-2- 



fram pink to crIjoc; and spors disoh&rg© thereafter f&ilS off sharply •vrith 

 light dischErgea lasting until around Jun« 10-.15. In some seaeons, epor« 

 development lags behind this so-oalled average or normal course, and in 

 others, it is ahead 6f fruit bud de7*lopment» In aay season, leavas under 

 any particular tree may vary considerably regarding the time at which the 

 scab fungus reaches the spore-discharge stage. 



One reason for the above mentioned variation among leaves is the 

 difference in the tine scabbed leave* drop from the tree. Those that drop 

 first, other factors being equal, usually develop winter spores first the 

 follw;ing spring. Mild, wet weather in the fall between leaf drop apd the 

 onset of winter usually favor* marked development of the young perithecia 

 (winter spore-caseS) before winter weather forces them into a dormant state. 

 Such perithecia are therefore likely to produce spores somewhat ahead of 

 schedule the following spring. Hence, either premature defoliation or a *alld, 

 damp fall may result in early winter apore maturity the following spring. 



An unusually late anow cover ysuaily is followed by a comparatively 

 late period of winter spore Maturity. Likewise, regardless of what trans- 

 pired in the fall and winter, a dry spring usually contributes to late spore 

 maturity and delayed discharge, as oqcufred during the unusu&lly warm, dry 

 ftpring of 1942 which forced fruit bude far ahead of the normal season. Con- 

 versely, a wet spring, starting about the time fruit buds begin to swell, 

 favors scab spore development even though the temperature may be so low that 

 fruit buds make very slow progress. Such prolonged wet periods early in the 

 8pri3:>g are usually accompanied by cold v;eather, and such weather is likely to 

 constitute a back^vard season for plant growth, as occurred in 1943. 



IThat is the situation this spring? premature defoliation last fall 

 was common for scabbed leaves, and was followed by a comparatively dry fiill. 

 There was very little snow cover during the winter, and spring, this year, 

 started out cold and wet« At present, apple fruit buds are about two or three 

 days earlier than in the very late season of 1943. Mcintosh buds jumped into 

 silver-tip stage in Amherst on April 9-10 and they have remained there until 

 the present (April 18), due to low temperatures. In Block A of the College 

 orchard, on April 3 v;ith fruit buds dormant, the farthest advanced perithecia 

 showed asci formed, but not spores. On Api:*il 11 with buds in the silver- tip 

 stage, immature spores were plentiful, but no ripe ones. On April 17 with 

 buds still in the silver tip stage, a small per cent of winter spores had 

 reached maturity and discharged during the preceding night. In Block D, scab 

 spores viere equally developed on April 11, following the warm period which 

 forced fruit buds into the silver tip stage. 



Other orchards in Amherst ahow various intermediate stages of spore 

 development, between sligf;tly earlier than normal and the stage in Block p at 

 the College. If the season is normally wet from the present until blosscming 

 time a majority of the spores in our Blo»k D will have been discharged by that 

 time. And if scab spore development in commereisl orchards in other parts of 

 the state is correspondingly early, which ia probably the case, there v/ill be 

 an abundance of spores ready for discharge when the fruit buds reach the. delay- 

 ed dormant stage. This means that, generally over the state, growers will have 

 to be doubly cautious to prevent primary infection^, beginning at the full de- 



