- 6 - 



CIEilCAL TlilimiNG OF APPLES 



Results ob tained in 1943 . The vifork in 1948 consisted of testing trro 

 dinitro materials (Elgetol and a dinitm povfder, DN ^^l) and the sodiiim salt of 

 naphthalene acetic acid (App-I—Set), As you all appreciate, the pollination 

 vreather this spring vms not conducive to a heav^' set. Consequently, thinning 

 vms not generally nuch of a problem this year in some sections of the state 

 except where biennial bearing varieties of good vigor blossomed heavily and v;ere 

 inter^planted v,dth many good cross-pollinating varieties. 



Some of our results and observations may be tabulated as follows: 



1, Of the blossom thinning materials, the dinitro pov.'der DIJ -..j-l is an effective 

 material and mucli less injurious to apple foliage than Elgetol, A v.-et, 

 cool spring is conducive to severe foliage "burn" from Elgetol, Elgetol 

 appears to be on the v;ay out as a thinning material for apples, 



2, The hormone material, App-L-Set, seem.s much more likely to cause permanent 

 leaf injury cjid dwarfing when applied near bloom or early cal^'.TC thcsi it 

 does at late cal^o: or 2 to 4 weeks after caly:':. This seons to be true 

 even though heavier concentrations are put on later, 



3, It appears that apples can be thiinned up to 4 \Tecks from cal^.":! T.^ith 

 hormone. The concentration, hoivevcr,- must be increased markedly as one 

 gets further av/ay from calyx. Also, soi.ie of the benefits in size and 

 annual blooming of some varieties may oo lost the later one delays putting 

 on the material but the chances of over thinning may be considerably 

 reduced. It is considerably easier to forecast the set 2 weeks after 

 caljc-c than it is at calp:, 



4, A tree v.'hich is not excessively thinned by chemicals at blossom time 



or calyx may outyield and produce fruit of larger sizo than a tree thinned 

 to the same degree by hand a month later, 



5, From measurements of bud size it a.ppears that the hoiTiione type materials 

 thin off a larger proportion of flov:ers and ^''oung fruits fran the less 

 vigorous flov.'ering spurs than they do frcm the vigorous ones. This means 

 thp,t the greatest thinning is apt to trJre place on the inside and lower 

 shaded limbs than it v;ill on the outer, better exposed places on the 

 tree T;hich generally produce the more vigorous spurs, 



6, From data' obtained by counting all flo\-;ers and young fruits falling from 

 the trees, up to and including the June drop, that have been sprayed 

 vdth a horraono t^.-pe matoz'ial at oal^-cc and up to 4 v/eeks later, it appears 

 that the drop is delayed for a few days shortly after the material is 

 applied. After this short period of delay the rr.to of urop is mar]:cdly 

 accentuated so that total drops exceed that occurring on unspraycd 

 trees. Apparently the liomone "sticks" them on for a short while before 

 the opposite effect talccs place. 



