242 Diseases of Truck Crops 



narium resembles the organism of bean anthraaaose, 

 see p. 263. The watermelon fungus has a peculiar 

 ability to remain dormant during dry weather; but 

 it is easily revived by rains or dew. This is why 

 anthracnose often appfears overnight in carloads 

 shipped to market. The fruits of the fungus are 

 borne in masses on the pustules which take on a 

 salmon color. The spores are tjrpical of all Colleto- 

 trichums — ^that is, oval, one-celled, and hyaline. The 

 setae in C. lagenarium are not very plentiful. In 

 pure culture it resembles C. lindemuthianum; how- 

 ever, pathologically it is distinct from the latter, since 

 nxomerous attempts by the writer and by others 

 have failed to infect growing bean plants with the 

 watermelon anthracnose or the watermelon with 

 that of the bean. 



Control. With this disease, prevention is, of course, 

 the cheapest method of control. Prom what has 

 been said, it is evident that it is never wise to grow 

 watermelons too long on the same land. In prevent- 

 ing the disease from gaining a foothold on the land, 

 a three-year rotation will probably answer the pur- 

 pose. On lands in which the crop has suffered severely 

 from anthracnose, a Ipnger rotation, say six years, 

 may be necessary. The disease is carried over in the 

 soil from year to year on the dead leaves, vines, and 

 diseased fruits which remain in the field. These, 

 therefore, should never be plowed, but destroyed 

 by fire. Spraying, too, will help to keep the disease 

 in check. Bordeaux in this case is the standard 

 fungicide to use. However, it should be borne in 



