-8-. 



Paj/ietimes light applications of fertilizer are used in Icwbush blueberry fields. 

 Since the fertilizer stimulates both herbaceous and vroody weeds as well as blue- 

 berries, the use of fertilizer often results in little or no increase in yield 

 because of weed competition. Also, if v:eeds become too thick harvesting becomes 

 •^nery difficult or impossible. Therefore, in order to evaluate correctly the results 

 of fertilizer applications, weeds need to be reduced to a minmum or eliminated. 



The weed problem has been under study for several years. The ideal weed 

 killer would be one -vjhich vrould eliminate all plant growth except blueberries and 

 kill all ueed seeds. The large number of different species competing with the 

 blueberries, the' great differences between them and the close relationship betvreen 

 blueberries and some species of competing weeds make the goal look a long way off ^ 

 The best v;e can hope for at present is to find materials or methods that will con- 

 trol the more troublesome weeds. Already ways have been .foujnd for controlling 

 some of these weed pests. For example, eweet fern ( Comptonia peregrina ) can be 

 controlled by spraying with a dilute aolution of 2,I|-D during the summer. Likevd.se, 

 a dilute solution of 2,U,5-T ester sprayed on bpyberries during the summer will 

 control it. Many vioody weeds can be controlled by spot apolications of 2,U^5-T or 

 2,U-D plus 2,lt,5-T esters in oil during the donnant season^ 



The common brake or bracken (Pteridium latinsculum) is extremely troublesome 

 in many areas. The tops are very easily destroyed but the large fleshy root stocks 

 are very difficult to kill. Several materials have been tried but so far only one, 

 polyborchlorate , looks at all promising. To avoid serious injury to the crop this 

 material iTill have to be applied the year of the bum. However, the exact time of 

 year when application will give best results and the optimum amount to apply have 

 not been fully worked out. It looks as if this material would have the advantage 

 of controlling many other weeds besides bracken. 



J. S. Bailey 



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CHEMICAL THINNINO OF APPLES 



A recent bulletin by Teutner & Mumeek from Missouri gives a very fine dis- 

 cussion on hov: hormones, such as naphthalene acetic acid, are able to thin apples. 

 The authors found that naphthalene acetic acid causes embryo abortion v;hich results 

 in increased fruit drop that produces the thinning effect. Just why the material 

 does not induce embryo abortion in all the fruits is not known at present, although 

 the degree of embryo abortion appears to be related to the stage of embryo develop- 

 ment at the time the hormone is applied. In other v7ords, the effectiveness of a 

 thinning spray may depend on the stage of seed development in the young apples at 

 the time of application. 



This may or may not account for the differences in the degree of thinning 

 obtained in different seasons from applications with the same timing. Temperatures 

 folla\'fing bloom could vary enough from year to year so that the stage of embryo 

 development would not be the same each year for the same timing of applications. 



