18 MISC. PUBLICATION" 16 8, U.S. DEPT. OF AGEICULTUEE 



surface mycelium, northwestern anthracnose is indicated. If yel- 

 lowish sjoore masses occur and the rotten spots are small and rather 

 numerous, the causal fungus is probably Fu^sarmm. Fisheye rot 

 usualh^ carries a very downy surface mycelium without spores, and 

 the affected flesh has a tough, stringy or spongy texture. Spots 

 of this rot are more sunken than those of the other rots here under 

 discussion (pi. 2, B). 



Spots caused by Sporotrichum are oval or circular in outline, 

 usually less than an inch in diameter and only slightly depressed. 

 The affected tissues are watery but firm and can readily be separated 

 from the surrounding healthy flesh. Xo surface mycelium is pro- 

 duced except under very moist conditions. There is nothing par- 

 ticularly noteworthy about the Eamularia rot except that affected 

 spots have the general bullseye appearance already described. 



The northwestern anthracnose fungus and the perennial canker 

 fungus produce cankers on twigs and branches from which spores 

 may be washed- by rain to apples growing beneath the cankers. 

 The other fungi are not known to have any parasitic stage other 

 than that on the fruit, but it seems certain that 2 or 3 of them are 

 able to develop to some extent on dead wood, bark, twigs, or leaves 

 of the apple or even on other plant material common in orchards. 



Of these six rots, the most common on the market are perennial 

 canker, anthracnose, and fisheye rots. All of these are able to 

 develop at 32° F. but do so rather slowly and are not often found 

 in stored lots until January or February following harvest. There 

 is no evidence that they can spread in transit or storage. The other 

 four develop slowly but do not spread at cold-storage temperatures, 

 and do not usually become of commercial importance in stored 

 lots until rather late in the season. (:^<9, 30.) 



CONTROL MEASURES 



Careful spraying with Bordeaux mixture is the best means of con- 

 trolling northwestern anthracnose in the orchard. Such spraying 

 coats the limbs with a substance toxic to the fungus and in most cases 

 gives a protection that means for the following year (1) more vigor- 

 ous trees, (2) fewer cankers, and (3) less rot on the fruit. One appli- 

 cation should be made as soon as possible after the fruit is picked, 

 and another 2 or 3 weeks later ; in cases of severe attack it is advisable 

 to make one application 2 or 3 weeks before the fruit is picked. 



Kemoval of limbs affected with anthracnose and the excision and 

 painting of cankers are helpful measures, but should never be con- 

 sidered as more than merely supplementary to spraying. When 

 cankers are cut out the material removed should be destroyed and the 

 wound disinfected and coated with a waterproof elastic wound 

 dressing. 



For the control of perennial canker rot a thorough application of 

 Bordeaux mixture, 4-4-50, is advised. Ordinarily this should be 

 applied about September 10, or before the fall rainy season starts. 

 Spray residue from Bordeaux mixture forms a heavy coating on the 

 apples which interferes with the development of normal coloring of 

 the fruit, hence it is desirable to delay the spraying as late as is 

 compatible with satisfactory control. Since the tree cankers are the 



