-9- 



Another possible factor for differences in the degree of thinning from year 

 to year may be the effect of weather on the amount of active material absorbed by 

 the foliage follo\ving application. Cool, cloudy, damp weather following application 

 may increase absorption and thus increase thiiming \;hile warm, bright weather vjhich 

 favors quick drying may reduce the amount of active material VJhich is taken in by 

 the leaves and result in less thinning. 



Our recommendations for chemical thinning do nd differ materially from those 

 of last year, but we would suggest g^o^vers pay more attention to weather conditions 

 when applying the thinning sprays. It appears that vre can expect more foliage in- 

 jury and increased thinning vchen the thinning sprays are applied under conditions 

 of high relative humidity which favor slow drying. This condition could be favored 

 by sprays applied in late afternoon or evening in contrast to sprays applied eai'lier 

 in the day. 



Our revised thinning circular may be obtained from your County Extension Service 

 Office or direct from the Mailing Room at the University here in Amherst. Ask for 

 Special Circular No, l89, "Chemical Thinning of Apples and Peaches," 



^W. D. Weeks 



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OBSERVATIONS IN CAIIFGRNIA 



I'm gradually getting to travel vdth the University of California staff to 

 more and more of their experiiaental plots and se-ing a number of their fruit 

 sections. Since soil and climatic conditions are often much different from those 

 in New England, it is perhaps not surprising that the performance of fruit trees 

 and the methods of orchard management vary considerably from ours. In general 

 throughout the deciduous fruit areas in California, the vdnters are vary mild, by 

 our standards. The lowest minimums in many fruit sections of this state may be 

 above 15° F during the ranter. These mild winter temperatures have a profound 

 influence on many species of fruit. Lack of a sufficient number of hours below 

 kO°- kS° F tends to delay the opening of flower and leaf buds so that the bloom 

 period here often extends over a much longer period than ours, even though the 

 late vdnter and spring days are fairly warm and sunny. Almonds began to bloom 

 in early February, here, but some petals were still hanging on some varieties in 

 mid-March. Peaches reached full bloom around March 16, although some blossoms 

 opened in late February, Sweet cherries haven't opened yet, which is quite a 

 surprise to me, since they bloom ahead of peaches in the East, This difference 

 in time of bloorai-ng is apparently related to differences in chilling requirements 

 betvreen the two species. In the Watsonville apple section, the lower limbs are 

 going to flower ahead of those in the tops of trees. Also, in mild vdnters, many 

 apricot and peach flower buds fall off of some varieties before opening. In the 

 \7inters< apricot district, the bud drop is sufficiently heavy in some orchards to 

 reduce the size of the crop this year, 



Hovrever, in California they have wide variations in summer temperatures from 

 one fruit section to another. In seme of the coastal areas, the summer temperatures 

 may rarely go above 8^° F, This is the situation in the apple section at Watsonville, 

 whereas, at Davis ^n interior area) summer temperatures of 105° are coiranon. Yet, 



