, mean 

 a loss of about $6,300,000. Corn ear rots cause a loss of about 2 per 

 cent, whicla would mean a loss of $5,600,000. Crown gall has been esti- 

 mated to have damaged nursery stock about $45,000 annually. The loss 

 from apple scab is nearly $2,500,000. The alfalfa spot disease has dam- 

 aged the crop in Iowa about $1,000,000. A coniservative estimate places 

 the damage to crops of all kinds from fungus diseases in Iowa not ifiar 

 from $35,000,000. The damage to our crops is in a large measure con- 

 trolled by weather conditions. Much of the injury tO' our crops can be 

 prevented by treatment with fungicides and crop rotation. 



We may briefly summarize the disease as follows: During the year 

 1915 there was an abundance of the potato blight fungus ( Phytophthora 

 infestans) which was, undoubtedly, due to the great precipitation and the 

 unusually low temperature. The disease appearing from early August 

 to the middle oif the month. The year 1916 was on the whole charac- 

 terized with higli temperature, low humidity and small precipitaition. 

 This period of drought began in the month of June and continued to 

 September. The potato blight fungus (Phytophthora infestans) did not 

 occur in the state this season. 



Leaf rust of oats (Puccinia coronata) was not severe. It made its 

 first appearance early in June. The dry weather checked its develop- 

 ment. The crop was good and the quality of the grain excellent. Stem 

 rust of oats (Puccinia graminis) occurred to some extent, but not serious. 



Stem rust of wheat {Puccinia graminis) was not common and little 

 damage was done. 



Leaf rust of rye (Puccinia mhigo-vera) . The leaf rust on rye was 

 common and did some damage. In black soil it was much more common 

 than in sandy soil. The damage was not as great as in 1915. It was 

 common on rye. 



