THE APPLE SCAB OUTLOOK 



The number of scab spore cas 

 wintered leaves is abnormally large 

 heavily scabbed leaves. In the Coll 

 and fruit bud development are approx 

 date (March 26) last year. TJ'ith Mc 

 stage, about one-fifth of the old sc 

 maturity in a small percent of the p 

 thecia contain either no spores at 

 (ascospores). 



es (perithecia) developing in the over- 

 this spring due to the abundance of 

 ege orchards perithecial development 

 imately the sane as they were at this 

 Intosh fruit buds in the silver tip 

 abbed leaves show scab spores reaching 

 erithecia. The remainder of the peri- 

 all or only immature winter spores 



Scab spore development in one South Amherst orchard is in the same 

 stage as here at the College, while in another orchard perithecia are con- 

 siderably less advanced. The most advanced stage of ascospores so far ob- 

 served was in a leaf sample from Yfallace Pratt of Bridgewater (Plymouth 

 County) where 10/J of the leaves showed a goodly number of mature spores 

 at the sv;elled bud stage (llarch 19). 



Had it not been for the very dry v;eather during the past week of 

 mild temperatures, scab spore development would be even farther along than 

 it is now. Should cool, wet v/eather prevail in the near future, scab spores 

 will develop much faster than fruit buds. If the present kind of weather 

 (v/arm today v/ith showers predicted for tomorrow) should last for several 

 days, a small portion of the ascospore supply will be ready to shoot by the 

 time the fruit buds reach the green tip to early delayed dormant stage. 



Last year at this same date and corresponding fruit bud stage, the 

 weather turned very \^arm and remained so for a full week, bringing fruit 

 buds in Amherst into pre-pink by April 5. It is hoped, of course, that 

 such will not be the case again this year. 



The accompanying table indicates the time of season in past years 

 when Mcintosh fruit buds in Amlierst reached the silver tip stage, and the 

 corresponding stages of scab ascospore development; also when ascospoxes 

 were sufficiently matured to discharge in the orchard during each of rthose 

 years . 



Buds' in i 



Year 



1946 



Silver 

 Tip Stage 



Scab Ascospore 

 Stage 



First Spore Discharge 

 Date*~ 



March 24-27 Only a few ripe spores j }4/2(?) 

 I none shooting { 



Bud Stage 



Green tip (?) 



