YELLOW PICKLE IN CUCUMBERS. 5 



on the vines. A few that liad not turned yellow failed to grow aftei 

 standing still for such a long time, and finally dried up without becoming 

 yellow. The flowers from which these yellow pickles developed were self- 

 pollinated on .June 21, 1925. The pickles did not begin to turn yellow 

 until August 8, 1925, 48 days later. Some of them were three to four 

 inches long and a few had some \ iable seeds. 



Relatiox of Poi.lixatiox to the Development of Yellow Pickle 



Many cases of yellow pickle can be attributed to lack of pollination. 

 However, with certain varieties, when a pistillate flower is not pollinated, 

 its growing period is much shorter, and the pickle very seldom grows over 

 two inches. Often it does not have the characteristic yellow color found on 

 tlie larger pickles. In the case of the English variety it is possible to 

 mature large cucumbers without pollination, but this is not the case in 

 the ordinary varieties used in a study of this problem. Yellow pickles 

 were found, however, on English \ ines \\ hicli already had tliree or four 

 mature cucumbers. 



Interest in tlie yellow pickle problem prompted the bagging of a large 

 number of pistillate flowers to prevent visitation by insects. None of 

 these flowers developed ])ickles over two inches long. The color was a 

 grayish yellow and in some cases almost white. Some of these decayed in 

 a short time, wJiile others dried up and dropped off, a condition differing 

 trom that described ai)o\c. 



The Relation of Method of Gkowixc to Yellow Pickle 



Two methods of growing cucumbers in greenhouses are generally prac- 

 ticed; namely, the "A"" trellis metiiod, and the string method. Where the 

 "A" trellis is used, fewer plants are necessary and these develop more 

 normally than with the string method. With the string method the plants 

 are closer together, and are pruned so that each branch has only one or 

 two nodes, the main stem being twined around the string which extends 

 Irom a wire near the top of the house to the base of each plant. The 

 prevalence of yellow pickle depends somewhat on the method that is used. 



The number of pistillate flowers formed is largely determined by heredi- 

 tary factors. TiiiLS, there will be as many jaistillate flowers on the main 

 stem and first two nodes of the branches whether the plants are grown 

 (ill strings or trellises. In the string metiiod, a large amount of leaf 

 surface is removed in pruning, thus curtailing the amount of food the plant 

 lan manufacture and store. Such plants cannot develop as many of the 

 pistillate flowers as those on tlie "A" trellis where very little pruning is 

 done. Also, the plants are crowded more in the string method and less 

 soil nutrients are available to each plant. Tliis means that there are likely 

 to be more yellow pickles on the string plants under uniform conditions 

 of growtii. Tills lias been commonly obser\'ed, but not proved by tests 

 under controlled conditions. 



Relation of I'ahasitic Diseases to Yellow Pickle 



As was stated in the introduction, yellow or white pickle resemble.-, 

 symptoms of mosaic. It is also common to iind yellow i)ickles associated 

 with diseases produced by animal or plant parasites, but the yellow pickle 

 with which we are here concerned does not come within the category of anv 

 oi these diseases. When plants are affected with disease their health is 



